Effects Of Nitrogen On Growing Development And Leaves’ Microstructure Of Cotton(Gossypium Hirsutum L.)

With Bt-transgenic hybrid cotton variety Nongdamian 8 as material in 2012, with Bt-transgenic hybrid cotton variety Lumianyan 28 as material in 2013, applying four levels of nitrogen fertilizer: control treatment（N0） 0kg·hm^-2, low nitrogen（N1） 120kg·hm^-2, middle nitrogen（N2） 240kg·hm^-2, high nitrogen（N3） 480kg·hm^-2, under the field conditions to study the differences of morphological characteristics, the accumulation and distribution characteristics of dry matter, the yield index, the differences of physiological and biochemical characteristics and the anatomical structure of the leaves of upper fruit branches. The main results are as follows: 1 Effects of nitrogen fertilizer on morphological characteristics and growth of the upper fruit branches.The proper nitrogen fertilization treatments significantly increased plant height, stem diameter, number of bolls, improve the leaf area index, lessen the number of boll shedding. The proper nitrogen fertilization treatments significantly promote the growth of upper fruit branches, increased to 59.71%. The growth of cotton, the development of upper fruit branches were inhibited, by low nitrogen levels, go against the group structure of high yield cotton field. 2 Effects of nitrogen fertilizer on physiological and biochemical characteristics of the leaves of the upper fruit branches.Nitrogen fertilization treatments increased soluble protein content and chlorophyll content in upper fruit branches’ leaves, the content of middle nitrogen is the maximum. Boll shedding will cause the soluble protein content increase at the first, and then to decline, the chlorophyll content decreased in the upper fruit branches inner leaves. But the soluble protein content decreased, the chlorophyll content increased in outer fruit branches′ leaves. It shows that nitrogen plays an important regulative role to the content of dissoluble protein and chlorophyll in upper fruit branches’ leaves, boll shedding also influence both.The dissoluble sugar content and the MDA content in middle nitrogen lower than that in check treatment. Boll shedding will cause the soluble sugar content increase at the first, and then to decline, the MDA content increased in inner fruit branches′ leaves, but both all increased in outer fruit branches′ leaves. It shows that when available nitrogen was enough, leaves of upper fruit branches could keep biological activity in the late growth stage in cotton, dissoluble sugar transferred quickly, the membrane lipid peroxide kept at a lower level. Boll shedding was adverse to development of the subtending leaf. 3 Effects of nitrogen fertilizer on anatomical structure of the leaves of the upper fruit branches. Nitrogen application rate influenced anatomical structure of the leaves of the upper fruit branches. With increasing the nitrogen fertilizer, blade thickness, ratio of stockade tissue thickness to sponge tissue thickness, single trachea area in the main vein, single trachea area in petiole, the number of vessel in single vascular bundle in petiole, all have increasing tendency. 4 Effects of nitrogen fertilizer on accumulation and distribution characteristics of dry matter and boll growth.Accumulation of dry matter increases with increasing nitrogen fertilizer, that in check treatment was significantly lower than other treatments. The lack of nitrogenous fertilize make reproductive organs dry matter was too high in the late growth stage in cotton, two years respectively reached 56.91% and 57.43%, cause early maturity and early senescence; the overmuch of nitrogenous fertilize make reproductive organs dry matter was too low in the late growth stage in cotton, two years respectively reached 40.59% and 36.12%, cause over-green and later maturation. Fertilizing properly nitrogenous was helpful to dry matter distribution, decreasing the boll shedding percent, high yield cotton.In a word, middle nitrogen(240kg·hm^-2) can improve the morphological characteristics of population and individual, increased the number of bolls, coordinate the growth of upper fruit branches in the late growth stage in cotton. In this experiment, morphological characteristics, physiological and biochemical characteristics and accumulation and distribution characteristics about leaves of upper fruit branches under different nitrogen treatments were discussed and aimed to provide theoretical basis for regulation of keeping biological activity in leaves of upper fruit branches in the late growth stage in cotton.