Inhibitory action of five tannins on growth induced by several gibberellins

The following tannins, Chinese gallotannin, 1,2,3,4,6-pentagalloyl glucose, chebulinic acid, procyanidin dimers, and procyanidin trimers were tested and found to be antagonists of seven gibberellins (GAs). Each tannin inhibited the growth induced by any of the gibberellins GA(1), GA(3), GA(4), GA(7), GA(9), GA(13), and GA(14) in the dwarf pea assay. Endogenous growth was not affected. The highest ratio of tannin to gibberellin tested (1000:1 by weight) inhibited from 60 to 95% of the induced growth for all tannins and all gibberellins tested. The tannins were particularly inhibitory against GA(4) and GA(14) where a ratio of 10:1 (tannins: GA by weight) resulted in up to 85% growth reduction. Inhibition could be completely reversed by increasing the amount of gibberellin in all combinations studied. The procyanidin dimers and trimers were the first purified components of condensed tannins to be tested in this system and were potent inhibitors particularly against growth induced by GA(4) and GA(14). Inhibition by these compounds along with similar inhibition by previously tested hydrolyzable tannins demonstrates that the effect is general to tannins of all classes.     

Inhibitors from carob (Ceratonia siliqua L.)

Summary Inhibitory extracts of carob and abscisic acid (ABA) were compared and found to behave differently in three types of tests. The carob inhibitors remained at the origin upon thin-layer chromatography in two different solvent systems while a cis-trans mixture of ABA had Rf's of 2.5 and 3.5 in the first system (chloroform:acetic acid, 95:5), and 3.5 and 4.5 in the second system (benzene:acetic acid:water, 8:3:5). When ABA and carob extract were mixed and then chromatographed, the ABA had the same Rf values as ABA chromatographed alone.Assays utilizing light-grown, dwarf peas showed that a weight ratio of 1000: 1 ABA:gibberellic acid (GA₃) was necessary to inhibit GA₃-induced growth by 50% while carob fraction C is inhibitory to GA₃ at a ratio of 17:1. The amount of ABA which inhibited 50% of the growth induced by 0.05 g GA₃ reduced the endogenous growth of both dwarf and non-dwarf pea seedlings; in contrast, concentrations of carob extract up to 100 times greater than the amount necessary for 50% inhibition of the growth response caused by 0.05 g GA₃ did not affect endogenous growth.Only very small amounts of inhibitory activity from carob extract were transferred from water to chloroform at a pH (2.0) at which most of the ABA was transferred.     

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

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

Hormonal Regulation of Cell Elongation in the Hypocotyl of Rootless Soybean: An Evaluation of the Role of DNA Synthesis

A method was developed where soybean seedlings were grown without roots to study the influence of hormones of root origin on shoot growth. Excision of the root resulted in inhibition of apical section growth and DNA synthesis and inhibited elongating section growth. A synthetic cytokinin restored DNA synthesis in the apical section, but did not influence growth in either the apical or elongating sections. Low concentrations of gibberellin with the cytokinin restored growth in the apical section. Gibberellin alone was sufficient to restore growth in the elongating section.An inhibitor of DNA synthesis, 5-fluorodeoxyuridine, inhibited the increase in apical section DNA without inhibiting control or gibberellin-induced growth in the elongating section. Experiments with (14)C-thymidine resulted in no DNA labeling differences in the elongating section under conditions where gibberellin-induced elongation varied from 50% to 73% above controls. It was concluded that gibberellin-induced elongation in soybean hypocotyl occurred in the absence of DNA synthesis. Gibberellin does stimulate DNA synthesis in the apical tissue apart from its effect on cell elongation.Excised soybean hypocotyl elongated maximally at 10(-6)m auxin. At higher auxin concentrations, fresh weight and ethylene production increased, but elongation was reduced. Addition of GA to the higher auxin concentrations resulted in a 50% inhibition in auxin-induced ethylene production and resumption in maximal elongation. Added ethylene inhibited elongation 30% at 2 mul/l. Addition of up to 100 mul/l ethylene did not inhibit elongation with GA present in the incubation medium. Thus GA may counteract ehtylene inhibition of cell elongation in addition to inhibiting ethylene production in auxin-treated tissues.     

Changes in Nucleic Acids in Phytochrome-dependent Elongation of the Alaska Pea Epicotyl

Red light, which produces the physiologically active form of phytochrome (Pfr), inhibited epicotyl elongation in intact dark-grown Alaska pea seedlings. This red light response was detectable 3 hours after the light treatment and became pronounced after 5 hours. The growth inhibition was completely reversed by far red light applied immediately after the red or by pretreatment of the seedlings with the plant hormone gibberellin A₃.     

