摘要
以内生真菌感染 (endophyte- infected,EI)与不感染 (endophyte- free,EF)的黑麦草 (L olium perenne L.)种子建立实验种群 ,分别对其施加长时间不同强度的干旱胁迫 ,通过比较黑麦草体内过氧化物酶 (POD)、超氧化物歧化酶 (SOD)、多酚氧化酶(PPO)活性及其同工酶谱的变化以探讨保护酶系统在内生真菌——植物共生体的抗旱性方面所作的贡献。研究结果表明 ,水分胁迫和内生真菌对黑麦草 3种酶的影响不仅表现在总量上而且表现在同工酶的酶谱及各区带的酶活力上。就总酶活力而言 ,EI和 EF植株中 POD、SOD和 PPO的活性均随着干旱胁迫强度的增加而增加 ,进一步将 EI和 EF植株的酶活力进行比较 ,发现与 EF植株相比 ,EI植株中 POD和 PPO的活性相对较低 ,而 SOD的活性相对较高。从同工酶的谱带数量和强弱来看 ,POD同工酶各区带活力均随干旱胁迫强度的增加而增加 ,EI植株叶片增加的幅度高于 EF叶片 ,而且 EI叶片在重度胁迫下出现了 1条新带 ;SOD同工酶各区带活力在 EI叶片中有随干旱胁迫增加而增加的趋势 ,而在 EF叶片中有些区带酶活力增强 ,有些区带酶活力减弱 ,且 EI叶片在中度胁迫下出现了 1条新带 ;PPO同工酶随干旱胁迫的增强 ,EI和 EF叶片均表现为有些区带酶活力增强 ,有些区带酶活力减弱。总之 ,内生真菌的感?
Neotyphodium endophytes are a group of clavicipitaceous fungi that form symbiotic associations with a broad spectrum of grasses within the Pooideae family. The major benefits for grass endophytes are access to nutrients from the apoplast and a means of dissemination through the seed. Benefits to the host include protection from mammalian and insect herbivory, resistance to nematodes and some fungal pathogens, drought tolerance and greater field persistence. Since Read & Camp first reported the close relationship of endophyte infection to drought resistance of tall fescue in 1986, a lot of research work has been done on the effect of endophyte infection on drought resistance of its host grass. In response to endophyte infection, increased root dry matter and rolled leaves have frequently been reported in perennial ryegrass and tall fescue. Endophyte presence in shoots was shown to affect stomatal behavior in its host grass. Stomatal conductance of water-stressed endophyte-infected (EI) fescues declined earlier and faster than that of endophyte-free (EF) plants, suggesting more rapid stomatal closing. In some EI grasses, water content of tiller bases may be maintained at high levels than those in EF plants during drought. Here one question may be asked whether protective enzyme systems in the host grass are affected by endophyte infection. Recently we reported the effect of endophyte infection on protective enzyme activities in leaves of perennial ryegrass underv drought stress. In this paper Lolium perenne cv Pinnacle infected by Neotyphodium lolii was still chosen as the experimental material. Activities of POD, SOD, PPO and their isozymes were compared between EI and EF plants to study the contribution of the endophyte to improve the drought resistance of its host plant. Seeds of Lolium perenne cv Pinnacle (from Oregon Seed Company, USA) were treated in two different ways: some were placed on moist filter paper and germinated under room temperature to get EI plants, others were exposed to heat treatment in a bath (43℃ 15min, then 57℃ 35min) and then placed on moist filter paper to get EF plants. EI and EF plants were selected and transferred to plastic pots (25 cm in diameter and 21 cm in depth). A two-factor randomized-block design was used. The first factor was sustained drought stress with four levels of water stress imposed, which included the control (80% FC, Field water capacity), mild stress (60% FC), moderate stress (45% FC) and severe stress (30% FC). The other factor was endophyte status, including EI and EF. Each treatment was replicated three times. The drought stress was from October 5 to November 5, 1999. When the period ended, a newly expanded leaf was taken for the determination of activities of POD, SOD, PPO and their isozymes. Isozymes were analyzed by perpendicular discontinuous polyacrylamide gel electrophoresis. All of these isozymes were first electrophoresed under 180V constant pressure, when bromophenol blue went into the separation gel, constant pressure was changed to 250V for two to three hours until finished. The processes of electrophoresis were operated at 4℃. After staining, pictures were taken of the gels or they were scanned and analyzed by Pharmacia Image Master VDS immediately. Drought stress and endophyte infection affected activities of POD, SOD and PPO as well as spectrums and activities of their isozymes. Drought stress raised activities of POD, SOD and PPO, but the activities of POD and PPO of EI leaves were lower while SOD activity was higher when compared with EF leaves. POD isozymes' activity of both EI and EF leaves increased when drought stress was strengthened, but EI leaves increased more rapidly and had a new spectrum band under severe drought stress, which suggested that POD activities of EI leaves were more sensitive to drought stress than those of EF leaves. SOD isozymes' activity of EI leaves tended to increase following drought stress and a new band appeared under moderate stress, while SOD isozymes' activity of EF leaves increased or decreased in different spect
出处
《生态学报》
CAS
CSCD
北大核心
2004年第7期1323-1329,共7页
Acta Ecologica Sinica
基金
国家重点基础研究发展规划项目 ( G2 0 0 0 0 1860 1)
国家自然科学基金资助项目 ( 3 0 3 70 2 3 9)
教育部科学技术研究重点资助项目( 0 3 0 46)~~
