缺铁胁迫对温州盘菜幼苗叶片光合特性和抗氧化酶活性的影响

以五叶一心的温州盘菜幼苗为材料，利用Hoagland营养液进行正常供铁（100 μmol·L-1）和缺铁（01 μmol·L-1）处理20 d，取顶端完全展开叶探讨缺铁对盘菜幼苗叶片的光合色素、光合特性、叶绿素荧光参数和抗氧化酶活性的影响。结果表明：缺铁胁迫降低了叶片的叶绿素总量（Chl）、叶绿素a（Chl a）和叶绿素b（Chl b）含量及Chl a/b比值，类胡萝卜素含量（Car）变化不大；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CO2浓度（Ci）大幅度升高，表明Pn的下降主要是由非气孔因子引起；显著降低了PSⅡ的最大光化学效率（Fv/Fm）、有效量子产额（ΦPSⅡ）和光化学猝灭参数（qP），但非光化学猝灭参数（NPQ）明显升高；显著降低叶片超氧化物歧化酶（SOD）、过氧化氢酶（CAT）的活性和可溶性蛋白的含量，POD的活性有所升高，丙二醛（MDA）含量显著升高，说明缺铁胁迫后细胞膜脂过氧化水平升高；大幅降低植株的地上部和根的生物量，但对根冠比影响不大。缺铁胁迫显著降低了植株新叶Fe元素含量，Mn和Mg两种金属含量差异不大，Cu和Zn两种金属含量显著增加。综上所述，缺铁胁迫使盘菜幼苗叶片光合色素严重下降，引起光合速率大幅降低，缺铁也降低了Fv/Fm和抗氧化酶活性，引起细胞膜脂过氧化水平的升高，最终导致植株生物量的下降。

Effects of Fe|deficiency on the photosynthetic characteristics and the activities of antioxidant enzymes in seedling leaves of Brassica rapa L.

Photosynthetic pigments gas exchange， chlorophyll （Chl） fluorescence， and the activities of antioxidant enzymes and metal elements were characterized from the apical fully expanded seedling leaves in Brassica rapa L. ssp. rapifera at five|leaf and one|heart stage grown with either complete or Fe|deficient nutrient solution for 20 days. The results showed that Fe|deficiency severely decreased the content of total chlorophyll， chlorophyll a， chlorophyll b， and the ratio of Chl a/b， while the content of carotenoid （Car） was not affected. Due to the decline of photosynthetic pigment content， Fe|deficiency stress reduced net photosynthetic rate （Pn）， gas conductance （Gs） and transpiration rate （Tr）. However， the intercellular CO2 concentration （Ci） was markedly higher than that of control plants， demonstrating the decreased photosynthetic capacity was caused by the limitation of non|stomatal factors. Besides， Fe|deficiency stress also greatly decreased the maximal photochemistry of PSⅡ （Fv/Fm）， the effective quantum yield of PSⅡ （photochemical quenching coefficients）， while non|photochemical quenching coefficient （NPQ） highly increased as compared with that in control plants. The activities of superoxidase （SOD） and catalase （CAT） in Fe|deficient plants decreased markedly， while the activity of peroxidase（POD） slightly increased; the content of malondialdehyde （MDA） was highly increased， suggesting the higher degree of lipid peroxidation. In addition， the biomass of shoot and root was decreased， but the ratio of shoot to root was not changed significantly. Moreover, the content of Fe in Fe|deficient plants were markedly reduced, while the content of Mn and Mg were not changed, the content of Cu and Zn were significantly increased as compared with the control plants. Taken together， Fe|deficiency stress caused great decrease in content of photosynthetic pigments， Pn， Fv/Fm， photochemical chemistry and the activity of antioxidant enzyme, and therefore an increase in MDA content and finally decreased biomass.