Abstract: To properly explore the effects of IAA on the negative phototropism of rice(Oryza sativa L.)root,immunoassay of ELISA(enzyme linked immunosorbent assay) was employed to determine IAA concentration in root tip, unilateral application of agar block containing IAA on root tip was carried out to investigate the effect of exogenous IAA on phototropic response. And the bending part of the rice root was sliced into semi-thin sections to study its microstructure. Results showed that the growth of seminal roots could be regulated by exogenous IAA as well as light, the root was induced to bend toward the site of the application, caused asymmetric growth of the root cells at the elongation zone and resulted in the bending growth. IAA concentration on the shaded side of adventitions root increased much greater 1.5 h after the start of irradiation. The unequal lateral IAA distribution can be concluded to be the main cause for the negative phototropism of rice root.

Key words: rice, root tip, negative phototropism, indole acetic acid

摘要： 为了研究生长素在水稻根负向光性反应中的作用，用含有IAA的琼脂块贴附在种子根的根尖表面观测IAA对根的生长效应，用ELISA法测定根尖的IAA含量，并对种子根弯曲部分进行半薄切片，结果表明：(1) 种子根的生长方向既受光的调控也受外施的IAA的调控，根尖向贴有含IAA琼脂块的一侧弯曲生长;(2) 不定根在光照1.5 h后,背光侧的IAA含量明显大于向光侧；(3) 种子根尖发生弯曲生长是伸长区的细胞不均等生长所致。证实光引起根尖两侧IAA含量的差异导致根负向光性的形成。

关键词: 水稻, 根尖, 负向光性