Analysis of the Mechanism of Graviperception in Radish Seedling.

重力感受机制一直是植物向重力性研究中的一个主要问题，但对其机制了解甚少。目前认为植物根尖的柱细胞和围绕着维管束的内皮层细胞、淀粉鞘细胞是重力感受细胞。本研究以萝卜幼苗下胚轴为材料，研究了下胚轴感受重力的机制。内皮层重力感觉细胞的超微结构观察显示，在这些细胞的外切向壁存在特征性的胞间连丝束。在这项研究中，联合收割机这一观察与假设，即向重力性控制物质包含在淀粉体本身和释放，提出了一个新的假说的机制，植物重力感知。胞间连丝在植物向重力性假说中起主要作用。

The mechanism of gravity perception has been a main problem in the study of plant gravitropism, but the mechanism is little known. At present, the columella cell in root tip, and the inner cortical layr cell, starch sheath cell, which surround the vascular bundles of plant shoot, have been considered as the gravity perception cells. The sensor of gravity information has been believed to be the starch containing amyloplasts in these cells.In this study, the graviperception mechanism of the hypocotyl of radish seedling was studied. The ultrastructural observation of inner cortical "gravity perception cells" revealed the presence of characteristic bundle of plasmodesmata at the outer tangential wall of these cells. In this study, to combine this observation with the assumption that the gravitropism controlling substance is contained within and released from amyloplast itself, a novel hypothesis on the mechanism of plant graviperception is proposed. The plasmodesmata play a main role in this hypothesis on plant gravitropism.