Chlorophyll (Chl) content,especially Chl b content,and stomatal conductance (G_s) are the key factors affecting the net photosynthetic rate (P_n).Setaria italica,a diploid C_4 panicoid species with a simple genome and...Chlorophyll (Chl) content,especially Chl b content,and stomatal conductance (G_s) are the key factors affecting the net photosynthetic rate (P_n).Setaria italica,a diploid C_4 panicoid species with a simple genome and high transformation efficiency,has been widely accepted as a model in photosynthesis and drought-tolerance research.The current study characterized Chl content,G_s,and P_n of 48 Setaria mutants induced by ethyl methanesulfonate.A total of 24,34,and 35 mutants had significant variations in Chl content,G_s,and P_n,respectively.Correlation analysis showed a positive correlation between increased G_s and increased P_n,and a weak correlation between decreased Chl b content and decreased P_n was also found.Remarkably,two mutants behaved with significantly decreased Chl b content but increased P_n compared to Yugu 1.Seven mutants behaved with significantly decreased G_s but did not decrease P_(n )compared to Yugu 1.The current study thus identified various genetic lines,further exploration of which would be beneficial to elucidate the relationship between Chl content,G_s,and P_n and the mechanism underlying why C_4 species are efficient at photosynthesis and water saving.展开更多
Plant photosynthesis assimilates CO_(2)from the atmosphere,and CO_(2)diffusion efficiency is mainly constrained by stomatal and mesophyll resistance.The stomatal and mesophyll conductance of plants are sensitive to ab...Plant photosynthesis assimilates CO_(2)from the atmosphere,and CO_(2)diffusion efficiency is mainly constrained by stomatal and mesophyll resistance.The stomatal and mesophyll conductance of plants are sensitive to abiotic stress factors,which affect the CO_(2)concentrations at carboxylation sites to control photosynthetic rates.Early studies conducted relevant reviews on the responses of stomatal conductance to the environment and the limitations of mesophyll conductance by internal structure and biochemical factors.However,reviews on the abiotic stress factors that systematically regulate plant CO_(2)diffusion are rare.Therefore,in this review,the rapid and long-term responses of stomatal and mesophyll conductance to abiotic stress factors(such as light intensity,drought,CO_(2)concentration and temperature)and their physiological mechanisms are summarized.Finally,future research trends are also investigated.展开更多
In petroleum-producing territories of West Siberia(Russia),oil well gas flares have a thermal effect on nearby plant communities.Such communities can be used as models for studying plant acclimation to global warming....In petroleum-producing territories of West Siberia(Russia),oil well gas flares have a thermal effect on nearby plant communities.Such communities can be used as models for studying plant acclimation to global warming.In the present study on the effect of the hydrothermal regime at the flare sites on mesophyll and stomatal functional traits of Betula pubescens,leaves were collected from trees at250 m(control site[CS]),200,150 and 100 m(maximum impact site[MIS])from a flare.From the CS to MIS site,the average annual air temperature increased by 0.5℃and bog water level decreased by 17 cm.On plants from the MIS,stomata were 16%smaller and density was 20%lower compared to those at the CS,resulting in lower maximum stomatal conductance in plants from the MIS(mean±SE:MIS 0.84±0.05 mol·m^(-2)s^(-1),CS 1.24±0.06 mol·m^(-2)s^(-1);F=12.6,P<0.01).Mesophyll cell volume was 1.9 times lower at MIS than at CS.Chloroplast numbers per cell also declined with distance from the flares,from 21(MIS)to18(CS;F=15.6,P<0.001),and chloroplast volume was 24%higher at the CS,whereas the number of mesophyll cells and chloroplasts numbers per unit leaf area were 1.9 and 1.8 times higher at the MIS than at the CS,respectively.As a result,leaves from the MIS had a large total mesophyll cell(Ames/A)and chloroplast(Achl/A)surface area per unit leaf area,resulting in a 46%increase in mesophyll conductance in plants from the MIS.Thus,structural changes in leaf epidermis consisted of a decrease in stomatal size and number,could lower transpiration losses with higher temperatures and less water.To compensate for the reduction in leaf conductance due to a decrease in stomatal conductance under these conditions,an increase in the number of mesophyll cells and chloroplasts per unit area provides a greater gas-exchange area and mesophyll conductance.展开更多
Quantifying the variation in stomatal behavior and functional traits of trees with elevation can provide a better understanding of the adaptative strategies to a changing climate. In this study, six water-and carbon-r...Quantifying the variation in stomatal behavior and functional traits of trees with elevation can provide a better understanding of the adaptative strategies to a changing climate. In this study, six water-and carbon-related functional traits were examined for three dominant tree species, Schima superba, Pinus massoniana and Castanopsis chinensis, in a mixed coniferous and broad-leaved forest at two elevations(70 and 360 m above sea level,respectively) in low subtropical China. We hypothesized that trees at higher elevations would develop more efficient strategies of stomatal regulations and greater water transport capacity to cope with more variable hydrothermal conditions than those at lower elevations. Results show that the hydraulic conductivity did not differ between trees at the two elevations, contrary to our expectation. The C. chinensis trees had greater values of leaf mass per unit area(LMA), and the S. superba and C. chinensis trees had greater values of wood density(WD),relative stem water content(RWC), and ratio of sapwood area to leaf area(Hv) at the 360-m elevation than at 70-m elevation. The mean canopy stomatal conductance was greater and more sensitive to vapor deficit pressure at360 m than at 70 m for both S. superba and C. chinensis, while stomatal sensitivity did not differ between the two contrasting elevations for P. massoniana. The midday leaf water potential(ψL) in P. massoniana was significantly more negative at 360 m than at 70 m, but did not vary with increasing elevation in both S. superba and C. chinensis.Variations in Hvcan be related to the differential stomatal behaviors between the two elevations. The variations of stomatal behavior and ψLwith elevation suggested the isohydric strategy for the two broad-leaved species and the anisohydric strategy for the conifer species. The species-specific differences in LMA, WD, RWC, and Hvbetween the two elevations may reflect conservative resource use strategies at the higher elevation. Our findings revealed a close relationship between hydraulic and stomatal behavior and may help better understand the functional responses of forests to changing environmental conditions.展开更多
The greatest failure rate of reforestation programs is basically related to water deficit,especially at the seedling stage.Therefore,the main objective of this work is to investigate the responses of three accessions ...The greatest failure rate of reforestation programs is basically related to water deficit,especially at the seedling stage.Therefore,the main objective of this work is to investigate the responses of three accessions of carob trees(Ceratonia siliqua L.)with 2-year-old from different climate regions to drought generated by four water treatments:Tc(250 mm),T1(180 mm),T2(100 mm),and T3(50 mm).The first accession(A1)comes from the protected national park of Ichkeul in northern Tunisia.This zone belongs to the bioclimatic sub-humid stage.The second accession(A2)comes from Melloulech,located in the center-east of Tunisia,belonging to the bioclimatic semi-arid stage.The third accession(A3)comes from the mountain of Matmata,located in the south of Tunisia,belonging to the bioclimatic hyper-arid stage.The experiment was undertaken in a greenhouse.Gaz exchange indices(net photosynthesis(A),stomatal conductance(gs),transpiration rate(E),and internal CO_(2) concentration(Ci))were determined.Predawn(Ψpd)and midday(Ψmd)leaf water potentials,relative soil water content(SWC),and morphological parameters(plant height(H),number of leaves(NL),number of leaflets(Nl),and number of branches(NB))were estimated.The results showed that significant differences(P<0.001)were found between physiological and morphological parameters of each accession.The highest growth potential was recorded for Tc treatment in both accessions A1 and A2.Significant decreases in gs,E,Ci,and SWC were recorded with the increases in water stress applied from treatment T1 to T3.Positive and significant correlations were found between SWC andΨpd for all studied accessions.Ψpd andΨmd decreased as water stress increased,ranging from–0.96 to–1.50 MPa at sunrise and from–1.94 to–2.83 MPa at midday,respectively,under control and T3 treatments.C.siliqua accessions responded to drought through exhibiting significant changes in their physiological and morphological behavior.Both accessions A1 and A2 showed greater drought tolerance than accession A3.These seedlings exhibit different adaptive mechanisms such as stress avoidance,which are aimed at reducing transpiration,limiting leaf growth,and increasing root growth to exploit more soil water.Therefore,C.siliqua can be recommended for the ecological restoration in Mediterranean ecosystems.展开更多
