弱光对不同耐荫大豆苗期根系以及光合特性的影响

Effects of Low Light on Root System and Photosynthetic Characteristics of Different Shade Tolerant Soybean Seedlings

【目的】探究不同耐荫强度大豆品种幼苗对弱光胁迫的响应,为筛选改良适宜玉米-大豆带状套作的大豆品种提供理论基础。【方法】分别选用2个强耐荫和弱耐荫大豆材料,在盆栽试验条件下通过设置正常光照和弱光两个处理对大豆根系和地上部形态、各器官干物质分配、叶绿素含量和光合荧光特性进行研究。【结果】与正常光照相比,弱光下4个大豆品种的根长、根表面积、侧根数、根重和根体积差异均达到极显著水平(P<0.01),同时株高,下胚轴长,平均节间长均显著增加,而节数差异不明显。强耐荫品种地上部干重增加而弱耐荫品种减少,弱光下光合产物更多地向茎秆分配。弱光均导致4个品种的净光合速率(P_n)下降,但强弱耐荫品种间的气孔导度(G_s)和胞间二氧化碳浓度(C_i)则表现出相反的趋势。【结论】弱光对不同耐荫强度的大豆品种的影响是地下部和地上部同时存在的,但是强耐荫品种在弱光下有着更高的净光合率(P_n),并会增加气孔导度(G_s)、胞间二氧化碳浓度(C_i)和相对较高的暗适应最大荧光(F_m)来适应弱光环境。

【Objective】Low light has a significant effect on soybean root morphology and photosyntheticcharacteristics in maize-soybean relay intercropping.【Method】There are four different shade tolerantsoybean varieties, which have been studied in order to find out the response of them to low light.【Result】The root length, root surface area, root number, root weight, and root volume of four soybeanvarieties in low light was significantly lower than those in normal light. Opposite results were found inthe plant height, hypocotyl length, and average internode length. The shade tolerance varieties had highershoot dry weight, and more stem biomass in low light condition. However, the net photosynthetic rate（Pn）of four soybean varieties decreased in low light compared with that in normal light. Opposite trendsin the stomatal conductance （Gs）and intercellular carbon dioxide concentration （Ci）were found in thestrong and weak shade tolerant varieties.【Conclusion】The effect of low light on the soybean varietieswith different shade tolerance is the same as that of the underground part and the overground part. Butthe strong shade tolerant varieties has higher net photosynthetic rate （Pn） under low light, and willincrease stomatal conductance （Gs）, intercellular carbon dioxide concentration （Ci）and relatively high darkadapted maximum fluorescence （Fm） to adapt to the low light environment.