华北平原玉米叶片光合及呼吸过程对实验增温的适应性

Photosynthetic and respiratory acclimation of maize leaves to experimental warming in the North China Plain

利用典型农田生态系统的原位实验增温平台,探讨我国华北平原重要农作物玉米叶片光合及呼吸过程对实验增温的适应性,并深入分析其产生适应性的原因和机理。研究结果显示,实验增温使玉米叶片净光合速率(A_n)显著升高(P<0.001),同时增温也导致A_n的最适温度(T_(opt))升高1.56℃;相似地,实验增温也同样导致了光合作用过程中最大电子传递速率(J_(max))显著增加(P<0.001),并且其最适温度(T_(opt))升高了1.45℃,但并没有对最大羧化反应速率(V_(cmax))及其温度敏感性(Q_(10))产生显著的影响(P>0.05)。然而,实验增温却显著降低了玉米叶片的暗呼吸速率(R_d)及其Q_(10)值(P<0.05)。另外,研究结果还显示实验增温没有对R_d/A_g和J_(max)/V_(cmax)产生显著的影响(P>0.05)。此外,尽管实验增温显著提高了玉米叶片的蒸腾速率(T_r),但却并没有显著改变叶片的气孔导度(G_s)及水分利用效率(WUE)。研究结果表明,玉米可以通过调控叶片光合及呼吸等关键生理过程的最适温度对增温产生一定的适应性。然而,尽管玉米能够在叶片尺度上做出调整来适应增温环境,但这种适应能力却十分有限,以至于未来气候变暖仍可能会对华北平原玉米的生长发育过程和粮食产量造成一定的影响。

Temperature responses of photosynthesis and respiration are critical for understanding plant growth,primary productivity of the ecosystem,and carbon balance.Plants do not live under constant temperature conditions in natural ecosystems;instead,growth temperature shows diurnal and seasonal variations.Hence,temperature responses of photosynthesis and respiration are critical for understanding the balance between photosynthesis and respiration in plants and changes in the balance between the atmosphere and terrestrial biosphere.However,the mechanisms underlying thermal acclimation of photosynthesis and respiration in plants to experimental warming are still unclear,especially in agricultural ecosystems.In this study,we examined the acclimation of foliar photosynthesis and dark respiration in maize plants by performing a field-warming experiment with infrared heaters in a typical agriculture ecosystem in the North China Plain.We also discussed thermal acclimation mechanisms and verified five hypotheses for understanding thermal acclimation mechanisms underlying photosynthesis.The results showed that experimental warming significantly increased net photosynthetic rates（A_n,P 0.001） and increased the optimal temperature of A_n by 1.56 ℃.Similarly,we found that experimental warming significantly increased the maximum rate of photosynthetic electron transport（J_（max）,P 0.001）,and the optimal temperature of J_（max） was increased by 1.45 ℃;however,it had little effect on the maximum rate of Rubisco carboxylation（F_（cmax）） and its temperature sensitivity（Q_（10）,P 0.05）.In contrast,experimental warming significantly decreased foliar dark respiration（R_d） and its temperature sensitivity（Q_（10）,P 0.05）.Moreover,our results showed that experimental warming barely affected the ratios of R_d/A_g and J_（max）/F_（cmax）（P 0.05）.Experimental warming significantly increased transpiration rates,but it had no effect on stomatal conductance and water use efficiency in maize leaves.These results suggest that maize plants have a limited ability to acclimate to a warmer climate in the North China Plain and that thermal acclimation may be controlled by the adjustment of photosynthesis and respiration in maize leaves.Our results may be helpful in the management of agricultural ecosystems and estimation of crop- safety risk due to global warming.