Stimulatory effect of cytokinins and interaction with IAA on the release of lateral buds of pea plants from apical dominance

Lateral buds of pea plants can be released from apical dominance and even be transformed into dominant shoots when repeatedly treated with synthetic exogenous cytokinins (CKs). The mechanism of the effect of CKs, however, is not clear. The results in this work showed that the stimulatory effects of CKs on the growth of lateral buds and the increase in their fresh weights in pea plants depended on the structure and concentration of the CKs used. The effect of N-(2-chloro-4-pyridyl)-N'-phenylurea (CPPU) was stronger than that of 6-benzylaminopurine (6-BA). Indoleacetic acid (IAA) concentration in shoot, IAA export out of the treated apex and basipetal transport in stems were markedly increased after the application of CPPU or 6-BA to the apex or the second node of pea plant. This increase was positively correlated with the increased concentration of the applied CKs. These results suggest that the increased IAA synthesis and export induced by CKs application might be responsible for the growth of lateral shoots in intact pea plants.     

The Stability and Movement of Gibberellic Acid in Pea Seedlings

The stability and movement of gibberellic acid (GA) in intactdwarf pea seedlings growing in the light was studied by meansof both unlabelled GA and GA labelled with isotopic carbon (¹⁴C).After ¹⁴C-GA had been applied to the mature leaves of pea seedlingsmuch remained in association with the treated leaflets, but¹⁴C-GA was also extractable from the young shoots. The yieldwas approximately the same 5 to 96 hours after treatment. GApenetrated leaf surfaces only while the application solventwas moist (about 1 hour), but moved from the treated leafletsinto the shoots for at least 24 hours. Some hours after treatmentthere was an abrupt increase in the growth-rates of the plants,and crude estimates suggest that an effective dose of GA movedto the elongating tissue at about 5 cm/hr. The pattern of distributionof ¹⁴C was examined by autoradiography. The data suggest thatGA which enters the plant is redistributed from maturing leavesto immature leaves, passing through the elongating tissue, foras long as any of the substance is present. The hypothesis remainstenable that GA produces its growth effects by acting only uponexpanding tissue     

Effect of Gibberellic Acid on Dwarf and Normal Pea Plants

Gibberellic acid at concentrations between 10 and 100 mg/1 greatly stimulated the elongation growth of intact dwarf pea plant but showed little or no effect on that of Alaska pea. It showed no effect on the elongation growth of excised stem segments of either dwarf or normal pea when given alone. Indole-3-acetic acid stimulated the elongation of excised segments of both varieties. Gibberellic acid synergistically enhanced the indole-3-acetic acid-induced elongation of excised segments. Tryptophan also stimulated the elongation of these segments. Gibberellic acid showed a synergistic effect on the tryptophan-induced elongation, as on the indole-3-acetic acidinduced one. Gibberellic acid reduced the lag period of tryptophan-induced elongation, suggesting that gibberellic acid promotes the conversion of tryptophan to auxin.     

Relations between DNA, RNA and Protein Synthesis, and the Cellular Basis of the Growth Response in Gibberellic acid-Treated Pea Internodes

1. A study was made of the influence of gibberellic acid (GA₂)on nucleic acid, protein, and cell-wall synthesis in pea internodesin vivo. 2. GA₃-treated fifth internodes finally contained more thantwice as much total RNA and protein as comparable untreatedones, and the contents of RNA and protein were closely relatedto the length of internode cortical cells. 3. Cell elongation, RNA, protein, and cell-wall synthesis werestimulated 24–48 h before there was any demonstrable GA₃effect on DNA synthesis and cell division. 4. Treated fifth internodes finally contained twice as manycortical cells as control internodes, a response that was matchedby a proportionate increase in the amount of DNA. 5. Internodes treated with actinomycin D or cycloheximide failedto elongate in response to GA₃ treatment, indicating that bothRNA and protein synthesis are essential for gibberellin-stimulatedcell elongation to occur in this tissue. 6. 5-fluorodeoxyuridine at concentrations which completely blockcell division did not prevent cells from elongating in the presenceof GA₃. 7. With the possible exception of pectic substances there wasno change in the relative proportions of each of the major cell-wallconstituents in treated, as compared to control internodes.     

