Comparison of endogenous gibberellins in roots and shoots of elongating Salix pentandra seedlings

Gibberellins GA₁, GA₈. GA₁₉. GA₂₉. GA₂₀ and GA₅₆ (2-epi-GA₈). were identified by combined gas chromatography-mass spectrometry in root extracts of elongating Salix pentandra L. seedlings. The presence of GA₈ was also demonstrated for the first time in S. pentandra shoots. The levels of GA₁, GA₈, GA₁₉, GA₂₀ in shoot tissue and in roots were estimated by selected ion monitoring. While the amounts of GA₈ and GA₁₉ were similar in both plant parts. the levels of the biologically active GA₁ and its immediate precursor GA₂₀. were found to be much lower in roots than in shoots.     

Growth-promoting activity of gibberellins on shoot elongation in Salix pentandra is reduced by 16,17-dihydro derivatisation

The metabolism of GA₁₀ is thought to be under photoperiodic control in the woody plant Salix pentandra . However, in a recent study using 16,17-[³H₂]GA₁₉ as a mimic of Ga₁₀, no effect of photoperiod was found on its metabolism to 16,17-dihydro-GA₂₀ and 16,17-dihydro-GA₁. To investigate if this was due to differential action of exogenous 16,17-dihydro-GAs and GAs, the effects of the 16,17-dihydro-derivatives of the gibberellins GA₁₉, GA₁, and GA₁ as compared with their parent GAs, on shoot elongation in seedlings of S. pentandra were studied. 16,17-Dihydro-GA₁₉, and -GA₂₀ were both almost inactive, while 16,17-dihydro-GA₁ induced some shoot elongation in seedlings treated with ancymidol as well as under short days. GA₁₉, GA₂₀ and GA₁ were all able to counteract the inhibitory effect of ancymidol under continuous light, while inhibition induced by a 12-h photoperiod was antagonised only by GA₂₀ and GA₁. Thus, the growth-stimulating activity of the tested GAs is significantly reduced by 16,17-dihydro derivatisation, but the derivatives do not inhibit stem elongation in S, pentandra , as has been found in monocotyledons.     

Gibberellins and photoperiodic control of shoot elongation in Salix

Effects of exogenous gibberellins GA₅₃, GA₄₄, GA₁₉, GA₂₀ and GA₁ on photoperiodically controlled shoot elongation in seedlings of Salix pentandra L. were studied. Gibberellins GA₂₀ and GA₁ induced shoot elongation under short days (SD) and could substitute for a transfer to long day (LD), while gibberellins A₅₃, A₄₄ and A₁₉ were inactive. In seedlings exposed to a prolonged SD-treatment (30 days) there was a significant positive interaction between a transfer to LD and a treatment with GA₂₀ and GA₁ on shoot elongation. In addition, GA₁₉ enhanced the growth promotive effect of LD in these seedlings. The results are compatible with the suggestion that conversion of GA₁₉ to GA₂₀ is blocked under SD. This effect is supposed to be an early process leading to the cessation of shoot elongation under SD. Responsiveness of the seedlings to LD and to a GA-treatment gradually decreased with an increasing length of exposure to SD.     

Lack of influence of photoperiod on the metabolism of gibberellin A20 in Salix pentandra

The influence of photoperiod on the metabolism of GA₂₀ in Salix pentandra was studied by feeding [³H]-GA₂₀ to seedlings which had been grown previously under long day (LD) or short day (SD) conditions. After 48 h in LD or SD, metabolites were separated on sequential, silica gel partition columns and reversed-phase C₁₈ HPLC. The principal metabolite co-chromatographed with [³H]-GA₁ and this conversion was confirmed by feeding [²H]-GA₂₀, which was converted to [²H]-GA₁ as identified by gas chromatography-selected ion monitoring. Chromatographic evidence also indicated the minor conversion of [³H]-GA₂₀ to [³H]-GA₈ (via [³H]-GA₁) and trace conversion to [³H]-GA₂₉ (GAs A_1.8,20.29 are native in Salix). Ethyl acetate-insoluble [³H] metabolites were formed and could be cleaved by cellulase to release putative [³H]-GA₂₀ and [³H]-GA₁ suggesting the conversion to glucosyl conjugates of these GAs. Metabolism of [³H]-GA₂₀ was slightly more rapid in plants previously grown under LD than SD, an effect which reflected the generally increased shoot growth under LD. However, altering the photoperiod after [³H]-GA₂₀ addition had only a slight effect on the metabolism of [³H]-GA₂₀ in Salix seedlings. This indicates that the conversion of GA₂₀ to GA₁ is not a controlling step in the photoperiodic regulation of growth cessation in Salix.     

