Glycosidases and acid-invertase activities are not correlated with Phaseolus hypocotyl growth

Changes in α-galactosidase, β-galactosidase, β-glucosidase and acid invertase activities were examined in Phaseolus vulgaris hypocotyls treated with gibberellic acid (GA), naphthyl acetic acid (NAA) and distilled water (DW) (control) in light condition. The activities were estimated both in cytoplasmic and ionically wall-bound fraction. The upper segment showed considerable elongation growth while there was hardly any growth in lower segment. GA and NAA showed distinct promotion and inhibition respectively in hypocotyl growth in upper segment. The glycosidase activities were detected in both the fractions but the activity was more pronounced in cytoplasmic than in wall fraction. Acid invertase activity was present only in cytoplasmic fraction. In lower segment, in both cytoplasmic and wall fraction, the glycosidase activity, in general, showed a decreasing trend and no effect of treatment could be envisaged. In upper segment, though the trend was similar to the lower one, in α- and β-galactosidase NAA treated segment had more activity. Invertase activity also did not show a clear trend to implicate its function in hypocotyl elongation growth. The results are discussed in relation to establishing a correlation between an activity (glycosidase and invertase) and a physiological process (hypocotyl elongation). It is concluded that these wall-loosening enzymes have no role in elongation growth of Phaseolus vulgaris hypocotyls.     

Changes in peroxidase and IAA oxidase activities during cell elongation in Phaseolus hypocotyls

Cytoplasmic and salt-extracted peroxidase and IAA oxidase activities were studied in Phaseolus vulgaris hypocotyls treated with gibberellic acid (GA, 200 μM), naphthyl acetic acid (NAA, 100 μM) and distilled water control (DW). Peroxidase activity was assayed with four hydrogen donors during the initial phase of hypocotyl elongation. Though peroxidase activity showed a decreasing trend with time in all the hydrogen donors studied; considerable variation with different hydrogen donors was observed. NAA had maximum peroxidase activity as compared to DW or GA treatment. The activity showed a clear inverse correlation with hypocotyl growth. IAA oxidase activity showed a similar trend with growth as peroxidase activity. A highly significant correlation was observed between peroxidase and IAA oxidase activities and high molecular weight xyloglucan content (P<0.001). Finally, the possible role of peroxidase and IAA oxidase activities in hypocotyl elongation growth is discussed.     

Quantitative and qualitative changes in cell wall polysaccharides in relation to growth and cell wall loosening in Lactuca sativa hypocotyls

The correlation between hypocotyl elongation, cell wall loosening and changes in cell wall polysaccharides was studied using intact lettuce seedlings grown in the dark or in light together with gibberellic acid (GA) and/or 5-fluorodeoxyuridine (FUDR). The following results were obtained:
1) The production of pectic, hemicellulosic and cellulosic polysaccharides look place in parallel with hypocotyl elongation, which was substantially affected by different growth conditions.
2) The mole percentage sugar composition of pectic and hemicellulosic polysaccharides changed in response to dark, light, GA, or FUDR treatments.
3) The amounts of xylose and glucose in hemicellulosic polysaccharides and those of galactosc, rhumnose and uronic acid in pectic polysaccharides increased in parallel with hypocotyl elongation.
4) Statistical analysis of the quantitative relationship between sugars composing polysaccharides revealed that the uronic acid content changed in parallel with those of rhamnose and galactose in pectic polysaccharides, and the content of xylose varied in parallel with those of fucose and glucose.
5) The content of hemicellulosic polysaccharides was correlated with cell wall loosening represented by a decrease in the minimum stress-relaxation time. Changes in the stress-relaxation time value were correlated with those in the content of araltinose and galactose in hemicellulosic polysaccharides.
Based on these results, the relationship between hypocotyl elongation, changes in cell wall polysaccharides, and cell wall loosening is discussed with respect to the effect of GA and FUDR on hypocotyl elongation.     

Growth capacity and molecular mass distribution of cell wall polysaccharides along the hypocotyl of Pinus pinaster

The changes in the endogenous growth as well as in the cell wall composition were studied along the hypocotyl of Pinus pinaster Aiton. Cell elongation decreased as the distance from the cotyledonary node increased. Pectic polysaccharides underwent an important depolymerization accompanied by a decrease in their uronic acid content from the apical to basal region of the hypocotyl. Additionally, the molecular mass of pectic polysaccharides strongly decreased from the apical to the basal regions. Watersoluble hemicellulosic polysaccharides extracted with 4% KOH decreased notably from the cotyledonary node towards the base, while water-soluble polysaccharides extracted with 24% KOH showed few differences along the hypocotyl. The molecular mass of xyloglucan present in both hemicellulosic fractions was lower in the upper hypocotyl region as compared with the basal region. These findings are in agreement with an active xyloglucan depolymerization in the upper region as would be expected in a region exhibiting very active growth.     