Influences of ascorbic acid and gibberellic acid in alleviating effects of salinity in Petunia under in vitro

Salinity is one of the abiotic stresses that limits the growth and productivity of many crops. A possible survival strategy for plant under saline conditions is to use compounds that could minimize the harmful effects of salt stress on the plant development. The objective of the presented study was to investigate the effect of exogenous ascorbic acid (ASA) with or without gibberellic acid (GA3) on key growth and biochemical parameters in two petunia cultivars ‘Prism Rose’ and ‘Prism White’ under saline (150 mM NaCl) and non-saline in vitro condition. Nodal cutting with an axillary buds were used as explants. Application of 1 mM ascorbic acid with or without 0.05 mM gibberellic acid into the MS medium stimulated the length of shoots and the number of new shoots of ‘Prism Rose’; whereas, it decreased the root length and the number of roots of both ‘Prism Rose’ and ‘Prism White’ under non-saline condition. The addition of ascorbic acid with or without gibberellic acid into the MS medium under saline condition, increased the length of plants and the number of new shoots, but did not affect their root number and length. NaCl treatments increased the proline content and lipid peroxidation which was indicated by the accumulation of malondialdehyde (MDA). The study revealed a correlation between chlorophylls a and b content and the leaf pigmentation intensity – parameter a*. Addition of 1 mM ascorbic acid with 0.05 mM gibberellic acid into the MS medium plays a protective role in salinity tolerance by improving the shoot growth and the development as well as increasing the activities of the antioxidant enzymes and other antioxidant substances.     

Gibberellin-auxin interaction in pea stem elongation

Joint application of gibberellic acid and indole-3-acetic acid to excised stem sections, terminal cuttings, and decapitated plants of a green dwarf pea results in a markedly synergistic growth response to these hormones. Synergism in green tall pea stem sections is comparatively small, although growth is kinetically indistinguishable from similarly treated dwarf sections.

Gibberellin-induced growth does not appear to be mediated through its effect on auxin synthesis, since gibberellin pretreatment of dwarf cuttings fails to elicit an enhanced tryptophan-induced growth response of sections, whereas auxin-induced growth is strongly enhanced. Also, tryptophan-gibberellin synergism is not significant in sections and cuttings of green dwarf peas, while auxin-gibberellin synergism is.

Administration of gibberellic acid prior to indole-3-acetic acid results in greatly increased growth. In reversed order, the application fails to produce any synergistic interaction. This indicates that gibberellin action must precede auxin action in growth regulation.

     

Hormone interactions and regulation of PsPK2::GUS compared with DR5::GUS and PID::GUS in Arabidopsis thaliana

The putative pea PINOID homolog, PsPK2, is expressed in all growing plant parts and is positively regulated by auxin, gibberellin, and cytokinin. Here, we studied hormonal regulation of PsPK2::GUS expression compared with DR5::GUS and PID::GUS in Arabidopsis. PsPK2::GUS, DR5::GUS, and PID::GUS expression in Arabidopsis shoots is mainly localized in the stipules, hydathodes, veins, developing leaves, and cotyledons. Unlike DR5::GUS, PsPK2::GUS, and PID::GUS are weakly expressed in root tips. Both DR5::GUS and PsPK2::GUS are induced by different auxins and are more sensitive to methyl indole acetic acid, 4-chloro-indole acetic acid, and α-naphthalene acetic acid than others. GA(3) has no significant effect on GUS activity in DR5::GUS-transformed seedlings compared to the control, but induction by auxin and gibberellin in combination is synergistic. Cytokinin increases auxin transport in Arabidopsis seedlings. Auxin, gibberellin, and cytokinin all increase GUS activity in shoots of PsPK2::GUS transformed plants compared to the control. However, only auxin and gibberellin increase GUS activity in PID::GUS shoots. In conclusion, auxin, gibberellin, and cytokinin positively regulate PsPK2 expression in shoots, but not in roots. Auxin and gibberellin also upregulate AtPIN1 and LEAFY expression, which is similar to PsPIN1 and Uni in pea. With minor exceptions, the orthologous genes from both species are regulated similarly.     