Stimulation of shoot elongation in Salix pentandra by gibberellin A9; activity appears to be dependent upon hydroxylation to GAl via GA20

Cessation of shoot elongation in seedlings of Salix pentandra L. is induced by short photoperiod. Gibbereliin A₉ (GA₉) applied either to the apical bud or injected into a mature leaf, induced shoot elongation under a short photoperiod of 12 h, and GA₉ could completely substitute for a transfer to a long photoperiod. When [³H]GA₉ or [²H₂]GA₉ was injected into a leaf, no [³H]GA₉ was detected in the elongating apex and only traces of [³H]GA₉ were found in the shoot above the treated leaf. By the use of gas chromatography-mass spectrometry (GC-MS), [²H₂]GA₂₀ was identified as the main metabolite of [²H₂]GA₉ in both the shoot and the treated leaf. In addition, [²H₂]GA₁ and [²H₂]GA₂₉ were also identified as metabolites of [²H₂]GA₉. These results are consistent with the hypothesis that exogenous GA, promotes shoot elongation in Salix through its metabolism to GA₂₀ and GA,.     

Endogenous gibberellins in young seedlings of wheat (Triticum aestivum) cultivars

Gibberellins A₁, A₃, A₄ and A₇ were identified by combined gas chromatography mass spectrometry (GC-MS) in leaf and stem tissues of 17-day-old seedlings of wheat ( Triticum aestivum L. ), cvs Siete Cerros (semi-dwarf, Rht1) and Møystad (tall), of F₁, hybrids from the cross Møystad × Siete Cerros and of 2 selected lines from the cross Møystad x Sonora 64 (Rht1 and Rht2). GA, and GA, were identified by full scan mass spectra separately in all 5 extracts, GA₄ and GA₇, were identified by selected ion monitoring in a bulked fraction. About 90% of the biological activity (Tan-ginbozu dwarf rice bioassay) in all 5 extracts was due to the GA₁/GA₃-fraction.     

Effects of different gibberellins on elongation growth under short day conditions in seedlings of Salix pentandra

Fifteen different gibberellins (GA's) were tested for their ability to induce elongation growth under short day conditions in seedlings of Salix pentandra L. GA's were applied either to the apex or they were injected into a mature leaf. GA₃ was highly active and also GA₄₊₇ and GA₄ showed high activity. GA₁, GA₂, GA₅, GA₉, GA₁₃, GA₂₀, GA₃₆ and GA₄₇ showed moderate activity. GA₁₆, GA₁₇, GA₂₇ and GA₄₁ exhibited low or no activity in doses up to 10 μg per plant. In general, a better growth response was obtained with an application to the apex than with an injection into the leaf.     

Lack of effect of photoperiod on metabolism of exogenous GA19 and GA1 in Salix pentandra seedlings

