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     

A COMPARISON OF CLEISTOGAMOUS AND CHASMOGAMOUS FLORAL DEVELOPMENT IN COLLOMIA GRANDIFLORA DOUGL. EX LINDL. (POLEMONIACEAE)

An individual of Collomia grandiflora typically produces both closed or cleistogamous (CL) and open or chasmogamous (CH) flowers. The developmental origin of these dimorphic floral types within a plant was investigated using histological techniques, allometric relationships, and scanning electron microscopy. Prior to archesporal cell stage in the anthers, CL and CH meristems are indistinguishable. In the CL anther, an absence of ventral locule cell differentiation together with a shorter period of time between archesporial cell differentiation and meiosis in the two dorsal locules results in accelerated anther dehiscence and a smaller mature anther size and pollen grain number. Divergence between the CL and CH patterns of corolla development is coincident with microspore mitosis in the CH anther. At this point, there is an increase in growth in corolla length relative to growth in calyx length in the CH flower which does not occur in the CL flower. Calyx and ovary development are similar in the two floral forms; however, ovary expansion due to fertilization occurs earlier in the CL flower as a result of precocious anther development and stigma receptivity. The hypothesis that anther differentiation may trigger organ growth rate changes and differentiation events in the flower and hypothetical roles for abscisic acid and gibberellin in modifying floral development in C. grandiflora are discussed.     

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.     

AN ANATOMICAL BASIS FOR THE DIVERGENT FLORAL FORMS IN THE CLEISTOGAMOUS SPECIES,LAMIUM AMPLEXICAULE L. (LABIATAE)

The pattern of variation in mature corolla form has been documented throughout the main shoot inflorescence of the cleistogamous species Lamium amplexicaule L. A heteroblastic development occurs within the cymose inflorescence at a single node as well as between different nodes. Variation involves an increase in cell number and expansion in the upper corolla and also an increase in cell number in the anther sacs, expressed as pollen count increases, in progressively produced flowers in the inflorescence. The corolla base region in all flowers shows an increased cell expansion from the first produced cleistogamous (CL) flowers to the later produced chasmogamous (CH) flowers which expand at anthesis. Cell numbers are equivalent in the corolla base region of all flowers. It appears that in successively produced flowers in the inflorescence, prolonged cell division and expansion occurs in both the upper corolla region and the anthers until a threshold is reached, at which point flowers may undergo anthesis and become CH. The CL corolla form in Lamium amplexicaule is not caused by a lack of cell expansion alone; rather, both cell division and expansion are arrested in the upper corolla region.     

SPATIAL AND TEMPORAL VARIATION IN CHASMOGAMY AND CLEISTOGAMY IN OXALIS MONTANA (OXALIDACEAE)

Chasmogamous (CH) and cleistogamous (CL) flower production was investigated in natural populations of the perennial herb Oxalis montana in southern Quebec, Canada. Every 10–12 days during two flowering seasons, we recorded the reproductive output of approximately 2,000 plants distributed among five forest sites. The percentage of plants flowering, proportion of flowering plants producing CH and CL flowers, CH and CL flower number per flowering plant, and the proportion of flowers that are CL differed significantly among sites and corresponded to site differences in forest type and habitat quality. Unlike patterns in most CL species, however, reproduction by cleistogamy increased in sites with habitat conditions favorable to plant growth and sexual reproduction, and decreased in less productive sites. Chasmogamous and CL flower production increased with increasing plant size but plant size explained a significantly greater proportion of the variation in CL flower numbers. The percentage of flowering plants producing CH flowers decreased between years while the proportion of CL flowers increased at all sites during the second flowering season. The somewhat unusual aspects of reproduction in Oxalis may stem from its perennial habit which allows use of stored resources in adjusting the balance of cleistogamy versus chasmogamy in different environmental regimes.     