Inhibitors of animal phospholipase A2 enzymes are selective inhibitors of auxin-dependent growth. Implications for auxin-induced signal transduction

Auxin and elicitors reportedly activate phospolipase A. A number of inhibitors known to inhibit animal phospholipase A₂ were tested for their ability to inhibit hormone and fusicoccin-induced growth. To this end, growth induced by indolyl-3-acetic acid and 2,4-dichlorophenoxyacetic acid in hypocotyl segments of etiolated zucchini (Cucurbita pepo L.) seedlings was determined in the presence of the inhibitors nordihydroguajaretic acid (NDGA), aristolochic acid, 5,8,11,14-eicosatetraynoic acid (ETYA), PB_x (a prostaglandin derivative), and oleylethyl phosphocholine. Each chemical proved inhibitory to auxin-induced growth, oleylethyl phosphocholine being the least effective. The effects of the first three inhibitors were investigated in more detail. Growth induced by 10 μM 2,4-dichlorophenoxyacetic acid or 1 μM indolyl-3-acetic acid was inhibited 50% by about 30–50 μM NDGA, by about 25 μM aristolochic acid, and by about 10–20 μM EYTA. Growth inhibition was reversible and became apparent 0.5–1 h after inhibitor addition. Growth induced by 0.5 or 1 μM fusicoccin was much less inhibited by NDGA and by ETYA, whereas aristolochic acid was only slightly less effective on fusicoccin-induced than on auxin-induced growth. These three inhibitors were also tested for their effects on gibberellin-induced growth in light-grown peas (Pisum sativum L.) and on cytokinin-induced expansion growth in excised cotyledons from radish (Raphanus sativum L.) seedlings. In both tests, aristolochic acid had toxic side-effects although gibberellin-induced growth was still apparent. In the gibberellin test, neither NDGA at up to 100 μM nor ETYA at 80 μM was inhibitory to hormone-induced growth. Moreover, 40 μM ETYA was not inhibitory to kinetin-induced growth. We hypothesize that the selectivity of phospholipase A₂ inhibitors for auxin-induced growth implies a different signal transduction pathway for each of the different signal substances tested, and that auxins might use fatty acid(s) and/or lysophospholipid(s) or their derivatives as the preferred second messengers. Received: 24 September 1996 / Accepted: 18 January 1997     

The effects of podolactone-type inhibitors on fusicoccin-induced growth and proton efflux

Podolactones A and E and lycoritidinol inhibit growth induced by fusicoccin in dwarf pea ( Pisum sativum L.) hooks and tips; however the inhibition is reduced at the highest fusicoccin concentrations. In short term experiments (3 h) on pea stem tissues, growth and proton efflux induced by fusicoccin are only partially inhibited by podolactone A and lycoricidinol. Auxin-induced growth and proton efflux are completely suppressed by 10 μM lycoricidinol. The inhibitors do not affect ATP levels.     

Gibberellin-auxin interaction in pea stem elongation

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

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

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

     

Red-light-induced changes in the distribution of growth inhibitors A-2α and A-2β in dwarf pea seedlings

The distribution of the endogenous growth inhibitors, A-2 and A-2, was determined in light-grown dwarf pea seedlings (Pisum sativum L. cv. Progress No. 9). Red-light-induced changes in this distribution in dark-grown pea seedlings was monitored. The concentration of both inhibitors in light-grown pea seedlings was maximal in the terminal bud and decreased to the lower parts of the seedlings; their concentration in internodes was 7–10 times that in leaves of the same nodes. After the onset of continuous red-light-irradiation, the concentration of the inhibitors in dark-grown pea seedlings increased rapidly in the terminal bud, epicotyl hook and third internode, and the longitudinal gradients of the inhibitors showed a close correlation with the red-light-induced growth inhibition of the stem. The present results suggest that the endogenous growth inhibitors, A-2 and A-2 may be responsible for the red-light-induced growth inhibition of the dwarf pea seedlings.     