Shoot regeneration from cultured root explants of spinach (Spinacia oleracea L.): a system for Agrobacterium transformation

A reliable plant regeneration system is described for the production of adventitious shoots from root explants of spinach. Explants from roots of axenic shoots and roots induced on cultured hypocotyl explants were used for adventitious shoot induction. Explants from apical, middle and basal root regions were incubated on Nitsch and Nitsch medium supplemented with α-naphthaleneacetic acid, gibberellic acid and kinetin. Optimum shoot regeneration was from explants of apical and middle root regions on medium with 20 μm α-naphthaleneacetic acid and 5.0 μm gibberellic acid. Shoots originated directly from root tissues without an intervening callus phase. Adventitious shoots were rooted and were grown to maturity in the glasshouse. This plant regeneration procedure has been exploited in preliminary studies of Agrobacterium-mediated transformation. Received: 27 February 1996 / Revision received: 22 August 1996 / Accepted: 30 September 1996     

Effects of benzyladenine on cotyledon metabolism and growth of peas

Summary Application of benzyladenine to dry pea seed delayed the production of amylase and the concomitant breakdown of starch. The utilization of nitrogenous reserve food material was also delayed. Shoot growth was correlated with breakdown of reserve food.Benzyladenine given to one of the cotyledons did not affect the senescence of the other. Cotyledonary axillary shoots were released from apical dominance, but only those originating from the benzyladenine treated cotyledon continued to develop. The pattern of growth initiated by benzyladenine was not altered by gibberellic acid although this substance caused increased elongation of all growing shoots.     

Changes in the Pattern of Enzyme Development in Gibberellin-treated Pea Internodes

A study was made on the effect of gibberellic acid on amylase,cellulase, ß-fructofuranosidase, pectinesterase, andstarch phosphorylase activities in elongating dwarf-pea internodes. Hormonal stimulation of amylase and ß-fructofuranosidaseactivities correlated closely with internode growth, the activityof starch phosphorylase less so, and gibberellic acid had noimmediate effect on cellulase and pectinesterase activities. Injection of glucose (or glucose derivatives) into pea internodesmimicked the effect of gibberellic acid on fresh- and dry-weightaccumulation, cell elongation, cell division, and cell-wallsynthesis. It is proposed that the over-all effect of gibberellic acidon enzyme development is to provide more substrate (particularlyglucose) for general cell metabolism and wall synthesis withinelongating internodes.     

Arginine Decarboxylase and Putrescine Oxidase in Ovaries of Pisum sativum L. (Changes during Ovary Senescence and Early Stages of Fruit Development)

Enzymatic activities involved in putrescine metabolism in ovaries of Pisum sativum L. during ovary senescence and fruit set were investigated. Accumulation of putrescine was observed during incubation of extracts from gibberellic acid-treated unpollinated ovaries (young developing fruits) but not in extracts from untreated ovaries (senescent ovaries). Extracts from pea ovaries showed arginine decarboxylase (ADC) activity, but ornithine decarboxylase and arginase activity were not detected. ADC activity decreased in presenescent ovaries and increased markedly after induction of fruit set with gibberellic acid. Increases in ADC activity were also observed with application of other plant growth substances (benzy-ladenine and 2,4-dichlorophenoxyacetic acid), after pollination, and in the slender (la crys) pea mutant. By contrast, putrescine oxidase activity increased in presenescent ovaries but did not increase during early fruit development. All of these results suggest that ADC and putrescine oxidase are involved in the control of putrescine metabolism. Ovary senescence is characterized by the absence of putrescine biosynthesis enzymes and increased levels of putrescine oxidase and fruit development by an increase in ADC and a constant level of putrescine oxidase.     