The effect of photoperiod on metabolism of 16,17-[³H₂]GA₁₉, and 1.2-[³H₂]GA₁ applied to intact seedlings of Salix pentandra, was investigated. No difference was found in conversion of 16,17-[³H₂]GA₁₉ to 16,17-[³H₂]GA₂₀, and 16,17-[³H₂]GA₁, or in metabolism of 1,2-[³H₂]GA₁ to [³H]GA₈ between plants grown in continuous light and plants exposed for 14 days to a 12-h photoperiod. Also, leaf discs from plants grown in long or short days, converted 16,17-[³H₂]GA₁₉ both in light and darkness. These data on metabolism of 16,17-[³H₂]GA₁₉, contrast with previous results, which have indicated a photoperiodic control of the metabolism of GA₁₉ to GA₂₀ in S. pentandra. Presence of these applied labelled GAs and their metabolites in different parts of seedlings was recorded, after application to intact seedlings as well as to isolated plant parts. When 16,17-[³H₂]GA₁₉ was applied through the roots of intact plants, the relative amounts of 16,17-[³H₂]GA₁ present in leaves and shoot apices were higher than in roots and stems. In corresponding experiments with 1,2-[³H₂]GA₁, relatively higher amounts of [³H₂]GA₈ were found in roots and stems than in leaves and shoot apices. Twenty-four hours after application of 16,17-[³H₂]GA₁₉ to isolated plant parts, 16,17-[³H₂]GA₂₀ and 16,17-[³H₂]GA₁ were found in leaves and roots, but not in internodes. Incubation of isolated plant parts with 1,2-[³H₂]GA₁ for 24 h resulted in presence of [³H]GA₈ in all parts. The results mentioned above were obtained by monitoring metabolites by HPLC with on-line radio counting. The conversions of 17-[²H₂]GA₁₉ to 17-[²H₂]GA₂₀ and 17-[²H₂]GA₁ in shoot apices and whole seedlings, and of 17-[²H₂]GA₈ in whole seedlings, were confirmed by GC-MS.     

Phytohormonal changes in intact shoots of wheat and oilseed rape treated with the acylcyclohexanedione growth retardant prohexadione calcium

The effects of the acylcyclohexanedione-type growth retardant prohexadione calcium on seedling growth and endogenous levels of immunoreactive phytohormone-like substances in shoots of wheat ( Triticum aestivum L. cv. Kanzler) and oilseed rape ( Brassica napus L. ssp. napus cv. Lirajet) were studied. After treatment of seedlings with increasing retardant concentrations in hydroponics, plant height and fresh weight of shoots were reduced by up to 40%. Concomitantly, the amount of immunoreactive gibberellins decreased, on a fresh weight basis, when compared with levels in the shoots of control plants. In contrast, the levels of abscisic acid and dihydrozeatin riboside and isopentenyladenosine-type cytokinins were considerably elevated by the growth retardant. The content of 3-indoleacetic acid decreased slightly. These results suggest that, in addition to its effect on gibberellin content, prohexadione calcium also influences the levels of endogenous abscisic acid and cytokinins.     

Identification and quantification of endogenous gibberellins in apical buds and the cambial region of Eucalyptus

Endogenous gibberellins (GAs) were extracted and purified from apical buds of Eucalyptus nitens (Deane and Maid.) Maid. and the cambial region of E. globulus (Labill.). then analysed by capillary gas chromatography-mass spectrometry. GA₁ GA₁₉ GA₂₀ and GA₂₉ were identified by full scan mass spectra. Kovats retention indices and high resolution selected ion monitoring. Using deuterated internal standards. GA₁. GA₁₉. GA₂₀ and putative GA₂₉ and GA₅₃ were quantified in the apical buds, while GA₄. GA₈. GA₉ and GA₄₄ were shown to be either absent or present at very low levels. From the cambial region. GA₁ and GA₂₀ were quantified at levels of 0.30 ng (g fresh weight)-¹ and 8.8 ng (g fresh weight)-¹ respectively. These data suggest that the early 13-hydroxylation pathway is the dominant pathway for GA biosynthesis in Eucalyptus .     

