The role of gibberellins in the growth of floral organs of Pharbitis nil

Evidence that the synthesis of GA₃ is involved in the growthof floral orga'ns of Pharbitis nil is presented. GAs in floralorgans at different developmental stages were surveyed usingTLC followed by the bioassay with two dwarf rice seedlings,‘Tanginbozu’ and ‘Waito-C’. The amountof GAs in the petal and stamen increased rapidly after the petalemerged from calyx, reached a maximum 12 hr before anthesis,then declined markedly thereafter. The GA content in the calyxremained unchanged before and after anthesis, and that in thepistil increased after anthesis. Pharbitis flowers containedat least two active GAs, one of which was probably GA₃, theother appeared to be GA₁₉. GA₃ was detected in relatively largeamounts in both the petal and stamen during their rapid elongation.In the calyx, which showed little increase in fresh weight duringrapid flower growth, GA₉ was the dominant GA. Exogenously suppliedGA₃ promoted elongation of sections in excised young filaments.Sucrose was necessary for definite growth promotion by GA₃.GA₁₉ had little effect on filament elongation, and IAA was ratherinhibitive. (Received July 29, 1972; )     

Effects of Gibberellic Acid on Floral Development in vivo and in vitro in the Cleistogamous Species, Lamium amplexicaule L.

Using established developmental markers in the corolla and androeciumof Lamium amplexicaule L., we investigated the apparent inductionof open (chasmogamous — CH) from closed (cleistogamous— CL) flowers after application of GA₃ (0.1 mM). In vivotreatment of potentially CL flower primordia caused cell expansionbut not the increased cell division in anthers and corolla necessaryto convert a CL into a CH flower. Floral primordia that appearedto be of undetermined floral type were grown in vitro on a basalmedium supplemented with kinetin (0.1 p.p.m.) and grew to maturityas CL flowers. On media additionally supplemented with GA₃,flowers underwent anthesis, but no true CH flower was produced.Gibberellins appear to be directly responsible for anthesisin the CH flower; but additional, as yet unknown growth factorsare involved in the switch from CL to CH floral form in a developinginflorescence. floral morphogenesis, Lamium amplexicaule L, henbit, cleistogamy, gibberellin, kinetin, anthesis     

Dwarfism Caused by Floral-Bud Removal in Petunia and its Reversal by Gibberellin

The effect of floral-bud removal at different stages of developmenton the plant height and on the total number of buds of Petuniawas studied. Continuous removal of all the floral buds 2 d beforeanthesis caused a marked decrease in plant height and also increasedthe total number of floral buds formed thereafter. At otherstages of floral bud development, bud removal had a lesser effecton both phenomena. Moreover, the plants did not respond to budremoval at anthesis. GA₃ at 25 ppm applied to plants from which the buds had beenremoved, promoted stem elongation. The most pronounced effectwas on plants from which the buds were removed 2 d before anthesis,but it had no effect on plants from which the buds were removedat anthesis stage. The possible involvement of endogenous growth hormones in theresponse of Petunia plants to floral-bud removal and to applicationof GA₃ is discussed. Bud removal, bud number, dwarfness, GA₃, Petunia, plant height     

Physiological Controls on the Production of Cleistogamous and Chasmogamous Flowers in Lamium amplexicaule L

Plants of Lamium amplexicaule, grown under short-day field conditionsin Northern California produce predominantly closed flowers.Under long-day field conditions, plants may produce up to 50per cent open flowers, the same total number of flowers beingproduced under each daylength regime. A 20 ml drop of GA₃ or GA₇ (100µM) was applied to themain shoot apex of plants growing under short-day conditions,and all subsequently produced flowers opened. CCC, an inhibitorof gibberellin synthesis, was applied (0.06 per cent) to thesoil of seedlings grown under long-day conditions. The CCC-treatedplants were dwarfed and bore only closed flowers. With GA₇ appliedexogenously to the CCC-treated shoots, inhibition was released,resulting in elongated internodes and open flower production.The timing of flower production and internodal extension inLamium amplexicaule are positively correlated. When floral primordiawere removed from main shoots, the average internode lengthsdecreased. The number of nodes produced in treated plants wasincreased as a result of flower removal. Exogenous GA₇ (10 µM)applied to the nodes from which flowers were removed resultedin internodal extension but had no effect on node number. Twoprocesses that may contribute to the control of the productionof open and closed flowers in Lamium amplexicaule are: (1) anincreasing anther sac size from lower to upper node flowersthat may exert control locally, via GN production, on corollaexpansion, and (2) a photoperiodic control. Lamium amplexicaule L, henbit, cleistogamy, chasmogamy, gibberellins, gibberellic acid (GA₃), (2 chloroethyl) trimethylammonium chloride (cycocel)     