THE BALANCE BETWEEN CHASMOGAMY AND CLEISTOGAMY IN COLLOMIA GRANDIFLORA (POLEMONIACEAE)

The extent of cleistogamy (CL) and chasmogamy (CH) was investigated in natural populations of Collomia grandiflora Dougl. ex Lindl. The ubiquitous occurrence of CL flowers was documented in 18 populations from throughout the geographic range of the species. The interrelationship of environmental perturbation, vegetative weight, and the balance between CH and CL flowers was investigated by means of a factorial experiment which varied plant density, incident light and soil mix. An ANOVA revealed that total plant weight increased significantly under conditions of low density, low light and low sand content, with density accounting for most of the variance in plant weight. Interactions involving density were not significant. The number of CH and CL flowers and estimated percent outcrossing increased significantly with increased plant weight, low density, low light, and low sand content, although an analysis of covariance showed that plant weight and density accounted for most of the variance in these traits. Among large, multibranched plants, the proportion of CL flowers increased in a basipetal pattern, whereas most of the CH flowers were restricted to the terminal and upper inflorescences. The smallest plants produced only a single terminal inflorescence comprising entirely CL flowers. The proportion of reproductive effort allocated to outcrossing was dependent upon plant size as estimated from total weight, whereas the proportion allocated to ***selfing was relatively independent. Studies of outcrossed vs. inbred progenies of five populations revealed little evidence for immediate inbreeding depression with respect to plant weight and the number of CH or CL flowers, but indicated that significant quantitative genetic differences exist for these traits among populations of diverse ecological or geographical origin.     

ECOLOGICAL CONSEQUENCES AND PHENOTYPIC CORRELATES OF PETAL SIZE VARIATION IN WILD RADISH,RAPHANUS SATIVUS (BRASSICACEAE)

In this paper we examine some ecological consequences and phenotypic correlates of flower size variation in wild radish, Raphanus sativus. Mean corolla diameter varied significantly among individuals within natural populations of R. sativus in California. On the average, almost 40% of flower biomass was allocated to corolla tissue. In field experiments, pollinator visitation increased significantly with corolla size. Large flowers also accumulated more nectar when pollinators were excluded from plants. In three populations, corolla size was positively correlated with allocation to pollen per flower (either anther weight or pollen grain number), but there was usually no phenotypic relationship between corolla size and several measures of female allocation (ovule number per flower, proportion fruit set, and total seed mass per fruit). Plants growing in the field produced fewer large flowers per unit of stem, and stem biomass was negatively related to corolla size for plants grown under controlled greenhouse conditions. Male and female fitness may covary differently with allocation to attractive floral features in species such as R. sativus, where seed production is often limited by resources rather than by pollen.     

ABA and GA3 affect the growth and pigment composition in Andrographis paniculata Wall.ex Nees., an important folk herb

In this study, 5 μmol·L⁻¹ abscisic acid (ABA) and gibberellic acid (GA₃) were used to study the effect of both growth regulators on the morphological parameters and pigment composition of Andrographis paniculata. The growth regulators were applied by means of foliar spray during morning hours. ABA treatment inhibited the growth of the stem and internodal length when compared with control, whereas GA₃ treatment increased the plant height and internodal length. The total number of leaves per plant decreased in the ABA-treated plants, but GA₃ treatment increased the total number of leaves when compared with the control. Both growth regulators (ABA and GA₃) showed increased leaf area. ABA and GA₃ treatments slightly decreased the total root growth at all the stages of growth. The growth regulator treatments increased the whole plant fresh and dry weight at all stages of growth. ABA enhanced the fresh and dry weight to a larger extent when compared with GA₃. An increase in the total chlorophyll content was recorded in ABA and GA₃ treatments. The chlorophyll-a, chlorophyll-b, and carotenoids were increased by ABA and GA₃ treatments when compared with the control plants. The xanthophylls and anthocyanin content were increased with ABA and GA₃ treatments in A. paniculata plants.     