Studies on fertilization management of species native to the Amazon for energy plantations contribute to the diversity of species use and reduce biological risk due to the excessive use of clones or hybrids of Eucalyp...Studies on fertilization management of species native to the Amazon for energy plantations contribute to the diversity of species use and reduce biological risk due to the excessive use of clones or hybrids of Eucalyptus.This study evaluates the effect of precipitation seasonality and phosphorus and potassium fertilization on gas exchange in a Tachigali vulgaris plantation.Three levels of P(zero,65.2,130.4 kg ha^(-1))and three of K(zero,100.0,200.0 kg ha^(-1))were applied in a 3×3 factorial randomized block design.Gas exchange measurements were conducted in April and November 2018.In low rainfall,high irradiance period,photo synthetic rates were up to four times higher than in the high rainfall period,reaching 20.3μmol m^(-2)s^(-1)in the treatment with 130.4 g kg^(-1)of P and 100.0 g kg^(-1)of K.Factor analysis and principal component analysis reduced the initial eight gas exchange variables to two and three principal components in periods of high and low rainfall,respectively.The multivariate method used in this study readily identified variations in the variables as a function of rainfall,with high reliability in explaining the data set.展开更多
In South-Eastern forests of France,risks linked to the effects of tropospheric ozone(O_(3))are real;its annual impact has been observed specifically near the coastline and in high altitude mountains during the period ...In South-Eastern forests of France,risks linked to the effects of tropospheric ozone(O_(3))are real;its annual impact has been observed specifically near the coastline and in high altitude mountains during the period 2017-2019.In this study,the risk assessment of O_(3)pollutant was carried out using two approaches based on forest response indicators such as O_(3)specific foliar visible injury and by stomatal O_(3)flux.Phytotoxic O_(3)dose values(POD_(0))were obtained by the DO_(3)SE model.The model requires hourly O_(3)concentration for POD_(0)calculation.A modified approach that uses measurements from passive samplers(monthly average O_(3)concentration)was tested for the calculation of POD_(0)and test results showed good agreement with the POD_(0)calculated using hourly O_(3)data.In the model input file,the average O_(3)concentration is used for POD_(0),and this could be useful for POD_(0)calculation when the active monitor is limited.In this study,a flux-based assessment provided better correlation with O_(3)specific leaf injury,which is also species-specific.Foliar visible injury in response to O_(3)indicates that Pinus cembra and Pinus halepensis are more affected and therefore more sensitive than Pinus sylvestris.The POD_(0)and stomatal conductance(Gsto)seem to be induced by environmental factors,primarily rainfall and the soil water potential(fSWP).The correlation between the O_(3)flux metric and environmental variables with forest response indicators by Spearman rank test confirms P.cembra as one of the most sensitive species to O_(3).展开更多
The need to mitigate climate change cannot be more emphasized, which arises, as a result of increases in CO<sub>2</sub> emissions due to anthropogenic activities. Given the current world energy problems of...The need to mitigate climate change cannot be more emphasized, which arises, as a result of increases in CO<sub>2</sub> emissions due to anthropogenic activities. Given the current world energy problems of high fossil fuel consumption which plays a pivotal role in the greenhouse effect, Jatropha curcas biodiesel has been considered a potential alternative source of clean energy (biodiesel is carbon neutral). However, the ability of Jatropha curcas, as a candidate source of alternative of clean energy, to grow in marginal and dry soils, has been poorly elucidated. This study, therefore aimed at investigating whether Jatropha curcas leaves could switch from carrying out C<sub>3</sub> photosynthetic pathway to Crassulacean Acid Metabolism (CAM) as a strategy to improve its water deficit tolerance. Thirty-five-day-old Jatropha curcas accessions, from three different climatic zones of Botswana, viz., Mmadinare (Central zone), Thamaga (Southern zone) and Maun (Northern zone), were subjected to water stress, by with-holding irrigation with half-strength Hoagland culture solution. Net photosynthetic rate, transpiration and stomatal conductance were measured at weekly intervals. The leaf pH was measured to determine whether there was a decrease in pH (leaf acidification) of the leaves during the night, when the plants experienced water deficit stress. All the accessions exhibited marked reduction in all the measured photosynthetic characteristics when experience water deficit stress. However, a measurable CO<sub>2</sub> uptake was carried out by leaves of all the accessions, in the wake of marked decreases in stomatal conductance. There is evidence to suggest that when exposed to water stress J. curcas accessions switch from C<sub>3</sub> mode of photosynthesis to CAM photosynthetic pathway. This is attested to by the slightly low leaf pH at night. Thamaga accession exhibited an earlier stomatal closure than the other two accessions. This resulted in Thamaga accession displaying a slightly lower dry weight than both Mmadinare and Maun accessions. It could be concluded that Jatropha curcas appeared to tolerate water deficit stress due to its ability of switching from C<sub>3</sub> photosynthetic pathway to the CAM photosynthetic pathway, but with a cost to biomass accumulation, as demonstrated by slightly more reduced CO<sub>2</sub> assimilation by Thamaga accession, than the other two accessions.展开更多
Soil drought occurrence during dry season has been the main constraint, besides prolonged flooding during rainy season, in increasing cropping intensity and rice productivity in tropical riparian wetland. Use of droug...Soil drought occurrence during dry season has been the main constraint, besides prolonged flooding during rainy season, in increasing cropping intensity and rice productivity in tropical riparian wetland. Use of drought tolerant rice genotype might be a suitable option for overcoming such problem. This study focused on the effects of gradual soil drying during early vegetative growth stage on morphological and physiological traits of five Oryza glaberrima genotypes, namely RAM12, RAM14, RAM59, RAM97 and RAM101, and two Oryza sativa subsp japonica genotypes, i.e. Koshihikari and Minamihatamochi. The plants were subjected to 6 d of gradual soil drying condition from 15 days after transplanting(DAT) to 20 DAT, and were allowed to recover until 22 DAT. Gradual soil drying reduced plant growth as indicated by dry mass accumulation. Drought reduced stomatal conductance and increased leaf rolling score of all the genotypes. All the genotypes showed comparable response on stomatal conductance, but O. glaberrima genotypes performed higher in leaf rolling recovery. Meanwhile, O. sativa genotypes decreased total leaf area and specific leaf area, but increased specific leaf weight in order to avoid further damages due to drought stress. Drought tolerance mechanisms in RAM101, RAM12, RAM59 and RAM14 were associated with leaf morpho-physiological responses, root traits and dry biomass accumulation.展开更多
The maximum carboxylation rate of Rubisco(Vcmax)and maximum rate of electron transport(Jmax)for the biochemical photosynthetic model,and the slope(m)of the Ball-Berry stomatal conductance model influence gas exchange ...The maximum carboxylation rate of Rubisco(Vcmax)and maximum rate of electron transport(Jmax)for the biochemical photosynthetic model,and the slope(m)of the Ball-Berry stomatal conductance model influence gas exchange estimates between plants and the atmosphere.However,there is limited data on the variation of these three parameters for annual crops under different environmental conditions.Gas exchange measurements of light and CO2 response curves on leaves of winter wheat and spring wheat were conducted during the wheat growing season under different environmental conditions.There were no significant differences for Vcmax,Jmax or m between the two wheat types.The seasonal variation of Vcmax,Jmax and m for spring wheat was not pronounced,except a rapid decrease for Vcmax and Jmax at the end of growing season.Vcmax and Jmax show no significant changes during soil drying until light saturated stomatal conductance(gssat)was smaller than 0.15 mol m^–2 s^–1.Meanwhile,there was a significant difference in m during two different water supply conditions separated by gssat at 0.15 mol m^–2 s^–1.Furthermore,the misestimation of Vcmax and Jmax had great impacts on the net photosynthesis rate simulation,whereas,the underestimation of m resulted in underestimated stomatal conductance and transpiration rate and an overestimation of water use efficiency.Our work demonstrates that the impact of severe environmental conditions and specific growing stages on the variation of key model parameters should be taken into account for simulating gas exchange between plants and the atmosphere.Meanwhile,modification of m and Vcmax(and Jmax)successively based on water stress severity might be adopted to simulate gas exchange between plants and the atmosphere under drought.展开更多
