Hormonal Regulation of Gametangial Formation in the Moss Bryum argenteum Hedw

Phytohormones such as auxins, cytokinins, gibberellins, andabscisic acid differentially affect gametangial induction inmale and female clones of Bryum argenteum. Both IAA and GA³increased the percentage of fertile gametophores in the maleclone, and inhibited the response in the female clone. GA₃ wasmore effective than IAA in eliciting the response in the maleclone. Cytokinins, on the other hand, increased the productionof fertile gametophores in the female clone, and inhibited itslightly in the male clone. The two cytokinins tested (kinetinand DMAAP) were almost equally effective for the female clone. An Interaction of IAA and kinetin nullified their individualinhibitory effects on the female and male clones, respectively.Cyclic AMP prevented the inhibitory effect of kinetin in themale clone; whereas, in the female clone, it stimulated theresponse elicited by kinetin. Abscisic acid (ABA) acted as ageneral inhibitor of vegetative growth and gametangial inductionin this moss. However, the inhibition of gametangial inductionwas greater in the female clone which is also more sensitiveto ABA than the male clone.     

Auxin-gibberellin relationships in their effects on hypocotyl elongation of light-grown cucumber seedlings VI. Promotive and inhibitory effects of kinetin

The interaction of kinetin with IAA and GA₃ on the elongationof hypocotyl sections of Cucumis sativus L. cv. National Picklingwas studied. Kinetin in the concentration range of 10^–7M to 10^–4 M markedly inhibited IAA-induced elongation,while in a lower range from 10^–10 M to 10^–8 M, itsynergistically enhanced IAA-induced elongation. Kinetin alonein this range had no effect. A 5-to 15-min pulse treatment seemsenough to induce the maximum effect for both inhibition andpromotion. Since the magnitude of the maximum inhibition dependedon the concentration and not on the duration of treatment, thereaction in the cell caused by kinetin seemed to be completedwithin a short period. Washing of the sections with distilledwater after kinetin treatment (30 min) did not significantlyeliminate the kinetin effect. This probably indicates that thebinding of kinetin molecules to a supposed acceptor is not reversible.Interaction of kinetin with GA₃ in their pretreatment effectson IAA-induced elongation shows that in the inhibitory concentrationrange, the kinetin effect was partly overcome by GA₃, and thatin the promotive range, the magnitude of the enhancement wasdetermined by kinetin regardless of the presence of GA₃. Theeffect of kinetin seems to dominate over that of GA₃ indicatingthat the modes of their pretreatment effects differ from oneanother. (Received June 24, 1977; )     

Effects of Plant Growth Regulators on Grain-filling and Yield of Rice

Effects of three phytohormones (IAA₁, GA₃ and kinetin) on grain-fillingand the pattern of ³²P translocation from individual leavesto grains were studied at intervals of 7 days during the progressof reproductive development of rice (Oryza saliva L. cv. Jaya).The plants were sprayed with 100 µg ml^–1 aqueoussolutions of the hormones at 100 days, when the plants wereentering the reproductive stage. Kinetin produced a pronouncedeffect on grain-filling as well as on ³²P mobilization fromindividual leaf to grains and increased yield, possibly by increasingleaf longevity. GA₃ and IAA also increased the grain-fillingand ³²P mobilization significantly over control but the effectswere less marked than those of kinetin. Oryza sativa L., rice, grain yield, translocation, growth regulators, gibberellic acid, indol-3-yl acetic acid, kinetin     

Interaction between Hormones, Light, and Nutrition on Extension of Lateral Buds in Phaseolus vulgaris L.

Gibberellic acid (GA₃), kinetin, and indol-3yl-acetic acid (IAA)contained in lanolin were applied in various combinations andconcentrations to decapitated stems and petioles and to budsof Phaseolus vulgaris L. GA₃ applied alone usually promotedgrowth of main stems and laterals but this was by no means consistentand occasionally it acted in the opposite way. IAA applied alonereduced lateral bud extension slightly, but not consistently;however, when applied with GA₃ or GA₃ plus kinetin, it oftenmarkedly inhibited the promotion caused by these compounds.On occasions, however, GA₃ and IAA acted synergistically topromote and sometimes to inhibit lateral shoot growth. Kinetinalone showed few significant effects on lateral shoot growthbut applied with GA₃ it often dramatically increased GA₃-inducedgrowth of main stems and laterals. The diversity of these results,which parallels that found in the literature, was shown to bepartly dependent on the point of hormone application and ageof the plant or bud, on concentration of hormone and on lightintensity or nutrition. However, no meaningful relationshipswere found and it is concluded that growth of laterals and mainstems is dependent on a hormone balance which can be criticallymodified by a wide range of internal and external factors thenature of which is still to be determined.     

