Correlation between the Lipid Composition and the Responsiveness of Avena sativa Stem Segments to Gibberellic Acid

Abstract

The lipid compositon of Avena sativa stem segments was malated using BASF 13-338 (formerly Sandoz 9785) and growth temperature, in order to establish whether there were correlations between responsiveness of the tissue to gibberelic acid (GA3) and the presence, before hormone treatment, of specific lipid components. High correlations were obtained between GA3-induced growth and total phospholipid, individual phospholipids, and fatty acids (except for lnolenic acid), total saturated fatty acids, stigmasterol content, and the unsaturated/saturated fatty acid ratio. It was concluded that, although the Upid composition, and particularly the total saturated fatty acid content, seem to be important contributory determinants of the GA,-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 GA3 action in this tissue.Previous studies using Avena sativa stem segments showed that short-term GA3 treatment resulted in no marked changes in lipid components, although significant growth response to the hormone was achieved (6, 7). Moreover, it was suggested (8) that GA3 in this system may be acting in a similar way to GA3 in the liposomal system of Wood and Paleg (16), ie. by interaction with a membrane phospholipid component. Evidence suggests that in model membrane systems lipid composition markedly affects hormonemediated responses (11,15), and hormone-phospholipid interaction was influenced by fatty acid composition (9). This hypothesis could be further tested by examining the GA3-response of Avena stem segments with different lipid compositions before hormone treatment. One of the most obvious ways by which this could be achieved is by alteration of growth temperature. The degree of unsaturation of fatty acids in the membrane systems of many plants and ectothermic organisms is strongly influenced by the environmental temperature (4, 14). Exposure to low temperature seems invariably associated with an increase in unsaturation of the fatty acid chains of phospholipids in a wide variety of species at all levels of biological organization. Similar changes in membrane protein have not been found (5, 12), apart from those occurring as a consequence of changes in the lipid moiety of the membrane in response to the low temperature (17).Another method of altering lipid composition is through the use of compounds which are thought to selectively inhibit synthesis of a membrane component. One such component is BASF 13-338 (4-chloro-5-[dimethylaminoJ-2-phenyl-3[2H]-pyridazinone) (formerly known as Sandoz 9785), a pyridazinone herbicide which reportedly selectively blocks the synthesis of linolenic acid (18:3), thus producing a decrease in 18:3 accompanied by an increase in linoleic acid (18:2), without a shift in the relative proportion of unsaturated/saturated fatty acids of the tissu...

Low Temperature-Induced GA3 Sensitivity of Wheat

“…The case of linolenic acid (18:3) deserves special mention as it was the only fatty acid constituent of PC and PE to have an insignificant r value. This is similar to the results reported by Jusaitis, Aspinall, and Paleg (14) in which 18:3 was always poorly correlated with the GA3-induced growth response ofAvena sativa stem segments. The fact that only 18:3 seems to be poorly correlated with two different responses of two different tissues to GA3 is quite remarkable.…”

Nutritive evaluation and milk quality of including of tomato or olive by-products silages with sunflower oil in the diet of dairy goats

“…Despite SFO supplementation, not many differences were found in diets' FA profile apart from the higher percentages of PUFA and linoleic acid (LA; C18:2 n-6) detected in the TSD, that could have been caused by the richness in those FA in tomato seeds (Romano et al, 2010). The reasons for having a high content in LA and linolenic acid (LNA; C18:3 n-3) in CD could be ascribed to the oats hay because oats grains, that come mixed in the hay, are rich in LA (Elke and Zannini, 2013) while a high content in LNA has been reported in oats stems (Jusaitis et al, 1982).…”