DOWN THE TUBE: POLLINATORS, PREDATORS, AND THE EVOLUTION OF FLOWER SHAPE IN THE ALPINE SKYPILOT, POLEMONIUM VISCOSUM

Abstract We address how a conflict between pollinator attraction and avoidance of flower predation influences the evolution of flower shape in Polemonium viscosum. Flower shape in P. viscosum is the product of an isometric relationship between genetically correlated (r_A= 0.70) corolla flare and length. Bumblebee pollinators preferentially visit flowers that are more flared and have longer tubes, selecting for a funnel‐shaped corolla. However, flower shape also influences nectar‐foraging ants that sever the style at its point of attachment to the ovary. Surveys of ant damage show that plants having flowers with flared, short corollas are most vulnerable to ant predation. Consistent with this result, the ratio of corolla length to flare is significantly greater in a krummholz (high predation risk) population than in a tundra (low predation risk) population. To explicitly test whether the evolution of a better defended flower would exact a cost in pollination, we created tubular flowers by constricting the corolla during development. Performance of tubular flowers and natural controls was compared for defensive and attractive functions. In choice trials, ants entered control flowers significantly more often than tubular ones, confirming that the evolution of tubular flowers would reduce the risk of predation. However, in a bumblebee‐pollinated population, tubular flowers received significantly less pollen and set fewer seeds than controls. A fitness model incorporating these data predicts that in the absence of the genetic correlation between corolla length and flare, intermittent selection for defense could allow tubular flowers to spread in the krummholz population. However, in the tundra, where bumblebees account for nearly all pollination, the model predicts that tubular flowers should always confer a fitness disadvantage.     

Effect of Gibberellic Acid and Phosfon on the Critical Dark Period Reqnirement for Flowering of Impatiens balsamina cv. Rose

The critical dark period requirement for flowering of Impatiens balsamina L. cv. Rose, an obligate short day plant, is about 8.5 hours. While GA₃ completely substituted for the dark period requirement, Phosfon prolonged it to 9.5 hours. GA₃ hastened and Phosfon delayed the initiation of floral buds under all photoperiods. Floral buds opened into flowers only during 8 and 14 hour photoperiods in control and Phosfon-treated plants but during all photoperiods in GA₃-treated ones. The delay in floral bud initiation and flowering was correlated with shifting up of the node bearing the first floral bud and flower respectively. While GA₃ increased the numher of floral buds and flowers in all photoperiods except 8-hour, Phosfon increased their number in the 14-hour photoperiod only. The number of flowering plants decreased with increasing photoperiod regardless of GA₃ and Phosfon application. The effect of Phosfon was completely or partially overcome, depending upon the photoperiod, by simultaneous application of GA₃.     

The role of abscisic acid (ABA) in ethylene insensitive Gladiolus (Gladiolus grandiflora Hort.) flower senescence

Gladiolus flowers are ethylene insensitive and the signals that start catabolic changes during senescence of gladiolus flower are largely not known. Therefore, experiments were performed to understand the role of abscisic acid (ABA) in ethylene insensitive floral senescence in gladiolus (Gladiolus grandiflora Hort.). It was observed that ABA accumulation increased in attached petals of gladiolus flowers as they senesced. Exogenous application of ABA in vase solution accelerated senescence process in the flowers due to change in various senescence indicators such as enhanced membrane leakage, reduced water uptake, reduced fresh weight and ultimately vase life. Enhancement of in vivo ABA level in petals by creating osmotic stress also upregulates the same parameters of flower senescence as those occurring during natural senescence and also akin to exogenous application of ABA. Attempts to increase vase life of flowers by application of putative ABA biosynthesis inhibitor fluridone in vase solution to counteract ABA effect were unsuccessful. In contrast, ABA action was mitigated by application of GA₃ in holding solution along with ABA which is basically an antagonist of ABA action. The present study provides valuable insights into the role of ABA as a hormonal trigger in ethylene insensitive senescence process and therefore would be helpful for dissecting the complex mechanism underlying ABA-regulated senescence process in gladiolus.     

Why is there variation in mean seed size among plants within single populations? test of the fertilization efficiency hypothesis

We tested the fertilization efficiency hypothesis, which attempts to explain mean seed size variation among plants within single populations, by comparing the patterns of seed size variation between chasmogamous (CH) flowers and cleistogamous (CL) flowers in Impatiens noli-tangere and Viola grypoceras, respectively. The fertilization efficiency hypothesis predicts that larger plants produce larger seeds if the number of pollen grains captured by a plant increases with increased allocation of resources to its attractive structures (e.g., corolla and nectar), but with diminishing gains. Thus, seed size should depend on plant size in seeds from CH flowers because of the diminishing gains of capturing pollen in these flowers, whereas seed size should not depend on plant size in seeds from CL flowers because CL flowers need not capture outcross pollen. We found significant positive correlations between mean seed size per plant and plant size for seeds from CH flowers in both species. However, there was no significant positive correlation between these two factors for seeds from CL flowers of both species. The results of the present investigations were thus consistent with the fertilization efficiency hypothesis.     

