缺镁对菜薹光合作用特性的影响

 研究了缺镁对菜薹光合作用特性的影响, 结果表明, 菜薹叶片净光合速率( Pn) 、气孔导度和蒸腾速率的日变化均呈单峰曲线变化, 且均随缺镁程度的加大而降低, 缺镁还使Pn的高峰提早出现; 缺镁降低了叶片的光补偿点、光饱和点和饱和光强下的Pn max; 缺镁使叶片的CO₂ 补偿点提高, CO₂ 饱和点下降(Mg 1 mmol·L ^{- 1} ) 或提高(Mg 0) , 饱和CO₂ 下的Pn max下降。菜薹叶片细胞间隙CO₂ 浓度的日变化、对光强和外界CO₂ 浓度的响应受缺镁处理的影响很小, 表明缺镁菜薹光合作用主要是受非气孔限制。

Effects of Magnesium Deficiency on Photosynthesis Characteristic of Flowering Chinese Cabbage

The effects ofmagnesium deficiency on photosynthesis characteristic of flowering Chinese cabbage (Brassica campestris L. ssp. chinensis var. utilis Tsen et Lee) were studied. Net photosynthesis rate (Pn) , stomatal conductance and transpiration rate changed in one-peak curve in daytime, and those decreased with the decrease of magnesium supply. The Pn peak reached earlier in Mg-deficiency leaves. Light compensation point, light saturation point and Pn maximum at saturated light decreased in Mg-deficiency leaves. CO₂ compensation point increased, CO₂ saturation point decreased (Mg 1 mmol·L ^{- 1} ) or increased (Mg 0) , Pn maximum at saturated CO₂ concentration decreased inMg-deficiency leaves. There were little effects in the changes of intracellular CO₂ concentration (Ci) in daytime, the response of Ci to light and CO₂ concentration byMg-deficiency, those indicated that photosynthesis inhibition in flowering Chinese cabbage by Mg-deficiency was mainly due to non-stomatal factors.