In order to study the effects of different levels of salt stress and nitrogen(N) on physiological mechanisms,carbon isotope discrimination(△13C),and yield of two wheat cultivars(cv.),a two-year field experiment was c...In order to study the effects of different levels of salt stress and nitrogen(N) on physiological mechanisms,carbon isotope discrimination(△13C),and yield of two wheat cultivars(cv.),a two-year field experiment was carried out during 2013-2015.The treatments included three levels of salt stress(1.3,5.2,and 10.5 dS m^-1),three levels of N(50,100,and 150 kg N ha-1),and two wheat cultivars,Bam and Toos.Under salt stress,N application(100 and 150 kg N ha^-1) produced a significant effect on both cultivars with respect to physiological traits,i.e.,net photosynthetic rate(Pn),stomatal conductance(gs),chlorophyll index(Cl),Na^+/K^+ ratio as well as the grain yield(GY).The salt-tolerant and-sensitive cultivars exhibited the maximum values of physio-biochemical and yield attributes at 100 and 150 kg N ha-1,respectively.The results of △13C showed a significant difference(P<0.001) between wheat cultivars under the control and salt stress.According to our result,salt-tolerant cultivar Bam seems to be more efficient in terms of higher GY,Pn,gs,Cl,and lower Na^+/K^+ ratio as well as higher △13C as compared with salt-sensitive cultivar Toos,under salt stress.Therefore,a significant positive correlation that observed between △13C and GY,indicated that △13C may be an effective index for indirect selection of yield potential in wheat under irrigation regimes with saline water.展开更多
A drought event can cause entire crops to fail or yield loss.In order to study the effects of continuous drought on photosynthetic characteristics,yield,and water use efficiency(WUE)of winter wheat(Triticum aestivum L...A drought event can cause entire crops to fail or yield loss.In order to study the effects of continuous drought on photosynthetic characteristics,yield,and water use efficiency(WUE)of winter wheat(Triticum aestivum L.),the winter wheat variety“Aikang 58”was selected as test material with controlling the water of the pot-planted winter wheat under a mobile rainout shelter.Based on foot planting and safe wintering,winter wheat was evaluated under different drought conditions,including light,moderate and severe drought at the jointing(B),heading(C),and filling(G)stages.The soil water content was controlled in a range of 60%to 70%,50%to 60%,and 40%to 50%of the field capacity,respectively.In the experiment,there were 9 single-stage droughts,3 three-stage droughts,and 1 test control(totaling 13 trials).The results are as follows:Under a single-stage drought,the change of net photosynthetic rate(Pn)and stomatal conductance(Gs)have similar trends,and they both decrease significantly with the severity of the drought.Under three-stage continuous droughts,the change curve of Gs shows a constant downward trend;the change curve of Pn showed a“valley shape,”and the minimum value of Pn appeared at the heading stage.All droughts will reduce the yield of winter wheat.Under the three-stage continuous drought conditions,except for light drought,moderate drought and severe drought will cause significant yield reduction,mainly due to lack of water at the jointing and heading stages.Continuous drought will reduce the WUE,and the difference will reach a significant level under moderate and severe drought.The present results suggested that when water resources are scarce,it is a better irrigation model to save water and achieve high grain yield by applying appropriate water stress(60%–70%FC)during the critical growth period of winter wheat.展开更多
In face of climate change catastrophes, understanding the thermal limits and optimal physiological thermal window food crop is of particular urgency. This research aims to evaluate: 1) how physiological performances o...In face of climate change catastrophes, understanding the thermal limits and optimal physiological thermal window food crop is of particular urgency. This research aims to evaluate: 1) how physiological performances of plant will change with increasing chronic and acute heat stress;2) if the examined parameters form a hierarchy in terms of thermal tolerance;and 3) the optimal thermal window and critical temperatures of the examined plants with response to chronic and acute heat stress. Six temperate vegetables were subjected to chronic and acute heat stress and a suite of physiological parameters were evaluated. Dose responses were observed in shoot fresh weight, photosynthetic gas exchange, photosynthetic oxygen evolution, electron transfer rate, photo- and non-photochemical quenching with significant drop in performance as early as 28°C for selected species. Conversely, ratio of variable to maximum fluorescence (F<sub>v</sub>/F<sub>m</sub>) was not affected by heat stress until 46°C in chronic heat stress. Examining the temperature at which a measured parameter’s performance dropped by 50% compared to control (LT<sub>50</sub>), a distinct hierarchy of the indices was observed for Canasta, recombinant inbred line 141, Lactuca serriola and Lactuca sativa (L. “Salinas”): shoot fresh weight, representing the highest integrated level of photosynthesis was the most sensitive to thermal stress (28°C - 30°C), followed by oxygen evolution (35°C - 45°C) while non-photochemical and photochemical quenching which is subcellular function of stress alleviation had a much higher capacity failure temperature (47°C - 60°C). It is expected that F<sub>v</sub>/F<sub>m</sub> ratio, a measurement of sub-cellular structural integrity, will approach that of non-photochemical and photochemical quenching, if not exceeding it. By examining the photosynthetic parameters via their hierarchy of biological organization, it can be inferred that plants like Arugula and recombinant inbred line 192 are already operating near their thermal limit and have less energetic investment into heat stress mediation whereas L. serriola prioritizes thermal tolerance at the expense of photosynthesis efficiency.展开更多
The use of tolerant crop varieties is a strategy that mitigates the water deficit effect in a sustainable way.The generation of these varieties is more efficient when variables associated with this tolerance have been...The use of tolerant crop varieties is a strategy that mitigates the water deficit effect in a sustainable way.The generation of these varieties is more efficient when variables associated with this tolerance have been identified,since they can facilitate the breeding processes.This study aimed to establish the relationships between water deficit tolerance of four cotton varieties(Nevada-123,Oasis-129,Guatapuri,and Festivalle)and morphological variables(monopodial branches,boll weight,root/shoot ratio,and leaf and root dry matter),physiological variables(relative water content,net photosynthesis,stomatal conductance,electron transport rate,photochemical quenching,photochemical efficiency of PSII,chlorophyll a/b ratio(Chl a/b),C^(12)/C^(13)isotope ratio,and electrolyte leakage),and biochemical variables(contents of sugars,proline,carotenoids,and malondialdehyde).Furthermore,calibrated predictive models of the drought tolerance indices were developed based on the key variables identified.For this purpose,a pot experiment was established where plants were subjected to a moderate or severe water deficit during the blooming stage for 12 days.The stress tolerance index(STI)and mean productivity(MP)were calculated.For the evaluated variables,the differences between well-watered and water deficit plants(Δ)were calculated and ANOVA,partial least squares,Pearson’s correlation,and multiple linear regression analyzes were performed.A model was generated that explained 95% of the STI and was composed of Δmalondialdehyde,Δproline,and Δboll weight.For MP,the model was comprised of Δstomatal conductance,Δroot/shoot ratio,and ΔChl a/b,and explained 89% of the MP.The analysis of the assessed variables allowed the identification of key variables and the development of calibrated predictive models that can be used in screening to obtain cotton varieties with different levels of water deficit tolerance.展开更多
Although tropical high ambient temperature and humidity severely reduced the productivity of temperate plants, temperate vegetable crops such as lettuce have been successfully grown in Singapore by only cooling its ro...Although tropical high ambient temperature and humidity severely reduced the productivity of temperate plants, temperate vegetable crops such as lettuce have been successfully grown in Singapore by only cooling its root-zone. In this paper, a cool Meditteranean vegetable, Eruca sativa, was studied to understand how different RZTs can impact its shoot productivity, photosynthesis and nutritional quality. All plants were cultivated using aeroponic systems in a tropical greenhouse under hot ambient conditions where roots were subjected to four different root-zone temperatures (RZTs) of 20°C-RZT, 25°C-RZT, 30°C-RZT and fluctuating ambient temperatures ranged from 25°C to 38°C [25°C/38°C (ambient)]-RZT. Parameters studied include shoot fresh weight (FW), photosynthetic gas exchange, midday chlorophyll (Chl) fluorescence F<sub>v</sub>/F<sub>m</sub> ratio, Chl fluorescence photochemical quenching (qP), non-photochemical quenching (qN) and electron transport rate (ETR), total phenolic compounds and mineral content such as potassium (K), calcium (Ca), magnesium (Mg) and iron (Fe). Among the 4 different RZT treatments, E. sativa plants grown under ambient-RZT (25/38°C-RZT) had the lowest shoot and root FW while those plants grown under 20°C-RZT had highest productivity of shoot and root. However, there were no significant differences in shoot and root FW in plants grown at 25°C- and 30°C-RZT. Compared to plants grown under 25°C/38°C (ambient-RZT), light-saturated photosynthetic CO<sub>2</sub> assimilation rate (A<sub>sat</sub>) and stomatal conductance (g<sub>ssat</sub>) were similarly higher in 20°C-, 25°C- and 30°C-RZT. All plants had midday Chl fluorescence F<sub>v</sub>/F<sub>m</sub> ratio lower than <0.8 ranged from 0.785 to 0.606 with the highest and lowest ratios recorded in 20°C-RZT and ambient-RZT plants, respectively. These results indicate that cooling the RZ of E. sativa plants protected their PS II from photoinactivation during midday in the greenhouse. There were no significant differences observed in photochemical quenching (qP), non-photochemical quenching (qN) and electron transport rate among plants grown under 20°C-, 25°C- and 30°C-RZT. However, plants grown under ambient-RZT had lower qP, qN and ETR compared to all other plants. E. sativa at 20°C-RZT with the best developed roots had the highest dietary mineral (K, Mg, Ca and Fe) contents but lower total phenolics content. In contrast, ambient-RZT, plants with poorly developed roots had the lowest mineral content but highest total phenolic content. The results of this study suggest that cooling of roots is a feasible method for the cultivation of E. sativa in the tropic, which enhances the content of dietary minerals in shoots.展开更多
