交替呼吸途径对低温弱光下黄瓜叶片光合作用的保护研究

PROTECTIVE ROLES OF ALTERNATIVE OXIDASE PATHWAY IN PHOTOSYNTHESIS OF CUCUMBER LEAVES UNDER LOW TEMPERATURE AND WEAK LIGHT

以津研4号黄瓜品种为实验材料,采用1 mM的水杨基氧肟酸(SHAM)抑制47%~48%交替呼吸途径(AOX途径)活性,研究了交替呼吸途径对低温弱光(100μmol·m^(-2)·s^(-1),8℃)下黄瓜叶片光合作用的保护作用。结果表明,低温弱光处理虽然降低了净光合速率,但未引起光化学反应、热耗散和光合电子传递的变化,也未改变弱光下吸收光能在PSII光化学反应Y(II)、PSII调节性能量耗散Y(NPQ)和非调节性能量耗散部分Y(NO)之间的分配比例,这可能归功于低温弱光诱导交替呼吸途径的上调。低温弱光下抑制AOX活性虽然完全抑制了光化学反应和光合电子传递,并限制了净光合速率,但诱导了热耗散能力的增强,从而未引起光抑制的发生。由此可见,低温弱光下AOX途径活性的上调可有效地保护黄瓜叶片的光合电子传递链,并优化光合作用;而抑制AOX活性后,黄瓜叶片也可通过促进热耗散防御低温弱光下光抑制的发生。

In order to study the protective roles of alternative oxidase pathway in photosynthesis of cucumber leaves under low temperature（LT, 8 ℃） and weak light（100 μmol·m-2·s-1）, a cucumber cultivar ＂Jinyan No. 4＂ was selected as experimental material, and the AOX inhibitor salicylhydroxamic acid（1 m M; SHAM） was used to inhibit AOX activity in vivo in both normal temperature（NT） and LT leaves. The results indicated that leaf AOX pathway was up-regulated after LT. Although net photosynthetic rate（P_n） decreased in leaves under LT, there were no change in photochemical reaction, thermal energy dissipation and photosynthetic electron transport were not changed. Also, LT was not influenced the energy distribution ratio between Y（II）, Y（NPQ） and Y（NO）. Inhibition of AOX pathway under LT decreased photochemical reaction and photosynthetic electron transport, and restricted P_n completely. However, photoinhbition did not occur because of the increase of thermal energy dissipation, which was induced by the down-regulation of AOX activity in leaves under LT. Taken together, up-regulation of AOX pathway would protect the photosynthetic electron transport chain and optimize photosynthesis in cucumber leaves under low temperature and weak light.