Effects Of NaCl Stress And N Form On Growth Of Rice Seedlings

Salinization is one of the most important factors that effect the productivity of soil.It seriously restricts the food production and sustainable agriculture development. The experiments were carried out with rices(Wuyujing 3,yangdao 6 and Huaidao 9) to studiy the effects of NaCl stress on shoot and root growth of rice seedings and distribution of some ions. The effects of N form on nutrients uptake, some physiological-biochemical characters of rice seedings and pH of the culture solution under salt stress had been discussed in this paper. The results were summarized as follows:(1) With increasing of NaCl stress, dry weight, K⁺ concentration, K⁺/Na⁺ ratios and [Na⁺]root / [Na⁺] shoot ratios of rice seedlings of Wuyujing 3 and Yangdao 6 decreased under salt stress conditions, while Na⁺ concentration increased. K⁺/Na⁺ ratios in shoots were higher than those in roots. Both rice varieties had a minimum value of SK, Na(transportation coefficient)respectively, which were most likely their limit value of salinity tolerance of both varieties. Higher Ca²⁺ concentration was observed in shoots of Wuyujing 3 seedlings under salt stress conditions compared with the controlwithout any NaCl. Ca²⁺ concentration in shoot of Yangdao 6 seedlings treated with high concentration of NaCl was significantly higher than that with low concentration of NaCl, whereas no significant differences were shown in Ca²⁺ concentration among all treatments with NaCl below 34 mmol.L^-1. Ca²⁺ concentration increased much more in Wuyujing 3 seedlings caused by salt stress than that in Yangdao 6 seedlings. The concentration of Mg²⁺ in shoots of rice treated with salt stress had little change within 1g.kg^-1. In this experiment Wuyujing 3 showed higher sensitivity to NaCl stress compared with Yangdao 6..(2)The roots are very important organ for nutrients absorption of rice. The growth and biomass accumulation of rice lie on the development of the roots. The dry weight, the volume and the total surface area of root of Wuyujing 3 and Yangdao 6 decreased with the increase of NaCl concentration. The proportion of the various diameter roots of both rice varieties was different under NaCl stress. The shoot of Wuyujing 3 was more inhibitted by NaCl stress .(3) It had been found that some effects of N form on nutritional characters of rice seedings existed in the experiment . The rice had some different response to 0, 43, 86 mmol.L-1 of NaClunder different ratio of NH₄⁺-N to NO₃^--N (9/ 1,5/ 5å’Œ1/9 ). The results obtained were as follows. Treated with NH₄⁺-N / NO₃^--N at 1/9, the biomass accumulation, nitrogen uptake, nitrogen concentration of rice seedings was the least, and pH of culture solution after cultivation was the highest under the three salt concentration conditions. Rice seedings treated with NH₄⁺-N /NO₃^--N at 1/9 absorbed the least amount of phosphorus and had the least P concentrations under NaCl at 0 and 86 mmol·L-1. The highest potassium concentration of plant were respectively found in the treatment of NH₄⁺-N /NO₃^--N at the ratio of 1/9 in both 0 and 43 mmol·L-1 of NaCl solution condition. But potassium concentration of rice seedings decreased with decrease of the ratio of NH₄⁺-N /NO₃^--N at 86 mmol·L-1 of NaCl concentration. Effects of N form on K+ concentration of rice seedings were no significant difference under salt stress in the experiment condition.(4) MDA concentration of rice leaves increased with increase of the concentration of NaCl solution. MDA concentration of rice leaves was no significant difference among nitrogen form treatments under the same concentration of NaCl condition, Anyway the tendency was found that MDA and chlorophyll concentrations, biomass accumulation in leaves of rice treated with NH₄⁺-N/NO₃^--N at 1/9 were the least under three salt stress conditions respectively.Pro. of rice leaves increased with increasing NO₃^--N ratios under the same salt concentrations. NR increased with increasing NO₃^--N ratios under light stress, while it was contrary under heavy stress.