水稻的侧根发育及其影响因素

为了探明水稻侧根发育的过程和影响因素，以日本晴(粳稻)、扬稻6号(籼稻)的不定根和种子根为材料，观察了侧根发育过程中的形态和细胞结构的变化；研究了生长调节物质、光照等因子对侧根发育的影响。结果显示，水稻侧根的发生起始于中柱鞘。相邻的内皮层细胞参与了侧根原基的发生和生长。侧根原基通过顶端生长点的分裂、分化和基部细胞伸长向外生长，侧根在露出过程中改变了母根皮层和表皮结构。外源生长素可促进侧根的发生，但浓度过高则抑制侧根原基的露出；稻苗切除芽后侧根发生减少，主根生长量下降；切除根尖打破了主根顶端优势，促进侧根发生和生长。单侧照光能诱导向光侧的侧根发生。脱落酸在低浓度下对侧根发生有促进作用；Ca²⁺促进侧根发生和主根生长，而EDTA抑制侧根发生和主根生长。种子根和不定根的生长对试验因子的响应趋势基本一致。

Rice Lateral Root Development and Its Impact Factors

The adventitious roots and primary roots of Nipponbare, Yangdao 6were used to measure lateral root number and the growth increment by Image J software with scanning photograph. Morphological and structural changes of lateral root primodia were observed by applying Spurr resin embedding and semi-thin sectioning, and light microscopy. Impacts of the lateral root emergence on the parent root structure was observed by fluorescence microscopy and scanning electron microscopy. Treatments with plant hormones, metal ions, illumination, and cutting off shoots or root tips were set up to analyse their influence on lateral root development. Results showed that rice lateral root initiation occurred from the pericycle. The endodermis also participatedin the lateral root primodia formation and played protective as well as assistant roles in the process. The outward growth of lateral root primordia was realized by cell divisions of apical meristem and cell elongation at the base area. The cortex and epidermis structures of parent roots were also altered during the process of lateral root emergence. Exogenous IAA promoted the occurrence of lateral roots, but its high concentrations inhibited lateral root emergence. The number of lateral roots and growth of primary rootswere significantly decreased when shoots were cut off. The apical dominance of root was lost when root tips were cut off, so that the growth of lateral roots and secondary lateral roots was accelerated. Unilateral illumination induced the increase of lateral roots in the light side. Abscisic acid at low concentrations promoted the formation of lateral roots. The formation of lateral roots and growth of primary root were promoted by Ca²⁺, while mostly inhibited by EDTA. The growth tendency of both adventitious roots and primary roots responsive to the treatments was basically consistent.