水分胁迫对冬小麦CO_2同化作用的影响

比较了两个小麦品种陕合6号和郑引1号经受不同程度的水分胁迫处理后,叶片多种光合参数:净光合速率(P_n)、气孔导度(G_s)、细胞间隙CO_2浓度(G_i)、表观量子需要量和羧化效率以及Rubis CO蛋白量与活性等的变化。在轻度水分胁迫下,叶片光合速率降低的根本原因在于气孔导度的下降;而在严重胁迫下,非气孔因素起主要作用。

Effects of Water Stress on CO_2 Assimilation of Two Winter Wheat Cultivars with Different Drought Resistance

The effects of water stress on photosynthesis and RuBP carboxylase (RubisCO) from the leaves of two cultivars of winter wheat drought resistant Shaanhe 6 and drought sensitive Zhenyin 1 were studied. Under mild water stress (-0.5 MPa, 24 h), net photosynthetic rate (P_n), stomatal conductance (G_s) and intercellular CO, concentration (C_i) decreased, but apparent quantum requirement remained unchanged, carboxylation efficiencv increased slightly, as compared with those in control. Furthermore, the amount of RubisCO protein did not change, but the enzyme activity increased slightly. These results show that the decline in photosynthesis is due to the decline of G_s. However under severe water stress (at -0.5 MPa for 96h or-1.0 MPa for 24h), in addition to the decrease of G_s, the decline in P_n for both cultivars was accompanied by an increase in C_i and the content and activity of RubisCO tended to decrease. These results suggest that the decline in photosynthetic rate is due mainly to nonstomatal factors and probably involves a decrease in the content and activity of RubisCO. When subjected to water stress, the shift from stomatal factor to nonstomatal factor occurred earlier in Zhenyin 1 than Shaanhe 6. The content and activity of RubisCO decreased significantly in Zhenyin 1, but remained unchanged in Shaanhe 6 after being subjected to -1.0 MPa for 24 h and when water stress was prolonged to 96 h they decreased in Shaanhe 6, too, but to a lesser extent. These data demonstrate that Shaanhe 6 is a drought resistant cultivar.