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     

Effects of some metabolic inhibitors on flowering of Lemna gibba G3, a long-day duckweed

Flowering of Lemna gibba G₃, a long-day duckweed, was inhibitedby adding CuSO₄, AgNO₃, HgCl₂, Na₂WO₄ or iodoacetamide to themedium at the concentrations inducing long-day flowering inLemna paucicostata 6746, a short-day duckweed. This suggeststhat these metabolic inhibitors affected the photoperiodic sensitivityrather than directly affecting flower initiation. Ferricyanidepromoted flowering in both of these short-day and long-day duckweeds. (Received July 7, 1977; )     

Flowering of Cultivated Green and SAN 9789-Treated Chenopodium rubrum Plants Exposed to White,Blue, and Red Light

Green plants and plants devoid of photosynthetic pigments were compared with regard to their ability to flower under various growth conditions. Green plants of Chenopodium rubrum L. and plants treated with norflurazon SANDOZ-9789 (SAN) were grown on sucrose-containing media with or without hormones (GA₃, BA, IAA, ABA) under short-day photoperiodic or continuous illumination with white, blue, or red light. Green and SAN-treated albino plants produced flowers only under short-day conditions. The flowering of green plants was independent of the presence of sucrose and hormones in the medium as well as of the light quality. The albino plants produced flowers under white and blue light but did not flower in red light. The addition of GA₃ or BA to the medium induced flowering of albino plants exposed to red light. The functional interaction of photoreceptors in the flowering control is discussed.     

INTRA-INFLORESCENCE VARIABILITY IN POLLEN/OVULE RATIOS IN THE CLEISTOGAMOUS SPECIES LAMIUM AMPLEXICAULE (LABIATAE)

A comparative study was made of the various floral forms in the main shoot inflorescence of the cleistogamous species Lamium amplexicaule L. (Labiatae). This study revealed significant differences in pollen/ovule (P/O) ratios between successively produced flowers. The variation in P/O ratio is due to a change in pollen count/flower and not in ovule number. The study included two plant populations, one grown in November when only closed flowers are produced, and the other grown in April when open flower production occurs at the upper nodes. The intra-inflorescence variation in P/O ratio among the spring population showed a correlation between P/O ratio and breeding system. The cleistogamous flowers had low P/O ratios of about 200 while the chasmogamous flowers had higher P/O ratios of about 600.     

Flowering and Endogenous Levels of Plant Hormones in Lemna Species

The occurrence and endogenous level of various plant hormoneswere measured for the short-day plants Lemna paucicostata 151and 381 and the long-day plant Lemna gibba G3 to determine whetherany of them are involved in the photoperiodic control of flowering.ABA, IAA, GA₁, GA₂₉, GA₃₄, GA₅₃, trans- and cis-zeatin, trans-and cis-ribosyl zeatin, N⁶-(²-isopentenyl) adenine and N⁶-(²-isopentenyl)adenosine were definitely detected in each species, while GA₄was only detected in L. gibba G3 and GA₂₀ was only detectedin L. paucicostata 151. The endogenous levels of ABA and IAAwere in the range of 1–7 ng/g fr wt and were not significantlydifferent in vegetative and flowering plants. The endogenousgibberellin levels were generally higher in Lemna grown underlong-day rather than short-day conditions. The endogenous cytokininlevels were almost the same in both flowering and vegetativeplants of L. paucicostata 151 and 381. In L. gibba G3, however,the level of cis-ribosyl zeatin, N⁶-(²-isopentenyl) adenineand N⁶-(²-sopentenyl) adenosine were higher in vegetative thanin flowering plants. These results indicate that there is not necessarily a directrelation between endogenous plant hormone levels and flowering,and that the chemical basis for the photoperiodic control offlowering cannot be explained solely by changes in hormone levels.The possibility remains, however, that one or more of the planthormones has some influence of secondary importance on the floweringprocess in Lemna. (Received January 29, 1986; Accepted July 12, 1986)     

The Interactive Effects of Carbon Dioxide Enrichment and Daylength on Growth and Development inPetunia hybrida

Plants were grown at either 350 or 1000 µl l^-1CO₂and inone of three photoperiod treatments: continuous short days (SD),continuous long days (LD), or short switched to long days atday 41 (SD–LD). All plants received 9 h of light at 450µmol m^-2s^-1and LD plants received an additional 4 h oflight at 8 µmol m^-2s^-1. Growth of SD plants respondedmore positively to elevated CO₂than did LD plants, due largelyto differences in the effect of CO₂on unit leaf rate. High CO₂increasedheight and decreased branching under SD conditions, but hadno effect under LD conditions. Elevated CO₂also increased thenumber of buds and open flowers, the effect for flower numberbeing greater in short than in long days. The specific leafarea of plants grown at 1000 µl l^-1CO₂was reduced regardlessof daylength. High CO₂also decreased leaf and increased reproductiveallocation, the magnitude of these effects being greater underSD conditions. Bud formation and flower opening was advancedunder high CO₂conditions in SD plants but bud formation wasdelayed and there was no effect on flower opening under LD conditions.The effects of CO₂on plants switched from SD to LD conditionswere largely intermediate between the two continuous treatments,but for some parameters, more closely resembled one or the other.The results illustrate that daylength is an important factorcontrolling response of plants to elevated CO₂. Petunia hybridaHort. ex Vilm; carbon dioxide; photoperiod; functional growth analysis; daylength; global change; development; phenology     

