METABOLIC CHANGES AND SENESCENCE IN CULTURED PEA ROOT TISSUE

Abstract

SummaryThe changes occurring during the maturation, senescence and death of cells in pea roots grown in sterile culture were followed for 30 days after growth by cell extension had ceased. Gross analysis of DNA content and various enzyme activities, analyses of several nitrogen fractions showed that complex changes occurred between the cessation of cell expansion and the death of the root cells. Although the tissue analysed was not homogeneous in cell type, histochemical and anatomical investigations of the distribution and number of nuclei within the root, DNA content of these nuclei and acid phosphatase distribution enabled gross changes to be correlated with changes in the cells of various regions within the root cortex.From the changes observed in the root segment as a whole, two types of process were associated with changes in the cells of the root cortex. The first was a rise in the DNA and protein content of certain areas of the root cortex. It is suggested that this is a consequence of the interaction between the older and younger regions of the root and is not a general characteristic of senescence in cells. The majority of the changes observed were, in general, very similar to those already found in other higher plant systems such as ageing fruits and starving leaves, and were associated with the senescence and death of cortical cells.