RESUMEN
The lipid composition of Avena sativa stem segments was manipulated using BASF 13-338 (formerly Sandoz 9785) and growth temperature, in order to establish whether there were correlations between responsiveness of the tissue to gibberellic acid (GA(3)) and the presence, before hormone treatment, of specific lipid components. High correlations were obtained between GA(3)-induced growth and total phospholipid, individual phospholipids, and fatty acids (except for linolenic acid), total saturated fatty acids, stigmasterol content, and the unsaturated/saturated fatty acid ratio. It was concluded that, although the lipid composition, and particularly the total saturated fatty acid content, seem to be important contributory determinants of the GA(3)-induced growth response in this system, they may not be obligatory prerequisites, nor the only endogenous factors capable of influencing the response. However, the results are consistent with the hypothesis that membranes are involved in the hormonal mechanism and/or very early stages of the mode of GA(3) action in this tissue.
RESUMEN
A micro-growth measuring technique was used to determine the growth response of stem segments of Avena sativa cv. Avon to a variety of gibberellic acid (GA(3)) concentrations over a range of incubation temperatures. Growth rate varied with GA(3) concentration, the temperature at which the rate was measured, and the growth temperature of the plants prior to excision of the segments. The curves relating segment extension rates to temperature were affected by GA(3) such that the linear portion of the curve was shifted to higher rates as GA(3) concentration was increased. The results seem to be analogous to the GA(3)-induced shifts of thermally induced phase transitions in glucose leakage from liposomes, observed earlier (Wood, Paleg 1974 Aust J Plant Physiol 1: 31-40).