这个词是什么意思？
The directional growth of organisms in response to gravity. In plants, the main root is positively gravitropic (growing downwards) and a main stem is negatively gravitropic (growing upwards), irrespective of the positions in which they are placed. Plant gravitropism is thought to be controlled by auxin (AUXINS), a plant growth substance. (From Concise Dictionary of Biology, 1990)
中文名称索引；定义为 MeSH 英文原文，尚未逐条译审。MESH:D018522 · MeSH 2026。
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