Effects of exogenously applied growth regulators on shoot growth of inbred lines of Plantago major differing in relative growth rate: differential response to gibberellic acid and (2-chloroethyl)-trimethyl-ammonium chloride

The possibility of modulating shoot growth charaeteristics of seedlings of two inbred lines of Plantago major L., differing in relative growth rate (RGR), by exogenously applied 6-benzylaminopurine (BA), α-naphthalene acetic acid (NAA), (gibberellic acid (GA₃) and (2-chloroethyl)-trimethyl-ammonium chloride (CCC) was investigated. BA completely inhibited growth of the shoot at a concentration of 1 m M , while lower concentrations had no effect. NAA reduced growth of the shoot at 10 ü M , while 1 m M completely inhibited growth. Addition of 10 μ M GA₃ or higher stimulated shoot fresh weight up to 20% and leaf area up to 30% for the slow growing inbred line (W9), but less for the fast growing line (A4). Application of 1 m M CCC, an inhibitor of gibberellin metabolism, reduced growth of both inbred lines, but to a larger extent in the fast growing seedlings.
The lower shoot growth of W9 was associated with a lower specific leaf area (SLA) and a higher dry matter percentage of the shoot, as compared with A4. NAA reduced growth by reducing SLA and increasing leaf thickness, but the percentage dry matter of the leaves was unaffected. Stimulation of the shoot growth by GA₃ application was associated with higher SLA and lower dry matter percentage. Application of CCC had opposite effects on SLA and dry matter percentage as compared with GA₃. GA seems to be involved in the regulation of at least part of the genetic difference in RGR in Plantago major .     

Effects of seasonal temperature on shoot growth dynamics and shoot morphology of common reed (Phragmites australis)

The shoot growth during the vegetation period andshoot morphology at the end of the season wereinvestigated in four monoclonal aquatic reed stands(Phragmites australis) with differentproductivity in Berlin and Brandenburg. Investigationswere conducted over a period of six years (1991–96) toascertain the effects of differences in temperatures.All clones showed significant year-to-year variationin shoot morphology. The mean final shoot length ofthe two clones with highest variation ranged from252 cm (1991) to 388 cm (1993; Templiner See), andfrom 170 cm (1993) to 229 cm (1994; Parsteiner See).In spite of this considerable variation, morphologicalparameters measured at the end of the growing seasonshowed only a slight relation to the average airtemperature either during the main growth phase (Aprilto June) or during the period of bud formation (Augustto October of the previous year). Contrary to meanshoot length at the end of the growing season, shootelongation during the main growth phase (from April toJune) was clearly related to the sum of daily averagetemperatures. Thus, taking into account temperaturemay enhance the accuracy of studies on reed growthwhenever these studies are carried out at localitiesdiffering in temperature or in different years.     

De novo shoot morphogenesis and plant growth of mustard (Brassica juncea) in vitro in relation to ethylene

Role of ethylene in de novo shoot morphogenesis from explants and plant growth of mustard ( Brassica juncea cv. India Mustard) in vitro was investigated, by culturing explants or plants in the presence of the ethylene inhibitors aminoethoxyvinylglycine (AVG) and AgNO₃. The presence of 20 μ M AgNO₃ or 5 μ M AVG in culture medium containing 5 μ M naphthaleneacetic acid and 10 μ M benzyladenine were equally effective in promoting shoot regeneration from leaf disc and petiole explants. However, AgNO₃ greatly enhanced ethylene production which reached a maximum after 14 days, whereas ethylene levels in the presence of AVG remained low during 3 weeks of culture. The promotive effect of AVG on shoot regeneration was overcome by exogenous application of 25 μ M 2-chloroethylphosphonic acid (CEPA), but AgNO_3-induced regeneration was less affected by CEPA. For whole plant culture, AVG did not affect plant growth, although it decreased ethylene production by 80% and both endogenous levels of 1-aminocyclopropane-1-carboxylate (ACC) synthase and ACC by 70–80%. In contrast, AgNO₃ stimulated all 3 parameters of ethylene synthesis. Both AgNO₃ and CEPA were inhibitory to plant growth, with more severe inhibition occuring in AgNO₃. Leaf discs derived from plants grown with AVG or AgNO₃ were highly regenerative on shoot regeneration medium without ethylene inhibitor, but the presence of AgNO₃ in the medium was inhibitory to regeneration of those derived from plants grown with AgNO₃.     

