Effects of gibberellic acid and zeatin on the growth response of cucumber cotyledons

In contrast to cytokinin, gibberellic acid has no effect on the growth of the isolated cucumber cotyledon in darkness. Like cytokinins in light, gibberellic acid causes increases in fresh weight and area of the cotyledon at concentrations from 10^–7 to 10^–3 M. Radiant energies in the blue, red, and far-red regions of the spectrum all induce the growth responses to gibberellic acid. The effect of the far red is greater than that of the red, which is greater than that of the blue. Gibberellic acid is ineffective in the promotion of chlorophyll development, whereas cytokinins are very effective. Although zeatin and gibberellic acid both cause an increase in fresh weight and area of the cotyledons in light, they appear to have entirely separate actions in the growth responses.     

Red light enhancement of the phototropic response of etiolated pea stems

In the subapical third internode of 7-day-old etiolated pea seedlings, the magnitude of phototropic curvature in response to continuous unilateral blue illumination is increased when seedlings are pre-exposed to brief red light. The effect of red light on blue light-induced phototropism becomes manifest maximally 4 or more hours after red illumination, and closely parallels the promotive action of red light on the elongation of the subapical cells. Ethylene inhibits phototropic curvature by an inhibitory action on cell elongation without affecting the lateral transport of auxin. Pretreatment of seedlings with gibberellic acid causes increased phototropic curvature, but experiments using ¹⁴C-gibberellic acid indicate that gibberellic acid itself is not laterally transported under phototropic stimuli. Neither red light nor gibberellic acid treatment has any promotive effect on blue light-induced lateral transport of ³H-indoleacetic acid. Under conditions where phototropic curvature is increased by red light treatment, low concentrations of indoleacetic acid applied in lanolin paste to the apical cut end of the seedling cause an increased elongation response in subapical tissue. This could explain increased phototropic curvature caused by red light treatment.     

Gibberellic Acid-Promoted Lignification and Phenylalanine Ammonia-lyase Activity in a Dwarf Pea (Pisum sativum)

The effects of gibberellic acid on lignification in seedlings of a dwarf and a tall cultivar of pea (Pisum sativum) grown under red or white light or in the darkness, were studied. Gibberellic acid (10⁻⁶-10⁻⁴ m) promoted stem elongation in both light and dark and increased the percentage of lignin in the stems of the light-grown dwarf pea. The gibberellin had no effect on the lignin content of the tall pea although high concentrations (10⁻⁴ m) promoted growth of the tall plants. Time course studies indicated that the enhanced lignification in the gibberellin-treated dwarf plants occurred only after a lag period of several days. It was concluded that gibberellic acid-enhanced ligmification had no direct relation to gibberellic acid-promoted growth. The activity of phenylalanine ammonia-lyase (E.C. 4.3.1.5) was higher in gibberellin-treated dwarf plants grown under white or red light than in untreated dwarf plants. Gibberellic acid had no detectable effect on the activity of this enzyme when the plants were grown in darkness, just as it had no effect on lignification under dark conditions. The data suggest that in gibberellin-deficient peas the activity of phenylalanine ammonia-lyase is one of the limiting factors in lignification.     

Actions of gibberellic Acid and phytochrome on the germination of grand rapids lettuce seeds

Red light and gibberellic acid were about equally effective in promoting germination of Grand Rapids lettuce (Lactuca sativa L.) seeds. With initial far red light treatment more than 80% remained dormant in subsequent dark storage. After 2 days of dark storage, red light effectively promoted germination, while gibberellic acid action was weak. With between 2 and 10 days of dark storage, gibberellic acid had little effect, while promotion by red light decreased slowly and finally disappeared. After 10 days of dark storage, both gibberellic acid and red light were required for germination. The dark storage treatment interferes with phytochrome-independent germination processes and cannot be overcome by added gibberellic acid. However, storage may also decrease the effectiveness of endogenous gibberellins. Phytochrome-dependent germination seems to require only low levels of endogenous gibberellin activity or the addition of gibberellic acid. Gibberellins and red light appear to act on germination by regulation of sequential sites of a branched-looped pathway.     