Hormonal Regulation of Hypocotyl Elongation in Lactuca sativa L.: I. EVIDENCE AGAINST THE INVOLVEMENT OF GIBBERELLINS IN THE ELONGATION OF HYPOCOTYL IN SEEDLINGS GROWN IN THE DARK

The kinetics of extension induced by GA₃¹ in the hypocotyl ofintact seedlings of Lactuca sativa are similar in the dark andin the light, and differs fundamentally from the kinetics ofelongation in the dark without GA₃. Both in continuous lightand in the dark, GA₃-induced promotion starts 24 h after incubation.In the dark, even low concentrations of GA₃, which do not affectthe length measured after 6 d when the extension of hypocotylalmost ceases, remove the lag period of 48 h which precedesextension, and prolong the high rate of elongation. FollowingGA₃ supply the hypocotyl length in the dark and in the lightdoes not differ until 48 h; thereafter the rate of elongationin the light is less, so that the final length of the hypocotylis 40 per cent shorter than that of the dark-grown seedlingswithout GA₃. IAA supplied apically to light-grown seedlings induces a weakpromotion at a concentration of 1 mg l^–1 only. With anincreasing concentration of GA₃ supplied simultaneously, theconcentration of IAA inducing a significant promotion decreases.A combined supply of both these regulators, however, does notrestore the light-mediated inhibition of hypocotyl elongationcompletely. The maximum decrease in hypocotyl length induced by the growthretardants AMO-1618, CCC, and B-9 supplied from the beginningin the dark does not exceed 70 per cent. Saturating doses ofGA₃ supplied in combination with any one of the retardants compensateonly a fraction of the decrease. The results have been interpreted to show that native GAs arenot involved in extension growth in the dark.     

Control of the Hypocotyl Hook Angle in Phaseolus mungo L.: the Role of Parts of the Seedling

Phaseolus mungo L. seedlings were grown in the dark for 5 d.They were either kept in the dark or exposed to 5 min red light.The location of the light-sensitive region (the hook) and theanatomy of light-induced opening are described. The responsewas phytochrome-mediated. The time course of light-induced openingand its far-red reversal are described and the implicationsfor the mechanism of light-induced opening discussed. The lagphase between irradiation and the start of opening was >8h, for 3 h of which the response remained completely photoreversible.This implies that some critical level of a factor is requiredbefore hook opening can be initiated. The terminal parts (leavesand cotyledons) kept the hooks shut in the dark, but did notdirectly affect the light response. The necessity for distinguishingbetween treatment effects on hook angle and on light-inducedopening is noted. We hypothesize that the terminal parts produceda hook-maintaining factor whose level declined after their removal.This factor was dispersed or inactivated following irradiation,or the hook cells were rendered less sensitive to it. Differencesbetween the responses of P. mungo and those reported for otherspecies are discussed.     

Identification and Quantification of Cambial Region Hormones of Eucalyptus globulus

Gibberellins GA₁, GA₄, GA₈, GA₉, GA₁₉, GA₂₀, GA₂₉, GA₄₄, GA₈₁,indole-3-acetic acid (IAA) and abscisic acid (ABA) were identifiedin cambial region tissues of Eucalyptus globulus by comparingmass spectra and Kovats retention indices with those of authenticstandards. Using stable isotope labelled internal standardsGA₁₉, GA₂₀ and GA₄₄ were quantified at levels of 2–7 ng(g fr wt)^-1, other GAs were present at levels < 1 ng (g frwt)^-1. Levels of IAA and ABA ranged from 417–1, 140 ng(g fr wt)^-1 and 86–305 ng (g fr wt)^-1 respectively. Thepresence of brassinosteroid-like substances was also indicatedbased on activity in the rice seedling leaf inclination assay. (Received April 28, 1995; Accepted June 20, 1995)     

Effects of Auxin and Gibberellin on Conidial Germination and Elongation of Young Hyphae in Gibberella fujikuroi and Penicillium notatum

In Gibberella fujikuroi and Penicillium notatum, IAA, 2,4-Dand GA₃ promoted conidial germination and the elongation ofyoung hyphae. The promotive effects of IAA and GA₃ were additive.In both fungi, the concentrations of endogenous auxin and gibberellinin the culture media were 10^–10 to 610^–12M. (Received April 27, 1985; Accepted August 12, 1985)     

Inoculation with Azospirillum lipoferum Affects Growth and Gibberellin Status of Corn Seedling Roots

