摘要
以玉米品种郑单958(抗旱性强)和陕单902(抗旱性弱)为材料,采用盆栽控水试验,设置3个干旱处理(轻度干旱,中度干旱,重度干旱)和正常灌水,研究了干旱胁迫对玉米苗期叶片光合速率、叶绿素荧光以及相关生理指标的影响。结果表明:(1)干旱胁迫下2个品种叶片净光合速率(Pn)和气孔导度(Gs)显著下降,胞间CO2浓度(Ci)出现了先下降后上升,而气孔限制值(Ls)上升后下降,说明中度干旱胁迫下叶片Pn下降是气孔因素引起的,重度干旱胁迫下Pn降低主要由非气孔因素引起的。(2)随着干旱胁迫的加剧,2个品种叶片光系统Ⅱ(PSⅡ)的实际量子产量(φPSⅡ)、电子传递速率(ETR)和光化学猝灭(qP)一直下降,而非光化学猝灭(qN)上升后下降,说明中度干旱下热耗散仍是植株重要光保护机制,重度干旱时叶片光合电子传递受阻,PSⅡ受到损伤。(3)干旱胁迫下2个品种叶片的超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性先升高后降低,而丙二醛(MDA)含量一直升高,说明干旱胁迫初期对保护系统酶活性升高有诱导作用,重度胁迫下活性氧清除酶的活性下降,导致细胞膜伤害。这些结果暗示,轻度和中度干旱胁迫下2个玉米品种通过减少光捕获、热耗散和酶活性调节协同作用稳定了光合机构功能,是Pn下降的气孔限制因素;而重度干旱胁迫下光系统Ⅱ和抗氧化酶系统损伤,是Pn下降的非气孔限制因素;郑单958的各生理参数比陕单902受旱影响小,干旱胁迫下仍具有较高的光合效率和较强的保护酶活性是郑单958抗旱的主要生理原因。
Drought is a major limiting factor affecting maize growth,development and yield mainly in arid and semiarid regions of China.But the physiological mechanism related to simultaneous comparison of photosynthetic response and protective enzyme activity,which could be useful for identifying differences in maize cultivars under drought stress,remains unclear.The objective of this study was to investigate the effects of drought stress on the photosynthetic characteristics of the different maize cultivars at the seedling stage and to offer a theoretical basis and technical parameters for saving-water and high yield cultivation of maize.Two maize cultivars,zhengdan958（drought tolerance） and shandan 902（drought sensitive） grown in pots experiment in greenhouse were subjected to three different drought treatments（mild drought,moderate drought,severe drought） and compared to normal irrigation.The gas exchange,chlorophyll fluorescence,and protective enzyme activity were tested.The results showed that：（1） the onset of drought stress caused an increase of leaf′s net photosynthetic rate（Pn） and stomatal conductance（Gs）,furthermore,intercellular CO2 concentration（Ci） decreased and then increased,but reversible,stomatal limits（Ls） increased and then decreased under drought stress in two cultivars.This suggested that reductions in Pn resulted from stomatal limitations under mild and moderate drought stress;and from non-stomatal limitations under the severe drought stress in both cultivars.（2） In the chlorophyll fluorescence parameters,leaf′s the quantum yield（φPSⅡ）,electron transport rate（ETR）,photochemical quenching（qP） decreased with increasing drought stress,however,non-photochemical quenching（qN） of photosystem Ⅱ（PSⅡ） activity increased significantly with the developing of drought stress,indicating that photoprotection was effective,whereas severly drought stress caused the inhibition of photosynthetic electron transport leading to damage of PSⅡ in the two cultivars.（3） Under drought stress the activities of superoxide dismutase（SOD）,peroxidase（POD）,catalase（CAT） obviously increased and then decreased rapidly.The increase of enzyme activities in drought tolerance zhengdan958 was greater than that in drought sensitive shandan902.malondialdehyde（MDA） contents increased continuously,being significantly higher than that of the control,the increase of MDA contents in drought sensitive shandan 902 was greater than that in drought tolerance zhengdan958,which contributing to regulate activity of the protection system during the initial phase of drought stress,and the negative effects of drought during the stress period were observed.These results implied that drought stress depressed Pn significantly,which induced by stomatal limitation and non-stomatal factors at seedling stage,under the moderate drought stress the decreased Pn were mainly due to stomatal limitations through stomatal regulation,the enhance of thermal dissipation and antioxidant enzyme jointly;under the severe drought stress major non-stomatal limitations responsible for reduction in Pn were associated with the impairment of PSⅡ and antioxidant enzyme system.At same time,the change range of all physiological parameters were smaller in zhengdan958 than in shandan902.Base the above results,we speculate that zhengdan958 maintains the higher photosynthesis function and the better oxidative enzyme defense system′s ability to eliminate reactive oxygen compared to shandan902 under drought stress,which can be considered as the major physiological traits for its higher yield and drought tolerance.
出处
《生态学报》
CAS
CSCD
北大核心
2011年第5期1303-1311,共9页
Acta Ecologica Sinica
基金
国家重点基础研究发展规划(973计划)项目(2009CB118604)
国家自然科学基金项目(30971722)
陕西省自然科学基金项目(2010JM3002)
关键词
玉米
干旱胁迫
气体交换
叶绿素荧光
保护酶
maize
drought stress
gas exchange
chlorophyll fluorescence
protective enzyme activity
