Metabolism of Steviol and Its Derivatives by Gibberella fujikuroi

Steviol (ent-13-hydroxykaur-16-en-19-oic acid)* is metabolized by Gibberella fujikuroi in the presence of inhibitors of gibberellin biosynthesis, such as quaternary ammonium salt-type growth retardants, to afford 7β-Miydroxy- and 6β,7β-dihydroxysteviol, gibberelhns A₁, A₁₈, A₁₉, A₅₃ and 7β,13-dihydroxykaurenolide. Steviol acetate (ent-13-acetoxykaur-16-en-19-oic acid) is also metabolized to the 6β,7β-dihydroxy-derivative and to the 13-acetyl derivatives of gibberellins A₁₇ and A₂₀ and steviol methyl ester (methyl ent-13-hydroxykaur-16-en-19-oate) into the monohydroxy-, dihydroxy- and hydroxyoxo-derivatives. These results indicate a low substrate specificity of the enzymes in the fungus and provide a useful preparative methodology of several important plant gibberellins carrying the 13-hydroxyl group.     

Metabolism of gibberellins in a cell-free system from immature seeds of Phaseolus vulgaris L.

The biosynthetic steps from gibberellin A₁₂-aldehyde (GA₁₂-aldehyde) to C₁₉-GAs were studied by means of a cell-free system from the embryos of immature Phaseolus vulgaris seeds. Stable-isotope-labeled GAs were used as substrates and the products were identified by gas chromatography-mass spectrometry. Gibberellin A₁₂-aldehyde was converted to GA₄ via non-hydroxylated intermediates and to GA₁ via 13-hydroxylated intermediates. 13-Hydroxylation took place at the beginning of the pathway by the conversion of GA₁₂-aldehyde to GA₅₃-aldehyde. The conversion of GA₂₀ to GA₅ and GA₆ was also shown but no 2-hydroxylating activity was found. Endogenous GAs from embryos and testas of 17-dold seeds were re-examined by gas chromatography-selected ion monitoring using stable-isotopelabeled GAs as internal standards. Gibberellins A₉, A₁₂, A₁₅, A₁₉, A₂₃, A₂₄, and A₅₃ were identified for the first time in P. vulgaris, in addition to GA₁, GA₄, GA₅, GA₆, GA₈, GA₁₇, GA₂₀, GA₂₉, GA₃₇, GA₃₈ and GA₄₄, which were previously known to occur in this species. The levels of all GAs, except the 2-hydroxylated ones, were greater in the embryos than in the testas. Conversely, the contents of GA₈ and GA₂₉, both 2-hydroxylated, were much higher in the testas than in the embryos.Abbreviations GA_n gibberellin A_n - GC-MS gas chromatography-mass spectrometry - GC-SIM gas chromatography-selected ion monitoring - HPLC high-performance liquid chromatography - TLC thin-layer chromatography - m/z ion of mass     

Influence of an inhibitor of gibberellin biosynthesis, paclobutrazol, on apple seed gibberellin content

Tissue-culture-propagated own-rooted cv. Spartan apple trees (Malus domestica Borkh.) planted in 1979 were treated in 1983 and 1985 via a soil-line trunk drench with the plant growth retardant paclobutrazol [(2RS, 3RS)-1-(4-chlorophenyl)-4.4-dimethyl-2-(1,2, 4-triazol-1-yl) pentan-3-ol]. Seeds of immature fruits from untreated and treated trees were sampled in 1989 ca 75 days after full bloom. After seeds were freeze-dried, gibberellins (GAs) were extracted, purified and fractionated via C₁₈ reversed-phase high-performance liquid chromatography (HPLC). Gibberellins A₁, A₃, A₄, A₇, A₈, A₉, A₁₅, A₁₇, A₁₉, A₂₀, A₂₄, A₃₄, A₃₅, A₄₄, A₅₁, A₅₃, A₅₄, A₆₁, A₆₂, A₆₃ and A₆₈ were identified by using C₁₈ HPLC, gas chromatography-selected ion monitoring and Kovats retention indices. Eight of the GAs identified were also quantified by using deuterated internal standards. The paclobutrazol applications caused a 55% reduction of vegetative shoot elongation in 1989, but both treated and untreated trees had developed a biennial bearing pattern by that time (heavy bloom or “on year’in 1989). Levels of early 13-hydroxylation pathway GAs, viz. GA₅₃, GA₁₉, GA₂₀, GA₁ and also GA₃, were not altered by treatment. However, GA₄, GA₇ and GA₉ were increased 13.4, 6.5 and 3.8 times, respectively, in seeds of fruit from treated compared to untreated trees.     