Phyllody Malformation in Flowers of Rosaxhybrida cv. Motrea: Effects of Rootstocks, Flower Position, Growth Regulators and Season

Phyllody, a common malformation of Rosaxhybrida cv. Motrea,is characterized by the formation of vegetative structures inplace of stamens and carpels. The incidence of phyllody in thiscultivar is dependent on the type of the root system. The highestproportion of malformed flowers was found in ungrafted plants,this decreased in plants grafted on R. indica major and waslowest on R. canina inermis. Flowers formed on shoots, whichwere located closer to the roots, were more prone to phyllodythan those grown on the upper part of the plants. The incidenceof phyllody was lower in winter than in summer, while shadingof the plants reduced the proportion of malformed flowers regardlessof their root system and the season. Application of gibberellicacid (GA₃) or benzylaminopurine (BAP) greatly promoted the incidenceof phyllody, while paclobutrazol (PBZ) reduced it. The activityof endogenous cytokinins in the xylem exudates from ungraftedplants was higher than in exudates from those grafted on R.indica major, and the lowest activity was found in exudatesfrom plants grafted on R. canina inermis. The involvement ofplant hormones in the development of floral organs in rose flowersis discussed. Key words: Cytokinins, flower malformation, gibberellic acid, homeosis, phyllody, roses     

Flower-Promoting Effects of Iron and EDDHA in Lemna paucicostata 151

Lemna paucicostata 151 cultured in 1/10 strength M medium containing50 µM FeCl₃ easily flowered in response to short days,although it scarcely flowered under any photoperiod when themedium contained the standard amount of iron (2 µM FeCl₃).The flowering response was accomparied by an increase in theiron content of the plants, which was maximal at pH 5.0. Instandard M medium containing 50 µM FeCl³, this plant didnot flower even though it had a high iron content. Ethylenediamine-di (o-hydroxyphenylacetic acid) (EDDHA) inducedflowering of this strain under continuous light even in theabsence of iron and copper, and its effect was slightly loweredby the presence of iron in the medium. Thus the flower-inducingactivity of EDDHA could not be attributed to the action of ironor copper. EDTA inhibited both the iron uptake and floweringin Fe-rich medium under short-day conditions. (Received May 16, 1986; Accepted July 25, 1986)     

Effects of Low Irradiance Stress on Gibberellin Levels in Pea Seedlings

Using gas chromatography-selected ion monitoring with internalstandards we analyzed endogenous levels of GA₁, GA₈, GA₁₉, GA₂₀,GA₂₉, GA₄₄ and GA₅₃ in shoots of pea cv. Alaska grown underdifferent levels of irradiance: high irradiance, 386±70µmolm^-2s^-1, control (100%); medium (50%); low (10%); darkness (0%).The average plant heights for medium and low irradiance anddark grown plants were 157%, 275%, and 460% of the control plants,respectively. Plants grown in medium and low irradiance developedthe same numbers of internodes as control plants but plantsin darkness developed fewer internodes and exhibited suppressedleaf expansion. The endogenous levels of GA₁ GA₈ and GA₂₉ werehigher in medium and low irradiance grown plants than thoseof the high irradiance control. In particular, the GA₂₀ levelof low irradiance plants was markedly higher (7.6-fold) thanthat of control plants. In dark-grown plants GA₁, and GA₈ levelsalso slightly increased but GA₂₀ and GA₂₉ levels decreased andthe levels of GA₁₉, GA₄₄ and GA₅₃ did not change. Feeding ofGA₁, and a GA biosynthesis inhibitor (uniconazole) to plantsgrown at reduced irradiance and in darkness suggests that theresponsiveness of plants to GA₁, also increased at low irradianceand in darkness. In conclusion, plants increase both GA₁, andGA₂₀ biosynthesis or altered catabolism and GA₁, responsivenessunder low irradiance stress ¹Present address: Dept. of Plant Physiol., Warsaw AgriculturalUniversity, Rakowiecka 26-30, 02-528 Warsaw, Poland     

