Masson P H
Laboratory of Genetics, University of Wisconsin-Madison 53706.
Bioessays. 1995 Feb;17(2):119-27. doi: 10.1002/bies.950170207.
When a plant root is reoriented within the gravity field, it responds by initiating a curvature which eventually results in vertical growth. Gravity sensing occurs primarily in the root tip. It may involve amyloplast sedimentation in the columella cells of the root cap, or the detection of forces exerted by the mass of the protoplast on opposite sides of its cell wall. Gravisensing activates a signal transduction cascade which results in the asymmetric redistribution of auxin and apoplastic Ca2+ across the root tip, with accumulation at the bottom side. The resulting lateral asymmetry in Ca2+ and auxin concentration is probably transmitted to the elongation zone where differential cellular elongation occurs until the tip resumes vertical growth. The Cholodny-Went theory proposes that gravity-induced auxin redistribution across a gravistimulated plant organ is responsible for the gravitropic response. However, recent data indicate that the gravity-induced reorientation is more complex, involving both auxin gradient-dependent and auxin gradient-independent events.
当植物根在重力场中重新定向时，它会通过引发弯曲做出反应，最终导致垂直生长。重力感知主要发生在根尖。这可能涉及根冠柱细胞中的淀粉体沉降，或者检测原生质体质量对其细胞壁两侧施加的力。重力感知激活信号转导级联反应，导致生长素和质外体Ca2+在根尖不对称重新分布，并在根尖底部积累。由此产生的Ca2+和生长素浓度的横向不对称可能传递到伸长区，在那里发生细胞伸长差异，直到根尖恢复垂直生长。Cholodny-Went理论提出，重力诱导的生长素在受重力刺激的植物器官中重新分布是向重力性反应的原因。然而，最近的数据表明，重力诱导的重新定向更为复杂，涉及生长素梯度依赖性和生长素梯度非依赖性事件。
