Studies on Auxin-membrane Permeability Relations in Fruit and Leaf Tissues

Abstract

Studies of fruit and leaf tissues demonstrate that auxin (indoleacetic or naphthalene acetic acids) delays senescence by effecting maintenance of membrane properties. Whereas in water-treated tissues permeability changes occur in ca. 4 days, the addition of auxin delays this process for up to 30 days. Permeability changes in bean endocarp are indicated by liquid-logging of air spaces, increased rate of plasmolysis, exudation from tissue surfaces and increased leakage of cellular materials. Although the QO2 of water- and auxin-treated endocarp is comparable over a 9-day-period, water-treated tissue loses respiratory activity by 22 days while auxin-treated endocarp respires for over 45 days. Water-treated slices of Rhoeo discolor leaves exhibit liquid-logging of air spaces, cellular dissociation, browning and loss of anthocyanins within 5 days. These phenomena are delayed for 30 days by addition of 4 ppm auxin. Similar effects are obtained with segments of leaves of Mesembryanthemum. The possible relationship between permeability changes and phenomena attending senescence of certain fleshy fruits is discussed.