超高产夏玉米花粒期不同部位叶片衰老与抗氧化酶特性

为探讨超高产玉米叶源衰老特征, 揭示其抗氧化关键酶及膜脂过氧化特性, 为玉米衰老调控和高产栽培提供依据, 本研究在大田条件下, 以我国创高产纪录的夏玉米为例, 从单株水平上对高产纪录试验(EHYR)和普通生产田(MCFF)玉米叶片衰老及抗氧化酶特性比较表明, EHYR产量达19 349 kg hm^-2, 是MCFF的2.28倍。MCFF和EHYR叶片分别在开花后30 d和50 d进入速衰期, MCFF叶片衰老比EHYR提前20 d；速衰期EHYR叶面积降幅比MCFF低5.7%。EHYR在籽粒灌浆后期, 中上部叶片净光合速率较高, 可溶性蛋白含量明显高于MCFF, 而MDA含量则维持较低水平。在叶片衰老过程中, 自开花后20 d开始, EHYR上部和中部叶片SOD活性较高, 下部叶片则以SOD、POD和CAT三者活性较高；MCFF仅中部叶片POD和CAT活性较高。EHYR叶片衰老程度与CAT活性极显著负相关, MCFF叶片衰老与SOD和POD活性显著负相关, 且二者叶片衰老进程中SOD、POD、CAT的直接作用大于间接作用。与MCFF相比, EHYR叶片除具较高SOD和POD活性外, 在籽粒灌浆后期同时保持较高CAT活性和可溶性蛋白含量是降低膜脂过氧化程度, 延缓叶片衰老的重要原因。开花后20 d是EHYR与MCFF叶片衰老出现差异的生理临界点, 因而在此时期之前调控更有利于延缓衰老。

Characteristics of Senescence and Antioxidant Enzyme Activities in Leaves at Different Plant Parts of Summer Maize with the Super-high Yielding Potential after Anthesis

Grain yield improvement of maize (Zea mays L.) has been evidently associated with delayed leaf senescence during the grain-filling period after anthesis. The object of this study was to explore senescence characteristics and antioxidant enzyme activities after flowering in different position leaves of summer maize with high yield record for providing references of regulating the leaf senescence and achieving the higher yield in China. A field experiment planted Denghai 661, a new hybrid with high-yielding potential, was carried out to compare the experiment of maize with high yield record (EHYR) and the maize grown in conventional farmers’ field (MCFF) in individual level from 2005 to 2007. And the parameters related to the leaf senescence, such as leaf area (LA), LA reduction, net photosynthetic rate (P_n), soluble protein content, activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), and malondialdehyde (MDA) content, were determined in this research. The grain yield of EHYR was 2.18 times greater than that of MCFF, reaching 19 349 kg ha^-1. The rapid senescence time of EHYR leaves and MCFF leaves were found at 30 and 50 days after anthesis, respectively. Therefore, the leaf senescence of EHYR was 20 days earlier than that of MCFF. At the rapid senescence stage, the leaf area reduction of EHYR was 5.7% lower than that of MCFF. During the later period of leaf senescence, the net photosynthetic rate was higher in top and middle leaves than in bottom leaves. Furthermore, the soluble protein content in leaves of EHYR was higher than that of MCFF, but the MDA content was on the contrary. At 20 days after anthesis, the SOD activities in top and middle leaves of EHYR were higher than those of MCFF, while the SOD, POD, and CAT activities in bottom leaves of EHYR were higher than those of MCFF. On the contrary, the POD and CAT activities in middle leaves of MCFF were higher than those of EHYR. Results of both correlation analysis and path analysis indicated that the leaf reduction was negatively correlated with the CAT activity significantly in EHYR, also with the SOD and POD activities significantly in MCFF, and the direct effects were higher than the indirect effects of SOD, POD, and CAT in both EHYR and MCFF. Compared with MCFF treatment, besides higher SOD and POD activities, EHYR had higher CAT activities and soluble protein content resulting in declined lipid peroxidation during grain-filling period, which caused delayed leaf senescence and leaf senescence degree. There were obvious differences at 20 days post-anthesis in maize leaf senescence physiologically. Between EHYR and MCFF suggesting that the 20–30 days after anthesis is a critical period, and all the related agronomy measures should be recommended to be taken before this phase in maize production.