Flower-bud Blasting Research Articles

Hormonal regulation of the growth of leaves and inflorescence stalk in Muscari armeniacum Leichtl.

It is known that chilling of <em>Muscari</em> bulbs is necessary for the growth of the inflorescence stalk and flowering, but not for the growth of leaves. Gibberellic acid (GA) accelerated stem growth and flowering in chilled <em>Muscari</em> bulbs. In the present experiment it was shown that in unchilled derooted <em>Muscari</em> bulbs the growth of leaves, but not the growth of the inflorescence stalk, was observed when bulbs were stored in water, GA at a concentration of 50 and 100 mg/L, benzyladenine (BA) at a concentration of 25 and 50 mg/L, or a mixture of GA+BA (50+25 mg/L), but abscisic acid (ABA) at a concentration of 10 mg/L greatly inhibited the growth of leaves. In chilled derooted <em>Muscari</em> bulbs the growth of leaves and inflorescence stalk was observed when bulbs were stored in water or GA, but BA and GA+BA treatments totally inhibited the growth of the inflorescence stalk without an effect on the growth of leaves. These results clearly showed that the growth of leaves and inflorescence stalk in <em>Muscari</em> bulbs are controlled by plant growth regulators in different ways. ABA totally inhibited the growth of leaves and inflorescence stalk in chilled derooted <em>Muscari</em> bulbs. It was shown that after the excision of the inflorescence bud in cultivated chilled <em>Muscari</em> bulbs, the inflorescence stalk died, but application of indole-3-acetic acid (IAA) 0.5% in the place of the removed inflorescence bud induced the growth of the inflorescence stalk. IAA applied under the inflorescence bud inhibited the development of flowers (flower-bud blasting) and induced the growth of the inflorescence stalk below the treatment site. These results are discussed with reference to hormonal regulation of stem (stalk) growth in tulip, narcissus, hyacinth, and <em>Hippeastrum</em>.

Anatomical Characterization of Flower-bud Blasting and Suppression Following Hormone Application in Eustoma grandiflorum (Raf.) Shinn.

Flower-bud blasting is a constraint for producing Eustoma grandiflorum so a preventative strategy is needed. Flower-bud blasting occurs under low light intensity and high fertilizer input. To gain insight into the mechanisms of flower-bud blasting, we conducted a detailed characterization of flower development under normal and blast-inducing conditions. We found that floral buds under low light intensity ceased to grow at the stamen and gynoecium differentiation stages, although sepals and petals were initiated normally. Aborted flowers rarely had normal ovules. Moreover, an expanded apical meristem was observed. These results show that the differentiation and development of reproductive organs are critically suppressed by blast-inducing conditions; however, combined application of 300 ppm benzylaminopurine and 200 ppm gibberellic acid-3 to floral buds resulted in about five-fold greater frequency of flower opening compared to controls. Blasting inhibition also resulted from excising the inflorescent branch, suggesting the decrease in assimilates in flower buds would be attributed to flower-bud blasting. Moreover, hormone application combined with excision had an additive effect for preventing flower-bud blasting, suggesting that these treatments independently inhibit flower-bud blasting. These results suggest that flower-bud blasting in Eustoma is a break in floral development around the stamen and gynoecium initiation stages and is integrally induced by the factors related to hormone biosynthesis and the decrease in assimilates.

シンビジウムの花蕾における呼吸変化と「花飛び」現象との関連について

Respiratory changes leading to flower bud blasting in the orchid Cymbidium × Sazanami 'Haru-no-umi' at high temperature were examined. When plants bearing inflorescences grown between 5° to 20°C (low) were transferred to a phytotron kept at 30° day/25°C night (high), CO2 evolution by the flower buds decreased rapidly and reached about 1/3 of the initial rates during two weeks with rise of temperature coefficient (Q10) near to 3. Flower stalks and bracts showed similar but slower reductions in CO2 evolution. Their Q10 values were around 2 and not different from those of the control inflorescences placed at low temperatures (20°/15°C). Both respiratory rates and Q10 values remained relatively constant in the control inflorescences. Respiratory rates of flower buds grown at natural low temperatures were high on fresh weight basis and increased with flower bud development on flower bud basis. The respiratory quotient (RQ) was between 1.15 and 1.35. On the contrary, the rates of those grown under natural high temperatures (25°C ?? ) showed lower values and did not increase on flower bud basis. The RQ decreased dramatically from 1.5 to 0.7. Application of gibberellic acid (GA3), which prohibited flower buds from blasting, suppressed the reductions of respiratory rates and RQ values. The results indicate that reduction of respiratory rates, RQ decrease and Q10 rise, are involved in the blasting of Cymbidium flower buds caused by high temperature.