The endogenous gibberellins of vegetative and reproductive tissue of G2 peas

The gibberellins (GAs) of both vegetative (leaves and stems) and reproductive (pods and seeds) tissue of the G2 strain of peas Pisum sativum L. were characterized in purified extracts by a combination of sequential silicic-acid partition column chromatography, and gas chromatography-mass spectrometry. Gibberellins A₁₉, A₂₀, A₂₉ and an A₂₉ catabolite were identified in both types of tissue. Gibberellins A₉, A₁₇ and A₄₄ were also found in pods and seeds.Abbreviations FID Ilame ionization detector - GA(s) gibberellin(s) - GC gas chromatograph(y) - HPLC high performance liquid chromatograph(y) - LD long day - MS mass spectrum(a) or mass spectrometer(ry) - SD short day     

COEFFICIENTS OF ASSOCIATION AND SIMILARITY, BASED ON BINARY (PRESENCE-ABSENCE) DATA: AN EVALUATION

Forty-three association (similarity) coefficients were collected and evaluated in this survey. Some of them are synonyms or direct correlates with earlier described indices (A₈, A₉, A₁₂, A₃₁, A₃₃), others are mere transforms from one range of values to another (A₁₀, A₂₄, A₃₃). Several coefficients are incompatible with suggested admissibility conditions of the minimum-maximum value (A₁₃, A₁₆, A₂₇, A₂₈, A₂₉, A₃₁), symmetry (A₁, A₂, A₁₃, A₁₆, A₂₆), discrimination between positive and negative association (A₂₇, A₂₈, A₃₁) or monotonicity with (χ²) (A₁₉, to A₂₄); A₁₇ yields very low and erratic values. As a result, 23 coefficients were excluded and the remaining 20 measures were subjected to an empirical trial on interspecific association data among fungi of the genus Chaetomium, with the use of a cluster analysis. The classification produced five main clusters of related coefficients, with several subgroups. It was then demonstrated that representative indices from different clusters yield different dendrograms of interspecific association among Chaetomium, and A₃₄, A₁₄, possibly also A₃₆ and A₄₀ seemed to be less sensible. A set of measures that generally work well (at least in the interspecific association) comprises A₄ (Jaccard), A₄ (Dice-Sφrensen), A₇ (Kulczyński), A₁₁ (Driver-Kroeber-Ochiai) and, with some reservation A³⁰ (Pearson tetrachoric) and A₃₂ (Baroni-Urbani-Buser). For some purposes, however, other ‘admissible’ coefficients would be more optimal, and the choice of a measure should be related to the nature of the data. It is tentatively suggested that three or so alternative coefficients be used and the results compared on the same data basis; moreover, significance tests on association should be carried out whenever possible.     

Synthetic Studies on Nephritogenic Glycosides. Synthesis of β-Glc-(1→6)-α-Glc-(l→6)-α-Glc-(1→Asn)

Gibberellins (GAs) A₉, A₁₅, A₁₉, A₂₀, A₂₉, A₃₅, A₄₄, A₅₀ and A₆₁ were identified by capillary gas chromatography/selected ion monitoring (GC/SIM) in immature seeds of loquat (Eriobotrya japonica Lindl). Furthermore, five unknown GA-like compounds with apparent parent ions of m/z 418, 504 or 506 (as methyl ester trimethylsilyl ether derivatives) were found by GC/mass spectrometry (GC/MS) in the biologically active fractions. The m/z 418 and 504 compounds may have been C-11β hydroxylated GA₉ and dehydro-GA₃₅, respectively. The bioassay and GC/MS results suggest that the major GAs were GA₅₀ and the five unknown GA-like compounds. In the immature seeds, at least two GA metabolic pathways may thus exist, one being the non-hydroxylation pathway of GA₁₅→GA₂₄→GA₉, and the other, the early C-13 hydroxylation pathway of GA₄₄→GA₁₉→GA₂₀→GA₂₉. A late C-11β hydroxylation pathway is also possible.     

