Department of Botany, The University, G12 8QQ, Glasgow, UK.
Planta. 1974 Jan;121(3):237-51. doi: 10.1007/BF00389324.
Transport of indolyl-3-acetic acid (IAA) was studied during the phototropic responses of intact shoots and detached coleoptiles of Zea mays L. and Avena sativa L. The use of a high specific activity [5-(3)H]IAA and glass micropipettes enabled asymmetric application of the IAA to be made to individual coleoptiles with minimal tissue damage.A unilateral stimulus of 2.59×10(-11) einstein cm(-2) of blue light, probably in the dose range of the first positive phototropic response, caused significant net lateral movement of radioactivity from [5-(3)H]IAA away from the illuminated side of intact shoots and detached coleoptile apices of both Avena and Zea. The magnitude of the net lateral movement was 15.3% in Zea seedlings and 12.3% in Avena seedlings. Chromatographic analyses indicated that the movement of radioactivity reflected that of IAA. A phototropic stimulus of 1.24×10(-7) einstein cm(-2), which was probably in the second positive dose range, caused significant lateral movement of radioactivity in intact shoots and detached coleoptiles of Zea but not of Avena.In intact Zea seedlings, neither phototropic dosage affected the longitudinal transport of IAA. In intact Avena seedlings, first positive stimulation inhibited longitudinal transport only when the IAA was applied to the illuminated side of the coleoptile, but second positive stimulation inhibited basipetal movement of IAA regardless of the side of application.Exposing the intact seedlings to red light before phototropic stimulation abolished lateral transport after a first positive stimulus in Zea and in Avena.Phototropic stimulation can thus induce a lateral transport of IAA towards the shaded side of the coleoptiles of both Zea and Avena seedlings, and can affect longitudinal movement of IAA in the coleoptile of Avena. However, since phototropic curvature was observed under certain conditions in the absence of either of these effects, the extent to which they are involved in the induction of asymmetric growth in a stimulated coleoptile has yet to be resolved.
玉米和燕麦完整枝条和切段胚芽鞘的向光性反应过程中，研究了吲哚乙酸（IAA）的运输。利用高比活度[5-(3)H]IAA 和玻璃微量移液器，可将 IAA 不对称地应用于单个胚芽鞘，同时对组织造成的损伤最小。单侧刺激 2.59×10(-11) einstein cm(-2) 的蓝光（可能在第一正向光性反应的剂量范围内），导致完整枝条和两种玉米和燕麦切段胚芽鞘顶端的放射性物质从[5-(3)H]IAA 显著地向光侧净侧向移动。玉米幼苗的净侧向移动幅度为 15.3%，燕麦幼苗为 12.3%。色谱分析表明，放射性物质的移动反映了 IAA 的移动。1.24×10(-7) einstein cm(-2) 的光刺激（可能在第二正向剂量范围内），导致玉米完整枝条和切段胚芽鞘中放射性物质的显著侧向移动，但燕麦中则没有。在完整的玉米幼苗中，两种光剂量均不影响 IAA 的纵向运输。在完整的燕麦幼苗中，第一正向刺激仅在 IAA 施加于胚芽鞘受光侧时抑制 IAA 的纵向运输，但第二正向刺激抑制 IAA 的向基运动，而与施加侧无关。在光刺激之前用红光照射完整的幼苗，可消除玉米和燕麦中第一正向刺激后的侧向运输。因此，向光性刺激可以诱导 IAA 向玉米和燕麦幼苗胚芽鞘的遮光侧侧向运输，并影响燕麦胚芽鞘中 IAA 的纵向运动。然而，在某些条件下，即使没有这些影响中的任何一种，也观察到了向光性弯曲，因此它们在刺激的胚芽鞘中诱导不对称生长的程度仍有待解决。