Identification and Semi-Quantification of Gibberellins from the Pollen and Anthers of Zea mays by Immunoassay and GC/MS

Radioimmunoassays and enzyme-linked immunosorbent assays formethyl esters of gibberellins A₁, A₃, A₄, and A₇ were establishedusing an antiserum specific for GA₁-Me. The antiserum was characterizedby high titer and specificity for such C₁₉-GAs with 3ß-hydroxylgroup as GA₁, GA₃, GA₄ and GA₇. Combination of this antiserumand HPLC enabled us to identify and quantify GA, and GA₄ fromthe pollen of Zea mays with a high degree of reliability. Similarly,identification and quantification of GA₉ and GA₂₀ were alsomade possible by use of an antiserum specific for GA₂₀-Me. Combineduse of immunoassays and GC/MS enabled us to identify nine GAsfrom the pollen and four from the anthers of Zea mays. The identificationof non-13-hydroxylated GAs, such as GA₄ and GA₉, in additionto 13-hydroxylated GAs from the pollen and the anthers suggeststhat the early-non-hydroxylation pathway, as well as the early-13-hydrox-ylationpathway, operates in the male reproductive organs of Zea mays,and that the organ-specific biosynthesis and/or localizationof GAs in Zea mays is similar to that in Oryza saliva. (Received May 7, 1990; Accepted August 20, 1990)     

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)     

Effects of Gibberellins and Prohexadione on the Activities of Oryzain and {alpha}-Amylase in Rice Seeds

Oryzains, cysteine proteinases of rice seeds, are induced byGA₃ in germinating rice seeds [Abe et al. (1987) Agric. Biol.Chem. 51: 1509]. The effects of GA₁, GA₃, GA₄, GA₉, and GA₂₀on the production of oryzain and -amylase were investigatedin embryoless half- and whole-seeds of rice (cv. Nipponbare).When gibberellins (GAs) were incubated with embryoless half-seeds,GA₁, GA₃ and GA₄ induced oryzain and -amylase, but GA₉, andGA₂₀ did not. GA₉ and GAM induced oryzain and -amylase productionin whole seeds, but this production was inhibited by the simultaneousapplication of prohexadione, an inhibitor of 2ß- and3ß-hydroxylation of GAs. Prohexadione did not inhibitthe activities of oryzain and -amylase induced by GA₁. Theseresults suggest that GAs possessing the 3ß-hydroxylgroup induce activities of oryzain and -amylase in rice seedsand that GA₉ and GA₂₀ have activity only after they are convertedmetabolically to active GAs, probably GA₄ and GA₁, respectively.GA₁, was more active than GA₄ in both half seeds and wholeseeds incubation. Oryzain and -amylase activities induced byGA₄ were significantly inhibited in the presence of 10^–4M prohexadione. This suggests that the conversion of GA₁, toGA₄ (13-hydroxylation) might be inhibited at a high dose ofprohexadione in whole seeds. ⁴Present address: Institute of Food Development, Kyung Hee University,Suwon 449-701, Korea     

Prolongation of Embryo Sac Viability in Pear (Pyrus communis) Following Pollination or Treatment with Gibberellic Acid

