THE KINEMATICS OF PLANT-GROWTH
THE KINEMATICS OF PLANT-GROWTH
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DOI：
10.1038/scientificamerican0580-134
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发表时间：
1980-01-01
影响因子：
3
通讯作者：
SILK, WK
中科院分区：
文献类型：
--
作者：
ERICKSON, RO;SILK, WK
在有记载的艾德历史中，植物形态的美丽曾照亮并激励过诗人、艺术家和科学家。云杉树的圆锥形，橡树优雅的不规则形状，许多花朵近乎完美的径向对称，松果或向日葵头的数学规则性以及枫叶或常春藤叶的特征形状都是人类集体意识的一部分。也许不那么明显的是，植物的许多部分的形状，至少是尺寸，在植物的一生中是不断变化的。一张今天拍摄的豆类植物的照片会显示出与昨天或明天拍摄的照片略有不同。对这些变化的分析揭示了与成熟形式的对称性一样引人注目的发展趋势。如果一个人仔细观察一株生长中的植物，他很快就会发现，茎下部的一片叶子或一个分支（或附着在那里的标签）可能不会改变它的位置，即使植物的高度可能以一个可接受的速度增加。原因是生长仅限于顶端区域，也就是说，长度的生长仅发生在茎尖附近。一片叶子或一个标记放在叶尖下面，但仍然在生长区域，将改变其相对于叶尖和地面的位置。从这个简单的观察可以清楚地看出，生长中的植物组织在尺寸增加的同时，也在改变它们相对于植物其他部分的位置。同样清楚的是，如果人们对生长区域中细胞的行为感兴趣，则不可能确定空间固定位置处细胞变量随时间的变化率，因为细胞会在需要的时间内移动做出决定。需要一种足够精细的分析方法，以考虑组织元素的位移和扩张。
The beauty of plant form has de· lighted and inspired poets, artists and scientists throughout record ed history. The conical shape of the spruce tree, the gracefully irregular form of the oak, the nearly perfect radi al symmetry of many flowers, the math ematical regularity of a pine cone or a sunflower head and the characteristic shape of a maple leaf or an ivy leaf are part of the collective human conscious ness. It is perhaps less immediately obvi ous that the forms, or at least the dimen sions, of many parts of a plant are con tinually changing throughout the plant's life. A photograph made of a bean plant today will show slight differences from one made yesterday or tomorrow. An analysis of these changes reveals devel opmental regularities that are as striking as the symmetries of the mature form. If one carefully observes a growing plant, one soon discovers that a leaf or a branch on the lower part of the stem (or a tag attached there) may not change its position even though the height of the plant may be increasing at a considera ble rate. The reason is that the growth is limited to the region of the apex, that is, growth in length occurs only near the tip of the stem. A leaf or a mark placed below that tip but still in the growing region will change its position with re spect to both the tip and the ground. From this simple observation it is clear that growing plant tissues are simultaneously increasing in size and changing their position in relation to other parts of the plant. It is also clear that if one were interested in the behav ior of cells in the growing region, it would not be possible to determine the rate of change over time of a cellular variable at a fixed position in space, since the cell would move during the time needed to make the determination. A method of analysis is required that is subtle enough to take into account both the displacement and the expansion of tissue elements.