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Thomas L. Davenport David W. Pearce Stewart B. Rood 《Journal of Plant Growth Regulation》2000,19(4):445-452
Stems of mango (Mangifera indica L.) rest in a nongrowing, dormant state for much of the year. Ephemeral flushes of vegetative or reproductive shoot growth are periodically evoked in apical or lateral buds of these resting stems. The initiation of shoot growth is postulated to be primarily regulated by a critical ratio of root-produced cytokinins, which accumulate in buds and by leaf-produced auxin, which decreases in synthesis and transport over time. Exogenously applied gibberellic acid (GA3) delays initiation of bud break but does not determine whether the resulting flush of growth is vegetative or reproductive. We tested the hypothesis that endogenous GA3, which influences release of these resting buds, may decrease in stem tips or leaves with increasing age of mango stems. GA3 and several other GAs in stem tip buds and leaves were identified and quantified in stems of different ages. The major endogenous GAs found in apical buds and leaves of vegetative mango stems were early 13-hydroxylation pathway gibberellins: GA1, epi-GA1, GA3, GA19, GA20, and GA29, as identified by gas chromatography-mass spectrometry (GC-MS). A novel but unidentified GA-like compound was also present. The most abundant GAs in apical stem buds were GA3 and GA19. Contrary to the hypothesis, the concentration of GA3 increased within buds with increasing age of the stems. The concentrations of other GAs in buds were variable. The concentration of GA3 did not change significantly with age in leaves, whereas that of most of the other GAs declined. GA1 levels were greatest in leaves of elongating shoots. These results are consistent with the concept that rapid shoot growth is associated with synthesis of GAs leading to GA1. The role of GA3 in delaying bud break in mango is not known, but it is proposed that it may enhance or maintain the synthesis or activity of endogenous auxin. It, thereby, maintains a high auxin/cytokinin ratio similar to responses to GA3 that maintain apical dominance in other plant species. 相似文献
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The Effect of Gibberellic Acid on Shoot Growth of Pea Seedlings 总被引:6,自引:0,他引:6
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ROLF BORCHERT 《Physiologia plantarum》1975,35(2):152-157
Wide variations of shoot growth patterns in saplings of pin oak (Quercus palustris Muenchh.) have been observed as a consequence of varying environmental conditions, experimental manipulations, and vigor of trees. Shoot growth patterns range from a series of recurrent, determinate flushes, constituting a genuine endogenous rhythm, to continuous, indeterminate growth. Observed growth patterns agree well with those predicted by a model of rhythmic growth which assumes the dependence of shoot growth on the functional equilibrium between shoot and root system. Indirect evidence suggests that cessation of shoot growth under favorable environmental conditions might be a consequence of internal water deficits. Observed differences in shoot growth patterns between young and mature trees are discussed as logical consequences of the model. 相似文献
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Interaction of Gibberellic Acid and Indole-3-acetic Acid in the Growth of Excised Cuscuta Shoot Tips in Vitro 总被引:3,自引:3,他引:0
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Gibberellic acid (GA3) induced a marked elongation of 2.5-centimeter shoot tips of Cuscuta chinensis Lamk. cultured in vitro. In terms of the absolute amount of elongation, this growth may be the largest reported for an isolated plant system. The response to hormone was dependent on an exogenous carbohydrate supply. The hormone-stimulated growth was due to both cell division and cell elongation. The growth response progressively decreased if GA3 was given at increasingly later times after culturing, but the decreased growth response could be restored by the application of indole-3-acetic acid (IAA) to the apex. Explants deprived of GA3 gradually lost their ability to transport IAA basipetally, but this ability was also restored by auxin application. The observations are explained on the basis that: (a) the growth of Cuscuta shoot tip in vitro requires, at least, both an auxin and a gibberellin; and (b) in the absence of gibberellin the cultured shoot tip explants lose the ability to produce and/or transport auxin. 相似文献
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Tobacco (Nicotiana tabacum L. cv. W. 38) callus grown on a shoot-forming medium was exposed to gibberellic acid (GA3) and abscisic acid (ABA) for varying lengths of time and at different periods during culture. The results suggest that if the tissue accumulated sufficient GA3 prior to the initiation of meristemoids and shoot primordia, repression of shoot formation occurred. This repression was not reversed by increasing the levels of auxin or cytokinin in the medium, but ABA could partially overcome the GA3 repression of shoot formation. 相似文献
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Inhibitors from Carob (Ceratonia siliqua L.) I. Nature of the Interaction With Gibberellic Acid on Shoot Growth 总被引:3,自引:3,他引:0