Effect of sub-optimal root zone temperatures at varied nutrient supply and shoot meristem temperature on growth and nutrient concentrations in maize seedlings (Zea mays L.)

Maize seedlings were grown for 10 to 20 days in either nutrient solution or in soils with or without fertilizer supply. Air temperature was kept uniform for all treatments, while root zone temperature (RZT) was varied between 12 and 24°C. In some treatments the basal part of the shoot (with apical shoot meristem and zone of leaf elongation) was lifted up to separate the indirect effects of root zone temperature on shoot growth from the direct effects of temperature on the shoot meristem.Shoot and root growth were decreased by low RZT to a similar extent irrespective of the growth medium (i.e. nutrient solution, fertilized or unfertilized soil). In all culture media Ca concentration was similar or even higher in plants grown at 12 as compared to 24°. At lower RZT concentrations of N, P and K in the shoot dry matter decreased in unfertilized soil, whereas in nutrient solution and fertilized soil only the K concentration decreased.When direct temperature effects on the shoot meristem were reduced by lifting the basal part of the shoot above the temperature-controlled root zone, shoot growth at low RZT was significantly increased in nutrient solution and fertilized soil, but not in unfertilized soil. In fertilized soil and nutrient solution at low RZT the uptake of K increased to a similar extent as plant growth, and thus shoot K concentration was not reduced by increasing shoot growth rates. In contrast, uptake of N and P was not increased, resulting in significantly decreased shoot concentrations.It is concluded that shoot growth at suboptimal RZT was limited both by a direct temperature effect on shoot activity and by a reduced nutrient supply through the roots. Nutrient concentrations in the shoot tissue at low RZT were not only influenced by availability in the substrate and dilution by growth, but also by the internal demand for growth.     

Clacium ion involvement in growth inhibition of mechanically stressed soybean (Glycine max) seedlings

A 40–50% reduction in soybean [ Glycine max (L.) Merr. cv. Century 84] hypocotyl elongation occurred 24 h after application of mechanical stress. Exogenous at 10 m M inhibited growth by 28% if applied with the Ca²⁺ ionophore A23187 to the zone of maximum hypocotyl elongation. La³⁺ was even more inhibitory than Ca²⁺, especially above 5 m M . Treatment with ethyleneglycol-bis-(β3-aminoethylether)-N, N, N', N'-tetraacetic acid (EGTA) alone had no effect on growth of non-stressed seedlings at the concentrations used but negated stress-induced growth reduction by 36% at 4 m M when compared to non-treated, stressed controls. Treatment with EDTA was ineffective in negating stress-induced growth inhibition. Calmodulin antagonists calmidazolium, chlorpromazine, and 48/80 also negated stress-induced growth reduction by 23, 50, and 35%, respectively.     

外源调节剂对淹涝水稻幼苗株高及碳水化合物消耗的影响

为研究淹涝条件下水稻幼苗株高及碳水化合物消耗对不同外源生长调节剂的响应,本试验选用籼型常规稻IR64和导入耐淹涝基因Sub1的IR64-Sub1为试验材料,秧龄20 d时喷施1-氨基环丙烷-1-羧酸(ACC)、多效唑(PB)、赤霉素(GA)3种外源生长调节剂,以喷施清水为对照(CK).喷施处理2 d后进行0、4、8、12、16 d没顶淹涝胁迫,淹涝胁迫结束后常温恢复7 d,取样分析不同外源生长调节剂对水稻成活率、株高、叶绿素降解及恢复、地上部非结构性碳水化合物(NSC)消耗的影响.结果表明:淹涝导致水稻幼苗株高显著增长,叶片SPAD值快速下降,叶片可溶性糖迅速消耗,但耐淹涝品种IR64-Sub1淹水前茎鞘NSC含量明显高于IR64,淹涝中NSC消耗速率低于IR64,淹水结束后地上部淀粉含量高于IR64.外源PB处理显著抑制水稻幼苗株高增长、叶绿素降解及NSC消耗,提高存活率,且对IR64-Sub1效果更为显著.外源GA处理水稻幼苗叶绿素降解、株高增长和NSC消耗最快,植株恢复能力最低,耐淹涝能力最差,但与IR64相比,GA对IR64-Sub1淹涝耐性的抑制明显减弱.外源ACC促进伸长效果明显低于外源GA处理.淹水前喷施PB可有效抑制植株水下伸长,延缓叶绿素降解,减缓NSC消耗,保留更多NSC,为淹水胁迫解除后水稻快速恢复提供有利条件,这对于易涝地区减轻涝渍危害具有重要意义.     