COMPARATIVE FLOWER DEVELOPMENT IN THE CLEISTOGAMOUS SPECIES VIOLA ODORATA. I. A GROWTH RATE STUDY

In Viola odorata, chasmogamous (CH) or open flowers and small, short-petioled leaves are produced under 11 hr or less of daylight, cleistogamous (CL) or closed flowers and large, long-petioled leaves under 14 hr or more of daylight, and intermediate floral and leaf forms under transitional photoperiods. CL flowers are approximately four times smaller than CH flowers and differ morphologically in repressed growth of the anterior petal spur and staminal nectaries, and recurving of the style which remains enclosed within the cone formed by anther appendages. Both CH and CL shoot systems conform to a (2 + 3) phyllotaxis with minor differences in leaf divergence angles and phyllotactic indices. The larger CL leaf grows significantly faster than the CH leaf, and an increased rate of leaf initiation occurs in the CL apex represented by a plastochron of 3.4 days compared to 4.3 days in the CH apex. The plastochron index was used to indirectly age young floral primordia nondestructively until prophase of meiosis I within the anthers. This event occurs 8 days earlier in the CL than the CH flower. Time from meiosis until flower maturity, determined by direct observation, is about 14 days for the CL flower, versus 21 days for the CH flower.     

Sex‐specific floral morphology,biomass, and phytohormones associated with altitude in dioecious Populus cathayana populations

Relationships between sex‐specific floral traits and endogenous phytohormones associated with altitude are unknown particularly in dioecious trees. We thus examined the relationships between floral morphology or biomass and phytohormones in male and female flowers of dioecious Populus cathayana populations along an altitudinal gradient (1,500, 1,600, and 1,700 m above sea level) in the Xiaowutai Nature Reserve in northern China. The female and male flowers had the most stigma and pollen at 1,700 m, the largest ovaries and least pollen at 1,500 m, and the smallest ovaries and greater numbers of anthers at 1,600 m altitude. The single‐flower biomass was significantly greater in males than in females at 1,600 or 1,700 m, but the opposite was true at 1,500 m altitude. The biomass percentages were significantly higher in anthers than in stigmas at each altitude, while significantly greater gibberellin A3 (GA₃), zeatin riboside (ZR), indoleacetic acid (IAA), and abscisic acid (ABA) concentrations were found in female than in male flowers. Moreover, most flower morphological traits positively correlated with IAA in females but not in males. The biomass of a single flower was significantly positively correlated with ABA or IAA in males but negatively with ZR in females and was not correlated with GA₃ in both females and males. Our results demonstrate a distinct sexual adaptation between male and female flowers and that phytohormones are closely related to the size, shape, and biomass allocation in the pollination or fertilization organs of dioecious plants, although with variations in altitude.     

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)     

Pleiotropic effects of the<Emphasis Type="Italic"> male sterile33</Emphasis> (<Emphasis Type="Italic">ms33</Emphasis>) mutation in<Emphasis Type="Italic"> Arabidopsis</Emphasis> are associated with modifications in endogenous gibberellins,indole-3-acetic acid and abscisic acid

Earlier, we reported that mutation in the Male Sterile33 (MS33) locus in Arabidopsis thaliana causes inhibition of stamen filament growth and a defect in the maturation of pollen grains [Fei and Sawhney (1999) Physiol Plant 105:165–170; Fei and Sawhney (2001) Can J Bot 79:118–129]. Here we report that the ms33 mutant has other pleiotropic effects, including aberrant growth of all floral organs and a delay in seed germination and in flowering time. These defects could be partially or completely restored by low temperature or by exogenous gibberellin A₄ (GA₄), which in all cases was more effective than GA₃ Analysis of endogenous GAs showed that in wild type (WT) mature flowers GA₄ was the major GA, and that relative to WT the ms33 flowers had low levels of the growth active GAs, GA₁ and GA₄, and very reduced levels of GA₉, GA₂₄ and GA₁₅, precursors of GA₄. This suggests that mutation in the MS33 gene may suppress the GA biosynthetic pathway that leads to GA₄ via GA₉ and the early 13-H C₂₀ GAs. WT flowers also possessed a much higher level of indole-3-acetic acid (IAA), and a lower level of abscisic acid (ABA), relative to ms33 flowers. Low temperature induced partial restoration of male fertility in the ms33 flowers and this was associated with partial increase in GA₄. In contrast, in WT flowers GA₁ and GA₄ were very much reduced by low temperature. Low temperature also had little effect on IAA or ABA levels of ms33 flowers, but did reduce (>2-fold) IAA levels in WT flowers. The double mutants, ms33 aba1-1 (an ABA-deficient mutant), and ms33 spy-3 (a GA signal transduction mutant) had flower phenotypes similar to ms33. Together, the data suggest that the developmental defects in the ms33 mutant are unrelated to ABA levels, but may be causally associated with reduced levels of IAA, GA₁ and GA₄, compared to WT flowers.Abbreviations ABA Abscisic acid - GA Gibberellin - GC-MS-SIM Gas chromatography-mass spectrometry-selected ion monitoring - IAA Indole-3-acetic acid - ms33 Male sterile33 mutant - PP333 Paclobutrazol - WT Wild type     

