摘要
利用气体交换观察、叶绿素荧光分析和ＱＢ蛋白含量的测定３种方法，研究了常绿灌木珊瑚树叶片的光合作用在上海深秋初冬自然条件下的光抑制，以便确定在除光以外不存在其它环境胁迫的自然条件下光合机构的破坏是否是引起光抑制的主要原因。经过中午３ｈ左右的强光照射以后，珊瑚树叶片的表观量子效率（ＡＱＹ）和ＰＳⅡ光化学效率（Ｆｖ／Ｆｍ）明显下降，表明珊瑚树叶在自然条件下经常发生光抑制。而且，经中午强光照射以后，叶片的初始荧光（Ｆ０）下降；非光化学荧光猝灭的慢弛豫成分（ｑＥｓｌｏｗ）上升；光饱和的光合速率略有下降；中午光照后降低了的ＡＱＹ和Ｆｖ／Ｆｍ在叶片离开强光１ｈ以后基本恢复；模拟中午光照的强光处理对叶片的ＱＢ蛋白含量没有明显的影响。这些事实都说明这种光抑制发生的主要原因是非光辐射能量耗散的增加，光合机构的破坏即使发生，也是很轻微的。
The photoinhibition of photosynthesis studied by chloroplasts and thylakiods was, in most cases, observed under extreme conditions. Although a few authors reported photoinhibition observed under natural conditions with no environmental stress besides high light, the cause of this type of photoinhibition is still unknown. To clarify it,we studied photoinhibition of Viburnumodoratissimum leaves under natural conditions.After exposure to midday stronglight, the apparent quantum yield (AQY) and PS Ⅱ photochemical efficiency (Fv/Fm ) measured in the afternoon declined compared to that measured in the morning (Table 1～5),indicating that photoinhibition frenquently occurs in Viburnum odoratissimumleaves under natural conditions withmidday high light as the only stress.More importantly, AQY and Fv/ Fm recovered almost to the level observed in the morning. 1 hour after shading following the decrease after exposure to midday high light (Table 3and 5). After 3 h of midday strong light, the light-saturated photosynthetic rate (Pmax) showed only an insignificant fall (Fig. 1), but the initial fluorescence (F0 ) decreased (Table 5 ).The content of QB protein in leaves did not show evident change after illumination imitating midday strong light (Fig. 3). These facts suggest that radiationless energy dissipation ratherthan the damages to the photosynthetic apparatus, is the predominent cause of this type of photoinhibition, and even if such damage takes place, it is negligible.
基金
国家自然科学基金
关键词
光抑制
珊瑚树
光合作用
叶
photoinhibition, apparent quantum yield. PS Ⅱ photochemical efficiency. fluorescence quenching. Q_B protein. Viburnum odoratissimum
