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.

Use of an in vitro tuberization system to study tuber protein gene expression

Abstract: Nodal cuttings from micropropagated potato plantlets give rise to microtubers when placed on Murashige and Skoog medium containing 6% sucrose and 2.5 mg/liter kinetin and incubated in the dark at 19 degrees C. Microtubers produced from the cultivar Superior were shown to contain the same characteristic group of proteins as field-grown tubers. As with field-grown tubers, the 40,000-dalton major tuber glycoprotein, patatin, accumulated to high levels in microtubers, reaching 3.7 +/- 0.2 mg/g fresh weight after 90 d. Also in agreement with field-grown plants, stems and leaves of micropropagated plantlets did not contain detectable levels of patatin, but small amounts of an electrophoretically distinct form accumulated transiently in roots. Patatin mRNA is readily detectable in developing microtubers 15 d after transfer of the cuttings to inductive medium. Patatin mRNA was also present in roots, but as with field-grown plants, was 50- to 100-fold less abundant and could be distinguished from that in tubers by primer extension. Microtuber development and patatin accumulation were inhibited by gibberellic acid.

Sucrose Loading in Isolated Veins of Pisum sativum: Regulation by Abscisic Acid, Gibberellic Acid, and Cell Turgor.

Abstract: Enzymatically isolated vein networks from mature pea (Pisum sativum L. cv Alaska) leaves were employed to investigate the properties of sucrose loading and the effect of phytohormones and cell turgor on this process. The sucrose uptake showed two components: a saturable and a first-order kinetics system. The high affinity system (Km, 3.3 millimolar) was located at the plasmalemma (p-chloromercuriphenylsulfonic acid and orthovanadate sensitivity). Further characterization of this system, including pH dependence and effects of energy metabolism inhibitors, supported the H+-sugar symport concept for sucrose loading. Within a physiological range (0.1-100 micromolar) and after 90 min, abscisic acid (ABA) inhibited and gibberellic acid (GA3) promoted 1 millimolar sucrose uptake. These responses were partially (ABA) or totally (GA3) turgor-dependent. In experiments of combined hormonal treatments, ABA counteracted the GA3 positive effects on sucrose uptake. The abolishment of these responses by p-chloromercuriphenylsulfonic acid and experiments on proton flux suggest that both factors (cell turgor and hormones) are modulating the H+ ATPase plasmalemma activity. The results are discussed in terms of their physiological relevance.

Hydrolysis of storage proteins in barley endosperms : analysis of soluble products.

Abstract: Soluble products, released by the hydrolysis of hordeins into the media of barley (Hordeum vulgare cv. Perth) half-seeds were analyzed. Large polypeptide fragments (methanol-insoluble) were identified using the Western immunoblot technique with the antibodies prepared against B and C polypeptides of hordein. A number of hordein IgG-reacting bands were noted in the samples from dry kernels. In samples incubated in the absence of gibberellic acid, polypeptide fragments in the size range of 25 to 30 kilodaltons appeared within 24 hours, and those in the size range of 40 kilodaltons became more prominent. In samples incubated in the presence of gibberellic acid, polypeptide fragments in the size range of 45 to 67 kilodaltons were less apparent and those in the size range of less than 15 kilodaltons were more pronounced. The hordein-related polypeptide fragments were present in low amounts after 72 hours in the presence of gibberellic acid. Methanol-soluble peptides were fractionated, on the basis of size, into two broad peaks. In the absence of gibberellic acid, there was no significant change in their profile over a 72 hour incubation period. In the presence of this growth substance, however, there was a decrease in the proportion of large size peptides (50-70 amino acid residues in length), and an increase in the levels of small peptides (15-35 amino acid residues in length) and amino acids. Our interpretation of the results is that the release of the initial large polypeptide fragments from hordein proteins is mediated by a protease(s) whose appearance is not dependent on the exogenously added gibberellic acid. Further hydrolysis is, however, mediated by proteases induced in the presence of this growth substance.

Patterns of modification in malting barley

Abstract: The modified regions of the starch endosperms of malted grains were fragile and, in thin sections, the cell walls in these regions did not stain readily with Congo Red or Trypan Blue, although scanning electron microscopy demonstrated some cell-wall material remained. Initially the enzymes causing modification came from the scutellum, but later more came from the aleurone layer. Patterns of modification in different grains differed significantly, but usually resembled those recorded previously6 except that often modification had advanced further by the nucellar sheaf cells. In grains treated with gibberellic acid modification advanced faster, particularly beneath the aleurone layer, after two days germination. In tumbled or commercially abraded grains, malted with gibberellic acid, modification was even more rapid, but in more than 99% of the grains the same patterns of modification occurred. Two-way modification was a rare event. Rapid, general sub-aleurone modification occurred in grains cut at the apex and dosed with gibberellic acid. Decorticated grains modified exceptionally quickly and, when treated with gibberellic acid, massive subaleurone modification occurred. The cell walls of the tissues that resisted modification fluoresced strongly in ultra-violet light, in contrast to those of the starchy endosperm.

Effects of Kinetin and Other Plant Growth Regulators on Starch Degradation

Abstract: IT has been known since the work of Hayashi1 that gibberellins stimulate the activity of amylase in germinating barley and wheat grains. This work has been extended by Paleg2–4, who has reported an increase in the activity of both α- and β-amylases in barley endosperm following treatment with gibberellic acid (GA3). So far as we are aware this communication is the first to suggest that kinetin may also play a part in starch degradation. This effect of kinetin was first suspected when young excised wheat coleoptiles treated with solutions of gibberellic acid and kinetin5 were stained with iodine. Starch was found to be present in the control coleoptiles whereas in those treated with the two growth regulators no starch was detectable. Estimations of reducing sugars in extracts of these coleoptiles, after treatment, also demonstrated that the growth response promoted by these two growth regulators was accompanied by starch breakdown (Table 1). When excised coleoptiles were grown in D-glucose solution alone the starch remained and yet the maximal growth response was as great as with kinetin. These results thus indicated that the growth responses induced by GA3 and kinetin in young coleoptiles could be explained, at least in part, simply in terms of the liberation of D-glucose. Indolyl-3-acetic acid produced no measurable effect on growth or starch breakdown (Table 1).