The Effects And Mechanism On The Cotton Growth Under The Available Phosphorus Levels

Phosphorus(P) is an essential element for cotton plant growth and development. There is considerable information available about relationships between phosphorus and cotton plant, although most studies concentrate on growth and development with little attention to the mechanism. So, we conducted the pot and field experiments by setting 1.5, 3.0, 6.0, 9.0, 12.0, 15.0, 20.0mg P per kg soil to explore the growth and development, physiological and biochemical characteristics of activity leaves, the accumulation of carbon and nitrogen product of cotton(CCRI 79). And we want to explain the mechanism of phosphorus affect cotton plant growth and development and provide a theoretical basis for efficient fertilization in cotton. The main results were as follows:1.Study the effects of different P nutrition levels on cotton yield and constitution to define the suitable scope of soil phosphorus levels of cotton. The main results were as follows:The cotton plant height, leaf area, shoot biomass and root biomass of cotton plant were increased with soil available P concentrations(between 1.3-9.3mg/kg), whereas the root/shoot ratio were decreased. The cotton leaf area, plant height and dry weight were the highest in the treatment with the soil available P content was 9.0mg/kg. Bud stage was significantly affected by soil available P among the whole cotton plant growth period.The P absorption efficiency was significantly increased with the increasing P application rates, whereas the P utilization efficiency was decreased. Over the date, the P absorption efficiency showed a growing trend, and the P utilization efficiency showed the firstly increase after downward trend at the same date.The boll number per plant, boll mass and yield were signification improved with the increasing P application rates, and no significant effects on lint percentage. The data showed, when the soil available P content was 10.9mg/kg, the yield of cotton was the highest. But the P fertilizer has no effect on fiber quality.2. Studying the effects of different P nutrition levels on the activity leaves to define the physiological and biochemical of phosphorus nutrition on the growth mechanisms of leaves.The main results were as follows:The P fertilizer has the significant effect on leaf area, dry weight and P absorption efficiency of activity leaf when the available P contents were 9.0-11.3mg/kg. The low P contents decreased the growth of the leaf, the high P contents can’t improve the leaf.When the soil available P content was 9.3mg/kg, the activity of SS, SPS and NADPase had a significant effect on the photosynthesis. The contents of chlorophyll and chlorophyll a were affected as greatly as the chlorophyll b. The effects of P on photosynthesis at the seeding and bud stage were more significant than other stages.When the soil available P content was 8.0mg/kg, the activity of SOD, POD and CAT were minimum, which indicated that the nutrient stress was minimal when the content of soil available P at 8.0mg/ kg.3. Studying the effects of different P nutrition levels on the accumulation of carbon and nitrogen product to define the mechanism of the soil phosphorus levels effect the carbon and nitrogen metabolism. The main results were as follows:The total amount of amino acids, amylum, soluble sugars and sucrose in response to different soil available P content was nearly the same. When the available P content was 9.3mg/kg, the effects of the accumulation of carbon and nitrogen metabolism were the highest. At the seeding stage, the P nutrition has a signification effect on amino acids, amylum and soluble sugars, while the sucrose at bud stage.