Sievers A, Volkmann D
Abteilung für Cytologie, Botanisches Institut der Universität Bonn, Bonn, Deutschland.
Planta. 1971 Jun;102(2):160-72. doi: 10.1007/BF00384870.
In the root cap of Lepidium sativum a complex of multiple rough endoplasmic reticulum develops above the morphological lower transverse cell walls during ontogenesis of the columella cells ("statocysts"). The cisternae of the ER-complex are preferentially oriented parallel to the transverse walls. In normal vertical exposure of the roots the amyloplasts ("statoliths") lie above the ER-complex. They do not touch the plasma membrane, but possibly they press against the ER-complex and thereby bring about geotropic equilibrium.In each storey of the root cap the transverse walls together with their ER-complexes have a parabolic shape. Therefore the surface areas of the central ER-complexes form a right angle and those of the peripheral ER-complexes an acute angle with the organ axis.Owing to the shape of the whole ER-complex within each storey, the amyloplasts in the physically upper peripheral columella cells do not press against the membranes of the ER in the case of horizontal exposition. On the other hand in the physically lower part the amyloplasts are still situated above the ER-complex and can press on the ER.Geoperception in roots may be a function of pressure exerted differentially by amyloplasts on the ER-complex.
在独行菜根冠中，在柱状细胞（“平衡囊”）个体发育过程中，多个糙面内质网复合体在形态学上较低的横向细胞壁上方形成。内质网复合体的潴泡优先平行于横向壁排列。在根正常垂直放置时，淀粉体（“平衡石”）位于内质网复合体上方。它们不接触质膜，但可能挤压内质网复合体，从而实现向地平衡。在根冠的每一层中，横向壁及其内质网复合体呈抛物线形。因此，中央内质网复合体的表面积与器官轴成直角，外围内质网复合体的表面积与器官轴成锐角。由于每一层中整个内质网复合体的形状，在水平放置的情况下，物理位置较高的外围柱状细胞中的淀粉体不会挤压内质网的膜。另一方面，在物理位置较低的部分，淀粉体仍位于内质网复合体上方，并可挤压内质网。根的向地感知可能是淀粉体对内质网复合体施加不同压力的一种功能。
