Some Physiological Changes Occurring during the Senescence of Auxin-Deprived Pear Cells in Culture

Publisher Website
Google Scholar
Abstract
Part of the changes in the hormonal balance involved in plant senescene is due to an auxin limitation. Some of its physiological consequences were studied using pear (P. communis L.) cells cultured in a continuously renewed medium in which 2,4-D was absent. In these conditions, an assessment was made of the absence of nutrient deficiency. In the period preceding cell death, the rate of respiration and ethylene production remain low and no major changes occurred in the total protein and RNA content of the cells. Beginning at .apprx. day 9, an important efflux of 3 amino acids (serine, threonine and aspartic acid) occurred among which serine represents > 52%. Exogenous serine supplied to the medium fails to show any senescence promoting effect. At the same time, leucine uptake and incorporation sharply and simultaneously increased. The presence of 2,4-D inhibits these phenomena and prevents cell death. Evidently, auxin deprivation is responsible for unmasking a program of synthesis of new proteins involved in cell death.