Die Wirkung von Schwachem Rotlicht und Chlorcholinchlorid auf Den Gibberellingehalt Normaler Erbsensämlinge und die Ursache der Unterschiedlichen Empfindlichkeit von Zwerg- und Normalerbsensämlingen Gegen IHR Eigenes Gibberellin

Zusammenfassung Sieben Tage alte Normalerbsensämlinge, die vier Tage lang in schaachem Rotlicht oder im Dunkeln gewachsen waren, und denen während dieser Zeit Chlorcholinchlorid (CCC) über die Wurzeln zugeführt wurde, wurden auf ihren Gibberellingehalt getestet.Im Rotlicht ohne CCC gewachsene Keimlinge enthielten mehr als das Zehnfache an Aktivität als im Dunkeln gewachsene.Durch CCC wird der Gibberellingehalt der Rotlichtpflanzen auf das Niveau der Dunkelpflanzen herabgedrückt. Der Verlust an Gibberellin ist nicht Folge, sondern Ursache der Wachstumshemmung durch CCC. Es wird geschlossen, daß Licht die Gibberellinproduktion fördert, CCC sie hemmt.Verschiedene Gibberelline wirken bei kombinierter Applikation nur in geringen Mengen additiv. Bei größeren Mengen ergibt sich eine deutliche Abweichung von der Additions-Erwartung. Die Ergebnisse sprechen dafür, daß das erbseneigene Gibberellin erst in den eigentlichen Wuchsstoff umgewandelt werden muß. Im Licht ist die Geschwindigkeit dieser Reaktion bei den Zwergen wachstumbegrenzend, bei den Normalen nicht.

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The effect of weak red light and chlorocholinchloride on the gibberellin-content of normal pea seedlings, and the cause of the different sensibility of dwarf and normal pea seedlings toward the endogenous gibberellin

Summary Seedlings of a normal growing cultivar of Pisum sativum were grown from the third to the seventh day after soaking in weak red light or darkness, with or without chlorocholinchloride (CCC), and afterwards extracted for gibberellinbiossay.Light grown seedlings without CCC contain more than ten times as much gibberellin-activity as dark grown plants. CCC depresses the gibberellin-content to the level present in darkgrown plants. This loss of gibberellin is the cause, not the effect of the growth depression by CCC. It is concluded that red light enhances and CCC hampers the production of gibberellin.Different gibberellins have an additive effect on growth of seedlings in red light only when applied in small amounts. With larger amounts of gibberellin growth is much less than that which would be expected if the effects of the gibberellins were additive. The results seem to indicate that the gibberellin endogenous in peas has to be structurally altered in order to become a growth promoter. This reaction controls the growth rate in light of dwarf but not of normal pea seedlings.

     

Interaction between Biological Activities on Rice Seedlings of Dehydroabietic Acid Derivatives and Gibberellin A3

Effects of hydrofluorene and hydrophenanthrene compounds derived from dehydroabietic acid on the second leaf sheath growth of rice seedlings were examined in the presence and absence of gibberellin A₃(GA₃). In the absence of GA₃, nineteen compounds at 100 ppm inhibited more than 20% the growth of normal rice seedlings. In the presence of GA₃ (1.5 ppm) with dwarf rice seedlings, nine compounds at 500 ppm suppressed the elongation caused by the hormone, and a compound was slightly promotive. Then, three compounds were selected and subjected to the bioassay under various conditions.     

Inhibitors from Carob (Ceratonia siliqua L.): II. Effect on Growth Induced by Indoleacetic Acid or Gibberellins A(1), A(4), A(5), and A(7)

Two inhibitory fractions (B₁ and C) from extracts of immature fruit of carob were tested for their ability to inhibit the action of indoleacetic acid (IAA) in three bioassays. There was no reduction of IAA-induced reactions in the Avena curvature test, abscission of debladed coleus petioles, or growth of cucumber hypocotyls. The highest ratio of inhibitor to IAA was 10,000 times greater than the ratio necessary to inhibit by 50% the growth caused by an equivalent amount of gibberellin A₃ in pea seedlings. At the highest concentration used, fraction C alone caused curvature of Avena coleoptiles. The inhibitory fractions appeared to enhance the effect of IAA in the cucumber test.     

Comparison of endogenous gibberellins and response to applied gibberellin of some dwarf and tall wheat cultivars

Summary A number of dwarf wheat cultivars of the Norin 10 type were compared with several tall forms. Applied gibberellic acid markedly stimulated the growth of seedlings of the tall cultivars but not the growth of dwarf seedlings. Several other gibberellins were also inactive when tested with one dwarf cultivar. De-embryonated grains of all cultivars formed -amylase in response to gibberellic acid. Gibberellic acid caused an increase in soluble carbohydrates in the leaves of the tall cultivars but not in those of the dwarfs.Germinating grains, light-grown seedlings and developing stems of the dwarf cultivars contained more endogenous gibberellin-like activity than those of tall cultivars. It is suggested that the dwarf cultivars have a block to the utilisation of gibberellin in the shoot.     