Conversion of [14C]gibberellin A12-aldehyde to C19- and C20-gibberellins in a cell-free system from immature seed of Phaseolus coccineus L.

A cell-free system prepared from developing seed of runner bean (Phaseolus coccineus L.) converted [¹⁴C]gibberellin A₁₂-aldehyde to several products. Thirteen of these were identified by capillary gas chromatography-mass spectrometry as gibberellin A₁ (GA₁), GA₄, GA₅, GA₆, GA₁₅, GA₁₇, GA₁₉, GA₂₀, GA₂₄, GA₃₇, GA₃₈, GA₄₄ and GA₅₃-aldehyde, all giving mass spectra with ¹⁴C-isotope peaks. GA₈ and GA₂₈ were also identified but contained no ¹⁴C. All the [¹⁴C]GA₁₂-aldehyde metabolites, except GA₁₅, GA₂₄ and GA₅₃-aldehyde, are known endogenous GAs of P. coccineus.Abbreviations GA_n gibberellin A_n - GC-MS combined gas chromatography-mass spectrometry - HPLC highperformance liquid chromatography - MVA mevalonic acid - S-2 2000-g supernatant     

Rhizobial-induced increase in internode length and identification of endogenous GAs of cowpea (Vigna unguiculata [L.] Walp) stems and nodules

Inoculation with Bradyrhizobium sp. strain 127E14 has been shown to cause a dramatic increase in the internode length of lima bean (Phaseolus lunatus L.), when compared to control plants inoculated with strain 127E15. This rhizobial-induced growth also occurs in cowpea (Vigna unguiculata [L.] Walp), an alternate host for the symbiont. Cowpea plants inoculated with strain 127E14 were 23% taller than those inoculated with strain 127E14 after 6 weeks of growth. Petiole length was found to be significantly greater in plants inoculated with strain 127E14. Cowpea plants treated at the apex with exogenous GA₃ or GA_4/7 responded by increasing internode length when compared to controls. As in lima beans, the rhizobial-induced growth response observed in cowpeas may be in response to an imbalance in the levels of GA-like substances within the plants. Gibberellins A₁, A₃, A₈, A₁₉, A₂₀, A₂₉, and A₄₄have been identified by GC-MS analysis in stems of cowpea, whereas the gibberellins A₁, A₁₉, A₂₀, A₂₉, and A₄₄ were found to be present in nodule tissue formed by strain 127E14. The presence of these GAs indicates that the early 13-hydroxylation biosynthetic pathway is operative in cowpea. GAs identified in cowpea nodules are similar to those found in lima bean nodules formed by the same rhizobia. The finding that rhizobial strain 127E14 induces GA-dependent growth responses in two host legumes further supports the hypothesis that the presence of this bacteria alters the GA balance within the plant.     

Gibberellins and the photoperiodic control of leaf growth in Poa pratensis

The role of gibberellins (GAs) in photoperiodic control of leaf elongation in Poa pratensis was studied by both application of exogenous GAs and analysis of endogenous GAs. Leaf elongation was strongly increased under long day (LD, 24 h) conditions at both 9 and 21°C, leaf length at 9°C LD being similar to that in plants grown in short days (SD, 8 h) at 21°C. However, even at 21°C leaf elongation was enhanced by LD. Exogenous GA₁ could completely compensate for LD at both 9 and 21°C. Gibberellins A₂₀, A₁₉ and A₄₄ could also partly replace LD, but they were significantly less active than GA₁, GA₅₃ was inactive when applied to plants grown at 9°C in SD and exhibited only marginal activity at 9°C LD and 21°C SD. The total level of GAs of the early 13-hydroxylation pathway (A₅₃, A₄₄, A₁₉, A₂₀ and A₁) increased rapidly when plants were transferred from SD to LD at 9°C. After transfer from 9 to 21°C, there was an increase in GA levels at both LD and SD, followed by a decrease under LD conditions. In all cases, GA₁₉ was the predominant GA, accounting for 60 to 80% of the analysed GAs. Levels of the bioactive GA₁ were low and increased transiently by LD four days after transfer from SD to LD. At both temperatures, the ratio GA₁₉ to GA₂₀ and GA₂₀ to GA₁ at 9°C was enhanced by LD compared with SD. Taken together, these results support the hypothesis that photoperiodic regulation of leaf elongation in Poa pratensis is GA-mediated, and they indicate a photoperiodic control of oxidation of GA₅₃ to GA₄₄ and GA₁₉ to GA₂₀, and perhaps also of 3β-hydroxylation of GA₂₀ to GA₁.     

