Effects Of Nitrogen On Growth And Physiological Characteristics Of "Boll-leaf System" Of Upper Fruit Branches Of Transgenic Bt Cotton (Gossypium Hirsutum L.)

With Bt-transgenic hybird cotton variety Lumianyan28as material, the differences ofmorphological characteristics of the upper fruit branches, the differences of physiologicaland biochemical characteristics of the leaves and cotton seeds of fruit branches, theaccumulation and distribution characteristics of dry matter were observe with four levels ofnitrogen fertilizer: control treatment（N0）0kg·hm-2,low nitrogen（N1）120kg·hm-2,middlenitrogen（N2）240kg·hm-2,high nitrogen（N3）480kg·hm-2.The effects of nitrogen fertilizerson “boll-leaf dystem” of upper fruit branches could be obtained by analysis above results.The main results are as follows:1Effects of nitrogen fertilizer on morphological characteristics and growth of the upperfruit branches are as follows:Nitrogen fertilization treatments significantly improved the branch length, leaf area,diameter ratio of near branch and far branch. Nitrogen fertilization treatments significantlypromote the growth of upper fruit branches and leaves, extended the leaf function period.Middle nitrogen treatment has the most significant effect. And the effect of middle nitrogenwas the most significant.The growth of upper fruit branches and outer leaves was inhibited by low nitrogenlevels.2Effects of nitrogen fertilizer on physiological and biochemical characteristics of theleaves of the upper fruit branches are as follows:Chlorophyll content of upper fruit branches’ leaves under the treatment ofmid-nitrogen and high treatment was higher than the other two treatments. Soluble proteincontent of upper fruit branches’ leaves under the treatment of mid-nitrogen was the highest.It shows that nitrogen plays an important regulative role in content of chlorophyll anddissoluble protein of upper fruit branches’ leaves.With the increase of nitrogen fertilizer, SOD activityof upper fruit branches’ seedsfirst decreased then increased， POD activityof upper fruit branches’ leaves first increasedthen decreased. Nitrogen deficiency treatment increased SOD content, but decreased PODactivityof the Upper fruit branches’ leaves, so the H2O2do harm to the growth of “source”. MDA content of upper fruit branches’ leaves under the treatment of mid-nitrogen wasleast. The diversity between inner and outer leaves was notable. When the nitrogen supplywas not enough, the leaves’ growth will be restrained. With the growth of boll, the shortageof nitrogen supply seriously impacted the growth of “source”.3Effects of nitrogen fertilizer on physiological and biochemical characteristics of the seedsof the upper fruit branches are as follows:Dissoluble protein content of upper fruit branches’ seeds under the treatment ofmid-nitrogen was significantly higher than the control and low fertilizer treatments. SODactivitywas the least. POD activitywas the highest. MDA content was the highest. It showsthat nitrogen plays an important regulative role in growth of upper fruit branches’ seeds.The soluble protein content of upper fruit branches’ inner seeds was higher than theouter seeds. The change of MDA content of inner seed was higher than the outer. So thatsuitable fertilizer was good for the growth of the outer seed.4Effects of nitrogen fertilizer on accumulation and distribution characteristics of drymatter are as follows:The change of inner boll weight under the treatment of mid-nitrogen was smaller thanthe outer ones. The weight change of the inner bolls was smaller than the outer ones’. Theincrease of inner boll weight was higher than the outer ones. The weight increase of theinner bolls was bigger than the outer ones’. It shows that the inner boll growth of upperfruit branches was better. The treatment of mid-nitrogen does well to the sink growth.Accumulation of dry matter under high level treatment was higher than others. Theboll distribution of dry matter under middle level treatment was the highest; the high leveltreatment was the least. It shows that nitrogen fertilizer is beneficent for the accumulationof dry matter, but its distribution is not coordinated.In a word, middle nitrogen (240kg·hm^-2) can coordinate the growth of “Boll-LeafSystem” of upper fruit branches. Middle nitrogen can promote the growth of upper fruitbranches. In other words it does well to the growth of “source”. It also scientificallyimpacts the physiological and biochemical characteristics of leaves and seeds. It alsoscientifically increased the boll weight and boll distribution of dry matter. In thisexperiment, morphological characteristics, physiological and biochemical characteristicsand accumulation and distribution characteristics about “boll-leaf system” of upper fruitbranches under different nitrogen treatments were discussed and aimed to providetheoretical basis for regulation of “source-sink” system.