水培条件下温州盘菜幼苗对缺铁的光合响应

Effects of Fe-deficiency upon the Photosynthetic Characteristics in Leaves of Hydroponic Brassica Campestris L. Seedlings

以5叶1心的温州盘菜幼苗为材料，利用Hoagland营养液进行正常供铁（100Ixm01）和缺铁（0Ixm01）处理20d。取顶端完全展开叶分析缺铁对盘菜叶片的光合特性的影响。结果表明，缺铁胁迫显著降低了温州盘菜叶片的叶绿素a、叶绿素b和总叶绿素含量（P〈0．05），但类胡萝卜素含量变化不大，缺铁也降低了叶绿素a／b比值，而类胡萝卜素和叶绿素含量比值升高。缺铁胁迫不仅降低光合色素含量的下降．而且也降低了叶片的净光合速率（Pn）、气孔导度（Gs）和蒸腾速率（Tr），但胞间CO：浓度（Ci）大幅度升高，说明缺铁植株光合速率的下降是由非气孔因子引起的；光合速率的下降导致叶绿体积累过剩能量，这与类胡萝卜素和叶绿素的比值上升是一致的，暗示热耗散增加以减轻过剩能量对光合器官的损伤。

Gas exchange and photosynthetic pigments were characterized from the apical fully expandedleaves in Brassica campestris L.seedlings grown with either complete or Fe-deficient nutrient solution for20 d. The results showed that Fe-deficiency severely decreased the content of chlorophyll （Chl）a, Chl band total Chl（P〈0.05）,while the content of carotenoid（Car）were not affected. Besides, Fe-defieieney stressalso decreased the ratio of Chl a/b, but the ratio of Car/Chl was greatly increased. Due to the decline ofphotosynthetic pigment content, Fe-deficiency stress reduced net photosynthetic rate （Pn）,gas conductance（Gs）and transpiration rate（Tr）. However, the intercellular CO2 concentration was markedly higher than thatof control plants, indicating the decreased photosynthetic capacity was caused by the limitation of non-stomatal factors. Besides, due to the sharp decrease in Chl content, the ratio of Car to Chl was muchhigher in Fe-deficiency plants than that of control group, implying the increased dissipation of thermal en-ergy was used to ameliorate the photoinhibition in Fe-deficient leaves.