There were fewer comparative studies on the adaptability of mangrove plants with two different salt secretion mechanisms to salinity stress. In this study,the seedlings of mangrove plants Aegiceras corniculatum and Ka...There were fewer comparative studies on the adaptability of mangrove plants with two different salt secretion mechanisms to salinity stress. In this study,the seedlings of mangrove plants Aegiceras corniculatum and Kandelia candel were selected as the research objects,and the methods of hydroponics with different salinity gradients were used. The salinity of 0‰,10‰,and 30‰ was applied respectively to simulate the adaptability of seedlings at low,moderate,and severe salinity stresses. Based on the results,the short-term responses of photosynthesis and chlorophyll content to salinity stress in two mangrove species with different salt secretion mechanisms were analyzed and discussed. The results show that A. corniculatum was more tolerant to10‰ salinity than K. candel,and the net photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance( Gs) and water use efficiency(WUE)were also relatively higher;both A. corniculatum and K. candel could acclimate the low salinity(0‰),but showed severe osmotic stress at 30‰ salinity;A. corniculatum was more sensitive to severe salinity(30‰) than K. candel. These results can be of help to provide a theoretical support for the selection of species for mangrove wetlands restoration and seedlings acclimatization in tidal flats.展开更多
Many modifications to growing environments and specific stress induction techniques exist which are supported by preliminary research to increase yield and/or concentration of secondary metabolites in <em>Cannab...Many modifications to growing environments and specific stress induction techniques exist which are supported by preliminary research to increase yield and/or concentration of secondary metabolites in <em>Cannabis sativa</em> L. One such technique is the modification of the spectral composition of light late in flowering-stage development. In this study, we evaluated the hypothesis that the addition of narrow bandwidth UV-A light and the combination of narrow bandwidth blue and red light, during the final two weeks of the flowering cycle affect the concentration of cannabinoids and terpenes, with no difference in harvest dry weight. Three treatments were used in this experimental design, 1) control-full spectrum illumination, 2) UV-A (~390 nm) at ~66 PPFD in addition to control lighting, and 3) blue (~450 nm) and red (~660 nm) at ~158 PPFD in addition to control lighting. Light treatments were initiated during the final two weeks of flowering to assess secondary metabolite concentration (cannabinoids and terpenes) and yield of three cannabis cultivars (Type I (Larry OG), Type II (Pootie Tang), and Type III (Super White)). With two of the three cultivars used in this study responding with enhanced production of THC our results support the potential beneficial effects of attributed light-mediated treatments on cannabinoid production. On the other hand, our results show contrasting trends for terpene production and yield of dry weight flower.展开更多
The objective of the research was to evaluate the effects of saline stress on the initial growth and physiological parameters of three varieties of cotton plants, being two cultivars of colored fiber (BRS Topázio...The objective of the research was to evaluate the effects of saline stress on the initial growth and physiological parameters of three varieties of cotton plants, being two cultivars of colored fiber (BRS Topázio and BRS Verde) and one of white fiber (BRS 286). The experiment was conducted under greenhouse conditions. After chemical depletion with sulfuric acid, five seeds were seeded in polyethylene pots of 20 kg, leaving only one plant per pot after thinning. The experimental design was completely randomized, with a factorial scheme of 3 × 5, with five replications, totaling 75 plots, being three cotton varieties and five saline stress treatments—1.1;3.1;5.1;7.1;9.1 dS m−1. The evaluations occurred at 15 and 30 days after the beginning of the treatments (DAT) for growth variables (plant height, stem diameter, number of leaves and leaf area) and gas exchange (stomatal conductance, net photosynthesis rate and transpiration. The variety that was most resistant to the salt stress levels studied was BRS 286, followed by BRS Topazio and BRS Verde.展开更多
Background:Few studies have evaluated the effect of drought on the morphophysiological characteristics of African C_(4) grasses.We investigated how drought affects leaf gas exchange characteristics,biomass partitionin...Background:Few studies have evaluated the effect of drought on the morphophysiological characteristics of African C_(4) grasses.We investigated how drought affects leaf gas exchange characteristics,biomass partitioning,and water use efficiencies of Enteropogon macrostachyus and Cenchrus ciliaris.Methods:The grasses were grown in a controlled environment under optimum conditions,that is,70%of the maximum water‐holding capacity(WHC)for the first 40 days.Thereafter,half of the columns were maintained under optimum or drought conditions(30%of maximum WHC)for another 20 days.Results:Under optimum conditions,C.ciliaris showed a significantly higher photosynthetic rate,stomatal conductance,and transpiration rate than E.macrostachyus.Drought decreased the photosynthetic rate,stomatal conductance and transpiration rate only in C.ciliaris.The net photosynthetic rate,stomatal conductance,and leaf transpiration of E.macrostachyus did not differ significantly under optimum and drought conditions.E.macrostachyus showed an increase in its water use efficiencies under drought to a greater extent than C.ciliaris.Conclusions:Our results demonstrate that C.ciliaris is more sensitive to drought than E.macrostachyus.The decrease in the intercellular CO_(2) concentration and the increase in stomatal limitation with drought in C.ciliaris and E.macrostachyus suggest that stomatal limitation plays the dominant role in photosynthesis of the studied African C_(4) grasses.展开更多
Aims We investigated the regulation of the water status in three predominant perennial C3 phreatophytes(Alhagi sparsifolia,Populus euphratica,Tamarix ramosissima)at typical sites of their occurrence at the southern fr...Aims We investigated the regulation of the water status in three predominant perennial C3 phreatophytes(Alhagi sparsifolia,Populus euphratica,Tamarix ramosissima)at typical sites of their occurrence at the southern fringe of the hyperarid Taklamakan Desert(north-west China).Methods In the foreland of the river oasis of Qira(Cele),we determined meteorological variables,plant biomass production,plant water potentials(WL)and the water flux through the plants.We calculated the hydraulic conductance on the flow path from the soil to the leaves(kSL)and tested the effects of kSL,WL and the leaf-to-air difference in the partial pressure of water vapour(Dw)on stomatal regulation using regression analyses.Important Findings Despite high values of plant water potential at the point of turgor loss,all plants sustained WL at levels that were high enough to maintain transpiration throughout the growing season.In A.sparsifolia,stomatal resistance(rs;related to leaf area or leaf mass)was most closely correlated with kSL;whereas in P.euphratica,~70%of the variation in rs was explained by Dw.In T.ramosissima,leaf area-related rs was significantly correlated with WL and kSL.The regulation mechanisms are in accordance with the growth patterns and the occurrence of the species in relation to their distance to the ground water.展开更多
基金supported by the National Natural Science Foundation of China (32241042 and 31771807)the National Key R&D Program of China (2021YFF1000103)+1 种基金the China Agricultural Research System (CARS-06-04)the Agricultural Science and Technology Innovation Program of the Chinese Academy of Agricultural Sciences。
文摘Chlorophyll (Chl) content,especially Chl b content,and stomatal conductance (G_s) are the key factors affecting the net photosynthetic rate (P_n).Setaria italica,a diploid C_4 panicoid species with a simple genome and high transformation efficiency,has been widely accepted as a model in photosynthesis and drought-tolerance research.The current study characterized Chl content,G_s,and P_n of 48 Setaria mutants induced by ethyl methanesulfonate.A total of 24,34,and 35 mutants had significant variations in Chl content,G_s,and P_n,respectively.Correlation analysis showed a positive correlation between increased G_s and increased P_n,and a weak correlation between decreased Chl b content and decreased P_n was also found.Remarkably,two mutants behaved with significantly decreased Chl b content but increased P_n compared to Yugu 1.Seven mutants behaved with significantly decreased G_s but did not decrease P_(n )compared to Yugu 1.The current study thus identified various genetic lines,further exploration of which would be beneficial to elucidate the relationship between Chl content,G_s,and P_n and the mechanism underlying why C_4 species are efficient at photosynthesis and water saving.