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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. 相似文献
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Root and Shoot Growth of Plants Treated with Abscisic Acid 总被引:4,自引:0,他引:4
Young seedlings of Capsicum annum L., Commelina communis L.and maize (Zea mays L.) were subjected to a mild water-stressingtreatment and/or treated with abscisic acid (ABA). Plants rootedin soil received a soil-drying treatment and their leaves weresprayed with a 104 M solution of ABA. Plants grown insolution culture were stressed by the addition of polyethyleneglycol (PEG) to the rooting medium and ABA was also added tothe rooting medium, either with or without PEG. The effectsof both treatments on the growth of roots and shoots and theultimate root: shoot dry weight ratio were very similar. Shootgrowth was limited both by water stress and by ABA application;while there was some evidence that mild water stress and/orABA application may have resulted in a stimulation of root growth.More severe water stress reduced the growth of roots but theoverall effect of stress was to increase the ratio of rootsto shoots. Capsicum annum L., Commelina communis L., Zea mays L., water stress, abscisic acid 相似文献
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The effects of foliar sprays of gibberellic acid (GA) on thegrowth of tomato plants cv. Potentate were studied in growthrooms and a glasshouse. Four sprays of GA (5 ppm) increasedleaf area and whole plant weight relative to water controlsgrown at constant temperatures (7, 17, 22, and 27 °C) for12 days, the largest plants being obtained with 5 ppm. Experimentsmade at four photoperiods (5, 10, 15, and 20 h) and at two lightintensities (7000 and 10 750 lx) showed that GA increased leafand whole plant weight at 15 h, leaf area at 10 and 15 h andstem height at all photoperiods; area, height, and weight increaseswere obtained at both light intensities, leaf growth being increasedmore by GA at 7000 lx and stem growth more at 10 750 lx. Four foliar sprays of GA (5 ppm) were combined with N supplementsapplied via leaf and/or root to plants in sand culture. Withlow supply to the roots (20 ppm N) GA failed to increase growth,but increased it at higher levels. Total N in leaf and stemwas increased by GA or by NH4NO3 (10 sprays 280 ppm N) at alllevels of N supplied to roots, but when applied together theeffect on total leaf N was more than additive except at thehighest level (540 ppm) GA increased the concentration of N(as per cent dry matter) in leaf and stem at all levels of Nsupplied to roots. GA and NH4NO3 together resulted in a greateramount and a higher concentration of N in the shoots (and usuallyalso in roots) than did NH4NO3 alone. Leaf thickness (as freshweight/unit area) could only be increased appreciably by sprayingwith a complete nutrient solution which reduced leaf area butnot dry weight. Growth increases induced by GA were detectable 43 days afterthe first of four sprays in the glasshouse and after 30 daysin the growth room. The persistence of GA effects was comparedwith those induced by sprays of NH4NO3. 相似文献
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Endogenous Gibberellins and Shoot Growth and Development in Brassica napus 总被引:5,自引:3,他引:2
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Greenhouse-grown oilseed rape (Brassica napus, annual Canola variety `Westar') plants were harvested at six dates from the vegetative phase until the early pod (silique)-fill/late flowering stage. Endogenous gibberellin (GA)-like substances were extracted from stems, purified, and chromatographed on silica gel partition columns prior to bioassay in serial dilution using the `Tan-ginbozu' dwarf rice microdrop assay. The concentrations of total endogenous GA-like substances were low during vegetative stages (1 nanogram GA3 equivalents/gram dry weight), and rose 300-fold by the time of floral initiation. After floral initiation the concentration of GA-like substances fell, then rose again during bolting to maximal levels during the early pod-fill stage (940 nanograms per gram dry weight). The qualitative profiles of GA-like substances varied across harvests, with higher proportions of a GA1-like substance at the early pod-fill stage. In a second study stems were similarly harvested at eight dates and the concentrations of endogenous GA1, the principal bioactive native GA of oilseed rape, were determined by gas chromatography-selected ion monitoring using [17,17-2H]GA1 as a quantitative internal standard. The concentration of GA1 increased at about the time of floral initiation and then subsequently fell, thus confirming the pattern noted above for total GA-like substances. The exogenous application of paclobutrazol (PP333), a persistent triazole plant growth regulator (PGR) which blocks GA biosynthesis, or another triazole, triapenthenol (RSW0411), prevented flowering as well as bolting; plants remained at the vegetative rosette stage. These results imply a causal role for endogenous GA, in the control of bolting, which normally precedes anthesis. Further, the rise in the concentration of total endogenous GA-like substances, including GA1, which was associated with floral initiation, and the prevention of visable floral development by the triazole PGRs, also indicates a role for endogenous GAs in the regulation of flowering in B. napus. 相似文献
