Fukaki H, Fujisawa H, Tasaka M
Department of Botany, Faculty of Science, Kyoto University, Japan.
Plant Physiol. 1996 Mar;110(3):933-43. doi: 10.1104/pp.110.3.933.
We have characterized the gravitropic response of inflorescence stems in Arabidopsis thaliana. When the inflorescence stems were placed horizontally, they curved upward about 90 degrees within 90 min in darkness at 23 degrees C, exhibiting strong negative gravitropism. Decapitated stem segments (without all flowers, flower buds, and apical apices) also showed gravitropic responses when they included the elongation zone. This result indicates that the minimum elements needed for the gravitropic response exist in the decapitated inflorescence stem segments. At least the 3-min gravistimulation time was sufficient to induce the initial curvature at 23 degrees C after a lag time of about 30 min. In the gravitropic response of inflorescence stems, (a) the gravity perception site exists through the elongating zone, (b) auxin is involved in this response, (c) the gravitropic curvature was inhibited at 4 degrees C but at least the gravity perception step could occur, and (d) two curvatures could be induced in sequence at 23 degrees C by two opposite directional horizontal gravistimulations at 4 degrees C.
我们已经对拟南芥花序茎的向重力性反应进行了表征。当花序茎水平放置时，在23℃黑暗条件下，它们在90分钟内向上弯曲约90度，表现出强烈的负向重力性。去顶的茎段（没有所有花朵、花芽和顶端）当包含伸长区时也表现出向重力性反应。这一结果表明，去顶的花序茎段中存在向重力性反应所需的最小元件。在约30分钟的延迟时间后，至少3分钟的重力刺激时间足以在23℃诱导初始弯曲。在花序茎的向重力性反应中，（a）重力感受位点贯穿伸长区存在，（b）生长素参与此反应，（c）在4℃时向重力性弯曲受到抑制，但至少重力感受步骤可以发生，并且（d）在23℃时，通过在4℃进行两次相反方向的水平重力刺激可依次诱导出两个弯曲。