基金supported by National Natural Science Foundation of China(32071963)the Chengdu Science and Technology Project,China(2020-YF09-00033-SN)+1 种基金a grant from the International S&T Cooperation Projects of Sichuan Province,China(2020YFH0126)the China Agriculture Research System of MOF and MARA(CARS04-PS19)。
文摘Plant photosynthesis assimilates CO_(2)from the atmosphere,and CO_(2)diffusion efficiency is mainly constrained by stomatal and mesophyll resistance.The stomatal and mesophyll conductance of plants are sensitive to abiotic stress factors,which affect the CO_(2)concentrations at carboxylation sites to control photosynthetic rates.Early studies conducted relevant reviews on the responses of stomatal conductance to the environment and the limitations of mesophyll conductance by internal structure and biochemical factors.However,reviews on the abiotic stress factors that systematically regulate plant CO_(2)diffusion are rare.Therefore,in this review,the rapid and long-term responses of stomatal and mesophyll conductance to abiotic stress factors(such as light intensity,drought,CO_(2)concentration and temperature)and their physiological mechanisms are summarized.Finally,future research trends are also investigated.
基金performed within the budget themes of the Institute Botanic Garden UB RASthe framework of the state assignment FEWZ-2020–0009 from the Ministry of Education and Science of the Russian Federation。
文摘In petroleum-producing territories of West Siberia(Russia),oil well gas flares have a thermal effect on nearby plant communities.Such communities can be used as models for studying plant acclimation to global warming.In the present study on the effect of the hydrothermal regime at the flare sites on mesophyll and stomatal functional traits of Betula pubescens,leaves were collected from trees at250 m(control site[CS]),200,150 and 100 m(maximum impact site[MIS])from a flare.From the CS to MIS site,the average annual air temperature increased by 0.5℃and bog water level decreased by 17 cm.On plants from the MIS,stomata were 16%smaller and density was 20%lower compared to those at the CS,resulting in lower maximum stomatal conductance in plants from the MIS(mean±SE:MIS 0.84±0.05 mol·m^(-2)s^(-1),CS 1.24±0.06 mol·m^(-2)s^(-1);F=12.6,P<0.01).Mesophyll cell volume was 1.9 times lower at MIS than at CS.Chloroplast numbers per cell also declined with distance from the flares,from 21(MIS)to18(CS;F=15.6,P<0.001),and chloroplast volume was 24%higher at the CS,whereas the number of mesophyll cells and chloroplasts numbers per unit leaf area were 1.9 and 1.8 times higher at the MIS than at the CS,respectively.As a result,leaves from the MIS had a large total mesophyll cell(Ames/A)and chloroplast(Achl/A)surface area per unit leaf area,resulting in a 46%increase in mesophyll conductance in plants from the MIS.Thus,structural changes in leaf epidermis consisted of a decrease in stomatal size and number,could lower transpiration losses with higher temperatures and less water.To compensate for the reduction in leaf conductance due to a decrease in stomatal conductance under these conditions,an increase in the number of mesophyll cells and chloroplasts per unit area provides a greater gas-exchange area and mesophyll conductance.
基金funded by the National Natural Science Foundation of China,grant number 32171501 and 31770646the Guangdong Basic and Applied Basic Research Foundation,grant number2021A1515012486。
文摘Quantifying the variation in stomatal behavior and functional traits of trees with elevation can provide a better understanding of the adaptative strategies to a changing climate. In this study, six water-and carbon-related functional traits were examined for three dominant tree species, Schima superba, Pinus massoniana and Castanopsis chinensis, in a mixed coniferous and broad-leaved forest at two elevations(70 and 360 m above sea level,respectively) in low subtropical China. We hypothesized that trees at higher elevations would develop more efficient strategies of stomatal regulations and greater water transport capacity to cope with more variable hydrothermal conditions than those at lower elevations. Results show that the hydraulic conductivity did not differ between trees at the two elevations, contrary to our expectation. The C. chinensis trees had greater values of leaf mass per unit area(LMA), and the S. superba and C. chinensis trees had greater values of wood density(WD),relative stem water content(RWC), and ratio of sapwood area to leaf area(Hv) at the 360-m elevation than at 70-m elevation. The mean canopy stomatal conductance was greater and more sensitive to vapor deficit pressure at360 m than at 70 m for both S. superba and C. chinensis, while stomatal sensitivity did not differ between the two contrasting elevations for P. massoniana. The midday leaf water potential(ψL) in P. massoniana was significantly more negative at 360 m than at 70 m, but did not vary with increasing elevation in both S. superba and C. chinensis.Variations in Hvcan be related to the differential stomatal behaviors between the two elevations. The variations of stomatal behavior and ψLwith elevation suggested the isohydric strategy for the two broad-leaved species and the anisohydric strategy for the conifer species. The species-specific differences in LMA, WD, RWC, and Hvbetween the two elevations may reflect conservative resource use strategies at the higher elevation. Our findings revealed a close relationship between hydraulic and stomatal behavior and may help better understand the functional responses of forests to changing environmental conditions.
文摘The greatest failure rate of reforestation programs is basically related to water deficit,especially at the seedling stage.Therefore,the main objective of this work is to investigate the responses of three accessions of carob trees(Ceratonia siliqua L.)with 2-year-old from different climate regions to drought generated by four water treatments:Tc(250 mm),T1(180 mm),T2(100 mm),and T3(50 mm).The first accession(A1)comes from the protected national park of Ichkeul in northern Tunisia.This zone belongs to the bioclimatic sub-humid stage.The second accession(A2)comes from Melloulech,located in the center-east of Tunisia,belonging to the bioclimatic semi-arid stage.The third accession(A3)comes from the mountain of Matmata,located in the south of Tunisia,belonging to the bioclimatic hyper-arid stage.The experiment was undertaken in a greenhouse.Gaz exchange indices(net photosynthesis(A),stomatal conductance(gs),transpiration rate(E),and internal CO_(2) concentration(Ci))were determined.Predawn(Ψpd)and midday(Ψmd)leaf water potentials,relative soil water content(SWC),and morphological parameters(plant height(H),number of leaves(NL),number of leaflets(Nl),and number of branches(NB))were estimated.The results showed that significant differences(P<0.001)were found between physiological and morphological parameters of each accession.The highest growth potential was recorded for Tc treatment in both accessions A1 and A2.Significant decreases in gs,E,Ci,and SWC were recorded with the increases in water stress applied from treatment T1 to T3.Positive and significant correlations were found between SWC andΨpd for all studied accessions.Ψpd andΨmd decreased as water stress increased,ranging from–0.96 to–1.50 MPa at sunrise and from–1.94 to–2.83 MPa at midday,respectively,under control and T3 treatments.C.siliqua accessions responded to drought through exhibiting significant changes in their physiological and morphological behavior.Both accessions A1 and A2 showed greater drought tolerance than accession A3.These seedlings exhibit different adaptive mechanisms such as stress avoidance,which are aimed at reducing transpiration,limiting leaf growth,and increasing root growth to exploit more soil water.Therefore,C.siliqua can be recommended for the ecological restoration in Mediterranean ecosystems.