Gibberellins inCitrus sinensis: A comparison between seeded and seedless varieties

The gibberellin (GA) content of the reproductive organs ofCitrus sinensis (L.) Osb., cv. Bianca Comuna and the seedless variety, Salustiana, were examined by combined gas chromatography-mass spectrometry (GC/MS) at different stages of development. Gibberellins A₁, A₂₀, and A₂₉ were identified in the reproductive buds of both cultivars 21 days prior to anthesis and in fruits 35 days after anthesis by comparison of their mass spectra and Kovats retention indices with those of standards. In addition, three uncharacterized isomers of GA₁ were detected, one in buds and two in fruits. The presence of GA₄ in both tissues, and of GA₈ in the reproductive buds, was indicated by the occurrence of characteristic ions at the expected retention times, although their spectra were too weak for full identification. Vegetative shoots of cv. Salustiana contained gibberellins A₁, A₁₉, A₂₀, and A₂₉, and the unidentified isomer of GA₁ present in reproductive buds. The presence of trace amounts of gibberellins A₈ and A₁₇ was also indicated. Although the two varieties did not differ qualitatively in the GAs present during flower and fruit development, the seedless variety contained slightly greater amounts. The concentrations of gibberellins A₁, A₄, and A₂₀ were determined by gas chromatography-selected ion monitoring (GC/SIM) throughout ovary development and early fruit growth. In both varieties, the maximum GA₁ concentration occurred at anthesis. Highest concentrations of gibberellins A₂₀ and A₄ were found in fruit 35 days after anthesis, although the GA₁ concentration at this stage remained low.     

The identification of gibberellins in immature seeds of Vicia faba,and some chemotaxonomic considerations

GA₁₇, GA₁₉, GA₂₀, GA₂₉, GA₄₄ and 13-hydroxy-GA₁₂, now named GA₅₃, were identified by GC-MS in immature seeds of Vicia faba (broad bean). Also identified were a GA catabolite, two polyhydroxykauranoic acids, and abscisic, phaseic and dihydrophaseic acids. The GAs of Vicia are hydroxylated at C-13, in common with those of other legumes. However the GAs of Vicia are not hydroxylated at C-3, nor do they appear to be readily conjugated. In these respects Vicia resembles Pisum, another member of the tribe Viciae. Vicia differs from Phaseolus and Vigna, of the tribe Phaseoleae, in both these respects.Abbreviations ABA abscisic acid - DPA dihydrophaseic acid - GA_n gibberellin A_n - GC gas chromatography - GC-MS gas chromatography mass spectrometry - KA kauranoic acid - PA phaseic acid - TLC thin layer chromatography     

Identification of Endogenous Gibberellins from Salix pentandra

Gibberellins A₁, A₁₉, A₂₀, and A₂₉ have been identified by sequential high-performance liquid chromatography retention time (Rt) and combined gas chromatography-mass spectrometry (Rt and characteristic mass spectra) from elongating shoots of Salix pentandra L. Gibberellins A₁ and A₁₉ were also detected in purified extracts from male and female flowers (catkins) of S. pentandra.     

Temperature responses of photosynthesis and respiration in <Emphasis Type="Italic">Populus</Emphasis><Emphasis Type="Italic">balsamifera</Emphasis> L.: acclimation versus adaptation

To examine the role of acclimation versus adaptation on the temperature responses of CO₂ assimilation, we measured dark respiration (R _n) and the CO₂ response of net photosynthesis (A) in Populus balsamifera collected from warm and cool habitats and grown at warm and cool temperatures. R _n and the rate of photosynthetic electron transport (J) are significantly higher in plants grown at 19 versus 27°C; R _n is not affected by the native thermal habitat. By contrast, both the maximum capacity of rubisco (V _cmax) and A are relatively insensitive to growth temperature, but both parameters are slightly higher in plants from cool habitats. A is limited by rubisco capacity from 17–37°C regardless of growth temperature, and there is little evidence for an electron-transport limitation. Stomatal conductance (g _s) is higher in warm-grown plants, but declines with increasing measurement temperature from 17 to 37°C, regardless of growth temperature. The mesophyll conductance (g _m) is relatively temperature insensitive below 25°C, but g _m declines at 37°C in cool-grown plants. Plants acclimated to cool temperatures have increased R _n/A, but this response does not differ between warm- and cool-adapted populations. Primary carbon metabolism clearly acclimates to growth temperature in P. balsamifera, but the ecotypic differences in A suggest that global warming scenarios might affect populations at the northern and southern edges of the boreal forest in different ways.     