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The Effects of Daylength and Treatment with Gibberellic Acid on Spikelet Initiation and Development in Clipper Barley 总被引:3,自引:0,他引:3
The effects of photoperiod, light quality and a single applicationof gibberellic acid (GA3) on the development of the main-stemapex in Clipper barley are reported. In 16 and 24 h days spikeletinitiation was rapid but extended over a short period whereasin 8 h photoperiods both spikelet initiation and developmentwere slower but occurred for a much longer time. Initiationalways stopped when the anther primordia were clearly visiblein the most advanced spikelet. Daylength extensions with lowintensity incandescent light were most effective when they followedrather than preceeded the 8 h period of high light intensity.Plants grown in 8 h high intensity followed by 8 h low intensitylight initiated spikelets almost as rapidly as those grown in16 h high intensity light. Thus, the effects of daylength onspikelet production were primarily mediated through photoperiodicallycontrolled processes rather than through photosynthesis andassimilate supply. The effects of applied GA3 were long livedand greatest in short days where the rates of both spikeletinitiation and development were promoted. The parallels betweenthe effects of long days and GA3 treatment are discussed togetherwith possible reasons for the cessation of initiation and thelong duration of the GA3 effect. daylength, gibberellic acid, spikelet initiation, Hordeum vulgare L., barley, main-stem apex, primordia 相似文献
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Influence of Gibberellic Acid on Growth and Endogenous Auxin Level in Epicotyl and Hypocotyl Tissues of Normal and Dwarf Bean Plants 总被引:1,自引:0,他引:1
Application of gibberellic acid to the apex of dwarf bean plants (cv. Alabaster) stimulated the elongation growth of epicotyl and hypocotyl but showed no significant effect on elongation growth in a normal cultivar (‘Blue Lake’). Gibberellin-treatment of dwarf plants was characterized by about twofold increase in the level of endogenous auxin. Maximum increase in IAA level was observed after 48 h of GA treatment. There was less increase in IAA content in normal bean plants. — Gibberellin treatment to excised epicotyl and hypocotyl sections of either dwarf or normal cultivar showed no effect on elongation growth. However, a considerable increase in the auxin level was observed in the sections of the dwarf cultivar. The maximum effect occurred with only 1 h incubation in basal medium containing gibberellin. — The indolo-α-pyrone spectro-fluoremetric method for IAA determination was used. 相似文献
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Physiological Effects of Gibberellic Acid. IX. Recovery of Gibberellic Acid Following Incubation with Endosperm 总被引:1,自引:1,他引:0
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To determine the fate of gibberellic acid (GA3), solutions were incubated for 24 hours with or without barley endosperm and were subsequently applied to dwarf maize seedlings. Hormone activity appeared to increase as a result of incubation with endosperm. This apparent increase in GA3 concentration was probably due to a synergistic interaction between GA3 and endosperm constituents, particularly carbohydrate, released during the incubation period. It is concluded that relatively little hormone is inactivated during the initiation of endosperm mobilization. 相似文献
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Treatment of pumpkin plants with 2-chloroethylphosphonic acid (CEPHA) induced a greater production of female flowers, shorter internodes and earlier fruit set while treatment with gibberellic acid (GA) induced a greater production of male flowers, longer internodes and later fruit set. Although CEPHA induced the production of a greater number of female flowers, the bulk of the flowers aborted and only a slight increase in the number of fruits per pumpkin plant occurred. The addition of equal concentrations of CEPHA and GA resulted in pumpkin plants with longer internodes and a greater number of female flowers than the untreated plants, although GA partially overcame the effect of CEPHA. The mode of action of CEPHA and GA on sex expression is discussed. 相似文献
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The effects of four consecutive daily sprays of gibberellicacid (GA3) on the growth of leaves of young tomato plants cv.Potentate were studied. Total leaf weight and area were increasedby GA3. The percentage changes were larger in the younger leavesthan in the older but the absolute increases of the middlleleaves accounted for most of the total response. Chlorophyllcontent, both total and per unit weight, was reduced by GA inthe older leaves and increased in the younger; on an area basisit was reduced in all but the youngest leaves. Palisade cell length and palisade cell number per unit sectionlength were reduced by GA3 in the oldest leaves and increasedin the youngest. There were larger intercellular spaces in bothmesophyll layers and a larger transectional area of the mid-ribsof the oldest and two youngest leaves in GA3 plants. The surfaceareas of epidermal cells were also increased by GA3 treatment.Leaf fresh weight per unit area was only a true index of laminathickness in the two oldest leaves. 相似文献