基金financed in part by the Coordenacao de Aperfeicoamento de Pessoal de Nível Superior–Brasil (CAPES)—Finance Code 001supported by the Fundacoo Amazonia de Amparo a Estudos e Pesquisas—FAPESPA。
文摘Studies on fertilization management of species native to the Amazon for energy plantations contribute to the diversity of species use and reduce biological risk due to the excessive use of clones or hybrids of Eucalyptus.This study evaluates the effect of precipitation seasonality and phosphorus and potassium fertilization on gas exchange in a Tachigali vulgaris plantation.Three levels of P(zero,65.2,130.4 kg ha^(-1))and three of K(zero,100.0,200.0 kg ha^(-1))were applied in a 3×3 factorial randomized block design.Gas exchange measurements were conducted in April and November 2018.In low rainfall,high irradiance period,photo synthetic rates were up to four times higher than in the high rainfall period,reaching 20.3μmol m^(-2)s^(-1)in the treatment with 130.4 g kg^(-1)of P and 100.0 g kg^(-1)of K.Factor analysis and principal component analysis reduced the initial eight gas exchange variables to two and three principal components in periods of high and low rainfall,respectively.The multivariate method used in this study readily identified variations in the variables as a function of rainfall,with high reliability in explaining the data set.
基金funded by the Alcotra program MITIMPACT(Grand No.1671/1450109240)the Scientific Grant Agency of the Slovak Republic,VEGA(Project No.2/0093/2)。
文摘In South-Eastern forests of France,risks linked to the effects of tropospheric ozone(O_(3))are real;its annual impact has been observed specifically near the coastline and in high altitude mountains during the period 2017-2019.In this study,the risk assessment of O_(3)pollutant was carried out using two approaches based on forest response indicators such as O_(3)specific foliar visible injury and by stomatal O_(3)flux.Phytotoxic O_(3)dose values(POD_(0))were obtained by the DO_(3)SE model.The model requires hourly O_(3)concentration for POD_(0)calculation.A modified approach that uses measurements from passive samplers(monthly average O_(3)concentration)was tested for the calculation of POD_(0)and test results showed good agreement with the POD_(0)calculated using hourly O_(3)data.In the model input file,the average O_(3)concentration is used for POD_(0),and this could be useful for POD_(0)calculation when the active monitor is limited.In this study,a flux-based assessment provided better correlation with O_(3)specific leaf injury,which is also species-specific.Foliar visible injury in response to O_(3)indicates that Pinus cembra and Pinus halepensis are more affected and therefore more sensitive than Pinus sylvestris.The POD_(0)and stomatal conductance(Gsto)seem to be induced by environmental factors,primarily rainfall and the soil water potential(fSWP).The correlation between the O_(3)flux metric and environmental variables with forest response indicators by Spearman rank test confirms P.cembra as one of the most sensitive species to O_(3).
文摘The need to mitigate climate change cannot be more emphasized, which arises, as a result of increases in CO<sub>2</sub> emissions due to anthropogenic activities. Given the current world energy problems of high fossil fuel consumption which plays a pivotal role in the greenhouse effect, Jatropha curcas biodiesel has been considered a potential alternative source of clean energy (biodiesel is carbon neutral). However, the ability of Jatropha curcas, as a candidate source of alternative of clean energy, to grow in marginal and dry soils, has been poorly elucidated. This study, therefore aimed at investigating whether Jatropha curcas leaves could switch from carrying out C<sub>3</sub> photosynthetic pathway to Crassulacean Acid Metabolism (CAM) as a strategy to improve its water deficit tolerance. Thirty-five-day-old Jatropha curcas accessions, from three different climatic zones of Botswana, viz., Mmadinare (Central zone), Thamaga (Southern zone) and Maun (Northern zone), were subjected to water stress, by with-holding irrigation with half-strength Hoagland culture solution. Net photosynthetic rate, transpiration and stomatal conductance were measured at weekly intervals. The leaf pH was measured to determine whether there was a decrease in pH (leaf acidification) of the leaves during the night, when the plants experienced water deficit stress. All the accessions exhibited marked reduction in all the measured photosynthetic characteristics when experience water deficit stress. However, a measurable CO<sub>2</sub> uptake was carried out by leaves of all the accessions, in the wake of marked decreases in stomatal conductance. There is evidence to suggest that when exposed to water stress J. curcas accessions switch from C<sub>3</sub> mode of photosynthesis to CAM photosynthetic pathway. This is attested to by the slightly low leaf pH at night. Thamaga accession exhibited an earlier stomatal closure than the other two accessions. This resulted in Thamaga accession displaying a slightly lower dry weight than both Mmadinare and Maun accessions. It could be concluded that Jatropha curcas appeared to tolerate water deficit stress due to its ability of switching from C<sub>3</sub> photosynthetic pathway to the CAM photosynthetic pathway, but with a cost to biomass accumulation, as demonstrated by slightly more reduced CO<sub>2</sub> assimilation by Thamaga accession, than the other two accessions.
基金funded by the Program of the United Graduate School of Agricultural Sciences, Kagoshima Universitysupported by Program Penelitian Unggulan Profesi Universitas Sriwijaya (Grant No. 0006/UN9/SK.LP2M.PT/2018)+1 种基金Program PMDSU (Grant No. 093/SP2H/LT/DRPM/IV/2018)Enhancing International Publication Program by Directorate of Higher Education of the Ministry of Research, Technology and Higher Education of the Republic of Indonesia
文摘Soil drought occurrence during dry season has been the main constraint, besides prolonged flooding during rainy season, in increasing cropping intensity and rice productivity in tropical riparian wetland. Use of drought tolerant rice genotype might be a suitable option for overcoming such problem. This study focused on the effects of gradual soil drying during early vegetative growth stage on morphological and physiological traits of five Oryza glaberrima genotypes, namely RAM12, RAM14, RAM59, RAM97 and RAM101, and two Oryza sativa subsp japonica genotypes, i.e. Koshihikari and Minamihatamochi. The plants were subjected to 6 d of gradual soil drying condition from 15 days after transplanting(DAT) to 20 DAT, and were allowed to recover until 22 DAT. Gradual soil drying reduced plant growth as indicated by dry mass accumulation. Drought reduced stomatal conductance and increased leaf rolling score of all the genotypes. All the genotypes showed comparable response on stomatal conductance, but O. glaberrima genotypes performed higher in leaf rolling recovery. Meanwhile, O. sativa genotypes decreased total leaf area and specific leaf area, but increased specific leaf weight in order to avoid further damages due to drought stress. Drought tolerance mechanisms in RAM101, RAM12, RAM59 and RAM14 were associated with leaf morpho-physiological responses, root traits and dry biomass accumulation.
基金This research was jointly supported by the National Natural Science Foundation of China(41375019,41730645,and 41275118)the China Special Fund for Meteorological Research in the Public Interest(Major projects)(GYHY201506001-2).
文摘The maximum carboxylation rate of Rubisco(Vcmax)and maximum rate of electron transport(Jmax)for the biochemical photosynthetic model,and the slope(m)of the Ball-Berry stomatal conductance model influence gas exchange estimates between plants and the atmosphere.However,there is limited data on the variation of these three parameters for annual crops under different environmental conditions.Gas exchange measurements of light and CO2 response curves on leaves of winter wheat and spring wheat were conducted during the wheat growing season under different environmental conditions.There were no significant differences for Vcmax,Jmax or m between the two wheat types.The seasonal variation of Vcmax,Jmax and m for spring wheat was not pronounced,except a rapid decrease for Vcmax and Jmax at the end of growing season.Vcmax and Jmax show no significant changes during soil drying until light saturated stomatal conductance(gssat)was smaller than 0.15 mol m^–2 s^–1.Meanwhile,there was a significant difference in m during two different water supply conditions separated by gssat at 0.15 mol m^–2 s^–1.Furthermore,the misestimation of Vcmax and Jmax had great impacts on the net photosynthesis rate simulation,whereas,the underestimation of m resulted in underestimated stomatal conductance and transpiration rate and an overestimation of water use efficiency.Our work demonstrates that the impact of severe environmental conditions and specific growing stages on the variation of key model parameters should be taken into account for simulating gas exchange between plants and the atmosphere.Meanwhile,modification of m and Vcmax(and Jmax)successively based on water stress severity might be adopted to simulate gas exchange between plants and the atmosphere under drought.