Promoting Effect of Fusicoccin on Seed Germination

The effects of fusicoccin on the germination of dormant, light-requiring or abscisic acid-inhibited seeds has been investigated. (1) Fusicoccin (10^?6M) induces germination in dormant wheat seeds (Triticum durum cv. Cappelli; 1972 crop) and stimulates it in seeds already relieved from dormancy (1971 crop), with an effect similar to that of gibberellic acid. (2) Fusicoccin (1.5 × 10^?6M) is more active than the two phytohormones gibberellic acid and benzyladenine and than white light in stimulating light-requiring lettuce seeds (Lactuca sativa cv. Grand Rapids) to germinate. Germination of radish seeds (Raphanus sativus) is also accelerated by fusicoccin, while benzyladenine and gibberellic acid are less active in this material. (3) Fusicoccin (1.5 × 10^?5M) removes almost completely the inhibitory effect of abscisic acid on germination of radish and lettuce seeds, whereas benzyladenine (10^?4M) and gibberellic acid (3 × 10^?4M) remove the inhibition only partially. The possible relationship between these results and previous information on growth by cell enlargement is discussed in terms of the mechanism of action of fusicoccin as compared with natural hormones.     

Loss of short-day requirement for dormancy breaking of bulbils from gibberellic acid-treated plants in Sedum bulbiferum

Sedum bulbiferum forms bulbils at superterranean nodes under long-day conditions, and the detached bulbils sprout after exposure to short-days [1]. When gibberellic acid was applied to the mother plant at the start of the long-day induction period, the number of bulbils formed increased slightly and these bulbils sprouted on incubation in the dark but not under short days of continuous light. However, when gibberellic acid was applied directly to detached bulbils during incubation, the short-day requirement for sprouting was conserved. Gibberellic acid application to the mother plants enhanced sprouting ability of detached bulbils when incubated under illumination with blue, green or far-red light. However, presence of gibberellic acid during bulbil exposure to light did not induced marked enhancement in sprouting under blue, green of far-red light. Thus, gibberellic acid application to the mother plant modified light and photoperiodic requirements for the sprouting of detached bulbils of S. bulbiferum.     

Responsivencess of Intact and Scarified Seeds of Barbarea vulgaris to Gibberellic Acid and Changes in Phytochrome

Either red light or millimolar levels of gibberellic acid promoted germination of seeds of yellow rocket (Barbarea vulgaris R. Br.), and their effects were generally additive. Buffering the substrate pH at 3.0, addition of 20 mM nitrate to the substrate, preliminary incubation at 10 or 30°C, and brief scarification of the seeds increased responsiveness of the seeds to gibberellic acid. Scarification increased several thousandfold the sensitivity of the seeds to gibberellic acid. Pretreatment of the seeds in darkness or far-red light did not lower their responsiveness to gibberellic acid. These results suggest that uptake of gibberellic acid is a limiting factor in the stimulation of germination in intact seeds and that there is only a minimal requirement for active phytochrome to express gibberellic acid action.     

Modification of logarithmic growth rates of tobacco callus tissue by gibberellic Acid

Logarithmic growth rates (either fresh or dry weight basis) of tobacco callus tissues grown on 10⁻⁴ to 10⁻¹ μm cytokinin are increased if gibberellic acid (10⁻³-2 μm) is incorporated into the medium. At higher (1-10 μm) cytokinin concentrations gibberellic acid has little effect on growth rate but extends the duration of logarithmic growth. The gibberellic acid effect is noticeable only after one weight doubling, is dependent on concentration, and occurs when either glucose or sucrose is used as carbon source. The gibberellic acid response includes a decrease in percentage of dry weight relative to control tissues. The maximum dry weight yield, although achieved sooner than controls, does not differ appreciably from yields of tissue not treated with gibberellic acid.     

The effect of light quality and gibberellic acid (GA3) on photosynthesis and respiration rates of pea seedlings

CO₂ exchange were measured on pea seedlings (Pisum sativum L. var. Bördi) cultivated from seeds imbibed either in water (C-plants) or in gibberellic acid (GA₃) at the concentration of 25 g/1 (GA-plants), and then grown under 17 W/m² blue light (B-plants) or 11 W/m² red light (R-plants).When measured under the same light conditions as during growth the net photosynthesis (APS) rate in B-plants was about twice higher than that in R-plants. Dark respiration (DR) rate was 70% higher in B- than in R-plants. Red light retarded the development of photosynthetic activity, but GA₃ suppressed this effect. The hormone enhanced net photosynthesis and dark respiration to the same extent.When measured under saturating white light net photosynthesis rate of C-plants was also two times higher in B-plants than in R-plants. Growth conditions had only a slight effect on the APS of GA-plants under white light. APS rates of GA-plants grown under red light were higher under white light than those of C-plants, but lower than those of plants grown under blue light.We assume that blue light induced formation of plants that were adapted to higher light intensity: red light had an opposite effect, whereas gibberellic acid induced formation of plants that were adapted to medium light intensity.     