Embryo sac development has been investigated in unpollinated,cross pollinated and gibberellic acid (GA₂) treated flowersof Pyrus communis L. While pollination and GA₃ treatments donot alter embryo sac development, they prolong embryo sac viability.In untreated unpollinated flowers, ovules degenerate between12 and 21 d after anthesis, while in cross pollinated and GA₃treated flowers this degeneration is postponed by about 10 d.Thus, in a cross pollinated flower this extends the period overwhich a successful fertilization can take place. This increasedperiod of viability is accompanied by an elongation of the embryosac itself. Elongation takes place two weeks prior to fertilizationin cross pollinated flowers. The extension of life span of embryo sacs following pollinationand treatment with gibberellic acid indicates that a stimulusinduced by ‘pollination’ could be mediated by GA₃Whatever its mechanism of operation, the prolongation of embryosac viability by pollination represents a selective advantage,in that the period at which the ovules are receptive to fertilizationmust be significantly extended. Embryo sac, gibberellic acid, Pyrus communis, pear, pollination     

Enhancement of Gibberellic Acid-stimulated Hypocotyl Elongation of Lettuce (Lactuca sativa L. cv. Grand Rapids) by Phlorizin and Light

The interaction of light, gibberellic acid (GA₃), and phlorizinin the growth of lettuce (Lactuca sativa L. cv. ‘GrandRapids’) hypocotyls was investigated. At all concentrationsof GA₃, phlorizin enhanced GA₃-induced growth at luminous intensitiesabove 50 ft-c (continuous light). Without GA₃, phlorizin hadno effect on hypocotyl growth in the light but it inhibitedgrowth in the dark. Both seedlings and hypocotyl sections respondedto phlorizin in the presence of GA₃. There was no iteractionbetween phlorizin and KCl. Water-growth was severly inhibitedby light. GA₃,-induced growth was slightly inhibited by light,and then only at luminous intensities above 50 ft-c. Thus, relativeto H₂O-growth, GA₃-induced growth increased with increasingluminous intensity up to 450 ft-c, where it reached saturation.It seems that a synergism may exist between light and GA₃ aswell as between phlorizin and GA₃. Lactuca sativa L, lettuce, hypocotyl elongation, gibberellic acid, phlorizin, light     

Seasonal Changes of GA1, GA19 and Abscisic Acid in Three Rice Cultivars

The levels of endogenous gibberellin A₁ and A₁₉ (GA₁ and GA₁₉)and abscisic acid (ABA) in three rice (Oryza sativa L.) cultivars,Nihonbare (normal), Tan-ginbozu (semid-warf) and Tong-il (semi-dwarf),were measured at various stages of internode elongation andear development. GA₁₉ was the main GA in Nihonbare and Tong-ilthroughout the life cycle but was not detected in Tan-ginbozu.The levels of GA₁ in the ears of all three cultivars were lowand reached their maxima after anthesis. Similarly, the earsof all three cultivars contained high ABA levels which peakedafter anthesis. Shoots contained low quantities of ABA throughoutthe life cycle. The roles of GAs and ABA are discussed withrespect to physiological phenomena, such as internode elongation,ear development and dwarfism. (Received May 9, 1981; Accepted July 18, 1981)     

Gibberellin Production in Cultured Cells of Nicotiana tabacum

Endogenous gibberellins (GAs) in several kinds of crown gallcells and cultured cells derived from normal tissue of Nicotianatabacum were systematically analyzed by gas chromatography-selectedion current monitoring (GC-SICM) after chromatographic purifications,and GA₁, GA₉, GA₁₉ and GA₂₀ were identified. Agrobacterium tumefaciens,a pathogen of crown gall, was confirmed not to produce GAs inits culture. We also investigated endogenous GAs of mother plant,tobacco, and found the same kinds of GAs as in cultured cells. ³ Present address: College of Agriculture, Chonnam NationalUniversity, Kwangju 500, Korea. (Received May 19, 1982; Accepted July 22, 1983)     

Effects of a New Plant Growth Regulator Prohexadione Calcium (BX-112) on Shoot Elongation Caused by Exogenously Applied Gibberellins in Rice (Oryza sativa L.) Seedlings

The effects of a novel plant growth regulator (PGR) prohexadionecalcium (BX-112; calcium 3,5-dioxo-4-propionylcyclohexanecarboxylate)on shoot elongation caused by exogenously applied GA₁, GA₃,GA₄₎ GA₁₉ and GA₂₀ were investigated in rice (Oryza sativa L.cv. Nihonbare and cv. Tan-ginbozu) seedling test. Dependingon the dose, BX-112 reduced shoot elongation in both cultivarscaused by GA₁₉ and GA₂₀, but not by GA₁. When a high dose ofBX-112 (e.g. 250 ng/plant and over) was applied with GA₁, orGA₄, shoot elongation was even promoted. This promotive effect,however, was not observed with GA₃. These results suggest thatBX-112 inhibits gibberellin (GA) biosynthesis in the rice plantat the 3ß- and 2ß-hydroxylation of GAs,namely steps of activation and inactivation, respectively. (Received September 6, 1989; Accepted November 27, 1989)     