Flower Bud Blast in Easter Lily Is Induced by Ethephon and Inhibited by Silver Thiosulfate

Interactions of ethephon and irradiance reduction were investigated in terms of flower bud blasting in Easter lily (Lilium longiflorum Thunb. `Nellie White'). Silver thiosulfate (STS) was investigated as an inhibitor of ethylene-induced bud abortion. Fourteen days of 92% irradiance reduction significantly increased bud abortion when plants were exposed to 2.1 mm ethephon. Bud abortion was 39% and 60% for plants grown in ambient and reduced irradiance, respectively. Silver thiosulfate was applied to plants 2 or 3 weeks after the date of the first visible bud, followed by ethephon treatment 2 days later. Bud abortion was significantly reduced by 1 or 2 mm STS, without phytotoxicity. Pretreatment with 1 or 2 mm STS as early as 4 weeks before ethephon exposure significantly reduced ethephon-induced bud abortion. Silver thiosulfate application could inexpensively reduce flower bud abortion during latter stages of greenhouse forcing of Easter lilies.

Participation of Ethylene in Flower Bud Blasting Induced by High Temperature in Cymbidium (Orchidaceae).

Ethephon, one of the chemicals releasing ethylene, induced flower bud blasting of a Cymbidium hybrid (C. ×Sazanami 'Haru-no-umi') regardless of the stage of flower buds. Both silver-thiosulphate (STS) and gibberellic acid (GA3) overcame the inhibition of flower bud development induced by high temperatures. There was, however, a distinct difference in the action between these chemicals. The stimulation of flower bud development by STS remained after subsequent applications of ethephon; that of GA3 was nullified by ethephon. Furthermore, inflorescences treated with STS evolved more ethylene than did the control, whereas inflorescences treated with GA3 evolved less ethylene than did the control. These results indicate that STS and GA3 function as inhibitors of ethylene action and ethylene synthesis, respectively. They also indicate that ethylene is involved in high temperature-induced blasting of Cymbidium flower buds.

Microsporogenesis and Flower Bud Blasting as Affected by High Temperature and Gibberellic Acid in Cymbidium(Orchidaceae).

To clarify at what stage of development flower buds are subject to blasting by high temperature, a correlation between the length of perianths and the stage of pollen formation in a miniature Cymbidium orchid (C. × Sazanami 'Haru-no-umi') was investigated.1. High correlations between the variables were obtained during the stages of sporogenous cells and pollen mother cells (PMC) regardless of the position of the flower buds. Flower buds exposed to high temperatures (30°C day/25°C night) at sporogenous cell stage became blasted without entering into the meiotic stage. Similarly, buds which were heated at premeiotic stage became blasted at various stages after chromosomes underwent meiosis.2. Flower buds reaching the meiotic prophase of PMC never responded to the high temperature and bloomed normally.3. The application of gibberellic acid (GA3) reduced the low temperature requirement for bud development. GA3-treated buds entered the meiotic cell differentiation stage and proceeded to develop normally with mature viable pollen, even when the GA3 spray was combined with the high temperature treatment.4. The results indicate that buds at premeiotic stage are very sensitive to blasting by exposure to high temperature, and that temperatures below 20°C are required for cells to undergo meiosis, form mature pollen, and develop normal flowers.5. Different patterns of microspore arrangement were observed even in the same anther.Most uninucleate microspores of blasted flower buds were diads, fewer progressed to tetrads.On the other hand, binucleate microspores of both blasted and normal flower buds were mainly in the tetrad stage. The patterns and kinds of tetrads were not changed by the GA3 treatment, whether the buds were blasted or normal.

The role of ethylene in the flowering response of bulbous plants

Ethylene induces the flower formation and stimulates the flower-bud development of some bulbous plants exposed to the gas when the apex is in the vegetative state. For iris bulbs cv. Ideal maximum responses have been found after exposure to 5 ppm for 8 h; lower concentrations, shorter exposure periods and, depending on seasonal conditions, low temperatures during gas treatment, gave intermediate responses. The effects are opposite to the ethylene induced flower-bud blasting which occurs when bulbous plants are exposed to the gas after completion of the flower formation.

