过量铁胁迫对豌豆幼苗光合特性和叶绿体膜的影响

Effects of excess iron stress on photosynthetic characteristics and chloroplast membranes in pea seedling leaves

研究了水培条件下过量铁胁迫对豌豆(Pisum sativum)幼苗光合特性和叶绿体膜组分及流动性的影响。结果表明,随着铁浓度的升高,幼苗净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、胞间CO2浓度(Ci)、水分利用效率(WUE)和羧化效率(CE)呈现不同程度的下降;叶绿素含量以及最大荧光(Fm)、最大光化学速率(Fv/Fm)、潜在光化学速率(Fv/Fo)、光合电子传递速率(ETR)、最大量子产额(Yield)以及光化学猝灭系数(qP)都逐渐下降,而初始荧光(Fo)与非光化学猝灭系数(qN)则逐渐上升;同时,过量铁胁迫造成叶片叶绿体膜饱和脂肪酸含量下降,不饱和脂肪酸含量相对增加,进而引起膜流动性的急剧升高。可见过量铁胁迫除导致幼苗光合作用的气孔抑制外,还直接伤害了光合机构,引起光能原初捕获能力和光能同化效率的降低,同时也造成了叶绿体膜不饱和度增加使得膜功能下降,引起幼苗光合能力的下降。

A hydroponic experiment was employed to study the effects of excess iron on the photosynthetic characteristics and on the compositions and fluidity of chloroplast membrane in pea （Pisum sat[rum） seed- ling leaves. The results indicated that with the iron concentration increased, net photosynthetic rate （Pn）, stomatal conductance （G,）, transpiration rate （Tr）, intercellular CO2 concentration （Ci）, water use effi- ciency （WUE） and carboxylation efficiency （CE） showed various degree of downward trends. Chlorophyll content and maximal fluorescence （Fro）, the PS I] maximal photochemical efficiency （Fv/Fm）, PS II poten- tial photochemical efficiency （Fv/Fo）, photosynthetic electron transport rate （ETR）, maximum quantum yield （Yield） and photochemical quenching coefficient （qP） also declined. However, primary fluorescence （Fo） and non-photochemical quenching coefficient （qN） increased. At the same time, content of unsaturated fatty acids and membrane fluidity of chloroplast increased, while the saturated fatty acids decreased. These results suggested that the iron stress not only caused stomata[ inhibition but also destroyed the photosynthetic structure directly. Furthermore, the iron stress also resulted in inactivation of photosynthesis center, decreases of both primary capture capacity and assimilation efficiency of light energy, and increasing leaf chloroplast membrane unsaturation degree, which caused a decline in photosynthetic capacity of pea seedlings finally.