The effect of plant hormones on the components of the secretory pathway in human normal and tumor cells

Plant hormones play a key role in plant growth and differentiation. Certain plant hormones are known to be potential antitumor agents, affect the secretory activity of animal cells, and are produced by mammalian cells as proinflammatory cytokines. The goal of this research was to study the effect of abscisic and gibberellic acids on the secretory system of human epidermoid A431 carcinoma cells and HaCaT keratinocytes. Immunocytochemical and morphometric analysis showed that a subtoxic concentration of abscisic and gibberellic acids induced extension of the ER network and increased the size of the Golgi complex. Electron-microscope studies confirmed the hypertrophic changes of the Golgi complex: swelling of cisternae in the trans-Golgi compartment after exposure to abscisic acid and swelling of cis- and trans-compartments after exposure to gibberellic acid. The Click-iT technique revealed elevation of total protein synthesis only in A431 cells exposed to abscisic acid. Our data suggest that the hypertrophy of Golgi may reflect enhanced secretory activity in A431 cells exposed to abscisic acid. In other experiments, Golgi hypertrophy was not accompanied with increased protein synthesis that suggested the stress-related changes of ER and Golgi complex. Our results demonstrate that morphologically similar reaction manifested in hypertrophy of Golgi complex, in response to plant hormones, is the result of different functional activities, and that molecular mechanisms underlying induced changes need further investigations.     

Inhibitors from Carob (Ceratonia siliqua L.) I. Nature of the Interaction With Gibberellic Acid on Shoot Growth

Concentrated whole extracts of the immature fruit of carob and 3 fractions derived from this extract have been shown to inhibit the gibberellic acid induced growth of pea seedlings. The inhibition can be completely reversed by increasing the amount of gibberellic acid. The inhibitors do not reduce the endogenous growth of seedlings but only that induced by gibberellic acid. One of the fractions is a newly separated one not previously reported.     

Auxin Physiology of Dwarfism in Pisum sativum

Similar levels of diffusible auxin are measured for the apices of both Little Marvel (dwarf) and Alaska (normal) cultivars of the pea when grown in sunlight and darkness. In sunlight, however, diffusible auxin disappears in the subtending internode of the Little Marvel plant but remains at 50 per cent of the level of the apex in the subtending internode of the Alaska plant. The enzyme preparation from the apex of the dwarf plant converts tryptophan and tryptamine to IAA more readily than that from the normal plant. Indoleacetyl aspartate synthetase activity is also higher in the dwarf plant than in the normal plant and the dwarf plant contains four times as much conjugate as the normal plant with or without treatment with gibberellic acid. Gibberellic acid (GA) does not affect the induction of the synthetase enzyme nor the enzymatic formation of indoleacetyl aspartate. The growth induced by GA is the result of an increased synthesis of auxin.     

Gibberellic Acid-enhanced Release of beta-1,3-Glucanase from Barley Aleurone Cells

A β-1, 3-glucanase of barley (Hordeum vulgare) aleurone cells accumulates when half-seeds are imbibed on water, and accumulation continues when the aleurone layers are incubated in buffer solution. The release of the enzyme is a gibberellic acid-dependent process, however. Although gibberellic acid stimulates glucanase release, it does not markedly affect the total amount of glucanase obtained from these cells when compared with water controls. β-1, 3-Glucanase release from aleurone cells is a function of gibberellic acid concentration and commences after a 4-hour lag period. Processes occurring during this lag period are also dependent upon gibberellic acid concentration. Removal of gibberellic acid from the incubation medium at the end of the lag period, however, does not affect subsequent release of glucanase. The release of glucanase from aleurone cells is an active process with a Q₁₀ greater than 3. Inhibitors of respiration and protein and RNA synthesis effectively inhibit the formation and release of glucanase. It is concluded that gibberellic acid functions primarily to enhance glucanase release rather than its formation.     

