Effects of ancymidol and gibberellins A3 and A4+7 on Tulipa gesneriana L. cv. Paul Richter during development in the greenhouse

The influence of soil drench applications of ancymidol (0.5 mg), GA₃ (25 mg), and Ga₄₊₇ (25 mg) was determined on the growth and development of the tulip under greenhouse conditions. Ancymidol applied on greenhouse day 1 or 6 significantly reduced the total length of the scape. Maximum reduction in growth occurred in the first internode, with a declining effect on internodes 2, 3 and 4. GA₄₊₇ applied simultaneously with ancymidol completely reversed the ancymidol effects. GA₃ was relatively ineffective. Compared to control plants, ancymidol reduced the number of cell divisions in the first internode, but not in the fourth internode. Cells of ancymidol treated plants were reduced in length and exhibited greater radial expansion. Ancymidol reduced the fresh weight of the stem and tended to conserve the fresh weight of the mother scales. The effect on the leaves and roots was variable. Ancymidol tended to increase the fresh weight of the daughter bulblets. There was no significant effect of ancymidol or the GA's on floral morphology or the number of days to flower in the greenhouse.     

Effects of growth-regulating chemicals on two cultivars of Mid-Century Hybrid lily

The effects on growth and flowering of Mid-Century Hybrid lilies ‘Enchantment’ and ‘Joan Evans’ of soil drench applications of ancymidol at 0, 5, 10 and 15 ppm have been compared with those produced by drenches of chlormequat chloride, chlorphonium chloride and ethephon at 25 000, 1000 and 1000 ppm, respectively.Ancymidol inhibited stem growth more effectively than a 5000-fold greater quantity of chlormequat chloride. Chlorphonium chloride had little dwarfing effect, and ethephon, although producing height reductions similar to those obtained with 5 ppm ancymidol, delayed flowering slightly in both cultivars (significantly in ‘Enchantment’), and adversely affected overall plant appearance.Ancymidol reduced the lateral spread of foliage, increased the proportion of the total stem length bearing dead leaves, did not significantly delay flowering in either cultivar and appeared to favour the initiation and survival of secondary flowers in ‘Enchantment’.     

The Influence of Foliar Applications of GA3 GA4,7 and PBA on Breaking Flower Bud Dormancy on Azalea CVS Redwing and Dogwood

Foliar applications of gibberellins (GA₃, GA₄,₇) and 6-benzylamino-9-(2-tetra- hydropyranyl)-9H-purine (PBA) were compared with untreated controls and the conventional low temperature treatment for breaking flower bud dormancy. GA₃ and GA₄, ₇ were compared for their role in promoting flower development. Treatments were initiated when microscopic examination showed the flower buds had reached Stage 6 (style elongated and closed). Plants that did not receive a dormancy-breaking treatment failed to reach anthesis. Application of GA₃ or GA₄, ₇ hastened flowering and increased flower size and pedicel length.     

Endogenous gibberellins and their effects on flowering and stem elongation in cabbage (Brassica oleracea var. capitata)

Summary

Endogenous gibberellins were extracted from cabbage shoots and were analysed using gas chromatography and mass spectrometry. Nine gibberellins (GA₁, GA₁₉, GA₂₀, GA₄₄, GA₁₂, GA₄, GA_15, GA₂₄ and GA₂₅) were identified. Two gibberellin biosynthesis pathways were suggested, an early-13-hydroxlyated pathway and a non-13-hydroxylated pathway, to operate in cabbage shoots. GA₁, GA₄ and prohexadione calcium, a gibberellin biosynthesis inhibitor, were applied to the shoot tip of cabbage ‘Sousyu’ and ‘Kinkei No.201’ with or without cold treatment. Without cold treatment, stem elongation was increased by gibberellins and was suppressed by prohexadione calcium in both cultivars. But prohexadione calcium treatment, followed by gibberellin, promoted stem elongation more than gibberellin alone. Flowering was not induced by gibberellin or prohexadione calcium without cold treatment. When gibberellin and prohexadione calcium were applied during a cold treatment, stem elongation after the cold treatment was increased by gibberellins and was suppressed by prohexadione calcium in both cultivars. Flower bud appearance was promoted by GA₁ and GA₄ in ‘Sousyu’, but in ‘Kinkei No. 201’ only GA₄ was markedly effective. Inhibition of stem elongation and delay of flower bud appearance by prohexadione calcium were overcome by applying GA₁ or GA₄. Neither gibberellin nor prohexadione calcium treatment changed the number of leaf nodes at anthesis. These results indicated that stem elongation and flower bud development are regulated by gibberellins, but gibberellins might have little effect on flower induction.     

Plant growth regulators and flowering of Brunonia and Calandrinia sp.

Brunonia australis R. Br (Goodeniaceae) and Calandrinia (Portulacaceae), native to Australia, are potential new flowering potted plants. This research investigated the role of daylength and growth regulators, Gibberellic acid (GA₃) and paclobutrazol (Pac), to control vegetative growth, peduncle elongation and flowering of Brunonia and Calandrinia. Plants were grown under long days (16 h), short days (11 h) and 8 weeks under short day then transferred to long day (SDLDs). Plants in each daylength were treated with GA₃, Pac, and GA₃+ Pac. GA₃ was applied as 10 μL drop of 500 mg L⁻¹ concentration to the newest mature leaf. A single application of Pac was applied as a soil drench at 0.25 mg a.i. dose per plant. Both Brunonia and Calandrinia flowered earlier in long days but still flowered in short days, so both can be classified as facultative LD plants. Brunonia under SDLDs were more vigorous and attractive than plants under LDs while still being more compact than plants under SDs. In Brunonia, GA₃ promoted earlier flowering and increased the number of inflorescences under SDs. Pac at 0.25 mg a.i. per plant applied alone or in combination with GA₃ had extended flower development in Brunonia, and resulted in a reduced number of inflorescences per plant compared to the control plants. Vegetative growth of Calandrinia was similar under LDs, SDs and SDLDs, whereas GA₃ application increased plant size. Pac-treated Calandrinia looked compact and attractive, and Pac application did not affect time to flower and flower number.     

