外源脱落酸对干旱胁迫下狗牙根幼苗光合特性的影响

Effects of exogenous ABA application on thephotosynthetic characteristics of bermudagrassseedlings exposed to drought stress

摘要:

【目的】 研究外源脱落酸（ABA）对干旱胁迫下狗牙根（Cynodon dactylon）光合特性的影响，为缓解狗牙根干旱损伤及抗旱栽培提供参考依据。【方法】 利用聚乙二醇（Polyethylene glycol-6000，PEG-6000）模拟中度和重度干旱胁迫，研究干旱胁迫和外源ABA（200，500 μmol/L）对狗牙根幼苗光合色素、净光合速率、气孔导度和叶绿素荧光参数等光合指标的影响。【结果】 干旱胁迫降低了狗牙根叶绿素含量、净光合速率、最大荧光（Fm）、可变荧光（Fv）、电子传递速率（ETR），提高了光化学猝灭（qP）和非光化学猝灭（NPQ）（P＜0. 05）。外源ABA 降低了干旱胁迫对光合的抑制作用，不过其效应与喷施浓度及干旱程度有关。中度干旱胁迫下，喷施500 μmol/L ABA 使叶绿素含量、PSII 最大光化学量子产量（F_v/F_m）、qP 显著提高（P＜0. 05）；重度干旱胁迫下，外源500 μmol/L ABA 提高了狗牙根叶绿素含量、净光合速率和水分利用率，降低了胞间CO2 浓度（P＜0. 05），但对叶绿素荧光参数影响不显著。【结论】 外源ABA 可通过提高光合色素含量、水分利用率及光能转化效率等形式缓解干旱胁迫对狗牙根幼苗的伤害，使植株更好地适应干旱环境，其中喷施浓度为500 μmol/L 效果较好。

Abstract:

【Objective】 Examine the impact of exogenous abscisic acid （ABA） on the photosynthetic characteris-tics of bermudagrass （Cynodon dactylon） under drought stress. This study aims to establish a theoretical foundationfor mitigating drought damage and promoting stress resistant cultivation of bermudagrass.【Method】 Bermudagrassseedlings were exposed to moderate and severe drought stress induced by polyethyleneide-6000 （PEG-6000）.The determination of photosynthetic pigments，net photosynthetic rate，stomatal conductance and chlorophyll fluores-cence parameters was conducted by foliar spraying 200 and 500 μmol/L ABA under drought stress.【Result】 The re-sults indicated a significant decrease in chlorophyll content，net photosynthetic rate，maximum fluorescence（ Fm），vari-able fluorescence（ F_v） and electron transport rate（ ETR） under drought stress ，accompanied by an increase in photo-chemical quenching （qP） and non-photochemical quenching （NPQ）（P＜0. 05）. However，the application of exog-enous ABA mitigated the inhibitory effects of drought on photosynthesis，and this mitigation was closely associatedwith concentration of applied ABA or severity of drought. Under moderate drought stress，500 μmol/L ABA signifi-cantly increased chlorophyll content，maximum photochemical quantum yield （F_v/F_m） and qPof PSII （P＜0. 05）. Inthe case of severe drought stress，the application of 500 μmol/L ABA resulted in increased chlorophyll content，netphotosynthetic rate and water use efficiency，along with a decrease in intercellular CO2 concentration （P＜0. 05）.However there was no significant effect on chlorophyll fluorescence parameters.【Conclusion】 Exogenous ABA dem-onstrates the ability to mitigate the damage caused by drought stress in bermudagrass seedlings. This mitigation isachieved by enhancing chlorophyll content，water use efficiency and light energy conversion efficiency，contributing tothe adaption of bermudagrass to arid environments. The findings suggest that the application of 500 μmol/L exog-enous ABA yields more favorable effects.