Effects of some SH-inhibitors and EDTA on flowering in Lemna perpusilla 6746

Lemna perpusilla 6746, a short-day duckweed, flowered undercontinuous illumination on M-sucrose medium containing CuSO₄,AgNO₃ and HgCl₂, which are SH-inhibitors. The optimum concentrationsof CuSO₄, AgNO₃ and HgCl₂ were 5, 1 and 20 µM, respectively.Other metal ions tested were ineffective, but at least two otherSHinhibitors, potassium ferricyanide and iodoacetamide, alsoinduced long-day flowering at the concentrations of 0.1-1 µM. Adding 50 µM EDTA to the medium prevented the effect ofcupric ion, but not that of other SH-inhibitors. EDTA at 200µM induced some long-day flowering when added to a mediumwith no SH-inhibitors. It also permitted some flowering whenadded together with cupric ion, and accelerated flowering inthe presence of the other SHinhibitors listed above. EDTA andSH-inhibitor effects appeared to be additive. (Received May 25, 1973; )     

Does Cytokinin Transport from Root-To-Shoot in the Xylem Sap Regulate Leaf Responses to Root Hypoxia?

We have examined the hypothesis that cytokinins transportedfrom roots to shoots affects leaf growth, stomatal conductance,and cytokinin concentration of leaves of Phaseolus and a hybridpoplar (Populus trichocarpa x Populus deltoides) with hypoxicroots. Because cytokinins may interact with other substances,potassium and calcium concentrations were determined in xylemsap of Populus plants with hypoxic and aerated roots while gibberellin(GA) concentrations were measured in shoot tissues. Root hypoxiadecreased leaf growth and closed stomata in both species. Inboth species, fluxes of cytokinins out of the roots were reduced,but no differences in bulk leaf concentrations were measuredbetween the hypoxic and aerated plants. Shoots with aeratedroots contained slightly higher concentrations of GA₁ and GA₃than shoots from hypoxic plants. There were no differences incalcium or potassium concentrations in xylem sap between aerationtreatments. Exogenously applied cytokinins did not alleviatethe growth or stomatal responses caused by root hypoxia. Informationon the site(s) and mechanism(s) of cytokinin action and theways in which cytokinins are compartmentalized within plantcells will be required to understand the physiological significanceof cytokinin transport in the transpirational stream. Key words: Cytokinins, hypoxia, Populus, Phaseolus     

The Interaction of Genetic, Environmental, and Hormonal Factors in Stem Elongation and Floral Development of Cucumber Plants

Hypocotyl length was found to vary between cucumber plants carryingdifferent genes controlling sex expression. Among lines havingonly unisexual flowers (genotype M/M), the homozygous monoeciousplants (st⁺/st⁺) had significantly longer hypocotyls than theirgynoecious counterparts (st/st), heterozygous gynoecious plants(st+/st) being intermediate. Similarly, hypocotyls of plantsof an andromonoecious line (st⁺/st⁺ m/m) were significantlylonger than in their hermaphrodite counterparts (st/st m/m).Differences in intemode length were also significant and inthe same direction. Since stem and particularly hypocotyl elongationin cucumber is known to be very sensitive to applied gibberellin,these findings suggest the existence of differences in the effectivelevels of endogenous gibberellins in the different sex types,higher levels being correlated with stronger male tendency.This conclusion is in good agreement with the known effect ofapplied gibberellin on sex expression (enhancement of the maletendency) in cucumber. Application of gibberellin (GA₄+GA₇) and exposure to ‘summer’conditions (long days and relatively high temperature) inhibitedthe development of pistillate flowers while ‘winter’conditions (short days, lower temperature) had a similar effecton staminate flowers. The effect was in either case specific,that is, limited to flower development. It is concluded thatexogenous and endogenous gibberellins affect not only the initiation,but also the further development, of flowers in the cucumber.     

Specific interactions in the physiology of flowering and gibbosity of Lemna gibba G3

Fronds of Lemna gibba G3 became conspicuously gibbous when ethrel,an ethylenereleasing compound, was added to the nutrient medium.Maximal gibbosity was obtained at ethrel concentrations of 1µg/ml and higher. Unlike the chelating agent, EDDHA, whichcauses profuse flowering and markedly gibbous fronds under long-dayconditions, ethrel did not affect flowering. In the presenceof an optimal concentration of EDDHA (10 µ/ml), ethreleven significantly inhibited flowering and caused developmentof excessively gibbous fronds. Autoclaved gibberellic acid specifically negated the ethreleffect as it does that of EDDHA. Three decomposition productsof GA₃, allogibberic acid, epiallogibberic acid and gibbericacid, also nullified flowering and gibbosity in the presenceof EDDHA. A fourth decomposition product of GA₃, epigibbericacid, inhibited gibbosity but hardly affected flowering. Salicylic acid was confirmed to affect flowering and gibbosityin L. gibba G3. However, contrary to an earlier report, it didnot induce flowering under short-day conditions. (Received January 10, 1976; )     

