In this study, variations in antioxidant systems and photosystem II activity under salt shock (500 mM NaCl) among two maize (Zea mays L.) genotypes (C955 and DKC7221) were investigated. Salt shock induced a marked reduction in plant height, fresh and dry matter gain in roots and shoots in C955 and DKC7221. For both genotypes, salt shock led to oxidative stress as indicated by the considerable increase in hydrogen peroxide and malondialdehyde content. Photosynthetic pigment content was found to be lowered in both genotypes probably as a result of salt shock-induced oxidative stress. Free proline content and guaiacol peroxidase activity were more remarkably increased by salt shock in the genotype C955 in comparison with DKC7221, which may be related to higher salt tolerance. Superoxide dismutase activity was not affected by salt shock in DKC7221 while it was considerably higher in C955. Ascorbate peroxidase and glutathione reductase activity were not induced by salt shock in maize genotypes, which could demonstrate that ascorbate–glutathione cycle was inactivated by salt shock. Changes in maximum fluorescence indicated restrictive effect of salt shock on electron transport reactions in photosystem II acceptor side in both genotypes while water-splitting reaction was more tolerant to salinity in C955 as shown by higher Fv/Fo ratio. Changes in JIP-test parameters demonstrated that electron movements were partly inhibited by salt shock in some specific points on the photosystem II units. As a consequence, the results of the present study showed that the metabolic responses of C955 and DKC7221 to salinity were similar. However, especially on the basis of the JIP-test parameters and antioxidant responses, it may be concluded that metabolic changes in C955 are associated with the regulatory mechanism(s), while it was related to salinity damage in DKC7221.

在这项研究中，两种玉米（玉米）在盐冲击（500 mM NaCl）下抗氧化系统和光系统II活性的变化L.）基因型（C955和DKC7221）进行了调查。盐胁迫导致C955和DKC7221的株高显着降低，根和芽的新鲜和干物质增加。对于这两种基因型，过氧化氢和丙二醛含量的显着增加表明，盐冲击导致氧化应激。发现这两种基因型的光合色素含量均降低，这可能是盐冲击引起的氧化应激的结果。与DKC7221相比，基因型C955的盐冲击使游离脯氨酸含量和愈创木酚过氧化物酶活性显着增加，这可能与更高的耐盐性有关。超氧化物歧化酶活性不受DKC7221中盐冲击的影响，而在C955中则高得多。盐胁迫对玉米基因型不产生抗坏血酸过氧化物酶和谷胱甘肽还原酶的活性，这可能表明盐胁迫使抗坏血酸-谷胱甘肽循环失活。最大荧光的变化表明盐冲击对两种基因型在光系统II受体侧电子传输反应的限制作用，而水分解反应在C955中对盐度的耐受性更高，如较高的Fv / Fo比所示。JIP测试参数的变化表明，在光系统II单元的某些特定点上，盐碱震动会部分抑制电子运动。结果，本研究的结果表明，C955和DKC7221对盐度的代谢反应相似。但是，尤其是根据JIP测试参数和抗氧化剂反应，