Cell elongation and cell division in elongating lettuce hypocotyl sections

The roles of cell division and cell elongation in the growth of sections excised from hypocotyls of lettuce (Lactuca sativa L. cv. Arctic) were investigated. Elongation of sections incubated in the light is inhibited compared to dark-grown sections and this inhibition is reversed by gibberellic acid (GA₃). The elongation of both dark-grown and GA₃-treated, light-grown sections can be enhanced by 10mM KCl. Under all conditions of incubation, elongation growth is greatest in the uppermost quarter of the hypocotyl section while the basal quarter does not elongate. In darkness the two apical segments of sections marked into four equal parts grow at the same rate, while in light, growth of the apical segment exceeds that of the second segment. Cell division in cortical or epidermal cells, as measured by mitotic index or cell number, is not affected by illumination conditions nor by GA₃ or KCl treatments. Although -irradiation and FUDR pretreatment eliminate or cause a marked reduction in cell division in the excised hypocotyl, sections from seeds irradiated with -rays or incubated in 5-fluorodeoxyuridine elongate in response to GA₃ and KCl treatment as do sections from non-pretreated controls. Therefore, since neither GA₃ nor darkness affect celldivision activity and since treatments which eliminate or significantly reduce cell division do not affect growth, we conclude that the effect of GA₃ and darkness in this material is to increase cell elongation.Abbreviations FUDR 5-fluorodeoxyuridine - GA(s) gibberellin(s) - GA₃ gibberellic acid     

Cell Elongation and Microtubule Behavior in the Arabidopsis Hypocotyl: Responses to Ethylene and Auxin

During elongation of the Arabidopsis hypocotyl, each cell reacts to light and hormones in a time- and position-dependent manner. Growth in darkness results in the maximal length a wild-type cell can reach. Elongation starts at the base and proceeds in the acropetal direction. Cells in the upper half of the hypocotyl can become the longest of the whole organ. Light strongly inhibits cell elongation all along the hypocotyl, but proportionally more in the upper half. The ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) is known to stimulate hypocotyl elongation in the light. Here we show that this stimulation only occurs in cells of the apical half of the hypocotyl. Moreover, ACC application can partially overcome light inhibition, whereas indole-3-acetic acid (IAA) cannot. On low-nutrient medium (LNM) in the light, elongation is severely reduced as compared to growth on rich medium, and both ACC and IAA can stimulate elongation to the levels reached on a nutrient-rich medium. Furthermore, microtubule orientation was studied in vivo. During elongation in darkness, transverse and longitudinal patterns are clearly related with rates of elongation. In other conditions, except for the association of longitudinally orientated microtubules with growth arrest, microtubule orientation is merely an indicator of developmental age, not of elongation activity. A hypothesis on the relation between microtubules and elongation rate is discussed.     

Turnover of cell wall components during internode growth in <Emphasis Type="Italic">Merremia emarginata</Emphasis>

The internodes of Merremia emarginata plant showed exceptionally high stretchability throughout the development period. Therefore, it provides excellent material to study the changes undergoing during cell elongation. In this study, the influence of the hormone treatments (GA₃, PAA and NAA) on the wall component synthesis was analyzed in relation to elongation growth during internode development. A clear increasing trend of wall components was observed with increase in internode length. The non-esterified pectic substances were markedly correlated with internode length while esterified pectic substances showed correlation only in hormone treated internodes. Low molecular weight xyloglucans content showed correlation only in GA₃ and NAA treated internodes, while high molecular weight xyloglucans were significantly correlated with length of internodes treated with PAA and NAA.     

High frequency of plant regeneration from hypocotyl explants of Brassica carinata A. Br.

