Mechanisms And Effects Of Nitrogen Forms On Phosphorus Absorption Of Maize (Zea Mays L.) Under Phosphorus Stress At Seedling Stage

Maize is a very sensitive crop to phosphorus deficiency, phosphorus is one of the lowest available nutrient elements. In the world, there are about5.7million hectares of cultivated land suffering from phosphorus deficiency, while the seasonal utilization efficiency of phosphate fertilizer was less than25%, causing total phosphorus content was as high as200to500times of the available phosphorus content in some areas of arable land. Therefore, how to efficiently use the large number of soil insoluble phosphorus resources and reduce the dependence of plants on phosphate have the significant effects on economic and ecological.The dissertation is aimed to the related mechanisms of nitrogen form regulation. Hydroponics experiments were carried out in the greenhouse, Anhui Science and Technology University, P. R. China. The mechanisms and effects included biological characteristic, water uptake and photosynthetic characteristic, nitrogen compounds contents, phosphorus absorption, phosphorus and acid phosphatase contents, et al. Results obtained were as follows.1After28days, compared with KH2PO4treatment, the biomass of maize plant under phosphorus stress supplied with NO3--N, NH4+-N, and the mixture of NO3--N and NH4+-N was reduced by20.6%,12.9%and15.4%, respectively. After36days, the reduction rate of biomass was38.1%、17.4%and20.8%, respectively. So the NH4+-N treatment was found more tolerant to phosphorus stress as compared to the other two nitrogen forms supplied plants. Maize root biological characteristics were due to the time of stress sustained, when the time of phosphorus stress, the root weight increased significantly. Nitrogen forms supply was a major factor, which affected the adaptive response of maize to phosphorus stress.2The photosynthetic rate and water uptake of maize was reduced obviously under phosphorus stress condition, compared with KH2PO4treatment, the photosynthetic rate under phosphorus stress supplied with NO3--N, NH4+-N, and the mixture of N03--N and NH4+-N was reduced by36.9%、9.70%and16.1%, respectively, the reduction rate of Chlorophyll was21.2%、1.89%and3.00%, respectively, and the increase rate of intercellular CO2concentration was11.3%、7.57%and20.8%. So the photosynthetic rate was affected by non-stomatal factor and chlorophyll content under different nitrogen forms supplied. In the aspect of photosynthetic rate and water uptake, the NH4+-N treatment was found more tolerant to phosphorus stress as compared to the other two nitrogen forms supplied plants.3Compared with KH2PO4treatment, the NH4+-N treatment under phosphorus stress could absorb and accumulate more nitrogen, the free amino acids and proline rate of NH4+-N supplied plants showed the lowest reduction rate, and had the highest content. So the NH4+-N treatment under phosphorus stress mingt have the ability to regulate the different nitrogen compounds distributed coordinately to maintain more tolerant to phosphorus stress.4Compared with KH2PO4treatment, the activity of acid phosphorus of maize plant under phosphorus stress increased significantly, the NH4+-N treatment had the obvious advantages in enhancing phosphorus uptake when compared to the other two nitrogen forms supplied plants. Phosphorus stress conditions changed the way of phosphorus absorption and utilization, the NH4+-N treatment accumulated more phosphorus in roots as compared to the other two nitrogen forms supplied plants.Summary of this total thesis showed that, the inhibition of plant growth supplied with NH4+-N was significantly lower as compared to the other two nitrogen forms supplied plants, and might have the ability to regulate the assimilation and different nitrogen compounds distributed coordinately to maintain more tolerant to phosphorus stress and higher photosynthetic rate. Phosphorus stress conditions changed the way of phosphorus absorption and utilization, the root would be retain more phosphorus when supplied with NH4+-N, and had obvious advantage in enhanced phosphorus uptake. In summary, when planting maize in the soil of phosphorus deficiency, we advise that farmers should appropriately apply the ammonium nitrogen fertilizer.