细胞内IP3-Ca2+途径对UV-B辐射下玉米幼苗光合特性的调控机制

使用外加0.15 Wm^-2 UV-B及不同钙效应剂处理玉米幼苗，研究细胞Ca²⁺信号系统对UV-B辐射下玉米幼苗光合作用的调控机理。结果表明，UV诱导的胞内Ca²⁺荧光增强受胞内IP3通道阻断剂肝素(Heparin)、胞内CaM活性抑制剂三氟啦嗪(TFP)抑制，降低玉米幼苗Chl a、Chl b及Chl T含量、原初光能转化效率(F_v/F_m)、PSII活性(F_v/F_o)、Hill反应活力、水分利用效率(WUE)，提高胞间二氧化碳浓度(C_i)，最终导致净光合速率(P_n)下降；细胞质膜钙通道阻断剂氯化镧(LaCl₃)引发的此效应较小。据此提出，UV-B辐射下，玉米幼苗叶片细胞IP3动员胞内钙库释放Ca²⁺，调节光合色素合成、Hill反应活性、WUE，CaM介导的下游反应调节G_s，是Ca²⁺信号系统最终实现对P_n调控的主要机制。

Regulation Mechanism of Intracellular IP3-Ca2+ on Photosynthesis in Maize Seedlings under UV-B Stress

UV-B radiation is one of the main adverse environmental factors, obviously affecting plants’ growth and development. Calciumion, as the second messenger in cell signal transduction system, mediates a series of physiological and biochemical reactions, which is helpful to alleviate the damage from adverse environmental factors. To investigate the regulational relation between calcium signal system and UV-B radiation in maize, we studied the effects of calcium signal on photosynthesis in maize (Zea mays L.) seedlings under UV-B stress.With the treatments of seedlings growing in natural condition (CK), 0.15 Wm^-2 UV-B radiation (UV-B), 0.15 Wm^-2 UV-B radiation+Heparin (UV-B+H), 0.15 Wm^-2 UV-B radiation+Trifluoperzine (UV-B+TFP), 0.15 Wm^-2 UV-B radiation+LaCl₃ (UV-B+LaCl₃), 0.15 Wm^-2 UV-B radiation+CaCl₂ (UV-B+CaCl₂), respectively. The Ca²⁺ fluorescence intensity increased rapidly when it was treated with UV-B. However, when the maize leaves were treated with Heparin (intracellular IP3 channel blocker) and Trifluoperazine (intracellular CaM activity inhibitor), the increase of Ca²⁺ fluorescence intensity was inhibited in the mean time, chlorophyll contents, Hill reaction activity, water use efficiency (WUE), efficiency of primary conversion of light energy (F_v/F_m) of PSII, and the potential activity of PSII (F_v/F_o) decreased significantly, which finally leads to the decrease of net photosynthetic rate(P_n). However, LaCl₃ (plasma membrane calcium channel blocker) had less effect on it. Therefore, we speculate that under UV-B stress, intercellular IP3/Ca²⁺ system may participate in the process of photosynthetic pigments synthesis, water utilization and Hill reaction activity. CaM downstream reaction can regulate Gs, which is considerd as the main mechanism that Ca²⁺ signal system eventually achieves the regulation of P_n.