Effects Of Nitrogen On The Growth And N Uptake Of Rice Under Different Water Conditions

Water supply and nitrogen management are two main factors, which influence the growth and nutrition of rice. As a result, the yield of rice is also greatly influenced by these factors. A series of solution cultivation experiments were carried out to study the characteristic of NO₃^--N, NH₄⁺-N uptake of rice and how do NO₃^--N, NH₄⁺-N affect the growth of rice root. We try to figure out how does NO₃^--N influence rice's uptake rate of NH₄⁺-N under normal water condition and water stress condition. So does NH₄⁺-N. How does rice react to different amount of nitrogen, is also what we want to know.Japonica rice is more sensitive to water stress than Indica rice. It grows better under normal water condition. While Indica rice can grow better under water stress condition. If NH₄⁺-N and NO₃^--N were supplied simultaneously in the solution, Indica rice can absorb more nitrogen. Japonica rice response better to NH₄⁺-N than to NO₃^--N, while Indica rice have an incline to absorb more NO₃^--N than NH₄⁺-N.NO₃^--N has more advantages to roots growth of rice than NH₄⁺-N. In sufficient water condition, rice absorbs more NH₄⁺-N than NO₃^--N. While it uptakes more NO₃^--N under water stress condition. With the supply of NO₃^--N, roots of rice grow better in sufficient water condition than water stress condition, which can be seen from the length, average diameter, volume, surface area and tips of roots. Contrary to NO₃^--N, roots of rice grow better under water stress condition when NH₄⁺-N is supplied. Under water stress condition, excessive supply of NO₃^--N, NH₄⁺-N will constrain the growth of rice root.Under sufficient water condition, the average diameter, volume and surface area of rice roots grow with the increasing supply of NO₃^--N. While under water stress condition, the length, average diameter, volume, surface area and tips of roots decreased with the increasing supply of NO₃^--N. Different amount of NH₄⁺-N in solution have little effects on the growth of rice.And in the short term absorption experiments, the results obtained are as follows: The uptake rate of NO₃^--N normally grew as the supply of NO₃^--N increased. While the uptake rate of NH₄⁺-N varied under different water condition.As for Japonica Rice, the presence of NH₄⁺-N in the medium considerably repress the uptake of NO₃^--N. If it was cultivated in water stress condition for a few days and then transplanted to normal water condition, presence of NH₄⁺-N induce the uptake of NO₃^--N. For Indica rice, the presence of NH₄⁺-N increased the uptake rate of NO₃^--N. While under water stress condition, less NO₃^--N were absorbed with the supply of NH₄⁺-N. Even if water stress were released, supply of NH₄⁺-N still reduce rice's uptake rate of NO₃^--N. As far as the uptake rate of NO₃^--N was concerned, more NH₄⁺-N were absorbed with the supply of NO₃^--N.