The role of cytokinins in relation to flower-bud blasting in Iris cv. Ideal: Cytokinin determination by an improved enzyme-linked immunosorbent assay

The effect of dark and light treatment on endogenous cytokinins in internodes and buds of Iris was determined. Plant material was purified by chromatographic methods and cytokinins were assayed by an immunoassay.

Low light intensity and flower bud abortion in Asiatic hybrid lilies. I. Genetic variation among cultivars and progenies of a diallel cross

When Asiatic lilies are forced during the winter period, additional light is needed to prevent flower bud abscission and flower bud blasting. Growth room experiments showed considerable differences among eight lily cultivars in their response to low light. Among these cultivars, ‘Connecticut King’ and ‘Enchantment’ appeared to be the most sensitive to low light conditions while ‘Uncle Sam’ and ‘Scout’ were the least sensitive.

Treatment of tulips with gibberellic acid by vacuum infiltration

SummaryInitial attempts to reduce the glasshouse period of tulips by vacuum infiltration with GA3 in 200 ppm (v/v) aqueous Tween 80 resulted in over 90% flower losses because of bulb, shoot or flower rot and floral bud blasting. In subsequent experiments fungicides (benomyl, etridiazole, formaldeyhyde and thiram) were added to the solution, GA3 solutions were tested with and without added surfactants (Tween 80 and Agral 90) and two infiltration techniques were tested using a range of vacuums and durations of treatments. The fungicides and surfactants used increased flower losses; vacuum infiltration itself caused some flower losses compared with untreated bulbs. In most cases these flower losses were reduced when GA3 (150-200 ppm) was added to the solution used for infiltration. For cv Apeldoorn previously cooled at 5°C for 12 weeks, vacuum infiltration with GA3 (150-250 ppm) at 10 torr for 5-15 min reduced the duration of the glasshouse period by 5-7 d, compared to untreated bulbs. GA3 treatments also re...

The existence of a critical period for the abscission and a non-critical period for blasting of flower-buds of Lilium ‘Enchantment’; influence of light and ethylene

Flower-bud blasting and abscission, 2 dissimilar phenomena occurring in buds of Lilium ‘Enchantment’, can both be evoked by darkness or ethylene (C 2H 4). Flower-bud abscission is influenced more strongly than bud blasting by short light periods and C 2H 4. Flower-bud blasting can occur through out inflorescence development, abscission only during a critical stage of development of the flower-buds, which proved to coincide with a peak in the endogenous production of C 2H 4 by the buds and with the end of the meiotic phase of the stamens. Both C 2H 4 production by the buds and the occurrence of flower-bud abscission were influenced by the length of time the bulbs had been stored before planting.

Assimilate distribution and the role of abscisic acid and zeatin in relation to flower-bud blasting, induced by lack of light, in Iris cv. Ideal

Flower-bud blasting in Iris occurs in the winter when low light intensities and short days prevail. After introduction of 14CO2 to one leaf the transport of assimilates was studied under controlled culture conditions in a control light treatment and in a treatment of 7 days darkness followed by standard light conditions. Little assimilate transport was found in the direction of the bud in dark-treated plants. However, zeatin injection into the flower buds of the plants subjected to the dark treatment clearly promoted assimilate transport ot these buds. Abscisic acid levels, determined by gas chromatography, were found to increase in the buds of dark-treated plants. Zeatin injection into the flower bud resulted in a suppression of the abscisic acid level. The latter treatment also resulted in higher percentage of flowering. Removal of flower parts was found to inhibit peduncle elongation. The peduncle elongation of complete flowers started in a well defined period, and the fresh weight of buds was found to increase mainly in the last part of that period. Assimilate transport under low light intensities in relation to abscisic acid and supposed gibberellin is discussed.