Floral organ growth and carbohydrate content during pollen development in Lilium

In order to understand floral sugar physiology, we correlated the growth of the organs with carbohydrate content in the flower of Lilium cv. “enchantment” during pollen development. In a previous work, we distinguished two phases in pollen ontogenesis: the anther growth phase, from the microspore mother cell until the vacuolated microspore, and the anther maturation phase, from the vacuolated microspore until anthesis. In the present work, we showed that during the growth phase, the anther underwent most of its size and dry weight growth, whereas the growth rate of nonanther organs was reduced. Anther and filament possessed the highest amounts of carbohydrates, which decreased progressively until the vacuolated microspore stage. During the maturation phase, sucrose and starch increased in all floral organs. Anther growth was completed at the Mi stage, whereas the nonanther organs began exponential growth. From these observations, we concluded that hierarchic nutritional correlations exist between the flower organs, in which the anther is the main actor: during the anther growth phase, the anther represents the highest sink strength floral organ, and mainly attracts assimilates through the filament. During the anther maturation phase, anther growth is achieved, its needs decrease, and assimilates are thus available for neighboring organs, which undergo intense growth until anthesis.     

EMASCULATION EFFECTS ON FILAMENT GROWTH IN IPOMOEA NIL (CONVOLVULACEAE)

Filament growth in the morning glory Ipomoea nil is promoted by gibberellic acid (GA₃) and inhibited by ethylene production during the earlier stages in development (Koning and Raab, 1987). The effects of anther removal on filament growth were examined in I. nil. Three-quarters of the calyx and corolla tissues were removed in order to emasculate the stamens. This removal caused filament growth to be inhibited in the intact stamens (69 hr before anthesis) as well as the emasculated stamens (69 to 21 hr before anthesis). When the ethylene biosynthesis inhibitors CoCl₂ and aminoethoxyvinylglycine (AVG) were applied in separate experiments (to eliminate wound ethylene generated by the damaged tissues), filament growth was promoted to control levels observed in intact flower buds (69 hr before anthesis). Our data suggest that the wounding effect from the calyx and corolla tissues and subsequent reduction in filament growth override any observable effects with anther removal on filament growth. Apparently, the removal of the calyx and corolla tissues severs a normal hormonal relationship between these floral organs and the developing filament.     

Inhibition of flowering and growth in Pharbitis nil by the growth retardant Ancymidol

Flower formation and growth of the short day plant Pharbitisnil, strain "Violet", were inhibited when the growth retardantAncymidol was applied prior to an inductive dark period viacotyledons or roots. Inhibition of flower formation by Ancymidolcould be completely reversed by an application of gibberellinA₃ (GA₃) to the plumule before the inductive dark period. Adose of 0.01 µg GA₃/plant was almost sufficient to restoreflowering, but about a hundred times more GA₃ was required torestore the internode length to that of control. Ancimidol greatlyreduced the endogenous gibberellin content. (Received July 18, 1980; )     

Inhibition of flowering and growth in Pharbitis nil by the growth retardant Ancymidol

Flower formation and growth of the short day plant Pharbitisnil, strain "Violet", were inhibited when the growth retardantAncymidol was applied prior to an inductive dark period viacotyledons or roots. Inhibition of flower formation by Ancymidolcould be completely reversed by an application of gibberellinA₃ (GA₃) to the plumule before the inductive dark period. Adose of 0.01 µg GA₃/plant was almost sufficient to restoreflowering, but about a hundred times more GA₃ was required torestore the internode length to that of control. Ancimidol greatlyreduced the endogenous gibberellin content. (Received July 18, 1980; )     