The Promotion of Indole-3-acetic Acid Oxidation in Pea Buds by Gibberellic Acid and Treatment

Terminal buds of dark-grown pea (Pisum sativum) seedlings have an indole-3-acetic acid oxidase which does not require Mn(2+) and 2,4-dichlorophenol as cofactors. Oxidase activity is at least 50 times higher in buds of tall peas than in dwarf seedlings. Administration of gibberellic acid to dwarf peas stimulates both growth and indoleacetic acid oxidase activity to the same levels as in tall seedlings. By contrast, indoleacetic acid oxidation assayed in the presence of Mn(2+) and 2,4-dichlorophenol proceeds at similar rates regardless of gibberellin application. Treatment of tall peas with the growth retardant AMO-1618 reduces growth and oxidase activity. Such treated seedlings are indistinguishably dwarf. The enzyme does not appear to be polyphenol oxidase, nor do the results suggest that reduced activity in dwarf buds is due to higher levels of a dialyzable inhibitor. The peroxidative nature of the oxidase is probable.     

Absence of Red Light-Induced Stimulation of Growth in the Hook of Etiolated Dwarf-Pea Seedlings

Red light inhibited the growth of the apical part of the hookin dark-grown seedlings of a dwarf variety (cv. Progress No.9) of pea (Pisum sativum L.), whereas it promoted such growthin a tall variety (cv. Alaska). In the elongation zone of theepicotyl of the dwarf variety the extent of inhibition of growthwas similar to or even smaller than that in the tall variety.Local irradiation of the apical part of the hook also causedinhibition of growth in the hook of the dwarf variety and promotionof growth in the tall variety. The inhibition of growth in theapical part of the hook of cv. Progress may be involved in thedwarfism induced by irradiation with red light of this cultivar. (Received May 15, 1989; Accepted April 27, 1990)     

Strigolactone may interact with gibberellin to control apical dominance in pea (Pisum sativum)

The role of strigolactones as plant growth regulators has been demonstrated through research on biosynthesis and signaling mutant plants and through the use of GR24, a synthetic analog of this class of molecules. Strigolactone mutants show a bushy phenotype and GR24 application inhibits the growth of axillary buds in these mutants, thus restoring the phenotype of a wild plant, which is characterized by a stronger apical dominance. In this work, we tested the effectiveness of this chemical on pea (Pisum sativum) plants following apex removal, which disrupts apical dominance and leads to axillary bud outgrowth. Moreover, we searched for relationships between the response to the strigolactone and gibberellin metabolism by applying GR24 to both climbing and dwarf peas, the latters being mutants for gibberellin biosynthesis. The results suggest that the endogenous level of the bioactive gibberellin GA₁ might modulate the response of decapitated pea plants to GR24, by changing bud sensitivity to the applied strigolactone.     

The effect of amputation of the epicotyl on the level of endogenous gibberellins in the roots of pea seedlings

The content of endogenous gibberellins was determined chromatographically in the roots 14–17 days old pea seedlings cultivated in water cultures in the dark. When the epicotyls are amputated from these plants, the content of endogenous gibberellins increases significantly within 6–12 hours after amputation as compared with the intact controls, then it falls off again considerably up to 24 hours after amputation. The initial increase of the gibberellin level in the roots can be explained by transport inhibition of the endogenous gibberellins from the root to the epicotyl, the later decrease of this level to be interpreted as inhibition of auxin transport from the epicotyl into the root. This is supported by the observation that spreading of a 0.5% paste with IAA over the epicotyl stump immediately after amputation prevents the mentioned decrease of the gibberellin level in the roots, whereas this decrease is intensified by using a paste with TIBA which inhibits the auxin transport. The results of this work support the possibility of direct gibberellin synthesis in the roots.     

The interaction of endogenous gibberellins in correlation with cotyledons and axillary buds in the pea (Pisum sativum L.)

After the decapitation and amputation of one cotyledon in germinating pea seedlings, the axillary bud of the amputated cotyledon always grows and the growth of the axillary bud of the remaining cotyledon is inhibited. Before morphological differences appear between the axillary bud of the amputated and preserved cotyledon, a higher endogenous gibberellin content can be demonstrated chromatographically in the axillary bud of the amputated cotyledon. This indicates that the increased growth of the axillary bud of the amputated cotyledon is in connection with an earlier increase in the activation of endogenous gibberellins.