Response of potted tulips to new and established growth-retarding chemicals

A range of growth-retarding chemicals was evaluated for their potential in the production of compact pot-grown tulips: ancymidol, piproctanyl bromide (Alden), dikegulac-sodium (Atrinal), a phenyl tetrazole compound (coded PP528), 2,3-dihydro-5,6-diphenyl-1,4-oxathiin (coded UBI-P293), chlorphonium chloride (Phosfon), 2-chloroethylphosphonic acid (Ethrel), and 5 morphactins. All chemicals were applied as single soil drenches 1–2 days after transferring plants to the glasshouse. Mid- and late-season forced bulbs of cultivars ‘Apeldoorn’, ‘Paul Richter’ and ‘Rose Copland’ were used. Piproctanyl bromide and chlorphonium chloride were ineffective, the former causing some stimulation of top internode extension. Ethrel at high concentrations gave a slight reduction in first internode length only, associated with a degree of flower-bud blasting. Dikegulac-sodium gave some reduction in stem and petal length, depending on cultivar. PP528 induced flower-bud blasting, adverse changes in flower colour and reduced petal length at concentrations which effectively shortened stems. Morphactins were toxic or caused flower-bud blasting and other floral abnormalities at high concentrations; at lower doses most morphactins reduced first internode length, while some increased length of the upper internodes, inducing nastic curvature and occasionally altering flower shape. Most effective height control was achieved with ancymidol and UBI-P293, the latter being the more active (at the concentrations tested); flower quality was good. In one experiment only, ancymidol slightly delayed flowering. High concentrations of UBI-P293 gave rise to some flower-bud blasting, especially in ‘Rose Copland’ which showed other adverse side-effects such as decreased length and longevity of the flowers, not only with UBI-P293 but also with higher doses of some other retardants.

Flower-bud blasting in tulip plants mediated by the hormonal status of the plant

Injection of GA 3, GA 4+7, BA, or kinetin into the flower bud prevented ethylene-induced flower-bud blasting, while injection of water or auxins stimulated the occurrence of the disorder. Single application of GA 4+7 and BA by means of injection into the bulb scales, spraying the shoots or drenching the soil were much less effective or had no effect. Injection of relatively high amounts of BA into the buds caused more than 100 % extra growth of the flower and upper internode; at the same time, the growth of daughter bulbs was reduced and exhaustion of the mother bulb was accelerated. GA 4+7 reduced the duration of the greenhouse period by about 30 %. On the basis of these findings and the enhanced growth of daughter bulbs accompanying flower-bud blasting, we assume that flower-buds compete with daughter bulbs for substrate. The distribution of substrate, which derives mainly from the mother bulb, might be determined by the growth-regulator status of the plant, cytokinins and gibberellins strengthening the sink of the flower-bud and ethylene weakening it.

Flower-bud blasting in tulips caused by ethylene

Several symptoms are described that characterize the extent of flower-bud blasting in tulips. The disorder could be induced by ethylene applied in concentrations of 0.3 ppm and higher during storage of the bulbs. When ethylene was applied late, the symptoms could be observed in most of the buds immediately after exposure. During subsequent storage in an ethylene-free environment, the injury often increased. When ethylene was applied early, symptoms of blasting appeared only after subsequent treatment for early flowering.

The effects of space flight factors and gamma radiation on flower production and microspore division and development in tradescantia

The interaction between 85Sr gamma radiation (average exposure approximately 220 R) and space flight factors (vibration, acceleration, weightlessness, etc.) on the number of flowers produced and on microspore division and development was studied in Biosatellite II. In the actual flight one package of 32 young Tradescantia clone 02 plants was irradiated during the two-day flight, and another package was used as an unirradiated flight control. Two similar packages, one of which was irradiated, were maintained as non-flight controls in a similar spacecraft at the launch site. Various postflight experiments were conducted in an attempt to attribute the effects observed in the orbited plants to specific flight factors. In these postflight ground tests plants were grown simultaneously in both the flight and non-flight spacecraft under conditions similar to those recorded during the actual flight. In the clinostat and additional vibration experiments individual packages rather than the whole spacecraft were used. After each treatment, open flowers were collected for at least 26 days. Some of the morphological and cytological effects observed in the flight material can be attributed to low gravity (weightlessness) and others to the internal environment of the spacecraft. Those effects attributed to weightlessness include (1) an increase in number of flowers produced in both orbited samples compared with their non-orbited controls and (2) various kinds of mitotic abnormalities associated with altered spindle behavior in microspores. Effects attributed to spacecraft environmental factors such as the increased concentration of ethylene measured in the flight vehicle include (1) an increase in the mortality rate of microspores, (2) an increase in the frequency of developmental abnormalities indicated by a change in the number and shape of the nuclei in young pollen, and (3) an increase in flower bud blasting which led to a change in the pattern of flower production.