Specificity of Gibberellin and Sucrose-promoted Flower Bud Growth in Gladiolus

A critical stage in flower bud growth in the spike of Gladioluswhich is initiated by gibberellic acid (GA₃) and sustained bysucrose has been identified. This corresponds to the stage atwhich separation of the outer bract occurs. In buds at differentdevelopmental stages isolated and held in water, it is the samebud stage that first shows increased growth. Buds not inducedby light were shown to respond more significantly to GA₃ andsucrose than those induced by light. Since the separation ofthe outer bract results in light-induced amylase productionand starch hydrolysis leading to petal growth, it is proposedthat growth promotion by GA₃ is related to light-induced petalgrowth at this specific stage. flower bud growth, Gladiolus natalensis, gibberellic acid, sucrose     

Stimulation of the Flowering of Pharbitis nil Chois. by Gibberellin A3 : Time Dependent Action at the Apex

Gibberellin A₃ (GA₃) stimulated flowering when it was appliedto the shoot apex of seedlings of Pharbitis nil, dwarf strainKidachi; but, not when it was applied to the cotyledons. GA₃applied to the plumule before or shortly after the start ofan inductive dark period promoted both flowering and shoot elongation;but, the later the time of application during the dark periodless the promotion of flowering, although marked promotion ofshoot elongation always took place. The variation with time in the response of flowering to GA₃indicates that early floral processes at the apex are stimulatedby GA₃, but that subsequent processes are insensitive to it.The early processes of floral stimulus produced by a 16 hr inductivedark period probably are completed within 20 hr at 28°Cafter the end of the dark period. At low temperatures, suchas 15 and 20°C, early floral processes continued for morethan 40 hr. When cotyledons were removed at various times, the export ofthe floral stimulus to the shoot apex was apparent within hoursof the generation of the floral stimulus in the cotyledons,which started with the passage of the critical 9-hr dark period. (Received February 18, 1981; Accepted March 24, 1981)     

Fruit Set and Growth in Strawberry, Fragaria x ananassa Duch.

The application of GA₃in aqueous solution to leaves or flowersof hermaphrodite cultivars of strawberry, Redgauntlet and Rabunda,prevented growth of the receptacle despite hand pollination.This inhibitory effect occurred only when GA₃ was applied priorto anthesis. Although viable pollen was produced and germinatedto grow down the styles of treated plants, no seeds were formed.Receptacle growth failed underneath the unfertilized carpels,but the basal region devoid of carpels enlarged and ripened.The effect of GA₃ was the same in vivo and for flowers grownin vitro. ABA and BAP also inhibited growth of pollinated flowersin vitro, but neither substance stimulated growth of the baseof the receptacle. 2-NOA stimulated receptacle growth of pollinatedflowers but did not overcome the inhibitory effect of GA₃. Removal of fertile carpels 9 days after pollination preventedfurther receptacle growth. GA₃ treatment of the bare receptaclere-started growth but was less effective than 2-NOA. No growth substance treatment induced parthenocarpic developmentin these cultivars when unopened buds were emasculated and culturedwithout pollination, although GA₃ induced some swelling of thereceptacle base. Fragaria x ananassa Duch., strawberry fruit set, fruit growth, growth regulators     

Dormancy in Dioscorea: Generality of gibberellin-induced dormancy in asexual dormant organs

Effects of GA₃ and CCC application on the sprouting of bulbilsor subterranean dormant organs of 10 species in the genus Dioscoreawere observed. Although the efficiency of both chemicals differedby species, in general GA₃ inhibited and CCC promoted the sproutingof the above dormant organs. In some species, however, dilutedGA₃ (0.003–0.3 µM) has a promotive and diluted CCC(3–30 µM) has an inhibitive effect on sprouting. Effects of GA₃ application on shoot elongation were tested onsprouted bulbils. GA₃ promoted elongation when applied directlyto the shoots and inhibited it when applied to the bulbous parts. These results suggest that GA activates two opposing reactions—sprouting-promotingand sprouting-inhibiting—in these organs. The complicatedrelation between GA₃ or CCC concentrations and sprouting wereexplainable by assuming that the two counteractive reactionswere activated by GA in different degrees. ¹ Present address: Department of Biology, Faculty of Science,Yamagata University, Yamagata 990, Japan. (Received June 21, 1976; )