种子植物具有极性。例如,将一株草本植物扳倒,不久,其枝条便会弯曲向上,其根则弯曲向下。这即表明,茎有负向地性,根有正向地性,植物生理学对这个现象解释为:因重力作用,生长素在近地侧含量高,刺激该侧组织生长迅速,枝条就向上弯曲。根则对生长素敏感,近地侧浓度高,反而抑制生长,故根向下弯曲。因此栽种或扦插植物,都应注意此种特性,将其顶端朝上,末端向下,不可颠倒。否则,不能成活,也不会发根。受风雨危害,庄稼倒伏,苗木歪斜,如不及时扶正,也会见到类似现象,时隔多日,就难以纠正。 Seed plants are polar. For example, a herb would be pulled down, and soon its branches would be bent upward and their roots bent downward. This shows that the stem has a negative geostatistics, the root has a positive character, plant physiology of this phenomenon is interpreted as: due to gravity, auxin content in the ground near the high side to stimulate the side tissue growth rapidly, the branches bent up . Roots are sensitive to auxin, high concentrations near the ground, but inhibit growth, so the root bending down. Therefore planting or cutting plants, should pay attention to this feature, the top of the upward, the end down, can not be reversed. Otherwise, can not survive, nor will it be hair roots. By the wind and rain hazards, crop lodging, seedlings skewed, if not righting Fuzheng, will also see a similar phenomenon, after many days, it is difficult to correct.