Study On The Photoreceptors And Influencing Factors Of Negative Phototropism Of Rice Root

All the seminal roots, adventitious roots and their branched roots of rice have clear negative phototropism when unilateral light was given to rice root.The process of negative phototropism of rice root is one of the plant directional movements and invoved a series of signal transduction.Our research use "Yangdaoliuhao"as the main material to study the light sensor and the photoreceptor by shading root,cut root cap,change light quality.pigment extraction,and SDS-PAGE for soluble protein of root cap. We also research the influencing factors of negative phototropism of rice rootmain from physical factors, chemical factors and Rice’s own factors.The results obtained from all the experiments were listed below:1.Under both water cultured condition air cultured condition,all the seminal roots, adventitious roots and their branched roots of rice have clear negative phototropism. The negative phototropic curvature varied between differe rice varieties.2.The roots of different plants respond differently to light,some have obvious negative phototropism,as Eleusine indica et al. some are not sensitive to light,as corn et al.3.The root cap was light sensor and the phototropin could be blue-light receptor, as the photoreceptor responging to blue/UV light and yellow/green,but not to red/orange light.4.Endogenous auxin of shade side is greatly more than that of the other side after adentitious root exposed to unilareral light.In the event of negative phototropism of rice growth curve process, the light side of the number of H+release more than the shaded side;The negative phototropic bending of the rice root was mainly due to the larger growth increment of root-tip cells of the irradiated side than that of the shaded side.5. The growth increment and curvature of rice root were both influenced by light intensity, the increasing of light intensity resulted in the increasing of the bending angle of rice root and the decreasing of the growth increment; After30min unilateral light, the rice seminal root will begin to occur negative phototropism, After60min unilateral light,the clear negative phototropismwill be seen; The negative phototropism of rice root growth and curvature is the vector total of light and gravity; Low intensity of water stress has little impact on the negative phototropism of rice root, but high intensity of water stress causes negative phototropism of rice root bending angle becomes smaller.6. The root elongation of rice is promote by low concentration of exogenous auxin, and be inhibited by high concentrations of auxin.At the same time, the bending angle of negative phototropism of rice root has a weak promoting effect by auxin, but not obvious:Low concentrations of H2O2promote the negative phototropism of rice root, while high concentration of H2O2inhibite the negative phototropism of rice root; The negative phototropism of rice root will be promoted when the Ca2+concentration in0.01-1mg.L-1, but it will be inhibited when the Ca2+concentration over100mg.L-l;EDTA inhibited the growth of rice roots and negative phototropism response; At pH-6, the negative phototropism of rice root and growth rate have reached the optimum level; Under salt stress, rice root growth was impacted obviously, but the bending angle of the negative phototropism of rice root is not affected; Heavy metal ions inhibit the negative phototropism of rice root obviously.7. Root of every stage of rice life cycle has a significant negative phototropism; The bending angle of negative phototropism, root quantity and growth will reach the maximum when the stem at15-30cm; The negative phototropism of rice root will be inhibited when the aerial part of rice was cut; The negative phototropism bending angle of high node adventitious root is greater than the low node ones.