| Abstract: | Fifteen serial sections, each 1.0 mm. in length, have been takenfrom the tip towards the base of the bean root. On correspondinggroups of sections determinations have been made of water content,protein content, and of dipeptidase, glycine oxidase, phosphatase,and invertase activities. The number of cells in each sectionof the series has also been determined. From these data unitcell values have been calculated which show how each of thequantities involved changes as the cell grows. It has been shown that four phases are involved in the earlydevelopment of the cell. In the first, which is traversed inthe meristematic zone of the root, the volume increases slightly,the protein content decreases, and the activities of three ofthe enzymes studied also decrease. In the second, volume, proteincontent, and all enzyme activities increase considerably. Inthe third, while the volume enlarges by increase in breadthonly, protein content and enzyme activities decrease. In thefourth, growth has ceased and protein content, and enzyme activitiescontinue to decrease. The significance of these changes in discussed. |