Maize (Zea mays L., hybrid Cargill 147) seedlings, grown inaseptic conditions, were inoculated with three strains of Azospirillumlipoferum (Al op 33, Al iaa 320, and ATCC 29708) or culturedin different concentrations of indol-3-acetic acid (IAA) orgibberellin A₃ (GA₃). After 48 h, root length, root surfacearea, root dry weight, and shoot dry weight were measured inall treatments. Gibberellin content was evaluated in selectedroots of control and Azospirillum inoculated seedlings by gaschromatography-mass spectrometry-selected ion monitoring withthe use of deuterated gibberellins as internal standards. Thethree strains of A. lipoferum, IAA (2 ng ml^–1), and GA₃(40 to 400 pg ml^–1) significantly enhanced root growth.Improvement of root hair growth and density was obtained mainlywith A. lipoferum strain Al op 33 and GA₃ 40 pg ml^–1.GA₃ was identified by gas chromatography-mass spectrometry (byboth, full scan and selected ion monitoring) in a free acidfraction from roots of the seedlings inoculated with A. lipoferum.In the roots of the non inoculated seedlings GA₃ was found afterhydrolysis of a fraction expected to contain glucosyl conjugates. (Received April 26, 1993; Accepted September 27, 1993)     

The influence of various plant hormones on the stimulatory action of red light on greening in excised etiolated cotyledons of cucumber

In etiolated cotyledons of cucumber (Cucumis sativus L. cv.Aonagajibai), preillumination with a short pulse of red lighteliminated the lag phase and stimulated Chl formation in thelinear phase during subsequent continuous illumination. Thistwofold effect was clearly distinguishable by varying the lengthsof the dark periods after preillumination. Pretreatment of excisedcotyledons with BA, GA₃ ethylene, or IAA stimulated Chl formationduring subsequent illumination. The effects of BA and GA₃ seemedindependent of both kinds of red light effects. However, ethyleneand IAA interacted with red light in increasing the rate ofChl formation during the linear phase. This may provide someclue to the red light action on Chl formation through its probablestimulation of ethylene production. (Received June 7, 1978; )     

Light and Hormone Interaction in Apical Dominance in Phaseolus vulgaris L.

Gibberellic acid (GA₂), kinetin, and indole-3yl-acetic acid(IAA) each at four concentrations (0, 0.5, 5, and 50 µM)were applied alone and in all possible combinations to rootsof Phaseolus vulgaris L. grown under four different light regimes(7000, 14 000, 21 000, and 28 000 lx). GA₃ increased growthof main stem and laterals but reduced apical dominance, especiallyin the absence of, or at low kinetin concentrations. A highlevel of kinetin lowered GA₃ induced growth of main stems and,to a lesser extent, laterals. Kinetin greatly reduced apicaldominance, especially in the absence of, or at low GA₃ concentrations.IAA slightly reduced growth of main stems and laterals and slightlyincreased apical dominance. Generally the magnitude of the IAAeffects were less than those of GA₃ or kinetin and there wereless interaction between IAA and other factors than betweenGA₃ or kinetin and other factors. Light affected growth of bothmain stem and laterals but the effect was dependent on GA₃ andkinetin levels and the interactions were complex. Generallya hormone balance seems to be operative with gibberellin-promotinggrowth of main stem and laterals and cytokinins and possiblyauxins preventing excessive elongation. Differential responsesbetween main stem and lateral may be due to different localhormone concentrations and over-all responses may be temperedby light intensity.     

Hormone Interaction in Apical Dominance in Phaseolus vulgaris L.

Gibberellic acid (GA₃), kinetin, and indole-3yl-acetic acid(IAA) were applied to roots of Phaseolus vulgaris under twodifferent light intensities and when either young or old leaveswere removed In all cases GA₃, promoted stem and lateral growth,especially when light intensity was reduced. Promotion by GA₃,of stem growth under reduced light was reduced if IAA and kinetinwere present; promotion of lateral growth under reduced lightwas reduced if IAA was added and eliminated if kinetin or kinetinplus IAA were added to GA₃. Removal of young and mature leavesreduced main stem growth; removal of young leaves promoted,and of mature leaves reduced, lateral shoot growth. We suggestthat shoot growth and apical dominance are governed by the balanceof hormones present in elongating internodes. There may be twoways of modifying this balance; firstly by altering light, temperature,or nutrients, or by applying hormones generally to the plant.Secondly, local modifications can be made by removing apicesor young leaves, or applying hormones in lanolin to specificareas. Knowledge of both the general and local conditions maybe necessary for a complete understanding of apical dominance.     

