| Northeast China was the largest commodity grain production base, the largest advantage of planting area of corn, and a tremendous impact on the domestic grain market. Liaoning Province was located in the corn belt in northeastern china which was the largest corn producing provinces, but in recent years, there were many obstacles in the factors in maize production, a prominent factor was the corn premature aging, especially in northern Liaoning corn frequent premature aging which sustained a serious impact on corn production and rural incomes. A large number of experiments showed that, premature aging was due to late growth stage of corn malnutrition, caused by the irrational fertilization, nitrogen was the most important impact of nutrients. Therefore, this research study corn pot experiment, nitrogen from different periods and two different nitrogen on maize chlorophyll content, soluble protein content, leaf morphology, physiological and biochemical indexes, and other aspects of chloroplast ultrastructure the impact of in-depth study to reveal the late nitrogen fertilizer on corn growth mechanism of leaf senescence, scientific fertilization of corn to provide a theoretical basis. The main results were:1. Different nitrogen application and nitrogen application time effected chlorophyll content, soluble protein content, leaf morphology, physiological and biochemical in varying degrees. With no N fertilizer application of nitrogen fertilizer significantly improved compared to the above indicators. With the increase of nitrogen improves the late growth stage of maize leaf chlorophyll content and soluble protein in the ear leaf content of protective enzymed SOD, POD activity, reducing the ratio and MDA content in leaves yellow, but after a period of high nitrogen in the milk and inhibition of the chlorophyll content, soluble protein content of protective enzymes SOD, POD activity increased. Nitrogen at 247.5 kghm-2, the corn growing period in all the circumstances were better able to delay the effects of premature senescence. In the case of nitrogen the same as the increase in the number of top dressing, corn ear leaf chlorophyll content and leaf soluble protein content in the protective enzymed SOD, POD activity tended to increase the proportion of leaf scorch and MDA were gradually decreased. When the nitrogen applied at the base, the jointing stage and the large bell of 1:3:1 fertilizer, the corn anti-aging was strongest.2. Control (no fertilizer) treatment ruptured ear of the Leaf and the disintegration of the cell wall, mitochondrial membrane and ridges within and outside the fuzzy, grana and stroma lamellae swell, causing the decline in chlorophyll content, photosynthetic capacity decreased and premature aging occurs. Compared with no N fertilizer, nitrogen fertilizer significantly improved the ultrastructure of leaf cells of maize, was conducive to the growth of corn. With the amount of nitrogen increased gradually complete chloroplast and mitochondrial structure, the base layer of varying particle density and regular arrangement along the long axis of the chloroplast. Chlorophyll content increased, the gradual extension of the function of leaves. In the case of the same nitrogen, when the nitrogen fertilizer applied at the base, with large bell jointing application of 1:3:1, the chlorophyll content, and structural integrity of chloroplasts and mitochondria, grana and stroma lamellae rich; When the number of top dressing fertilizer gradually reduced until the time when the chlorophyll content decreased by a long oval shape of chloroplasts tend to round, constantly capsule rupture, neatly arranged in the lamellar structure into chaos by the mitochondrial membrane is damaged, reducing the number of ridges. Therefore, a reasonable increased in the number of top-dressing could increase the chlorophyll content, chloroplast ultrastructure, and slowed down aging. |
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