基金funded by the International Atomic Energy Agency of Iran through a research project (Production of salt-tolerant mutant lines using morpho-physiological mechanisms and stable 15N and 13C isotope (A87A057)) of plant breeding group, Agriculture Researh School, Nuclear Science and Technology Research Institute (NSTRI) of Iran, Karaj
文摘In order to study the effects of different levels of salt stress and nitrogen(N) on physiological mechanisms,carbon isotope discrimination(△13C),and yield of two wheat cultivars(cv.),a two-year field experiment was carried out during 2013-2015.The treatments included three levels of salt stress(1.3,5.2,and 10.5 dS m^-1),three levels of N(50,100,and 150 kg N ha-1),and two wheat cultivars,Bam and Toos.Under salt stress,N application(100 and 150 kg N ha^-1) produced a significant effect on both cultivars with respect to physiological traits,i.e.,net photosynthetic rate(Pn),stomatal conductance(gs),chlorophyll index(Cl),Na^+/K^+ ratio as well as the grain yield(GY).The salt-tolerant and-sensitive cultivars exhibited the maximum values of physio-biochemical and yield attributes at 100 and 150 kg N ha-1,respectively.The results of △13C showed a significant difference(P<0.001) between wheat cultivars under the control and salt stress.According to our result,salt-tolerant cultivar Bam seems to be more efficient in terms of higher GY,Pn,gs,Cl,and lower Na^+/K^+ ratio as well as higher △13C as compared with salt-sensitive cultivar Toos,under salt stress.Therefore,a significant positive correlation that observed between △13C and GY,indicated that △13C may be an effective index for indirect selection of yield potential in wheat under irrigation regimes with saline water.
基金This research work was jointly funded by the National Nature Science Foundation of China(51779093)the Support Plan for Scientific and Technological Innovation Team of Colleges and Universities in Henan Province(17IRTSTHN026).
文摘A drought event can cause entire crops to fail or yield loss.In order to study the effects of continuous drought on photosynthetic characteristics,yield,and water use efficiency(WUE)of winter wheat(Triticum aestivum L.),the winter wheat variety“Aikang 58”was selected as test material with controlling the water of the pot-planted winter wheat under a mobile rainout shelter.Based on foot planting and safe wintering,winter wheat was evaluated under different drought conditions,including light,moderate and severe drought at the jointing(B),heading(C),and filling(G)stages.The soil water content was controlled in a range of 60%to 70%,50%to 60%,and 40%to 50%of the field capacity,respectively.In the experiment,there were 9 single-stage droughts,3 three-stage droughts,and 1 test control(totaling 13 trials).The results are as follows:Under a single-stage drought,the change of net photosynthetic rate(Pn)and stomatal conductance(Gs)have similar trends,and they both decrease significantly with the severity of the drought.Under three-stage continuous droughts,the change curve of Gs shows a constant downward trend;the change curve of Pn showed a“valley shape,”and the minimum value of Pn appeared at the heading stage.All droughts will reduce the yield of winter wheat.Under the three-stage continuous drought conditions,except for light drought,moderate drought and severe drought will cause significant yield reduction,mainly due to lack of water at the jointing and heading stages.Continuous drought will reduce the WUE,and the difference will reach a significant level under moderate and severe drought.The present results suggested that when water resources are scarce,it is a better irrigation model to save water and achieve high grain yield by applying appropriate water stress(60%–70%FC)during the critical growth period of winter wheat.
文摘In face of climate change catastrophes, understanding the thermal limits and optimal physiological thermal window food crop is of particular urgency. This research aims to evaluate: 1) how physiological performances of plant will change with increasing chronic and acute heat stress;2) if the examined parameters form a hierarchy in terms of thermal tolerance;and 3) the optimal thermal window and critical temperatures of the examined plants with response to chronic and acute heat stress. Six temperate vegetables were subjected to chronic and acute heat stress and a suite of physiological parameters were evaluated. Dose responses were observed in shoot fresh weight, photosynthetic gas exchange, photosynthetic oxygen evolution, electron transfer rate, photo- and non-photochemical quenching with significant drop in performance as early as 28°C for selected species. Conversely, ratio of variable to maximum fluorescence (F<sub>v</sub>/F<sub>m</sub>) was not affected by heat stress until 46°C in chronic heat stress. Examining the temperature at which a measured parameter’s performance dropped by 50% compared to control (LT<sub>50</sub>), a distinct hierarchy of the indices was observed for Canasta, recombinant inbred line 141, Lactuca serriola and Lactuca sativa (L. “Salinas”): shoot fresh weight, representing the highest integrated level of photosynthesis was the most sensitive to thermal stress (28°C - 30°C), followed by oxygen evolution (35°C - 45°C) while non-photochemical and photochemical quenching which is subcellular function of stress alleviation had a much higher capacity failure temperature (47°C - 60°C). It is expected that F<sub>v</sub>/F<sub>m</sub> ratio, a measurement of sub-cellular structural integrity, will approach that of non-photochemical and photochemical quenching, if not exceeding it. By examining the photosynthetic parameters via their hierarchy of biological organization, it can be inferred that plants like Arugula and recombinant inbred line 192 are already operating near their thermal limit and have less energetic investment into heat stress mediation whereas L. serriola prioritizes thermal tolerance at the expense of photosynthesis efficiency.
基金Corporación Colombiana de Investigación Agropecuaria-AGROSAVIA,Universidad Nacional de Colombia–Bogotá,and Agriculture and Rural Development Ministry of Colombia(MADR)who funded this researchderived from the research project“New Cotton Varieties with Agroindustrial Characteristics Adapted to Different Agroclimatic Conditions in Colombia”。
文摘The use of tolerant crop varieties is a strategy that mitigates the water deficit effect in a sustainable way.The generation of these varieties is more efficient when variables associated with this tolerance have been identified,since they can facilitate the breeding processes.This study aimed to establish the relationships between water deficit tolerance of four cotton varieties(Nevada-123,Oasis-129,Guatapuri,and Festivalle)and morphological variables(monopodial branches,boll weight,root/shoot ratio,and leaf and root dry matter),physiological variables(relative water content,net photosynthesis,stomatal conductance,electron transport rate,photochemical quenching,photochemical efficiency of PSII,chlorophyll a/b ratio(Chl a/b),C^(12)/C^(13)isotope ratio,and electrolyte leakage),and biochemical variables(contents of sugars,proline,carotenoids,and malondialdehyde).Furthermore,calibrated predictive models of the drought tolerance indices were developed based on the key variables identified.For this purpose,a pot experiment was established where plants were subjected to a moderate or severe water deficit during the blooming stage for 12 days.The stress tolerance index(STI)and mean productivity(MP)were calculated.For the evaluated variables,the differences between well-watered and water deficit plants(Δ)were calculated and ANOVA,partial least squares,Pearson’s correlation,and multiple linear regression analyzes were performed.A model was generated that explained 95% of the STI and was composed of Δmalondialdehyde,Δproline,and Δboll weight.For MP,the model was comprised of Δstomatal conductance,Δroot/shoot ratio,and ΔChl a/b,and explained 89% of the MP.The analysis of the assessed variables allowed the identification of key variables and the development of calibrated predictive models that can be used in screening to obtain cotton varieties with different levels of water deficit tolerance.