Gibberellins in immature seeds and dark-grown shoots of Pisum sativum

Gibberellins (GAs) A₁₇, A₁₉, A₂₀, A₂₉, A₄₄, 2OH-GA₄₄ (tentative) and GA₂₉-catabolite were identified in 21-day-old seeds of Pisum sativum cv. Alaska (tall). These GAs are qualitatively similar to those in the dwarf cultivar Progress No. 9 with the exception of GA₁₉ which does not accumulate in Progress seeds. There was no evidence for the presence of 3-hydroxylated GAs in 21 day-old Alaska seeds. Dark-grown shoots of the cultivar Alaska contein GA₁, GA₈, GA₂₀, GA₂₉, GA₈-catabolite and GA₂₉-catabolite. Dark-grown shoots of the cultivar Progress No.9 contain GA₈, GA₂₀, GA₂₉ and GA₂₉-catabolite, and the presence of GA₁ was strongly indicated. Quantitation using GAs labelled with stable isotope showed the level of GA₁ in dark-grown shoots of the two cultivars to be almost identical, whilst the levels of GA₂₀, GA₂₉ and GA₂₉-catabolite were significantly lower in Alaska than in Progress No. 9. The levels of these GAs in dark-grown shoots were 10²- to 10³-fold less than the levels in developing seeds. The 2-epimer of GA₂₉ is present in dark-grown-shoot extracts of both cultivars and is not thought to be an artefact.Abbreviations cv cultivar - GA_n gibberellin A_n - GC gas chromatography - GC-MS combined gas chromatographymass spectrometry - HPLC high-pressure liquid chromatography - KRI Kovats retention index - MeTMSi methyl ester trimethylsilyl ether     

Gibberellins and the Legume-Rhizobium Symbiosis : I. Endogenous Gibberellins of Lima Bean (Phaseolus lunatus L.) Stems and Nodules

The content of gibberellin-like substances in nodules formed by Bradyrhizobium species strain 127E14 on roots of lima bean (Phaseolus lunatus L.) has been previously found to be relatively high. The objectives of the present study were to purify and identify the endogenous gibberellins from the stems and nodules of lima bean. By sequential silica gel partition column chromatography, C₁₈ reverse-phase high performance liquid chromatography, and combined gas chromatography-mass spectrometry, the gibberellins A₁, A₃, A₁₉, A₂₀, A₂₉, and A₄₄ were identified from root nodules. Gibberellins A₁, A₃, A₁₉, A₂₀, and A₄₄ were also identified from lima bean stem tissue. These data provide the first mass spectral-based evidence that gibberellins are present in leguminous root nodules. The presence of the gibberellins identified indicates that the early 13-hydroxylation gibberellin biosynthetic pathway predominates in stem and nodule tissue. However, it is not known if the gibberellins within the nodules are produced in situ, or if they are imported from some remote host plant tissue.     

Structures of Gibberellins A39, A48, A49 and a New Kaurenolide in Cucurbita pepo L.

The structures of three new gibberellins A₃₀, A₄₈ and A₄₉ and a new kaurenolide, isolated from seeds of Cucurbita pepo L., were elucidated. The structures of GA₃₉, GA₄₈ and GA₄₉ were shown to be ent-3α,12β-dihydroxygibberell-16-ene-7,19,20-trioic acid (1), ent-2α,3α,10,12α-tetrahydroxy-20-norgibberell-16-ene-7,19-dioic acid 19,10-lactone (5) and the epimer at C–12 of GA₄₈ (8), respectively. The kaurenolide was shown to have the structure: ent-6β,7α,12β-trihydroxykaur-16-en-19-oic acid 19,6-lactone (14).     

