Yamamura S, Hasegawa K
Department of Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Yokohama 223-8522, Japan.
Chem Rec. 2001;1(5):362-72. doi: 10.1002/tcr.1020.
Most people are familiar with the sight of a young seedling bending towards a window or the brightest source of light to which it is exposed. This directional growth response is known as phototropism, which is caused by a lateral growth-promoting auxin in the bending organ (Cholodny-Went theory, cited in high school textbook). Recently, however, Bruinsma et al., Weiler et al., and Hasegawa et al. independently found that the shaded half did not contain more auxin than the illuminated one. Instead it was found that the even distribution of auxin was accompanied by a lateral gradient of growth inhibiting substances during phototropic curvature (Bruinsma-Hasegawa theory). We have isolated some photo-induced growth inhibitory substances related to phototropism, benzoxazolinones from light-grown maize shoots (Zea mays L.), raphanusanins from radish hypocotyl (Raphanus sativus var. hortensis f. gigantissimus M.), indolyacetonitrile from light-grown shoots (Brassica oleacea L.), 8-epixanthatin from sunflower hypocotyl (Helianthus annus L.), and quite recently uridine from oat coleoptile (Avena sativa L.). Chemical analyses have shown phototropic stimulations to cause curvature by inducing a local unequal distribution of growth-inhibiting substances that antagonize auxin in its cell-elongating activity. Finally, a model is presented for further studies on phototropism.
一株幼苗朝着窗户或它所暴露的最亮光源弯曲生长。这种定向生长反应被称为向光性，它是由弯曲器官中一种促进横向生长的生长素引起的（Cholodny-Went理论，高中教材中有引用）。然而，最近Bruinsma等人、Weiler等人以及Hasegawa等人分别发现，遮光的一侧所含生长素并不比受光的一侧多。相反，人们发现在向光性弯曲过程中，生长素的均匀分布伴随着生长抑制物质的横向梯度（Bruinsma-Hasegawa理论）。我们已经从光照培养的玉米幼苗（玉米）中分离出一些与向光性有关的光诱导生长抑制物质、苯并恶唑啉酮，从萝卜下胚轴（萝卜变种hortensis f. gigantissimus M.）中分离出萝卜素，从光照培养的嫩枝（油菜）中分离出吲哚乙腈，从向日葵下胚轴（向日葵）中分离出8-表山嵛菜素，以及最近从燕麦胚芽鞘（燕麦）中分离出尿苷。化学分析表明，向光性刺激通过诱导生长抑制物质的局部不均匀分布而导致弯曲，这些生长抑制物质在其细胞伸长活性方面拮抗生长素。最后，提出了一个模型以供进一步研究向光性。