An efficient tissue culture system for high frequency of plant regeneration from hypocotyl explants of Brassica carinata was developed via manipulation of culture medium and selection of explants. Explants grown on medium containing combinations of 2 mg l^-1 BA and 0.01 mg l^-1 NAA or 4 mg l^-1 kinetin and 0.01 mg l^-1 2,4-D regenerated shoots at 100% frequency. High frequency shoot regeneration occurred only from explants originating from 6 to 7-day-old but not younger or older seedlings. Explants showed higher regeneration capacity at the distal end than the proximal end, and the upper segment was more regenerative than the lower segment of hypocotyl. Regenerants were rooted on half-strength growth regulator-free medium, acclimatized and developed into normal, fertile plants.Abbreviations BA benzyladenine - 2-4-D 2,4-dichlorophenoxyacetic acid - NAA naphthaleneacetic acid - MS Murashige & Skoog     

Salinity-induced changes in peroxidase activity and cell-wall polysaccharides in<Emphasis Type="Italic">Vigna</Emphasis>

We investigated the effect of salinity on the development of seedlings of Vigna unguiculata. At various time intervals, the hypocotyls were measured to estimate the effect of salt concentration on growth parameters. Control plants were tallest and had the greatest fresh weights, whereas these values were lowest in seedlings treated with high levels of salt. Three hydrogen donors -- caffeic acid, ferulic acid, and pyrogalol - were studied to determine the changes in peroxidase activity for both cytoplasmic and wall-bound fractions. Activity was inversely correlated with hypocotyl elongation. A clear concentration effect was also observed for contents of pectic polysaccharides, low-molecular-weight xyloglucan, and high-molecular-weight xyloglucan, with control seedlings showing lower levels of those wall components than that recorded in the salt-treated seedlings. Here, we also discuss the role of peroxidase and wall components in hypocotyl elongation and growth ofVigna when seedlings undergo saline stress.     

Regulation of phenylalanine ammonia-lyase activity and growth in lettuce by light and gibberellic acid

Abstract The effects of light and gibberellic acid (GA3) on growth and phenylalanine ammonia-lyase (PAL) activity were studied in seedlings of lettuce (Lactuca sativa L.). Using an in vivo assay for PAL it was shown that wounding caused by excising hypocotyls results in an increase in PAL activity with time that can mask the effect of light on the activity of this enzyme. When hypocotyl sections were excised from light-treated seedlings immediately prior to the in vivo assay of PAL, light was shown to cause a marked increase in PAL activity. Experiments with an inhibitor of PAL activity, α-aminooxy-β-phenylpropionic acid (AOPP), confirmed that the volatile radioactive products measured in the in vivo assay resulted from the activity of PAL. Gibberellic acid suppresses the light-induced increase in PAL activity and there is an inverse relationship between GA₃-induced growth and the activity of PAL. Over a wide range of GA₃ concentrations, the activity of PAL is also inversely correlated with growth rate along the length of the hypocotyl section; the upper halves of sections elongate more rapidly and have lower levels of PAL than the lower halves. Despite the strong correlation between growth and PAL activity, experiments with AOPP and t-cinnamic acid show that it is unlikely that elongation is regulated directly by products of PAL activity.     

Gibberellins and auxin regulate soybean hypocotyl elongation under low light and high-temperature interaction

Soybean is an important oilseed crop grown globally. However, two examples of environmental stresses that drastically regulate soybean growth are low light and high-temperature. Emerging evidence suggests a possible interconnection between these two environmental stimuli. Low light and high-temperature as individual factors have been reported to regulate plant hypocotyl elongation. However, their interactive signal effect on soybean growth and development remains largely unclear. Here, we report that gibberellins (GAs) and auxin are required for soybean hypocotyl elongation under low light and high-temperature interaction. Our analysis indicated that low light and high-temperature interaction enhanced the regulation of soybean hypocotyl elongation and that the endogenous GA₃, GA₇, indole-3-acetic acid (IAA), and indole-3-pyruvate (IPA) contents significantly increased. Again, analysis of the effect of exogenous phytohormones and biosynthesis inhibitors treatments showed that exogenous GA, IAA, and paclobutrazol (PAC), 2, 3, 5,-triiodobenzoic acid (TIBA) treatments significantly regulated soybean seedlings growth under low light and high-temperature interaction. Further qRT-PCR analysis showed that the expression level of GA biosynthesis pathway genes (GmGA3ox1, GmGA3ox2 and GmGA3) and auxin biosynthesis pathway genes (GmYUCCA3, GmYUCCA5 and GmYUCCA7) significantly increased under (i) low light and high-temperature interaction and (ii) exogenous GA and IAA treatments. Altogether, these observations support the hypothesis that gibberellins and auxin regulate soybean hypocotyl elongation under low light and high-temperature stress interaction.     