Improvement of pistillate flowers yield with GA3 in heavy metals treated plants

GA₃ can be beneficial to improve the flowering yield in Lagenaria siceraria (Mol.) Standl. and Luffa cylindrica L. (Roem) treated with HgCl₂ and . This paper reviews the literature on the possible involvement of gibberellins in flower development and suggests that plants under the stress of heavy metals can be treated with GA₃ to improve growth parameters, to avoid delay in flowering and likewise quality of fruit can be improved. Applied GA₃ (400 mg/l) caused precocious flowering, increasing the number of flowers in the treated plants. All data was compared with control plants grown under similar conditions. Both heavy metals caused significant delay in flowering, consequently leading to reduction in the number of flowers. However, when GA₃ was applied with HgCl₂ and , there was less decrease in staminate and pistillate flowers, revealing the dominant effect of GA₃. Current work reveals that inhibitory effects of heavy metals on flowering can be partially restored with GA₃ application.     

Responses of ivy (Hedera helix L.) to combinations of gibberellic acid,paclobutrazol and abscisic acid

A reduction in concentration of gibberellins has been implicated in the phase change from juvenile to mature forms of ivy (Hedera helix L.). Attempts were made to increase the effective internal concentration of gibberellins by exogenous application of GA₃, and to decrease them by various applications of abscisic acid (ABA) and paclobutrazol (PP333), alone or in combination with GA₃. ABA and GA₃ were fed directly into the xylem of ivy plants by a wick system (a less drastic procedure than the defoliation or decapitation used by earlier workers) whereas PP333 was applied as a soil drench.Mature ivy responded to the application of GA₃ by reversion to the juvenile form, although this reversion was incomplete with respect to leaf lobing and red (anthocyanin) pigmentation and could occur spontaneously without the application of GA₃. Contrary to expectation, applications of ABA and PP333 caused the stimulation of growth in juvenile ivy. No adult characteristics were induced. As similar concentrations of ABA and PP333 produced severe retardation of growth (which could be alleviated by the application of GA₃) in other species, it is suggested that ivy may be an unsuitable model system for the investigation of phase change in woody plants.     

Floral induction by gibberellic acid in Impatiens balsamina,a qualitative short-day plant

Summary In the qualitative short-day plant Impatiens balsamina, gibberellic acid (GA₃) not only promoted the formation of floral buds in response to suboptimal photoinductive conditions and reduced the number of SD cycles that are required for their development into flowers, but also caused initiation of floral buds under non-inductive photoperiods. In plants treated with repeated applications of GA₃, the floral buds developed into flowers irrespective of whether the apex was left intact or was removed. In those that received a single application of GA₃ the floral buds developed into flowers only in decapitated plants.     

Relationship between gibberellin and cytokinin activity and flowering in Rosa damascena Mill.

Kinetin at 10 mg l^–1 increased the number of flowers produced on Rosa damascena plants while GA₃ inhibited flowering. In the leaves of non-flowering plants GA-like activity was high while specific cytokinin activity (fraction-II) was significantly higher in flowering plants. A novel compound 10- methyldihydrozeatin riboside and isopentenyl-adenine were identified from TLC fraction-II while TLC fraction-I yielded zeatin and 2-hydroxy-6-methylaminopurine.Abbreviations TLC thin layer chromatography - BA N⁶-benzyladenine - GA₃ gibberellic acid CIMAP communication No. 92-40J