Subsite Structure of α-Amylase II from Thermoactinomyces vulgaris R-47

We estimated the subsite structure of α-amylase II (TVA II) from Thermoactinomyces vulgaris R-47 expressed in Escherichia coli. TVA II has eight subsites, and the catalytic site is between the 5th and 6th subsite from the non-reducing end side. The subsite affinities, A_-5, A_-4, A_-3, A_-2, (A_-1+A₊₁), A₊₂, and A₊₃, were calculated to be -0.35, 0.93, 0.55, 2.56, 1.18, 1.71, and 0.01 kcal mol^-1, respectively.     

Thermoperiodic control of stem elongation and endogenous gibberellins in Campanula isophylla

The effect of day/night temperature regimes on stem elongation and on the content of endogenous gibberellins (GAs) in vegetatively propagated plants of Campanula isophylla cv. Hvit have been studied. Compared with a constant temperature regime at 18°C (18/18°C), stem and internode elongation was enhanced significantly by a combination of high day/low night temperature (21/15°C) and inhibited by an opposite regime (15/21°C). Gibberellins A₁, A₁₉, A₄₄, A₅₃, and A₉₇ were identified as endogenous components in Campanula. (GA₉₇ was earlier referred to as 2-OH-GA₅₃.) Quantitative analysis of the endogenous GAs indicates that temperature regimes that stimulate elongation growth are accompanied by an increase in the level of GA₁, GA₁₉, and GA₄₄. On the other hand, in plants grown under conditions that reduced stem elongation growth, there was an increased level of GA₉₇.Abbreviations DIF difference between day temperature and night temperature - GA gibberellin - HPLC high performance liquid chromatography - GC-MS gas chromatography-mass chromatography - SPE solid phase extraction - TMS trimethylsilyl - MSTFA N-methyl-N-TMS-trifluoroacetamide - KRI Kovats retention index - SIM selected ion monitoring - D2 deuterated     

Internode length in pisum. Mutants lk,lka, and lkb do not accumulate gibberellins

The levels of gibberellin A₁ (GA₁), GA₈, GA₁₉, GA₂₀, GA₂₉, and GA₄₄ in the short Pisum sativum L. mutants lk, lka, and lkb, and comparable wild-type plants, were determined by gas chromatography-selected ion monitoring (GC-SIM) using ²H or ¹³C internal standards. The mutants possessed similar GA₁ levels to wild-type plants, consistent with their classification as GA-sensitivity rather than GA-synthesis mutants. However, these mutants differ from certain sensitivity mutants in other species, in which substantial accumulation of GA₁ occurs. The results suggest that if the proposed feedback model for the regulation of GA synthesis occurs in peas it is not the reduced growth per se that is the trigger for elevated levels of C₁₉ GAs. The results are also consistent with the hypothesis that in those GA-sensitivity mutants which do not accumulate C₁₉ GAs, the biochemical lesion may be well down the transduction pathway which leads from GA₁ reception to stem elongation.     

The Effect of Gibberellins on Flowering in Roses

The gibberellins A₁, A₃, A₅, A₈, A₁₉, A₂₀, and A₂₉ were identified in vegetative shoot tips of Rosa canina by comparing their mass spectra and Kovats retention indices with those of standards. Most wild roses have a short flowering season of 2–4 weeks in spring, whereas most modern cultivars flower recurrently. `Félicité et Perpétue' is a short-season hybrid from a cross between a wild rose and a recurrent-flowering rose, whereas its sport, `Little White Pet,' flowers recurrently. The concentrations of gibberellins (GAs) were measured in shoot apices of both cultivars. In March (before floral initiation in spring) the concentrations of GA₁ and GA₃ were respectively threefold and twofold higher in `Félicité et Perpétue' than in `Little White Pet.' In April (after floral initiation) the concentrations of both gibberellins were substantially greater than in March, and concentrations of GA₁ and GA₃ were, respectively, 17-fold and 12-fold greater in `Félicité et Perpétue' than in `Little White Pet.' It is postulated that, in `Félicité et Perpétue,' floral initiation occurs when concentrations of GAs are low and is inhibited when concentrations of GAs are high, whereas in `Little White Pet' concentrations of GAs remain at permissive levels throughout the growing season. Applications of GA₁ and GA₃ to axillary shoots in March inhibited floral development in `Félicité et Perpétue' but not in `Little White Pet.' This suggests that the combined concentration of exogenous and endogenous gibberellins might have been raised to inhibitory levels in the former but not in the latter cultivar. Received January 10, 1999; accepted June 16, 1999