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

Rice root system plays an important role in absorbing water and nutrients. It also has the synthesis, transportation and fixed plant function. Its growth and development are closely related to the yield and quality formation. In the process of growth and development, the rice root will be affected by various environmental factors, such as temperature, moisture and hormone, etc. All the seminal roots, adventitious roots and their branched roots of rice will have clear negative phototropism when unilateral light is given to rice root. Affected by various environmental factors, the rice root has different negative phototropic curvature. Our research use "Yangdaoliuhao" as the material and adopted water-culture and air-culture method to explore the influence of environmental factors such as light, temperature, water, hormones and chemical factors on the growth and development and negative phototropism of rice root. The results obtained from all the experiments are listed below:1. The influence of physical factors on the growth and development and negative phototropism of rice root:(1) When the light is evenly given to rice root, the growth rate, lateral root quantity and adventitious root quantity are less than that in the darkness, but dry matter accumulation are more than that in the darkness.(2) Below the temperature of10degrees C, the rice root neither grows not bend. At30degrees C, the growth rate, lateral root quantity, adventitious root quantity, dry matter weight and negative phototropic curvature of rice root reach the maximum, and with the temperature rising the growth rate and negative phototropism begin to decline.(3) Moderate water stress can promote the growth rate of root elongation and dry matter accumulation, and when PEG concentration is10%, the growth rate, dry matter weight and negative phototropic curvature of rice root reach the maximum, but high intensity of water stress causes the growth rate and negative phototropic curvature becoming smaller.2. The influence of chemical factors on the growth and development and negative phototropism of rice root:(1) the root elongation and lateral root initiation are promoted by low concentration of exogenous auxin, and are inhibited by high concentration of exogenous auxin. When the concentration of exogenous auxin is10-12mol·L-1, the rice root grow fastest, and10-7mol·L-1is the fittest concentration for lateral root formation. At the same time, exogenous auxin has a weak promoting effect on the bending angle of negative phototropism of rice root.(2) NaCl concentration plays a role of stress in the growth and development of rice root. With the increasing of NaCl concentration, the growth rate, lateral root quantity, adventitious root quantity, dry matter weight and negative phototropic curvature of rice root are decreasing in different degree.(3) The growth and development of rice root are promoted by low concentration and are inhibited by high concentration of CaCl2. When the CaCl2concentration is1mg·L-1, the growth rate and negative phototropic curvature of rice root reach the maximum.50mmol·L-1is the fittest concentration for lateral root formation and1mmol·L-1is the fittest concentration for adventitious root formation. With the increasing of EDTA concentration, the growth rate and negative phototropic curvature of rice root are decreasing.(4)When the concentration of KC1is1000mg·L-1, the rice root grow fastest, but the growth rate and negative phototropism will be inhibited if the concentration of KC1is higher than1000mg·L-1.(5)10mg·L-1is the fittest sucrose concentration for the growth and development of rice root, but the bending angle of the negative phototropism is not affected by the sucrose concentration.(6)Along with Pb(Ac)2concentration increasing, the growth and development of rice root are inhibited obviously, and the growth rate and negative phototropic curvature of rice root are decreasing.(7) The growth and development and negative phototropism of rice root are weakly promoted by low concentration of FeSO4, and are inhibited by high concentration of FeSO4.3. The influence of some other factors on the growth and development and negative phototropism of rice root:(1) In the condition of air-culture, the growth rate and negative phototropic curvature of seminal roots and adventitious roots are obviously less than that in the water-culture condition.(2)When the aerial part of rice is cut, the seminal root can continue to grow and have a clear negative phototropism, but the lateral root initiation is inhibited. However, the seminal roots stop growing and don’t have negative phototropism and the lateral roots grow better when the root tip is removed.