Gibberellic acid

About: Gibberellic acid is a research topic. Over the lifetime, 6597 publications have been published within this topic receiving 109294 citations. The topic is also known as: GIBBERELLIN A3.

Gibberellin response in lettuce hypocotyl sections.

Abstract: Excised lettuce (Lactuca sativa L.) hypocotyl sections retain the ability to elongate in response to gibberellic acid (GA3) addition. In 48 hr at 30 C a GA3-treated segment more than doubles while a control segment elongates less than 50%. Auxin has no detectable effect on this system. Sensitivity to GA3 is not decreased by apex or root removal. Of the experimental variables tested, temperature, sucrose, and preincubation in water affect growth both with and without GA3. Blue and far red light inhibit growth without GA3; this inhibition is reversed by GA3. Potassium chloride stimulates growth of illuminated sections treated with GA3 but has no effect on control growth. When sections are incubated in the dark, KCl has a promotive effect on elongation.

Gibberellic Acid-Enhanced Synthesis andRelease ofa-Amylase andRibonuclease byIsolated Barley Aleurone Layers

Abstract: Summnary. Gibberellic acid enhances the synthesis of a-amylase in isolated aleurone layers of barley-seeds (Hordeumn vulgare var. Himalaya). In the presence of 20 mm calcium chloride the amount of enzyme obtained from isolated aleurone layers is quantitatively comparable to that of the half-seeds used in earlier studies. After a lag period of 6 to 8 hours enzyme is produced at a linear rajte. Gibberelflic acid does not merely trigger a-amylase synthesis, but it is continuously required during the period of enzyme formation. Enzyme synlthesis is inhibited by inhibitors of protein and RNA synthesis. Small amounts of actinomycin D differentially inhibit enzyme release and enzyme synithesis suggesting 2 distinct processes. Gibberellic acid similarly enhances the formation of ribonuclease which increases linearly over a 48 hotur period. During the first 24 hours the enzyme is retained by the aleurone cells and this is followed by a rapid release of ribonuclease during the next 24 hour period. The capacity to release the enzyme is generated between 20 and 28 hours after the addition of the hormone. Ribonuclease formation is inhibited by inhibitors o-f protein and RNA synthesis. These inhibitors also prevent the formation of the release mechanism if added at the appropriate moment.

Effects of gibberellic acid on patterns of carbohydrate distribution and acid invertase activity in Phaseolus vulgaris

Abstract: The application of gibberellic acid (GA3,10 μM) as a root drench to 16-day-old plants of Phaseolus vulgaris L. cv. Masterpiece stimulated growth of the stem internodes and reduced root growth. GA3 treatment did not affect the export of 14C from a primary leaf to which [14C]-sucrose was applied, but greatly increased upward translocation to the elongation region of the stem at the expense of transport to the hypocotyl and root system. The observed changes in the patterns of growth and [14C]-labelled assimilate distribution were correlated with an increase in the specific activity of acid invertase in the elongating stem internodes and a decrease in invertase activity in the hypocotyl and root. Sucrose concentration in the elongating internodes fell substantially after treatment with GA3 while the concentration of hexose sugars increased. We suggest that by stimulating acid invertase synthesis in the elongating internodes, GA3 acts to establish a more favourable sucrose gradient between these sinks and source leaves. Under source-limiting conditions this, in turn, will lead to a reduced rate of assimilate translocation to competing sinks in the root system.