Mitotic Activities and Levels of Nuclear DNA in the Apical Meristem of Silene armeria (strain SI.2) Following Application of Gibberellin A3

Strain S1.2 of Silene armeria was grown under an 8h-photoperiodand treated with GA₃ every day for 20 days. This growth substancecaused stem elongation, but no flowering in this long-day plant.Changes in the mitotic index and DNA content of cells in thevarious zones of the apical meristem before, during and afterGA₃ treatment were described. Mitotic activity and increasein the proportion of nuclei at the 4C level (S+G₂ phase of thecell cycle) were strongly stimulated in the rib-meristem, andto a lesser extent in the lateral zone, but not in the axialzone. This stimulation of apical activity reached a peak aftertwo GA₃ treatments and then declined gradually, so that after20 days the activity in GA₃-treated meristems was lower thanthat in untreated controls; at this point most cells were inthe G₁ phase. When the GA₃ treatment was discontinued, there was a gradualincrease in the mitotic activity which ultimately reached thesame level as that in controls. Stem elongation ceased and leavesformed aerial rosettes. It is concluded that in vegetative plants of strain S1.2 ofSilene armeria GA₃ acts mainly on the rib-meristem cells whichresults in stem elongation. Lack of response in the axial cellsexplains why GA₃ fails to induce flowering in this strain ofSilene armeria. (Received June 18, 1983; Accepted August 3, 1983)     

Effect of varying number of short days, gibberellic acid and ascorbic acid on the flowering of soybean

Both the cultivars of soybean, namely E.C. 2579 and Punjab I,studied were found to be qualitative short day plants. Evenone SD was sufficient to cause flower bud initiation in E.C.2579, although flower opening required 3 SDs. Pb. I did notshow flower bud initiation with less than 10 SDs. In Pb. I thenumber of flowers with 20 SDs was higher than continuous SD,indicating the favourable effect of long days prior to induction. Exogenous application of GA₃ and AA singly and in combinationsubstituted for the additional photoperiodic requirements ofincompletely induced plants of Pb. I, but were ineffective undercontinuous LDs. Treatment with these regulators of plants havingreceived 8 SDs resulted in initiation of flower buds, whichfailed to open into flowers. In plants subjected to 10 SDs flower buds were initiated withall these treatments except control. Floral buds did not openinto flowers with any treatment or combination not containingGA₃. (Received March 28, 1970; )     

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     

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; )     

Identification of Gibberellins in Cotyledonary Embryos of Phaseolus coccineus L.

Gibberellins present in cotyledonary embryos of Phaseolus coccineusL. have been identified by combined gas chromatography-massspectrometry as GA₁, GA₄, GA₅, GA₆; also an unidentified gibberellinwas present. The total amount of gibberellins was estimated by gas chromatographyto be 26.5 µg per g fresh weight; the individual gibberellinscontributed to the total amount as follows: GA₁ 18.4µg,GA₅ 2.6 µg, GA₄ 2.3 µg, GA₆ 1.9 µg, unidentifiedGA 1.3 µg. Data are discussed in relation to previousresults in P. coccineus seed as well as in relation to the embryo-suspensorsystem. (Received December 12, 1985; Accepted July 8, 1985)     

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; )     

EFFECTS OF WATER STRESS,ABSCISIC ACID,AND GIBBERELLIC ACID ON FLOWER PRODUCTION AND DIFFERENTIATION IN THE CLEISTOGAMOUS SPECIES COLLOMIA GRANDIFLORA DOUGL. EX LINDL. (POLEMONIACEAE)

The effects of water stress, abscisic acid (ABA), and gibberellic acid (GA₃) on flower production and differentiation by Collomia grandiflora were investigated. An untreated plant typically produced both small, closed cleistogamous (CL) and large, open chasmogamous (CH) flowers. The larger corolla of CH flowers was due to a greater cell number and size. When plants were water-stressed or sprayed with ABA, both the percentage of CH flowers and the total number of flowers were reduced significantly. The corolla dimensions and epidermal cell numbers and sizes of CL flowers produced by water-stressed and ABA-sprayed plants did not differ from those of CL flowers produced by control plants. Application of GA₃ to both well-watered and water-stressed plants significantly increased the percentage of CH flowers formed compared to well-watered controls. In the absence of GA₃, water-stressed plants produced almost entirely CL flowers. GA₃-sprayed plants produced CH flowers whose corolla dimensions were intermediate between those of CL and CH flowers formed by control plants. Epidermal cells of these intermediate corollas were reduced only in number and not in size when compared to control CH flowers. Endogenous levels of ABA and gibberellins may control the type of flower produced by C. grandiflora and may mediate some of the observable effects of water stress on flowering.