Combined Effect of Some Growth Regulators on Growth and Gametangial Formation in the Liverwort Riccia gangetica Ahmad

The present work deals with the effect of IAA-kinetin, IAA-GA³and GA³-ABA interactions on growth and gametangial formationin Riccia gangetica in vitro. Inhibitory effect of high concentrationof IAA on vegetative growth is overcome by the co-addition ofkinetin. The best response in terms of fresh and dry weightyields of thalli is obtained by a combination of 10^–5mol dm^–3 kinetin+ 10^–7 mol dm^–3 IAA. Interactionof IAA and kinetin has an additive effect on archegonial formation.Co-addition of IAA and GA³ decreases production of archegoniaand antheridia as compared to those produced in response toIAA and GA³ alone, respectively. Combination of GA³ and ABAreduces vegetative growth, as well as the number of anthendiaand archegonia. Key words: Riccia gangetica, growth, growth regulators, gametangial formation     

Effects of Auxin and Gibberellin on Elongation of Young Hyphae in Neurospora crassa

IAA, 2,4-D and GA₃ promoted the elongation of young hyphae inNeurospora crassa at the optimum concentrations of 10^–6,10^–6 and 10^–4 M, respectively. The effects of IAAand GA₃ were additive. (Received June 17, 1983; Accepted December 22, 1983)     

Biological Activities of the Methyl Ester of Gibberellin A73, a Novel and Principal Antheridiogen in Lygodium japonicum

The synthetic methyl ester of GA₇₃ (GA₇₃-Me) and the naturalantheridiogen of Lygodium japonicum showed almost the same activityto induce the formation of antheridia in dark-grown protonemataof L. japonicum at concentrations of 10^-14 M and higher. Thus,it appears that the principal antheridiogen in L. japonicumis GA₇₃-Me. GA₇₃-Me inhibited formation of ar-chegonia in light-grownprothallia of L. japonicum at concentrations of 10^-11 M andhigher and induced germination of spores in the dark in thisspecies at the same range of concentrations. GA₇₃(free acidform) promoted growth of seedlings of dwarf rice and hypocotylsof cucumber seedlings at dosages of and above 1 and 100 ng/plant,respectively. Eight compounds related to GA₇₃-Me, includingantheridiogens of Anemia phyllitidis and Anemia mexicana, wereactive in inducing an-theridial formation in L. japonicum, althoughtheir activities were considerably lower than that of GA₇₃-Me. (Received August 24, 1988; Accepted November 28, 1988)     

Unusual Branching in the Seedlings of Lotus japonicus--Gibberellins Reveal the Nitrogen-sensitive Cell Divisions within the Pericycle on Roots

We studied the effects of several plant-growth regulators onthe induction of nodule-like structures on roots of Lotus japonicus,which has been proposed as a candidate for a leguminous plantfor molecular genetic analysis. Contrary to our expectations,the addition of gibberellin A₃ (GA₃) at concentrations of 10^-4M to 10^-4 M resulted in the formation of nodule-like structureson roots when seedlings were plated on nitrogen-free Fahraeusagar medium. GA₄ also induced such outgrowths but was less activethan GA₃. Application of an inhibitor of auxin transport, N-(1-naphthyl)-phthalamicacid (NPA) and of kinetin, which have been reported to inducepseudonodules in other legumes, had no effect on L. japonicus.Microscopic observations showed that GA₃-induced nodule-likestructures were caused by cell divisions within the pericycleon the roots. In addition, the outgrowths elicited by GA₃ couldbe completely suppressed by the addition of 15 mM potassiumnitrate or ammonium nitrate. These results show that the pericyclecells of the roots of L. japonicus are specifically sensitiveto gibberellins and that potential for cell division might bemodulated by nitrogen compounds. We also examined the effectsof ancymidol and uniconazole [S-3307; (E)-1-(4-chIorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-ol],two synthetic plant-growth retardants. Both compounds at 3 x10^-5 M significantly increased the number of stunted lateralroots. The unusual branching could not be counteracted by theexogenous addition of GA₃ but by 10^-6 M brassinolide. We discussthe physiological role of brassinolide in the initiation oflateral roots. (Received August 4, 1995; Accepted March 11, 1996)     

Effect of kinetin on auxin uptake and distribution in normal and tumor-prone Nicotiana shoots

