Dependence of thermal responses of seeds on membrane transitions.

Transitions at 28-32 degrees C in membranes of many kinds of seeds influence their germination and subsequent growth. Changes at 28-32 degrees C in the rates of loss of endogenous amino acids from imbibed Barbarea verna and Lactuca sativa seeds indicate permeation of the plasma membrane. A transition in the same temperature range is shown by the change in fluorescence with temperature of substituted naphthalenesulfonate probe molecules associated with membrane fragments isolated from the seeds. Some other plant responses that appear to be causally connected with the membrane(s) transition(s) in the 28-32 degrees C region are growth of maize seedlings and tomato roots, flowering of some bulbs, and control of seed and fern spore germinations by light. Generality of the control is indicated.