从叶片光合作用分析绿豆和谷子对科尔沁沙地光照条件的适应能力

Different Capacities of Adaptation to High Irradiance of Horqin Sandy Land in Mung Bean and Millet Based on Their Leaf Photosynthesis

科尔沁沙地大田种植的绿豆和谷子两种作物 ,叶片净光合速率 (Pn)日变化曲线虽然均为单峰曲线 ,但Pn 峰值出现的时间不同 ,且 8:0 0后 ,谷子的Pn 总是大于绿豆的。分析认为 ,谷子对强光的适应性比绿豆高。非气孔因素造成6 :0 0～ 10 :0 0绿豆Pn 的降低 ,而 10 :0 0～ 12 :0 0谷子Pn 的降低主要是由气孔导度下降引起的。与净光合测定同步的叶绿素荧光检测表明 ,谷子中非光化学猝灭的量子效率明显高于绿豆中 ,说明谷子叶片能耗散更多的多余能量。同时 ,光系统Ⅱ的最初电子受体QA 的库容 (poolsize)在绿豆中基本保持恒定 ,而在谷子中有明显的中午下降 ,说明谷子叶片对流经光系统Ⅱ的电子传递具有较大的调控能力 ,以适应外界的强烈光照。

As two main crops cultivated in Horqin sandy land, mung bean and millet had apparent differences in their one-peak curves of net photosynthetic rate (P n) in the day course. The time when the peak values of their P n occurred was different, and P n in millet leaves was higher than that in mung bean after 8:00. It was suggested that millet could keep a higher P n than mung bean under high solar irradiance (>1 790 μmol·m -2·s -1). The decline of P n in mung bean from 6:00 to 10:00 was due to nonstomatal factors, while the decrease of stomatal conductance was mainly responsible for the P n decline in millet from 10:00 to 12:00. Simultaneously with measurements of P n, detecting leaf chlorophyll fluorescence showed that the quantum yield of non-photochemical quenching (Y N) was markedly higher in millet than in mung bean, indicating that more excessive absorbed energy was dissipated by millet leaves. The pool size of primary acceptor of photosystem Ⅱ (Q A) was approximately constant and larger in mung bean, while it exhibited an apparent trough from 8:00 to 18:00 in millet. It is suggested that millet leaves had higher capacity to control / regulate the reduction state of Q A, thus restricting the electron transport through photosystem Ⅱ, so as to fit the intense ambient irradiance.