Shen-Miller J, McNitt R E, Wojciechowski M
Division of Biological and Medical Research, Argonne National Laboratory, Argonne, Illinois 60439.
Plant Physiol. 1978 Jan;61(1):7-12. doi: 10.1104/pp.61.1.7.
We examined cell length, mitosis, and root meristem "cuticle" in different tissues of geostimulated, red light-exposed primary roots of corn (Zea Mays, Wisconsin hybrid 64A x 22R). The examination was done at 15-minute intervals for a period of 240 minutes. Differences in cell elongation between the upper and lower sides were most prominent between 1.5 and 2.5 mm from the root meristem; the outer cortex had the greatest elongation growth, and the upper cells showed a significant increase in length compared to the lower. A differential mitosis was also found, with the lower tissue being greater. We infer that the mitotic activity is indicative of cell division, and this division occurs strictly in the first 1.5 mm of the root meristem. The combined effect of differential cell elongation and cell division results in the localization of the geotropic curvature in the 1.5- to 2.5-mm region from the root meristem. Mitosis that occurs primarily in the cortex and stele were asynchronous; the peak of cortical division preceded that of the stele. Both peaks occurred before the peak of geotropism. A densely stained layer separates the cap from the root meristem. This layer is thinner at the apex of the root meristem. The area of the thin region increased with time and peaked at 180 minutes after geostimulation, which was coincidental with the peak of the geotropic response.
我们研究了地心引力刺激、红光照射的玉米（Zea Mays，威斯康星杂交种64A×22R）初生根不同组织中的细胞长度、有丝分裂和根分生组织“角质层”。每隔15分钟进行一次检查，持续240分钟。根分生组织上方和下方细胞伸长的差异在距根分生组织1.5至2.5毫米处最为显著；外皮层的伸长生长最大，上方细胞的长度与下方相比显著增加。还发现了有丝分裂差异，下方组织的差异更大。我们推断有丝分裂活性表明细胞分裂，这种分裂严格发生在根分生组织的前1.5毫米处。细胞伸长差异和细胞分裂的综合作用导致向地性弯曲定位在距根分生组织1.5至2.5毫米的区域。主要发生在皮层和中柱的有丝分裂是不同步的；皮层分裂的峰值先于中柱。两个峰值都在地向性峰值之前出现。一层染色浓密的层将根冠与根分生组织分开。这一层在根分生组织的顶端较薄。薄区域的面积随时间增加，并在地心引力刺激后180分钟达到峰值，这与向地性反应的峰值一致。
