Effects of Gibberellic Acid on Barley Endosperm

Abstract

When slices of barley endosperm are incubated with gibberellic acid in aseptic conditions the activities of salt‐soluble endo‐β‐glucanase and endopentosanase are greatly augmented and enzymes and soluble products of cell‐wall degradation (hexosan and pentosan) are secreted into the surrounding medium. This cytolytic action, together with the enhanced amylolytic activity which can be detected in isolated endosperms subjected to gibberellic acid, is sufficient to cause complete solubilization of the starchy endosperm in 3 days at 25° C. Gibberellic acid acts through the respiring aleurone layer; it has no effect on aleurone‐free endosperm or on endosperm slices in which the aleurone has lost the power of reducing tetrazolium salts. Gibberellic acid‐induced sugar secretion from endosperm slices is maximal at 30° C. and completely inhibited at 37° C. and secretion both of sugars and of endo‐β‐glucanase is unaffected in conditions which inhibit proteolysis. Excised barley embryos show no response to added gibberellic acid. It is suggested that, when barley germinates without additions of gibberellic acid, endogenous gibberellin present in the embryo is translocated to the aleurone where it induces secretion of hydrolytic enzymes from subcellular particles, so causing modification to proceed inwards from the aleurone; if this is so, then added gibberellic acid merely enhances the effects of the endogenous component.

Regulation of Bud Rest in Tubers of Potato, Solanum tuberosum L

“…10 JAc of L-leucine-U-14C (specific radioactivity 200 mc/mmole); 25 JAc of L-phenylalanine-3H (specific radioactivity 2.5 c/mmole); 50 ,uc of L-leucine-3H (specific radioactivity 2 c/mmole); 10 MAc of L-phenylalanine-4C + 9 X 10-5 M GA3; 10 Ac of L-leucine-…”

“…Application of gibberellic acid promotes sprouting of intact tubers during tuber development or after they are harvested as marketable (23,36,38). Gibberellins occur naturally in potato tubers and increase in concentration at about the time that sprouting begins (31,46 the level of enzymes associated with carbohydrate metabolism (4,19,25,32). There is mounting evidence that the hormone can induce synthesis of several hydrolytic enzymes (6,14,20,49,50).…”

Physiological Effects of Gibberellic Acid. IX. Recovery of Gibberellic Acid Following Incubation with Endosperm

“…To (letermmiie the fate of gibberellic acid (GA,.) (5,12,14), aIndI it is qtuite clear that the initial loctus of hormonal activity resides in the aleturoine layer which suirrotuinds the starchv portion of the en(losperm (5,11).As a l)ioassay for GA, the release of re(duicing suigar has proved to be a simple, specific, reliable aild extremely sensitive assay with several major aclvantages over other hioassay's (2,6 …”

“…Mlany areas of metabolism are involved, not only carbohydrates (5,12,14), aIndI it is qtuite clear that the initial loctus of hormonal activity resides in the aleturoine layer which suirrotuinds the starchv portion of the en(losperm (5,11).…”

“…The initiation of several different kinds of enzy-me activity in addition to amylolytic activit) has been observed (5,8,14). It has b)een determinie(d also that a-amylase is synthesized (le nlovo as a colnsequence of hormone action (12,13) ((fig 2).…”