Hoson T, Kamisaka S, Masuda Y
Department of Biology, Osaka City University, Japan.
Planta. 1996 May;199(1):100-4. doi: 10.1007/BF00196886.
Primary roots of six plant species were placed horizontally either in humid air or under water, and their growth and gravitropic responses were examined. In air, all the roots showed a normal gravitropic curvature. Under water without aeration, roots of rice (Oryza sativa L.), oat (Avena sativa L.), azuki bean (Vigna angularis Ohwi et Ohashi), and cress (Lepidium sativum L.) curved downward at almost same rate as in air, whereas the curvature of roots of maize (Zea mays L.) and pea (Pisum sativum L.) was strongly suppressed. Submergence did not cause a decrease in growth rate of these roots. When roots of maize and pea were placed horizontally under water without aeration and then rotated in three dimensions on a clinostat in air, they showed a significant curvature, suggesting that the step suppressed by submergence is not graviperception but the subsequent signal transmission or differential growth process. Constant bubbling of air through the water partly restored the gravitropic curvature of maize roots and completely restored that of pea roots. The curvature of pea roots was also partly restored by the addition of an inhibitor of ethylene biosynthesis, aminooxyacetic acid. In air, ethylene suppressed the gravitropic curvature of roots of maize and pea. Furthermore, the level of ethylene in the intercellular space of the roots was increased by submergence. These results suggest that the accumulation of ethylene in the tissue is at least partly involved in suppression of transmission of the gravity signal or of differential growth in maize and pea roots under conditions of submergence.
将六种植物的初生根水平放置在潮湿空气中或水下，检测其生长和向重力性反应。在空气中，所有根均表现出正常的向重力性弯曲。在未通气的水下，水稻（Oryza sativa L.）、燕麦（Avena sativa L.）、小豆（Vigna angularis Ohwi et Ohashi）和水芹（Lepidium sativum L.）的根弯曲向下的速率与在空气中几乎相同，而玉米（Zea mays L.）和豌豆（Pisum sativum L.）根的弯曲则受到强烈抑制。淹水并未导致这些根的生长速率下降。当将玉米和豌豆的根水平放置在未通气的水下，然后在空气中的回转器上进行三维旋转时，它们表现出明显的弯曲，这表明淹水所抑制的步骤不是重力感知，而是随后的信号传递或差异生长过程。通过水持续鼓入空气可部分恢复玉米根的向重力性弯曲，并完全恢复豌豆根的向重力性弯曲。添加乙烯生物合成抑制剂氨基氧乙酸也可部分恢复豌豆根的弯曲。在空气中，乙烯会抑制玉米和豌豆根的向重力性弯曲。此外，淹水会使根细胞间隙中的乙烯水平升高。这些结果表明，在淹水条件下，组织中乙烯的积累至少部分参与了对玉米和豌豆根重力信号传递或差异生长的抑制。