Obligate methylotroph <Emphasis Type="Italic">Methylobacillus arboreus</Emphasis> Iva<Superscript>T</Superscript> synthesizes a plant hormone,gibberellic acid GA<Subscript>3</Subscript>

An obligate methylotroph Methylobacillus arboreus Iva^Т (VKM B-2590^Т, CCUG 59684^T, DSM 23628T) is the first known aerobic methylotrophic bacterium capable of synthesis of the bioactive gibberellic acid GA₃. Primary separation and identification of gibberellic acid from the culture liquid of methanol-grown culture were carried out using thin-layer chromatography and high-performance liquid chromatography. The concentration and structure of the gibberellic acid GA₃ were determined by liquid chromatography?mass spectrometry (LC/MS). Biological activity of the isolated compound was confirmed by tests on sprouts of lettuce (Laсtuca sativa L.).     

Cyclization and hydroxylation stereochemistry in the biosynthesis of gibberellic acid

In Gibberella fujikuroi cultures, ent-[3β-³H,17-¹⁴C]kaurene is converted to gibberellic acid with retention of the tritium label at the 3α-position. This evidence for the stereochemistry of 3-hydroxylation also permits the stereochemistry of the ‘proton-initiated’ cyclization step in gibberellic acid biosynthesis to be deduced.     

The metabolism of soluble nucleotides in wheat aleurone layers treated with gibberellic Acid

The metabolism of soluble nucleotides was investigated in wheat (Triticum aestivum var. Olympic) aleurone layers treated with gibberellic acid. Whereas nucleotide levels were relatively unaffected by the treatment, a transient increase was observed in the incorporation of ³²P. The effect was maximal 30 to 60 minutes after gibberellic acid was administered, and by 180 minutes incorporation was lower than in the control. The greatest changes were detected in the nucleoside triphosphates, particularly in cytidine triphosphate. The findings are discussed in relation to the mode of action of gibberellic acid.     

Influences of Light Quality, Growth Regulators and Inhibitors of Protein Synthesis on Respiration of Protoplasts from Meristematic Cells in Barley Seedlings

The influences of light of different wavelengths and plant growthregulators on the respiration of protoplasts isolated from tissue0 to 5 mm above the basal intercalary meristem of barley (Hordeumvulgare L. cv. Patty) leaves were studied. Respiration was measuredusing oxygen electrodes and a Cartesian-diver technique. Red,far-red and blue light all stimulated respiration in the protoplastsbut not in mitochondria isolated from them. Gibberellic acid stimulated respiration in protoplasts but abscisicacid had the opposite effect. Physiological concentrations ofindole-3-acetic acid and kinetin had no influence in eitherdirection. Combinations of gibberellic acid with light of anywavelength always increased respiration. Red or far-red light treatments in the presence of abscisicacid decreased dark respiration and only blue light significantlyreversed the inhibitory effect of abscisic acid. Cycloheximidemarkedly increased dark respiratory activity; chloramphenicolwas without effect. These results indicate that mitochondrialactivity in the leaf basal intercalary meristem was partiallycontrolled through phytochrome and a blue light receptor, andby gibberellic and abscisic acids. Changes in cytosolic proteinsynthesis were important for the initiation of enhanced mitochondrialactivity in meristems. Hordeum vulgare L., barley, abscisic acid, Cartesian-diver microrespirometry, gibberellic acid, meristematic respiration, protoplasts     

Promotion by gibberellin of lettuce seed germiation as a function of presoaking period

Germination of lettuce seeds (Lactuca sativa L. cv. Grand Rapids)was examined in the presence of various doses (10^–5.0–10^–3.0M) of gibberellic acid applied at various times (hour 0–8)of soaking. Germination promotion by gibberellic acid was greateras the dose of gibberellic acid was increased and attenuatedwith the length of the presoaking period. As an exception, ca.95% germination was always evoked by the largest dose (10^–3M) of gibberellic acid given at any time of soaking. The dose-responsecurve obtained for each presoaking period had a distinct sigmoidalprofile. Synergistic and photoreversible promotion by red light of thegibberellin-induced germination was also investigated. Far-redlight pulse given 6 hr after the red pulse was still effectivein removing the red light action. Application of enzyme kineticsto the gibberellin action and also to the synergism betweengibberellin and red light was suggested. ¹National Institute for Basic Biology, Myodaiji, Okazaki 444,Japan. (Received December 18, 1979; )     

Requirement of sodium chloride for the action of gibberellic acid in stimulating hypocotyl elongation of a halophyte, Salicornia herbacea L.

