Fat Utilization and Composition in Germinating Cotton Seeds.

Abstract

Diminuition of the fat reserve and concomitant increase of carbohydrate during germination of oil seeds have been well established (3,7,10,11,12,13,16). Few studies, however, have compared illuminated and unilluminated seedlings, or have controlled the environmental conditions to the degree necessary for calculation of a rate constant and for prediction of fat content at various stages of growth. MacLachlan (9) found a greater utilization of fat during soybean germination in the light than in the dark. He concluded that there was no preferential utilization of unsatuirated fatty acids, because no change was observed in the average unsaturation of the fatty acids in the cotyledons. But Holman (6), also using soybeans, reported a decrease in the iodine value of the fat reserve and a preferential utilization of linoleic and linolenic acid. Crombie and Comber (2) found that during the germination of seeds of the watermelon (Citruillus vulgaris) all the major fatty acids, except oleic, disappeared at rates proportional to the quantities present in the seed fat. Oleic acid was metabolized relativelv faster than the other fatty acids.A better understanding of the relations of fats to general metabolism may be expectedI to result from quantitative physiological and chemical studies of germinating fatty seeds. The extent to which reserve fats and current photosynthate contribute to the material and energy requirements for seedling growth represents one aspect of the broad problem. There is also a need for more analytical data on the changes that occur in the fatty acid composition of the glycerides as the fat reserve is utilized.The experiments reported in this paper were undertaken to study the rate of utilization and the composition of the fat reserve during cotton seed germination under various growth condlitions. To correlate the decrease in fat content with the growth of the seedlings, measurements were made of the development of the root, hypoeotyl, and cotyledon. The cultures were put in the particular evironment under study, and the testas were slipped off 3.5 hours later. For the experiments in the light the cultures were placed on a rotating table (20). Concentric daylight fluorescent tubes and a Mazda bulb provided a light intensity of 5300 meter candles at the surface of the bobbinet and 6700 meter candles at the level of the cotyledons of plants that had grown for 7 days.At suitable time intervals the plants were dissected into cotyledons, hypocotyls, and roots. The cotyledons were dropped in boiling water for one minute to arrest enzyme activity. They were dried at 450 C to a moisture content of 5 %, and the remaining water was removed at 550 C in a vacuum oven. The dried cotyledons were passed through a 20-mesh screen in a Wiley mill, extracted (Soxhlet) with petroleum ether (b.p. 30 to 600 C) for 24 hours, ground to fine particles with a mortar and pestle, and then reextracted with petroleum ether during a 2nd 24-hour period. After the solvent had been removed in a vacuum oven at 400 C, the crude lipide w...

Lipolysis and the Free Fatty Acid Pool in Seedlings

“…This is clear from the data presented here where control of enzyme activity was achieved by raising the pH and by adding pCMB. White (19), and Crombie and Comber (6) accomplished the same purpose by boiling the seed before maceration. Ching (4) also shows a low FFA in Douglas fir seeds; in this instance it apparently was not necessary to destroy activity before maceration.…”

Adaptability of Pecan as a Species

“…During this dependency period, only about half of the seed's lipid content is used by the developing seedling. The long dependency and limited recycling of stored reserves contrasts markedly with the rapid depletion (4 to 14 d from germination) of reserve materials and the short dependency in many plants (Ching, 1963(Ching, , 1966Miller, 1938;Von Ohlen, 1931;Varner, 1965;White, 1958). During the dependency period, radicle (taproot) elongation is 20 to 25 cm before the epicotyl emerges, whereby conferring a competitive advantage in the acquisition of soil moisture during the critical germination period.…”

Fat Metabolism in Higher Plants

“…acids produced may vary during, for example, aging of potato tuber tissue (Willemot and Stumpf [43]) or alteration of oxygen available to plants (Harris and James [14]). White (42) found that cotton seeds deplete stored linoleic and saturated acids faster than oleic whereas germinating watermelon studied by Hardman and Crombie (13) showed a relatively unspecific breakdown of stored fat.…”