Inhibition of stem elongation in cucumis seedlings by blue light requires calcium

The effects of blue light and calcium on elongation of hypocotyl segments of Cucumber (Cucumis sativa L. cv Burpee's Pickler) were studied. Cucumber seedlings grown in dim red light showed a rapid decline in the rate of hypocotyl elongation when irradiated with high intensity (100 micromoles per square meter per second) blue light. In intact, 4-day-old seedlings the inhibition began within 2 minutes after the onset of blue-light irradiation and reached a maximum of approximately 55% within 4 minutes. Hypocotyl segments cut from 4-day-old seedlings also showed an inhibition of elongation in response to blue light when segments were floated on aqueous buffer and exposed to blue light for 3 hours. In the presence of 2 micromolar indole-3-acetic acid, blue light caused a 50% inhibition of elongation. Buffering free calcium in the incubation medium with 0.1 millimolar ethylene glycol bis(-aminoethyl ether)- N,N,N′,N′-tetraacetic acid eliminated the blue-light inhibition of segment elongation. Several experiments confirmed a specific requirement for calcium for the blue-light-induced inhibition of segment elongation. Treating segments with 0.2 micromolar fusicoccin abolished the inhibition of elongation by blue light as did buffering the medium at pH 4. Adding 1 millimolar ascorbate to incubation medium also eliminated the inhibition of segment elongation caused by blue light. Several compounds implicated in cell-wall redox reactions alter the magnitude of the blue-light-induced inhibition. The activity of peroxidase isolated from the cell-wall free space of cucumber hypocotyls was inhibited by ascorbate and low pH. The results are consistent with the hypothesis that blue light inhibits elongation by inducing an increase in cell-wall peroxidase activity and implicate calcium ions in the response to blue light.     

Physiology of gibberellin-induced elongation of epicotyl explants from Vigna sinensis

The physiological characteristics of the response of excised cowpea (Vigna sinensis cv Blackeye pea No. 5) epicotyls to gibberellins (GAs) were studied. Epicotyl explants, retaining the petioles and a 2-cm portion of hypocotyl, were placed upright in small vials containing water. Plant growth substances were injected into the subapical tissues as ethanol solutions.Epicotyl elongation resulting from treatment with 0.5 g of GA ranged between 5 and 13 times that of the control, depending on the GA applied. With GA₁, no differences were obtained with explants prepared from 5 to 9-day-old seedlings. The increase in elongation could be detected within 6 h of treatment, and the stimulus of a single application lasted at least 4 days. Final elongation was proportional to the logarithm of the amount of GA, applied, 0.01 to lug. The response to GA treatment was limited to the upper part, the most sensitive zone being located between 2 to 4 mm below the apex of the epicotyl; this effect was entirely due to cell elongation.The induction of epicotyl elongation by GAs seems to be specific and independent of the effect of auxin. IAA had no effect on elongation and 4-chloro-phenoxyisobutyric acid (PCIB) did not affect the response to GA₁ Abbreviations ABA abscisic acid - GA gibberellin - IAA Indole-3-acetic acid - TIBA 2,3,5-triiodobenzoic acid - PCIB 4-chloro-phenoxyisobutyric acid     

Use of a pH-response curve for growth to predict apparent wall pH in elongating segments of maize coleoptiles and sunflower hypocotyls

To determine the relationship between apparent pH of the wall solution and shoot segment elongation, curves for the initial growth rates as a function of pH of the external solution were determined for maize (Zea mays L.) coleoptiles and sunflower (Helianthus annuus L.) hypocotyls and used to predict apparent wall pH in segments responding to indole-3-acetic acid (IAA) and fusicoccin (FC). When a solution having a pH predicted for walls of coleoptile segments responding to IAA was applied to the segments in the presence of IAA, this pH was not maintained. However, when the same was done for coleoptile segments responding to FC, the predicted pH was maintained in the external solution. Sunflower hypocotyl tissue did not maintain the external pH at the predicted value in the presence of either IAA or FC. The results indicate that wall loosening in coleoptiles caused by IAA may not be solely controlled by pH in the wall, yet growth (wall loosening) caused by FC apparently is directly related to wall pH. In sunflower the growth response to neither IAA nor FC appears to be directly correlated with wall pH.     

