FRUIT MORPHOLOGY AND TERMINAL VELOCITY IN TRAGOPOGON-DUBIOUS (L)
FRUIT MORPHOLOGY AND TERMINAL VELOCITY IN TRAGOPOGON-DUBIOUS (L)
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DOI：
10.2307/2389623
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发表时间：
1989-01-01
影响因子：
5.2
通讯作者：
BRIGHAM, EJ
中科院分区：
文献类型：
--
作者：
MCGINLEY, MA;BRIGHAM, EJ
在操作实验中，对龙眼果的果实质量、锥体面积和终末速度的关系进行了如下预测：(1)终端速度应与圆盘装载量的平方根成正比（圆盘装载量=质量/面积）；(2)当pappus面积一定时，终端速度应与质量的平方根成正比；(3)当果实质量一定时，终端速度应与pappus面积的平方根成反比。虽然每个预测都得到了定性支持，但终末速度随浆液面积的增加而下降的速度比预测的慢，而随浆液质量的增加而增加的速度比预测的快。当磁盘负载保持不变时，具有较大乳头的水果比具有较小乳头的水果下降得更快。这些结果表明，由于两个原因，乳头的面积不能很好地估计其产生阻力的能力（其有效面积）：(1)因为乳头的径向形态导致产生阻力的十字毛的密度沿着乳头射线的长度减少；(2)因为如果乳头受到作用于它的阻力向上弯曲，乳头的投影面积可能会改变。因此，增加亲代对乳头的投入并不会像预期的那样迅速降低终端速度。
In a manipulative experiment the following predictions about the relationship betweent fruit mass, pappus area, and terminal velocity in the fruits of Tragopogon dubious (L.) were tested: (1) terminal velocity should be proportional to the square root of disk loading (disk loading = mass/area), (2) when pappus area is held constant, terminal velocity should be proportional to the square root of the mass and (3) when fruit mass is held constant, terminal velocity should be inversely proportional to the square root of pappus area. Although qualitative support was found for each prediction, terminal velocity declined more slowly than predicted with increasing pappus area and increased more quickly than expected when mass was increased. When disk loading was held constant, fruits with larger pappuses fell more quickly than fruits with smaller pappuses. These results suggest that the area of the pappus is not a good estimator of its ability to produce drag (its effective area) for two reasons: (1) because the radial morphology of the pappus causes the density of drag producing cross hairs to decrease along the length of the pappus ray and (2) because the projected area of the pappus may change if the pappus is bent upwards by the drag force acting on it. Thus, increasing parental investment in pappuses does not decrease terminal velocity as quickly as expected.