Stem segments of non-tumorous Nicotiana glauca and N. langsdorffiiplants and of their tumor-producing amphidiploid F₁ hybrid weretreated with 6-furfurylaminopurine (kinetin) prior to transporttests with applied labeled indoleacetic acid (IAA-2-¹⁴C). Kinetin-treatmentsincreased the uptake of IAA in non-tumorous shoots; the IAAuptake by N. langsdorffii segments was increased up to 3-fold.The auxin uptake in stem-segments of the tumor-forming hybrid,however, could not be increased significantly by kinetin. Theeven distribution of IAA-¹⁴C in segments of normal and tumorproneNicotiana shoots is stimulated by kinetin. Data are discussedin conjunction with previous results on auxin transport andtumorformation in Nicotiana. (Received August 8, 1972; )     

The Effects of Growth Substances on the Growth of Tapinanthus bangwensis (Loranthaceae) in vitro

The growth response of Tapinanthus bangwensis (Engler and K.Krause) Danser to exogenous growth substances, indole-3yl-aceticacid (IAA), kinetin, and gibberellic acid (GA₃), not only varieswith the concentrations of each of these substances in the mediumbut follows a similar trend in each case. Kinetin, IAA, andGA₃ were found to enhance growth but not by very appreciableamounts, kinetin being the most effective growth promoter. Highconcentrations of these substances (5.0 and 10.0 ppm) exceptGA₃ were toxic to the parasite. Gibberellic acid induced theproduction of accessory leaves at all the concentrations used.Kinetin was also effective in inducing accessory leaves butonly at a concentration of 1.0 ppm. Some of the lower concentrationsof the growth substances affected significantly some aspectsof the parasite's growth and development. Nevertheless, thegrowth in vitro was still slower than that in vivo.     

Interaction of a Brassinosteroid with IAA and GA3 in the Elongation of Cucumber Hypocotyl Sections

A synthetic brassinosteroid, 22,23(S,S)-homobrassinolide (hBR),was examined for its interaction with IAA and GA₃ in the elongationof hypocotyl sections of light-grown cucumber (Cucumis salivusL. cv. Aonagajibai) seedlings. hBR alone was less active thanIAA. Its optimal concentration was around 10 µM and thelowest effective concentration between 10 and 100 µM,which is more than 100 times higher than that of brassinolide.hBR was more active in sections from younger seedlings. Itsgrowth-promoting effect was negated or greatly reduced by inhibitorsof auxin-induced elongation such as p-chlorophenoxyisobutyricacid and kinetin. hBR acted synergistically with IAA and 2,4-Dbut not with GA₃ showing only an additive effect. Sequentialtreatment of sections with hBR and then with IAA also resultedin synergistic enhancement of auxininduced elongation, but whenthe order of treatment was reversed, hBR was inactive. The synergisticeffect was obtained with 1 h pretreatment with hBR and couldbe reduced by subsequent washing with water. There was no sequentialinteraction between hBR and GA₃. The synergistic pretreatmenteffects of hBR and GA₃ were simply additive to each other. Amembrane-bound ATPase inhibitor, dicyclohexylcarbodiimide, inhibitedthe hBR-induced elongation, but did not affect GA₃-induced elongation.The findings led to the conclusion that brassinosteroids enhanceauxin action and possess growth-promoting activity which isindependent of that of gibberellin. (Received November 9, 1984; Accepted February 18, 1985)     

Effects of Gibberellins on Seed Germination of Phytochrome-Deficient Mutants of Arabidopsis thaliana

Experiments were carried out to explore the involvement of gibberellins(GAs) in the light-induced germination of Arabidopsis thaliana(L.) Heynh, using wild type (WT) and phytochrome-deficient mutants(phyA, phyB and phyAphyB deficient in phytochrome A, B and Aplus B, respectively). Seed germination of WT and phytochrome-deficientmutants was inhibited by uniconazole (an inhibitor of an earlystep in biosynthesis of GA, the oxidation of ent-kaurene) andprohexadione (an inhibitor of late steps, namely, 2rß-and 3rß-hydroxylation). This inhibition was overcomeby simultaneous application of 10^-5 M GA₄. The relative activityof GAs for promoting germination of uniconazole-treated seedswas GA₄>GA₁=GA₉>GA₂₀. The wild type and the phyA and phyBmutants had an increased response to a red light pulse in thepresence of GA₁, GA₄, GA₉, GA₂₀ and GA₂₄ but there were no significantdifferences in activity of each GA between the mutants. Therefore,neither phytochrome A nor hytochrome B appears to regulate GAbiosynthesis from GA₁₂ to GA₄ during seed germination, sincethe conversion of GA₁₂ to GA₉ is regulated by one enzyme (GA20-oxidase). However, GA responsiveness appears to be regulatedby phytochromes other than phytochromes A and B, since the phyAphyBdouble mutant retains the photoreversible increased responseto GAs after a red light pulse. (Received February 13, 1995; Accepted July 11, 1995)