外源NO对干旱胁迫下君迁子幼苗光合作用的影响

摘要

一氧化氮( Nitric oxide, NO)作为一种气体信号分子,不仅参与植物生长和发育等生理代谢过程,而且对植物的抗逆性也具有一定的作用。以20%聚乙二醇PEG 6000溶液模拟干旱胁迫,100μmol/L SNP为NO供体,研究了NO对干旱胁迫下君迁子幼苗叶片电子传递、光能分配和反应中心开放等PSⅡ功能的影响,以探讨干旱条件下NO对植物光合作用的调节作用。结果表明：干旱胁迫的第1 d和第5 d,SNP处理增加了干旱胁迫下君迁子幼苗叶片的水势(ψw )和叶绿素含量,且恢复了PSⅡ的电子传递速率(ΦPSⅡ和Fm/Fo )及潜在活性( Fv/Fo )；干旱胁迫降低了光化学淬灭系数( qp )和PSⅡ反应中心捕获光能的转化效率,但SNP处理增加了捕获光能用于光化学反应的比例( Pr ),进而增加了PSⅡ开放反应中心的活性,促进了非辐射能量的散耗,减轻甚至避免了过剩光能对光合机构的破坏。因此,干旱条件下外源NO供体可能参与了君迁子幼苗叶片PSⅡ对光能的利用。%Nitric Oxide ( NO) has emerged as a key signal molecule involved in physiological metabolic processes of growth and development, and induced resistance to various abiotic stresses in plants. To characterize the role of NO in drought tolerance induced by polyethylene glycol ( PEG) , sodium nitroprusside ( SNP) of 100μmol/L as exogenous NO donor was applied to study the biologically protective effects of NO at a low concentration on PSⅡfunctions in Diospyros lotus seed-lings hydroponically grown under 20% PEG stress. Under drought stress, on the first and fifth days of SNP treatment, the wa-ter potential (ψw ) and chlorophyll content were increased, the electron transport velocity (ΦPSⅡand Fm/Fo ) and potential activity of PSⅡreaction centers (Fv/Fo) were maintained in favorable level. The photochemical quenching coefficient (qp) and the transformation efficiency of light energy captured by PSⅡsystem declined under drought stress, while SNP treatment raised the proportion of captured light energy used in photochemical reaction (Pr), thus promoted the activity of PSⅡreaction center, increased the dissipation of non-radiactive energy, and consequently alleviated and avoided the destruction of photo-synthetic apparatus by excessive light energy. In conclusion, SNP may participate in the utilization of light energy in PSⅡof Diospyros lotus seedlings under drought stress by PEG.