Temporal and Hormonal Control of β-1,3-Glucanase in Phaseolus vulgaris L

The endo-beta-1, 3-glucanase (beta-1, 3-glucan 3-glucanhydrolase, EC 3.2.1.6) extracted from Phaseolus vulgaris L. cv. Red Kidney had a pH optimum of 5 and a temperature optimum of 50 C. Excision of plant tissue resulted in an increase in beta-1, 3-glucanase activity after a 6-hour lag period. The increase could be prevented by indole-3-acetic acid, gibberellic acid, and cytokinins. Ethylene (half-maximal concentration = 0.1 microliter/liter) promoted the synthesis of beta-1, 3-glucanase, and 10% CO(2) overcame some of the ethylene effect. Cycloheximide prevented the induction of beta-1, 3-glucanase, but actinomycin D and chromomycin A(3) had only a partial effect.The amount of callose in sieve tube cells correlated with levels of beta-1, 3-glucanase, suggesting that this enzyme played a role in the degradation of beta-1, 3-glucans.     

Gibberellic Acid and Starch Breakdown in Pea Cotyledons

The stimulation of starch breakdown in the cotyledons of dwarfpea cultivars (Progress No. 9 and Dark Skin Perfection) whentreated with gibberellic acid (GA³) is mediated through theremoval of metabolites by the axis. When applied to excisedcotyledons, GA³ had only a minor effect on starch breakdown,as it did in the cotyledons of a tall pea (cv. Alaska) irrespectiveof whether they were attached to the plant or excised. Enzyme activity appears to be controlled by the level of solublesugars in the cotyledons, and GA³delays the increase in amylolyticactivity in the cotyledons through a direct effect on cotyledonmetabolism.     

Ethylene formation from 1-aminocyclopropane-1-carboxylic acid in homogenates of etiolated pea seedlings

Homogenates of etiolated pea (Pisum sativum L.) shoots formed ethylene upon incubation with 1-aminocyclopropane-1-carboxylic acid (ACC). In-vitro ethylene formation was not dependent upon prior treatment of the tissue with indole-3-acetic acid. When homogenates were passed through a Sephadex column, the excluded, high-molecular-weight fraction lost much of its ethylene-synthesizing capacity. This activity was largely restored when a heat-stable, low-molecular-weight factor, which was retarded on the Sephadex column, was added back to the high-molecular-weight fraction. The ethylene-synthesizing system appeared to be associated, at least in part, with the particulate fraction of the pea homogenate. Like ethylene synthesis in vivo, cell-free ethylene formation from ACC was oxygen dependent and inhibited by ethylenediamine tetraacetic acid, n-propyl gallate, cyanide, azide, CoCl₃, and incubation at 40°C. It was also inhibited by catalase. In-vitro ethylene synthesis could only be saturated at very high ACC concentrations, if at all. Ethylene production in pea homogenates, and perhaps also in intact tissue, may be the result of the action of an enzyme that needs a heat-stable cofactor and has a very low affinity for its substrate, ACC, or it may be the result of a chemical reaction between ACC and the product of an enzyme reaction. Homogenates of etiolated pea shoots also formed ethylene with 2-keto-4-mercaptomethyl butyrate (KMB) as substrate. However, the mechanism by which KMB is converted to ethylene appears to be different from that by which ACC is converted.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - IAA indole-3-acetic acid - KMB 2-keto-4-mercaptomethyl butyrate - SAM S-adenosylmethionine     

Phytochrome controlled C-sucrose uptake into etiolated pea buds: effects of gibberellic Acid and other substances

The previously reported red light enhancement of ¹⁴C-sucrose uptake into etiolated pea buds is inhibited by gibberellic acid applied no later than 2 hours after the light. Auxins, cytokinins and inhibitors of gibberellin biosynthesis are without effect, either alone or in the presence of gibberellic acid.