The Effect Of Environmental Factors On The Growth And Development Of Rice Root

Rice root system plays a vital role in absorbing nutrients and water. It is also an important synthesis place for a variety of hormones, organic acids and amino acid. Its growth and development are closely related to the yield and quality formation. Yet, rice roots are grown in dark conditions. With the limitations of research methods, the comprehensive research about the effects of environmental factors on the growth and development of rice root was still not perfect. In this study, yangdao 6 was used as material. We adopted water-culture method to explore the influence of environmental factors such as light, temperature, water, salinity on the growth and development of rice root.The main results were shown as follows:(1) The effect of Illumination on the growth and development of rice rootIllumination of the roots with white light inhibited root elongation by 40–50%. With the increase concentration of Ethylene, the inhibition of root growth was enhanced. Low Ethylene concentrations (0.04mg/l) increased the growth rate of root elongation, especially in seedlings grown in the dark, and 10mg/l Ethylene inhibited elongation to about the same extent as light. The negative phototropism of rice root was markedly stimulated by the 0.04mg/l Ethylene treatment. At 400 mg/l and higher concentrations, Ethylene inhibited root growth almost completely and rice root lost the negative phototropism. We also observed that the differences between the structure and the number of cells in rice root tip meristematic zone was not obvious .These observations implied that the inhibition of white light on root growth might be achieved by the inhibition of elongation zone cells.(2) The effect of water stress on the growth and development of rice rootModerate water stress(10%PEG treatment) could promote the growth rate of root elongation and root dry matter accumulation, yet with the enhancement of PEG concentration ,the elongation of rice roots at this time had been significantly inhibited and the accumulation of dry matter was also decreased. In addition, the number of root under different PEG concentrations treatment was shown for different degrees of reduction .Compared to seedling height, root length, root dry weight the variation of the numbers was the smallest. Under water stress cell wall of the sclerenchyma was significantly thickened in low land rice (Yangdao 6) compared with the control.(3) The effect of salinity stress on the growth and development of rice rootCompared with control ,with the increase of NaCl concentration, root length, seedling height and root growth rate decreased significantly. Dry matter weight of rice seedlings and roots was also decreased, especially with the increase of NaCl concentration. In addition, there was a significant difference in the number of adventitious roots of rice among different treatments. Compared with the control the number of small and medium-sized vacuoles was increased in root tip cortical cells. Under high salinity stress, rice root no longer had the performance of negative phototropism.(4) The effect of temperature on the growth and development of rice rootUnder the six temperature treatment, at the temperature of 15 degrees C, rice root growth virtually ceased, as the temperature increased, root growth rate was gradually increased, at 30 degrees C, we observed the fastest growth rate of rice root and the most active root activity, at 40 degrees C, root growth and root activity began to decline. Higher temperature conditions promoted the formation of aerenchyma and catheter of rice root compared with low temperature. Under high temperature (35 degrees C) treatment rice roots still showed the negative phototropism but the rice root under low temperature (4 degrees C) treatment no longer had the performance of negative phototropism.