文摘Although tropical high ambient temperature and humidity severely reduced the productivity of temperate plants, temperate vegetable crops such as lettuce have been successfully grown in Singapore by only cooling its root-zone. In this paper, a cool Meditteranean vegetable, Eruca sativa, was studied to understand how different RZTs can impact its shoot productivity, photosynthesis and nutritional quality. All plants were cultivated using aeroponic systems in a tropical greenhouse under hot ambient conditions where roots were subjected to four different root-zone temperatures (RZTs) of 20°C-RZT, 25°C-RZT, 30°C-RZT and fluctuating ambient temperatures ranged from 25°C to 38°C [25°C/38°C (ambient)]-RZT. Parameters studied include shoot fresh weight (FW), photosynthetic gas exchange, midday chlorophyll (Chl) fluorescence F<sub>v</sub>/F<sub>m</sub> ratio, Chl fluorescence photochemical quenching (qP), non-photochemical quenching (qN) and electron transport rate (ETR), total phenolic compounds and mineral content such as potassium (K), calcium (Ca), magnesium (Mg) and iron (Fe). Among the 4 different RZT treatments, E. sativa plants grown under ambient-RZT (25/38°C-RZT) had the lowest shoot and root FW while those plants grown under 20°C-RZT had highest productivity of shoot and root. However, there were no significant differences in shoot and root FW in plants grown at 25°C- and 30°C-RZT. Compared to plants grown under 25°C/38°C (ambient-RZT), light-saturated photosynthetic CO<sub>2</sub> assimilation rate (A<sub>sat</sub>) and stomatal conductance (g<sub>ssat</sub>) were similarly higher in 20°C-, 25°C- and 30°C-RZT. All plants had midday Chl fluorescence F<sub>v</sub>/F<sub>m</sub> ratio lower than <0.8 ranged from 0.785 to 0.606 with the highest and lowest ratios recorded in 20°C-RZT and ambient-RZT plants, respectively. These results indicate that cooling the RZ of E. sativa plants protected their PS II from photoinactivation during midday in the greenhouse. There were no significant differences observed in photochemical quenching (qP), non-photochemical quenching (qN) and electron transport rate among plants grown under 20°C-, 25°C- and 30°C-RZT. However, plants grown under ambient-RZT had lower qP, qN and ETR compared to all other plants. E. sativa at 20°C-RZT with the best developed roots had the highest dietary mineral (K, Mg, Ca and Fe) contents but lower total phenolics content. In contrast, ambient-RZT, plants with poorly developed roots had the lowest mineral content but highest total phenolic content. The results of this study suggest that cooling of roots is a feasible method for the cultivation of E. sativa in the tropic, which enhances the content of dietary minerals in shoots.
基金Supported by the Program of Science and Technology of Shenzhen(JCYJ20170818090224745)Special Fund Project for Marine Economic Development of Guangdong Province(2020059)。
文摘There were fewer comparative studies on the adaptability of mangrove plants with two different salt secretion mechanisms to salinity stress. In this study,the seedlings of mangrove plants Aegiceras corniculatum and Kandelia candel were selected as the research objects,and the methods of hydroponics with different salinity gradients were used. The salinity of 0‰,10‰,and 30‰ was applied respectively to simulate the adaptability of seedlings at low,moderate,and severe salinity stresses. Based on the results,the short-term responses of photosynthesis and chlorophyll content to salinity stress in two mangrove species with different salt secretion mechanisms were analyzed and discussed. The results show that A. corniculatum was more tolerant to10‰ salinity than K. candel,and the net photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance( Gs) and water use efficiency(WUE)were also relatively higher;both A. corniculatum and K. candel could acclimate the low salinity(0‰),but showed severe osmotic stress at 30‰ salinity;A. corniculatum was more sensitive to severe salinity(30‰) than K. candel. These results can be of help to provide a theoretical support for the selection of species for mangrove wetlands restoration and seedlings acclimatization in tidal flats.
文摘Many modifications to growing environments and specific stress induction techniques exist which are supported by preliminary research to increase yield and/or concentration of secondary metabolites in <em>Cannabis sativa</em> L. One such technique is the modification of the spectral composition of light late in flowering-stage development. In this study, we evaluated the hypothesis that the addition of narrow bandwidth UV-A light and the combination of narrow bandwidth blue and red light, during the final two weeks of the flowering cycle affect the concentration of cannabinoids and terpenes, with no difference in harvest dry weight. Three treatments were used in this experimental design, 1) control-full spectrum illumination, 2) UV-A (~390 nm) at ~66 PPFD in addition to control lighting, and 3) blue (~450 nm) and red (~660 nm) at ~158 PPFD in addition to control lighting. Light treatments were initiated during the final two weeks of flowering to assess secondary metabolite concentration (cannabinoids and terpenes) and yield of three cannabis cultivars (Type I (Larry OG), Type II (Pootie Tang), and Type III (Super White)). With two of the three cultivars used in this study responding with enhanced production of THC our results support the potential beneficial effects of attributed light-mediated treatments on cannabinoid production. On the other hand, our results show contrasting trends for terpene production and yield of dry weight flower.
文摘The objective of the research was to evaluate the effects of saline stress on the initial growth and physiological parameters of three varieties of cotton plants, being two cultivars of colored fiber (BRS Topázio and BRS Verde) and one of white fiber (BRS 286). The experiment was conducted under greenhouse conditions. After chemical depletion with sulfuric acid, five seeds were seeded in polyethylene pots of 20 kg, leaving only one plant per pot after thinning. The experimental design was completely randomized, with a factorial scheme of 3 × 5, with five replications, totaling 75 plots, being three cotton varieties and five saline stress treatments—1.1;3.1;5.1;7.1;9.1 dS m−1. The evaluations occurred at 15 and 30 days after the beginning of the treatments (DAT) for growth variables (plant height, stem diameter, number of leaves and leaf area) and gas exchange (stomatal conductance, net photosynthesis rate and transpiration. The variety that was most resistant to the salt stress levels studied was BRS 286, followed by BRS Topazio and BRS Verde.
基金Academy of Sciences for the Developing World,Grant/Award Number:TWAS‐DFG Cooperation Visits Program for scientist。
文摘Background:Few studies have evaluated the effect of drought on the morphophysiological characteristics of African C_(4) grasses.We investigated how drought affects leaf gas exchange characteristics,biomass partitioning,and water use efficiencies of Enteropogon macrostachyus and Cenchrus ciliaris.Methods:The grasses were grown in a controlled environment under optimum conditions,that is,70%of the maximum water‐holding capacity(WHC)for the first 40 days.Thereafter,half of the columns were maintained under optimum or drought conditions(30%of maximum WHC)for another 20 days.Results:Under optimum conditions,C.ciliaris showed a significantly higher photosynthetic rate,stomatal conductance,and transpiration rate than E.macrostachyus.Drought decreased the photosynthetic rate,stomatal conductance and transpiration rate only in C.ciliaris.The net photosynthetic rate,stomatal conductance,and leaf transpiration of E.macrostachyus did not differ significantly under optimum and drought conditions.E.macrostachyus showed an increase in its water use efficiencies under drought to a greater extent than C.ciliaris.Conclusions:Our results demonstrate that C.ciliaris is more sensitive to drought than E.macrostachyus.The decrease in the intercellular CO_(2) concentration and the increase in stomatal limitation with drought in C.ciliaris and E.macrostachyus suggest that stomatal limitation plays the dominant role in photosynthesis of the studied African C_(4) grasses.
基金European Union INCO-DC(Project No.ERBIC18CT980275).
文摘Aims We investigated the regulation of the water status in three predominant perennial C3 phreatophytes(Alhagi sparsifolia,Populus euphratica,Tamarix ramosissima)at typical sites of their occurrence at the southern fringe of the hyperarid Taklamakan Desert(north-west China).Methods In the foreland of the river oasis of Qira(Cele),we determined meteorological variables,plant biomass production,plant water potentials(WL)and the water flux through the plants.We calculated the hydraulic conductance on the flow path from the soil to the leaves(kSL)and tested the effects of kSL,WL and the leaf-to-air difference in the partial pressure of water vapour(Dw)on stomatal regulation using regression analyses.Important Findings Despite high values of plant water potential at the point of turgor loss,all plants sustained WL at levels that were high enough to maintain transpiration throughout the growing season.In A.sparsifolia,stomatal resistance(rs;related to leaf area or leaf mass)was most closely correlated with kSL;whereas in P.euphratica,~70%of the variation in rs was explained by Dw.In T.ramosissima,leaf area-related rs was significantly correlated with WL and kSL.The regulation mechanisms are in accordance with the growth patterns and the occurrence of the species in relation to their distance to the ground water.
