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Abstract：
The coenocytic tip-growing alga Vaucheria exhibits positive and negative phototropism, apical expansion, polarotropism, and branch induction from the illuminated region of the cell, all of which are caused by blue light. The bending response of Vaucheria is a blue light-mediated growth response. Differently from diffuse-growing cells or organs, the apical hemispherical dome of the Vaucheria cell is the site of not only maximum growth activity but also the site of blue light perception. Thence the phototropic response is initiated by the bulging mechanism: that is, a quick shift of the growth center to the adjacent subapical flank region. Since tip growth is driven by localized exocytosis, both phototropic bending and branch induction are considered to be closely related blue light-responses. Here I describe first how to prepare a highly useful culture medium for most freshwater algae, to establish unialgal and axenic culture of Vaucheria, and then describe several simple illumination systems using ordinary and/or inverted microscopes for the measurements of tip growth and for analyses of phototropism, polarotropism, and blue light-induced branching. Brief information is also included concerning the nature and function of aureochrome, the newly discovered, ochrophyte-specific blue light receptor. Aureochrome mediates blue light-induced branching, but its role in the phototropic response is still not elucidated.
摘要：
多核尖端生长的藻类Vaucheria表现出正和负向光性，顶端扩张，极化性,从细胞的照明区域分支诱导，所有这些都是由蓝光引起的。Vaucheria的弯曲反应是蓝光介导的生长反应。与弥散生长的细胞或器官不同，Vaucheria细胞的顶端半球形圆顶不仅是最大生长活性的部位，而且是蓝光感知的部位。因此，趋光响应是由鼓起机制发起的：也就是说，生长中心快速转移到相邻的根尖侧翼区域。由于尖端生长是由局部胞吐驱动的，向光弯曲和分支感应都被认为是密切相关的蓝光响应。在这里，我首先描述如何为大多数淡水藻类准备非常有用的培养基，建立Vaucheria的单藻和无菌培养，然后描述几个简单的照明系统使用普通和/或倒置显微镜的尖端生长的测量和向光性的分析，极化性,和蓝光诱导的分支。简要的信息也包括有关的性质和功能，新发现的,卵生菌特异性蓝光受体。Aureochrome介导蓝光诱导的分支，但其在趋光反应中的作用仍未阐明。