Gibberellins control Arabidopsis hypocotyl growth via regulation of cellular elongation

The gibberellins (GAs) are endogenous regulators of plant growth. Experiments are described here that test the hypothesis that GA regulates hypocotyl growth by altering the extent of hypocotyl cell elongation. These experiments use GA-deficient and altered GA-response mutants of Arabidopsis thaliana (L.) Heyhn. It is shown that GA regulates elongation, in both light- and dark-grown hypocotyls, by influencing the rate and final extent of cellular elongation. However, light- and dark-grown hypocotyls exhibit markedly different GA dose-response relationships. The length of dark-grown hypocotyls is relatively unaffected by exogenous GA, whilst light-grown hypocotyl length is significantly increased by exogenous GA. Further analysis suggests that GA control of hypocotyl length is close to saturation in dark-grown hypocotyls, but not in light grown hypocotyls. The results show that a large range of possible hypocotyl lengths is achieved via dose-dependent GA-regulated alterations in the degree of elongation of individual hypocotyl cells.Key words: Arabidopsis, cell elongation, gibberellin (GA), GA mutants, hypocotyl.      

Auxin-induced changes in the cell wall structure: Changes in the sugar compositions, intrinsic viscosity and molecular weight distributions of matrix polysaccharides of the epicotyl cell wall of Vigna angularis

Rapid effects of indole-3-acetic acid (IAA) on the mechanical properties of cell wall, and sugar compositions, intrinsic viscosity and molecular weight distribution of cell wall polysaccharides were investigated with excised epicotyl segments of Vigna angularis Ohwi et Ohashi cv. Takara.

• 1 IAA caused cell wall loosening as studied by stress-relaxation analysis within 15 min after the IAA application.
• 2 IAA stimulated the decrease in the content of arabinose and galactose in the hemicellulose 1 h after its application. The amounts of other component sugars in the cell wall polysaccharides remained constant during the IAA-induced segment growth.
• 3 The intrinsic viscocity of the pectin increased as early as 30 min after the IAA application. This effect was not prevented when elongation growth of the segment was osmotically suppressed by 0.15 M mannitol.
• 4 Gel permeation chromatography of the pectin on a Sepharose 4 B column demonstrated that IAA caused increase in the mass-average molecular weight of the pectin. Analysis of the sugar compositions of the pectin eluted from the Sepharose 4 B column indicated that IAA increased the molecular weight of the polysaccharides composed of uronic acid, galactose, rhamnose and arabinose. This effect became apparent within 30 min after the IAA application. Furthermore, IAA increased the molecular weight of the pectin when elongation growth of the epicotyl segments was osmotically suppressed by 0.15 M mannitol.
• 5 Hemicellulose of the cell wall chromatographed on a Sepharose CL-4 B column. Analysis of the neutral sugar compositions and the iodine staining property (specific for xyloglucans) of the polysaccharide solution eluted from the column indicated that the hemicellulose consisted of xyloglucans, arabinogalactans and polysaccharides composed of xylose and/or mannose. IAA caused a decrease in the arabinogalactan content and depolymerization of xyloglucans. These IAA effects became apparent within 30 min after the IAA application. These changes occurred even when elongation growth of the epicotyl segments was osmotically suppressed by 0.15 M mannitol.

Polymerization of the pectin, degradation of arabinogalactans and depolymerization of xyloglucans appear to be involved in the mechanism by which IAA induces cell wall loosening and therefore extension growth of cells.     

Change in XET activities,cell wall extensibility and hypocotyl elongation of soybean seedlings at low water potential

In dark-grown soybean (Glycine max [L.] Merr.) seedlings, exposing the roots to water-deficient vermiculite (_w=–0.36 MPa) inhibited hypocotyl (stem) elongation. The inhibition was associated with decreased extensibility of the cell walls in the elongation zone. A detailed spatial analysis showed xyloglucan endotransglucosylase (XET; EC 2.4.1.207) activity on the basis of unit cell wall dry weight was decreased in the elongation region after seedlings were transplanted to low _w. The decrease in XET activity was at least partially due to an accumulation of cell wall mass. Since cell number was only slightly altered, wall mass had increased per cell and probably led to increased wall thickness and decreased cell wall extensibility. Alternatively, an increase in cell wall mass may represent a mechanism for regulating enzyme activity in cell walls, XET in this case, and therefore cell wall extensibility. Hypocotyl elongation was partially recovered after seedlings were grown in low-_w vermiculate for about 80 h. The partial recovery of hypocotyl elongation was associated with a partial recovery of cell wall extensibility and an enhancement of XET activity in the hypocotyl elongation zone. Our results indicate XTH proteins may play an important role in regulating cell wall extensibility and thus cell elongation in soybean hypocotyls. Our results also showed an imperfect correlation of spatial elongation and XET activity along the hypocotyls. Other potential functions of XTH and their regulation in soybean hypocotyl growth are discussed.     

