水分胁迫对巨峰葡萄叶片PSⅡ光化学效率及光能分配的影响

Effects of water-stress on photochemical efficiency of PSⅡ and light energy allocation in Vitis vinifera Kyoho grape

以3年生自根‘巨峰’(Vitis vinifera‘Kyoho’)葡萄为试验材料,利用FMS-2荧光仪测定葡萄叶片的荧光指标,探讨干旱对葡萄叶片PSⅡ光化学效率以及光能分配的影响。结果表明,控水第1天,叶片过剩光能(Ex)便显著高于对照;控水第2天,叶片吸收的光能中应用于天线热耗散的份额(D)、非光化学猝灭(NPQ)显著高于对照,而用于光化学反应的份额(P)显著低于对照;控水第3天,叶片的天线转化效率(F′v/F′m)、实际光化学效率(ΦPSⅡ)显著低于对照,激发能在2个光系统间的分配不平衡性(β/α-1)显著提高;控水第4天叶片的光化学猝灭系数(qP)显著低于对照;最大光化学效率(Fv/Fm)在控水4d后显著低于对照。由此可见,在干旱胁迫下,植物叶片首先通过光能的分配来缓解过剩光能对光合机构的损伤;然后通过降低对光能的吸收来进行光保护;而后期水分胁迫加重,导致PSⅡ反应中心开放程度降低,光化学反应效率降低,最终发生光抑制。

In this study,the effects of drought on photochemical efficiency of PSff and light energy allocation in 3-year- old self-rooted Kyoho grape leaves were examined by a pulse-modulated fluorometer （FMS2, Hansatech, UK. ）. The results showed that excess light energy （Ex） significantly increased at first day of water stress. At the second day of water stress, the proportion allocated in antenna heat dissipation （D） and non-photochemical quenching （NPQ） increased significantly,while the absorbed light energy allocated to the photochemical reaction of PSⅡ （P） decreased significantly. At the third day of water stress,antenna efficiency at open centers in the presence of PSⅡ （F＇ v/F＇ m） and PSff actual photochemical efficiency （φPSⅡ） reduced significantly, but the imbalance of partitioning of excitation energy between PS T and PS Ⅱ（β/α- 1） increased significantly. The photochemical quenching （qP） decreased significantly at the fourth day of water stress. And the PS Ⅱ maximal photochemical efficiency （Fv/Fm） decreased significantly after water withheld for four days. In conclusion, during the drought stress, the leaves dissipated the excess energy to relieve the damage on photosynthetic apparatus by altering the allocation of the light energy, and then reduced the absorption of light energy. The severe water stress occluded the PSⅡ reaction center, decreased the photochemical reaction efficiency,eventually resulted in photoinhibition.