Department of Plant Sciences, Texas A&M University, College Station, Texas 77843.
Plant Physiol. 1970 May;45(5):548-52. doi: 10.1104/pp.45.5.548.
Conditions influencing the opening of the bean (Phaseolus vulgaris L.) and cotton (Gossypium hirsutum L.) hypocotyl hook were defined. Such hooks were shown to undergo geotropic curvature; orientation of the hook with respect to gravity greatly affected the observed opening. Cotton and bean hooks behaved exactly opposite in regard to the presence of the cotyledons and apical bud. The cotton hook required the cotyledons for opening, but the corresponding tissue slowed or inhibited opening of the bean hook. With cotton, lower hypocotyl and root tissues stimulated hook opening, but with bean, the tissues below the hook section had little effect. Kinetin and gibberellic acid both modified hook opening in light and dark; the former was inhibitory and the latter was stimulatory. Indoleacetic acid, at concentrations above 10(-5) M, caused pronounced hook closing in red light but not in the dark. These effects were generally the same with both plants. In opening of the cotton hook, the cotyledons were not necessary as a light receptor tissue. None of the growth substances tested were able to substitute completely for the cotton cotyledon. Coumarin was a pronounced inhibitor of opening of the cotton hook, and this response was expressed to such a degree as to cause hook closure with bean tissue. Reduced oxygen levels inhibited hook opening in bean. Oxygen was required in processes subsequent to the light reaction, but not for the photochemical process.
定义了影响菜豆（Phaseolus vulgaris L.）和棉花（Gossypium hirsutum L.）下胚轴钩弯曲的条件。这些钩都表现出向地性弯曲；钩相对于重力的方向极大地影响了观察到的弯曲。在子叶和顶芽的存在方面，棉花和菜豆钩的表现完全相反。棉花钩的打开需要子叶，但相应的组织会减缓或抑制菜豆钩的打开。对于棉花，下胚轴和根组织刺激钩的打开，但对于菜豆，钩节以下的组织几乎没有影响。激动素和赤霉素都在光照和黑暗中调节钩的打开；前者是抑制性的，后者是刺激性的。吲哚乙酸在浓度高于 10（-5）M 时，会在红光下引起明显的钩闭合，但在黑暗中不会。这两种植物的效果基本相同。在棉花钩的打开中，子叶不是必需的光受体组织。在测试的生长物质中，没有一种能够完全替代棉花子叶。香豆素是棉花钩打开的强烈抑制剂，这种反应的程度足以引起菜豆组织的钩闭合。低氧水平抑制了菜豆钩的打开。氧气是在光反应后的过程中需要的，但不是光化学过程所必需的。