NaCl stimulated hypocotyl elongation of the halophyte Salicorniaherbacea L. grown either in light or dark. Its optimal concentrationwas around 0.1–0.2 M and its promoting effect was muchmore prominent in the dark. Gibberellic acid at 10^–5 Mstimulated hypocotyl elongation in light but not in the dark.Indole-3-acetic acid and kinetin were ineffective in promotinghypocotyl elongation. In light, gibberellic acid and NaCl synergisticallyenhanced hypocotyl elongation when both were given simultaneously.The action of NaCl could be replaced by KCl, but not by mannitol.Osmotic pressure of the epidermis of the Salicornia hypocotylincreased in response to gibberellic acid and/or NaCl treatment.Na⁺ content in the hypocotyl increased with NaCl application.Gibberellic acid and NaCl when given alone increased the extensibilityof the hypocotyl cell wall. Synergistic interaction in increasingthe extensibility was observed between gibberellic acid andNaCl. Stress-relaxation analysis of mechanical properties ofthe hypocotyl wall revealed that gibberellic acid and NaCl actedsynergistically in decreasing minimum relaxation time. Basedon these results, a possible mechanism by which gibberellicacid and NaCl regulate hypocotyl elongation of Salicornia herbaceaL., a typical halophilic plant, is discussed. ¹ Present address: Laboratory of Biology, Tezukayama College,Gakuen Minami, Nara 631, Japan. (Received June 13, 1978; )     

Effect of gibberellic acid on photosynthesis and glycollate dehydrogenase in Anacystis nidulans

Gibberellic acid at 10^-4 Mxxx was optimal for enhancement of growth, O₂ evolution, photosystem II and I and the activity of glycollate dehydrogenase of Anacystis nidulans. A stimulatory effect was observed on photosystem II. Other concentrations of gibberellic acid were inhibitory to O₂ evolution and photosystem I. Syntheses of phycocyanin, phycoerythrin and -carotene were significantly enhanced after 48 h incubation with gibberellic acid at 10^-3 Mxxx but the chlorophyll content began to increase 3 h after adding 10^-4 Mxxx gibberellic acid.The author is with the Department of Biological Sciences, Faculty of Science, University of Science and Technology, Irbid, Jordan.     

Influence comparée de l'(±)-acide abscissique,de la coumarine,de l'acide p-coumarique et de certains de leurs dérivés sur la croissance de la première feuille de blé

Summary The activities of (±)-abscisic acid and a number of compounds derived from p-coumaric acid and coumarin and their interaction with gibberellic acid in the control of the elongation of the first wheat leaf are examined. (±)-Abscisic acid strongly inhibits leaf growth in the presence as well as in the absence of gibberellic acid, but the inhibition is greater in the presence of gibberellic acid (3 g/l already have an observable effect). Among other compounds, only ferulic acid and coumarin significantly reduce leaf elongation, and they are effective only at high concentrations (1.44 · 10^-4 M/l).     

Determination of GA3 in Chara vulgaris by capillary electrophoresis system

Method for simultaneous measurement of gibberellic acid was applied using capillary zone electrophoresis. Gibberellic acid was identified in extracts of apical part of thallus of Chara vulgaris L. The amount of gibberellins measured on the basis of activity determined by the micro-drop bioassay (59.8 mg·kg⁻¹; with gibberellic acid as a standard) was comparable with that estimated by capillary electrophoresis (54.9 mg·kg⁻¹).     

Effet de l'acide gibberellique (GA3) sur la croissance d'Asparagopsis armata (Rhodophycées,Bonnemaisoniales) en culture

Abstract

Effect of gibberellic acid (GA₃) on the growth of Asparagopsis armata in culture.—The gibberellic acid (GA₃) stimulates the growth of the Asparagopsis armata in culture. This effect was observed by adding doses of 6,5X10^?5M or 6,5X10^?7M of this acid in Von Stosch medium.     

On Dark-Germination and Antheridium Formation in Anemia phyllitidis

Schraudolf's finding is confirmed that gibberellic acid induces antheridia in Anemia phyllitidis and Lygodium japonicum. The activity spectra of gibberellic acid and the native antheridiogen of Anemia phyllitidis are similar: Both induce antheridia in the tested species of the family Schizaeaceae but are inactive towards the tested representatives of other fern families. However, the native antheridiogens of two schizaeaceous species are more species-specific in their action than is gibberellic acid. Anemia medium cancels the light requirement for spore germination as is the case with gibberellic acid. Chromatographic studies indicate that the dark-germination-inducing factor is identical with, or very similar to, the earlier demonstrated antheridiogen. The specificities of the active factors towards dark-germination in A. phyllitidis and L. japonicum are similar to those encountered with antheridium formation. Anemia medium induces dark-germination and induces antheridia on the dark-grown protonemata to a concentration ca. 30 times lower than it induces antheridia on light-grown prothalli. The studies indicate that this differential activity results from a differential competence of the prothalli to react to the active substance in light and darkness.