水稻、大豆、玉米光合速率的日变化及其对光强响应的滞后效应

用LI-6400光合测定系统对水稻、大豆和玉米3种作物在不同生育时期叶片光合速率的日变化规律进行了研究。结果表明:在各个生育时期,C3作物(水稻、大豆)叶片的光合作用均存在午休现象。而午休现象的产生是气孔因素与非气孔因素共同作用的结果。其中“气孔因素”是高温加剧蒸腾作用,气孔对蒸腾作用的反馈抑制造成的。C3作物(水稻、大豆)叶片的光合速率对光强的响应在上午和下午存在明显差异,上午利用光能的能力明显大于下午。这主要表现在上午的表观初始量子效率比下午大。光合产物对光合作用的反馈抑制会造成这种量子效率的差异性。无论是气孔限制还是光合产物反馈抑制都可能是导致光合速率对光强响应产生“滞后效应”的主要原因。C4作物(玉米)的午休现象不明显,光合速率对光强的响应在上午和下午的差异也不明显,不存在明显的“滞后效应”,这可能与C4作物(玉米)自身的生理特性适应高温的能力有关。

Diurnal Changes of Photosynthesis and Its Hysteresis to Light in Rice (Oryza sativa L.), Soybean (Glycine max L. Merrill) and Maize (Zea mays L.)

Primary productivity by photosynthesis is the support and basic drive for the beginning and evolution of ecosystem productivity.Photosynthesis usually changed with variation of environmental conditions.In this study,we used leaf level gas exchange method(by Licor-6400) to study the diurnal changes of photosynthesis in rice,soybean and maize at different developmental stage,and we found that: There was noon depression of photosynthesis for all C3 plants at all developmental stages.Such depression was owing to stomatal and non-stomatal effects separately,or combined.The stomatal effects were caused by the high temperature,which resulted feedback inhibition effects owing to the increase of transpiration.The responses of C3 crops(rice,soybean) to light were different in the morning and afternoon.The light use efficiency was higher in the morning and apparent quantum yield owing the photosynthetic feedback inhibition,contrasting to that in the afternoon.The stomatal or non-stomatal effects and feedback inhibition effect were the main reasons to"hysteresis".While,there was no apparent noon depression C4 crop(maize),as well as"hysteresis",showing great acclimation of C4 crop to high temperature.