Effects of two growth retardants on tissue permeability in Pisum sativum and Beta vulgaris

The effects of growth retardants, 4-hydroxy-5-isopropyl-2-methylphenyltrimethylammonium chloride-1-piperidine carboxylate (AMO-1618 or AMO) and 2-chloroethyltrimethylammonium chloride (CCC), applied with and without gibberellic acid (GA₃), on -[³H]alanine uptake and leakage from pea (Pisum sativum L.) and betacyanin efflux from beetroot (Beta vulgaris L.) tissue were examined. Both compounds decreased the amount of -[³H]alanine taken up into pea leaf discs, and increased the quantity of radioactive label that subsequently leaked out of this tissue. Efflux of betacyanin from slices of beetroot was also found to be promoted by treatment with CCC or AMO-1618. In no case were these effects reversed by application of GA₃. It is concluded that the growth retardants may be altering tissue permeability by an interaction with the cell membranes, and this may account for some of the side effects of the retardants which cannot be explained on the basis of their inhibiting action on gibberellin synthesis.Abbreviations AMO-1618 4-hydroxy-5-isopropyl-2-methylphenyltrimethylammonium chloride-1-piperidine carboxylate - CCC 2-chloroethyltrimethylammonium chloride - GA₃ gibberellic acid     

Apical control of lateral bud development and shoot growth in mulberry (Morus alba)

Measurements of changes in the degree of dominance by upper laterals over lower ones in coppice shoots (1-year-old stems) of 12-year old low- pruned stumps of mulberry ( Morus alba L. cv. Shin-ichinose) were made by removal of upper stem sections (pruning) or of lateral buds (debudding.) before spring bud burst, as part of a study of the factors involved in dominance relationships between the developing buds and elongating shoots. Besides inhibition of lower laterals by the upper, leading shoots, there was evidence for mutual inhibition (competition) of neighboring laterals along the stem. Thus in stems in which every other bud, or 4 out of every 5 buds were removed, there was a delay in growth cessation of lower laterals and their greater elongation than in controls. Such competition was seen to exist even between the uppermost and sub-terminal laterals, since the former elongated more in the absence of the latter.
In contrast to high and middle pruned stems, the delay in sprouting of the buds in low-pruned stems resulted in limited elongation of the shoots from such buds. This inhibition was removed when all the stems on a stump were pruned to the same length, suggesting that it was associated with intact stems with actively growing laterals. Patterns of regrowth of the short shoots (lower laterals) after summer pruning (middle-pruned) depended on the extent of removal of other stems with vigorously growing, upper laterals. These results demonstrate that both acropetal and basipetal influences are important in bud and shoot dominance relationships.     

Effects of herbivory and genotype on growth and survivorship of sand-dune willow (Salix cordata)

Abstract.

• 1 The response of different clones of sand-dune willow, Salix cordata, to herbivory by a specialist herbivore, Altica subplicata, was studied in three glasshouse experiments. Plants were caged and exposed to three herbivory treatments: no beetles, low number of beetles, and high number of beetles.
• 2 Plants consistently had significantly higher growth rates in the absence of herbivory than under conditions of low or high herbivory (1.5–6 times higher).
• 3 Herbivore treatment influenced mortality from drought stress; more plants from the low and high herbivory treatments (40% and 80%) died from drought stress than did control plants (0%).
• 4 Clone genotype significantly influenced growth rates and the susceptibility of plants to drought stress. However, clones showed similar growth responses to herbivory, suggesting a lack of genetic variation in tolerance or resistance to herbivory.