Physiological Effects of Gibberellins

Changes in Thiol and Disulphide Contents in Barley Embryos During Dormancy and After-Ripening

“…There they initiate or stimulate the production of hydrolytic enzymes, possibly in association with thiol-containing compounds.18 In turn, these enzymes release amino acids and sugars from the endosperm, necessary for further growth of the seedling.13 .m. [17][18] In embryos of after-ripened wheat Kefford & Rijven6 found gibberellic acid to have a two-fold effect: (a) promotion of cell elonga tion in the embryo, and (b) mobilization of reserve substances in the endosperm. These findings perfectly fit in with the germination scheme described above.…”

“…".».» and MacLeod". 18 have made the suggestion that during germination of after-ripened barley these substances move from the embryo to the endosperm, where they induce the aleurone cells to produce hydrolytic enzymes: amylases, proteinases, endo-fl-glucanase, endopentosanase, etc. "»ia»1B«1* In turn, these enzymes release from the endosperm amino acids and sugars, which the seedling needs for growth.…”

Decapitated Peas and Diffusible Gibberellins

“…Certain features of the response are of interest in other respects, as well as in connection with the bioassay. As pointed out by Paleg (1965) there is conflicting evidence in the literature pertaining to the question of whether or not gibberellin can replace the pea stem apex in its ability to stimulate elongation of the sub tending internodes. Lockhart (1957) has suggested that GA3 can, and Vlitos and Meudt (1957) and Kuraishi andMuir (1963, 1964) have concluded that GA3 cannot replace the apical control of internode elongation in decapitated peas.…”

An Early Response to Gibberellic Acid Not Requiring Protein Synthesis

“…Himalaya) aleurone layers show phosphorylcholine glyceride transferase activity greater than that from control layers. The increase in activity is not prevented by a mixture of amino acid analogs nor by cordycepin under con-ditions in which it is demonstrated that the analogs and the cordycepin are entering the cells in effective concentrations.We conclude therefore that the GA3-dependent increase in phosphoryleholine glyceride transferase activity (which occurs within the first 4 hours of GA3 treatment) does not require RNA synthesis or protein synthesis.Gibberellins control the production and secretion of hydrolases in barley aleurone cells (19,22). At least three of these hydrolytic enzymes, a-amylase (9), protease (12), and ribonuclease (1), are synthesized de novo in response to added gibberellic acid.…”