Role of the outer tissue in abscisic acid-mediated growth suppression of etiolated squash hypocotyl segments

Exogenously applied abscisic acid (ABA) substantially suppressed the elongation of hypocotyl segments of etiolated squash ( Cucurbita maxima Duch. cv. Houkou-Aokawaamaguri) after a 3 h lag period, without changes in the osmolalities of the apoplastic and symplastic solutions in the segment.
Segments with the outer tissues removed elongated more rapidly than unpeeled segments (whole segments). ABA did not suppress the elongation of peeled segments. When the segments were incubated in [¹⁴C]-glucose, radioactivity was more effectively incorporated into the cell wall fractions of the outer than into those of the inner tissue. ABA significantly inhibited the incorporation of radioactivity into hermicellulose and cellulose of the outer tissue prior to the suppression of segment elongation, but it did not inhibit the incorporation into the pectic traction of the outer tissue or into any of the cell wall fractions of the inner tissue. These results indicate that ABA primarily affected the outer tissue, in which it specifically reduced the synthesis of hemicellulose and cellulose prior to the ABA-mediated suppression of growth.     

UDP-Glucose level as a limiting factor for IAA-induced cell elongation in Avena coleoptile segments

The effects of galactose on IAA-induced elongation and endogenous level of UDP-glucose (UDPG) in oat ( Avena sativa L. cv. Victory) coleoptile segments were examined under various growth conditions to see if there was a correlation between the level of UDPG and auxin-induced growth. The following results were obtained:

• (1)

  Galactose (10 m M ) inhibited the auxin-induced cell elongation of oat coleoptile segments after a lag of ca 2 h. Determinations of cell wall polysaccharides and UDP-sugars indicated that galactose, when inhibiting the cell wall polysaccharide synthesis, decreased the level of UDPG but caused an increase in the levels of Gal-1-P and UDP-Gal.
• (2)

  When coleoptile segments treated with IAA and galactose were transferred to galactose-free IAA-solution, the segment elongation was restored and the amounts of cell wall polysaccharides increased. During this period, the amount of UDPG increased and the levels of Gal-1-P and UDP-Gal slightly decreased or leveled off. The UDP-pentoses changed similarly as UDPG did.
• (3)

  Addition of sucrose (30 m M ) enhanced IAA-induced cell elongation and removed growth inhibition by 1 m M galactose. Sucrose increased the amounts of the cell wall polysaccharides and the level of UDPG in the presence or absence of IAA and also counteracted the decrease in UDPG caused by galactose.

These results indicate that the level of UDPG is an important limiting factor for cell wall biosynthesis and, thus, for auxin-induced elongation.     

Inhibition of the synthesis of cell wall polysaccharides in oat coleoptile segments by jasmonic acid: Relevance to its growth inhibition

The inhibitory mode of action of jasmonic acid (JA) on the growth of etiolated oat (Avena sativa L. cv. Victory) coleoptile segments was studied in relation to the synthesis of cell wall polysaccharides using [¹⁴C]glucose. Exogenously applied JA significantly inhibited indoleacetic acid (IAA)-induced elongation of oat coleoptile segments and prevented the increase of the total amounts of cell wall polysaccharides in both the noncellulosic and cellulosic fractions during coleoptile growth. JA had no effect on neutral sugar compositions of hemicellulosic polysaccharides but substantially inhibited the IAA-stimulated incorporation of [¹⁴C]glucose into noncellulosic and cellulosic polysaccharides. JA-induced inhibition of growth was completely prevented by pretreating segments with 30 mm sucrose for 4 h before the addition of IAA. The endogenous levels of UDP-sugars, which are key intermediates for the synthesis of cell wall polysaccharides, were not reduced significantly by JA. Although these observations suggest that the inhibitory mode of action of JA associated with the growth of oat coleoptile segments is relevant to sugar metabolism during cell wall polysaccharide synthesis, the precise site of inhibition remains to be investigated.Abbreviations JA jasmonic acid - ABA abscisic acid - IAA indoleacetic acid - T ₀ minimum stress relaxation time - TFA trifluoroacetic acid - TCA trichloroacetic acid - HPLC high-performance liquid chromatography - EtOAc ethyl acetate - TLC thin-layer chromatography - JA-Me methyl jasmonate - GLC-SIM gas-liquid chromatography-selected ion monitoring