Response Of Rhizosphere Processes Of Different Cotton Cenotypes To Phosphate Fertilizers

Rhizosphere is a place of the interaction between crop and soil environment, and the must pass through of crop absorption of nutrients and moisture in soil. Especially for soil phosphorus' mobility is weak, the rhizosphere is an important factor to improve crop soil phosphorus use efficiency. Efficient genotype cotton plays important roles in promoting low phosphorus(P) stress from the perspective of the root morphology.To reveal that the mechanism of Soil phosphorus supply strength coordinated cotton root direct uptake pathway process by drip irrigation under mulch film. To provide a scientific basis for the screening of phosphorus efficient cotton that adapt to mulch drip irrigation distribution pattern of varieties Root morphological and physiological characteristics. The first, a pot experiment was carried out to compare with root morphology of different cotton genotypes under P stress and suitable P environment; Then, a simulate drip irrigation for root box experiment was carried out to compare difference of rhizosphere characteristic of different cotton genotypes under different phosphate levels. Determining the maximum suitable for phosphorus strength for coordination of cotton root to phosphorus efficiency; Finally, on the basis of the root box experiments, a field test was carried out to further verification for root morphology characteristic. The main conclusions are as follows:(1) Pot experiment : Cotton biomass, P amount, N uptake, K uptake, content of SPAD in the leaves,total root length, total root surface area, total root volume were significantly reduced by low P stress; Each physiological and total root parameter index, specific root length and the proportion of fine roots of P efficient genotype cotton were significantly higher than P inefficient, average root diameter of P efficient genotype cotton was significantly less than P inefficient cotton in the low phosphorus stress environment.Cotton root morphology changes of dynamic performance that, P efficient genotype cotton and P inefficient showed rapid growth process in post-emergence 45 d and 75 d in low P stress. Explained that root system of P efficient genotype cotton is more sensitive to the reaction in low P stress; Principal component analysis showed, the total root length, total root surface area, total root volume, middle root length and coarse root length could be used to distinguish two P genotype cotton, and could made great contributions to P amount of cotton; Regression analysis showed that, under different phosphate levels, affected the root P amount parameters vary. In summary, P efficient genotype cotton adapted to low P stress through greatly increasing proportion of fine roots, reducing overall fineness root, prompting an increase of specific root length, and increasing construction efficiency of root.(2) Root box test: Cotton biomass, P amount, phosphorus concentration and content of SPAD of various organs and the whole showed the first increase after decreasing trend with the increase of the amount of phosphorus. Cotton plants phosphorus use efficiency has decreasing trend with the increase of the amount of phosphorus, P200 reached at stable. Within 0-100 mg/kg of phosphorus range, XLZ19 genotypes of cotton growth indexes were higher than XLZ13 significantly; Cotton root morphological parameters has increasing first and then decreasing trend with the increase of the amount of phosphorus. Root parameters of XLZ19 genotype are better than XLZ13 in without phosphorus and phosphorus deficiency conditions;The proportion of fine roots increased significantly under low P stress, and the rate of increase of XLZ19 is bigger than XLZ13; The lower the amount of phosphorus in soil, the larger acid phosphatase activity in therhizosphere soil, and XLZ19 genotype Performances significantly. In conclusion, low P stress and excess P will affect the physiological characteristics and rhizosphere features of cotton. XLZ19 genotype representing XLZ13 genotypes, it can greatly increase the phosphorus use efficiency of plants and proportion of fine roots of root to absorb more phosphorus in the soil, which has accumulated more biomass to better adapt to low P environment.(3) Field test: the total root length, total root surface area and total root volume of cotton has increasing first and then decreasing trend with the increase of the amount of phosphorus, maximum phosphorus supply at P150. Total root parameter on whole layer of XLZ50 genotype cotton is more than XLZ13 in two phosphorus levels, and has achieves a significant difference at the bud stage; When the bud stage, in each diameter range of root length of XLZ50 genotype cotton greater than XLZ13 generally in two phosphorus levels. When the blooming period, middle root length of XLZ50 genotype cotton was significantly higher than XLZ13 in P0, P75 and P150 levels. In summary, under P deficiency and excess phosphorus conditions will affect the cotton root morphology on varying degrees. Root parameters of P efficient genotype cotton were better than P inefficient under low P stress, and there are differences between different genotypes of cotton root morphology, which is consistent with pot experiment and Root box test results.In short, root morphology and rhizosphere occurred plasticity in response to varying degrees at different phosphorus levels. Phosphorus stress and excess phosphorus will affect the physiological characteristics and rhizosphere characteristics of cotton. Phosphorus efficient genotypes of cotton compared with phosphorus inefficient, it can better adapt phosphorus stress environment. In excess phosphorus supply conditions, changes in morphological and physiological characteristics according to different varieties.