田间小麦叶片光合作用的光抑制

THE PHOTOINHIBITION OF PHOTOSYNTHESIS IN WINTER WHEAT LEAVES UNDER FIELD CONDITIONS

通过人为改变小麦旗叶与茎秆的夹角，比较了晴天田间小麦直立叶（１０°）与平展叶（９０°）光合作用光抑制程度的差别。在叶温高达３７．６℃、最高光强为１６００μｍｏｌ·ｍ－２·ｓ－１的晴天，田间小麦经午间强光照射４ｈ后，ＰＳⅡ光化学效率（Ｆｖ／Ｆｍ）明显下降。１４∶００平展叶的Ｆｖ／Ｆｍ与表观量子效率（ＡＱＹ）降低幅度明显大于直立叶，表明平展叶较直立叶发生了更为严重的光抑制。而在最高光强相近、叶温为３４．５℃的晴天，１４∶００平展叶与直立叶的Ｆｖ／Ｆｍ与ＡＱＹ则无明显差别。结果表明在水分充足的条件下。

The degree of photoinhibition of photosynthesis was compared between vertical (leaf angle 80° from the horizontal) and horizontal (leaf angle 0°) winter wheat ( Triticum aestivum ) leaves subjected to midday strong light stress under field conditions.This was done by measuring the PSⅡ photochemical efficiency (Fv/Fm) and the apparent quantum yield (AQY).On a clear day with maximum light level above 1600 μmol·m -2 ·s -1 and maximum leaf temperature 37.6℃,the Fv/Fm and AQY of the horizontal leaves were much lower than those of the vertical leaves after exposure to midday strong light for 4 hours,showing a more severe photoinhibition developed in horizontal leaves.Since the differences in leaf water potential and leaf temperature were negligible between horizontal and vertical leaves,the light intensity was the only factor causing difference in the degree of photoinhibition.On clear days with maximum leaf temperature 34.5℃,no difference in the extent of photoinhibition was observed between vertical and horizontal leaves,although the maximum light level was still higher than 1600 μmol·m -2 ·s -1 .Based on these results,we couclude that the photoinhibition of photosynthesis in wheat leaves under field conditions in the result of the synergistic effect of high temperature and light stress when soil water is freely available.