以‘鲁玉 14号玉米’ (‘Zeamayscv.Luyu 14’) 为材料, 研究了Ca2 + 对NaCl胁迫下玉米叶片的气孔导度、净光合速率、Mehler反应及其对超氧化物歧化酶SOD和抗坏血酸过氧化物酶APX活性的影响, 探讨了Ca2 + 在盐胁迫中的可能作用及其作用机制。正常生长条件下外施 2~ 16mmol·L-1Ca2 + 造成气孔导度下降, 但在盐胁迫条件下外施 2~ 8mmol·L-1Ca2 + 却能降低盐胁迫造成的气孔导度下降。另外, 无论正常生长条件下还是盐胁迫下, 依赖Mehler反应的电子传递都会因Ca2 + 的加入而增强, 但后者的增强程度较大。对照植株经 2~ 8mmol·L-1Ca2 + 处理后总电子传递明显降低, 而外施 2~ 8mmol·L-1Ca2 + 对盐胁迫植株的总电子传递却有明显的促进作用。8mmol·L-1Ca2 + 显著地提高了盐胁迫下SOD和APX的活性, 相比之下, Ca2 + 对APX活性的促进作用更加显著。Ca2 + 的加入明显减轻了盐胁迫对玉米的抑制作用, 这主要归因于Ca2 + 降低了盐胁迫造成的气孔关闭, 改善了光合作用, 并通过促进Mehler反应一方面直接耗散过剩的激发电子避免了电子传递链的过度还原, 另一方面建立跨膜的 pH梯度刺激依赖叶黄素循环的热耗散来耗散过剩光能, 从而缓解了盐胁迫下过剩光能对玉米造成的伤害。而Mehler反应产生的活性氧可以被活性提高的抗氧化酶所清除。

Zea mays cv. Luyu 14' was used to study the effects of Ca 2+ on stomatal conductance, net photosynthetic rates, Mehler reactions and the activities of the antioxidant enzymes, SOD and APX, under NaCl stress. Additions of 2-16 mmol·L -1 Ca 2+ suppressed stomatal conductance of maize leaves under normal growing conditions but significantly increased stomatal conductance under NaCl stress. Mehler reaction dependent electron transport rate was increased by the addition of 2-8 mmol·L -1 Ca 2+ both in controls and in the NaCl stressed maize leaves; however, the extent of the increase was greater in salt stressed maize leaves. The total electron transport rate was reduced in controls but increased in NaCl stressed maize leaves by the addition of 2-8 mmol·L -1 Ca 2+. The addition of 8 mmol·L -1 Ca 2+ significantly increased the activities of SOD and APX with the extent of the increase greater in APX than SOD. In conclusion, addition of Ca 2+ alleviated inhibition induced by NaCl stress in maize leaves, which was associated with the promotion of photosynthesis, the enhancement of Mehler reaction, and the activities of antioxidant enzymes. The enhanced Mehler reaction could not only consume excess excitation energy to avoid over reduction of the electron chain of photosynthesis but also promoted xanthophyll cycle dependent thermal dissipation by forming a transthylakoid membrane pH gradient (ΔpH) to efficiently protect maize leaves against photodamage under salt stress. Also, the active oxygen produced via the Mehler reaction was scavenged by the enhanced anti-oxidative enzymes.