Effect of exogenous growth regulators on flowering and cytokinin levels in azaleas

‘Alaska’ and ‘Redwing’ azaleas having dormant flower buds were sprayed with gibberellins (GA₃ or GA_{4 + 7}) alone and in combination with thiourea, N⁶ benzyl adenine (BA) or kinetin weekly for 3 or 4 weeks to test the efficacy of these materials in breaking bud dormancy. Additional plants received 6 weeks of cold storage at 4.5°C or glasshouse day temperatures of 21°C and above. The 2000 and 3000 mg l^?1 GA₃ and Ga_{4 + 7} sprays were better than 1000 mg l^?1 in promoting flowering, with ‘Redwing’ responding better than ‘Alaska’. GA-treated plants flowered in fewer days than those receiving cold storage. Flower diameter and pedicel length increased with higher levels of GA, and flower uniformity was comparable to cold-stored plants on most GA-treated ‘Redwing’-plants. Thiourea, BA and kinetin applied alone had no effect and considerable cytokinin activity was highest in GA-treated buds 14–21 days after treatment application. No increase in activity occurred on plants not receiving GA.     

The effect of chlormequat chloride (CCC) application at the bolting stage on the flowering and seed production of lettuce plants previously treated with water or gibberellic acid (GA3)

Lettuce plants were sprayed with gibberellin (GA₃) or water at the rosette (8-leaf) stage and subsequently with water or CCC (500 or 1500 ppm) at the onset of bolting. GA₃ induced rapid bolting and increased seed yield, but seed stalks were longer and thinner than those that had been sprayed with water at the same stage. Treatment with CCC (500 ppm) at bolting decreased the flower stalk height of plants that had been sprayed with water at the rosette stage, but not that of GA₃ treated plants. CCC (500 ppm) increased the number of inflorescence branches per plant as well as seed yield in the autumn sown crop, but had no effect on the winter sown crop. When a higher concentration of CCC (1500 ppm) was applied at bolting, flower stalk height decreased, irrespective of whether the plants had been previously treated with GA₃ or not, and seed stalk diameter increased. However, 1500 ppm CCC reduced the number of inflorescence branches per plant and mean seed yield. It is concluded therefore that although the application of 500 ppm CCC at the onset of bolting may increase seed yield in the autumn sown crop, this treatment does not improve the seed stalk strength (e.g. increasing diameter or reducing height) of GA₃ treated plants. On the other hand, whereas a higher concentration of CCC (1500 ppm) improves seed stalk characteristics, it reduces seed yield.     

The effect of day length,source of light and growth regulators on growth and flowering of Clerodendrum thomsonae Balf

The formation of flower buds in Clerodendrum seems not to be affected by day length, but the development of the buds is delayed in long days. When long days were established by means of low-intensity illumination with incandescent lamps, few flowers developed and the stems elongated considerably even at a day length of 16 hours. When fluorescent lamps were used for day-length extension, short shoots with many flowers were obtained even in 24-hour days. Flower development was also delayed by gibberellic acid (GA₃), but promoted by chlormequat both in short and long days. Shoot elongation was retarded by chlormequat and promoted by GA₃.Plants obtained from commercial greenhouses varied considerably with respect to growth and flowering. By selection a clone was obtained which flowered richly on short shoots. Shoot elongation stopped when flowering began. A ‘negative’ selection gave rise to a clone which flowered sparsely and in which shoot elongation was not influenced by flowering.     

Effects of Prohexadione Calcium on growth and gibberellins contents of Chrysanthemum morifolium R. cv Monalisa White

The effect of Prohexadione Calcium (Pro-Ca) and daminozide was observed on the growth characteristics and endogenous gibberellin contents of Chrysanthemum morifolium R. cv Monalisa White. Three concentrations viz. 100, 200 and 400 ppm of Pro-Ca and a single concentration of daminozide (800 ppm) were applied three times with 7 days interval on three weeks old plant under greenhouse condition. Pro-Ca suppressed the plant length up to 30.7% while daminozide inhibited up to 27.12% at optimum concentration. The chlorophyll contents and stem diameter were higher than control, while the fresh weight and flower number insignificantly reduced with such treatments. Gibberellin (GA) analysis showed that Pro-Ca and daminozide application significantly lowered bioactive GA₁ content, although the amount of its immediate precursor GA₂₀ was fractionally higher. Bioactive GA₄ content was slightly higher than the control while significant difference in GA₉ was found between the plants treated with Pro-Ca and daminozide. Current study showed that both early C13 hydroxylation and non-C13 hydroxylation pathways of GA biosynthesis are operational in C. morifolium.     

Growth and flowering of black iris (Iris nigricans Dinsm.) following treatment with plant growth regulators

The effects of application method and concentration of gibberellic acid (GA₃), paclobutrazol and chlormequat on black iris performance were assessed. Plants (10 cm high, 4 ± 1 leaves) were sprayed with 125, 250, 375 or 500 mg L⁻¹ or drenched with 0.25, 0.5, 1 or 2 mg L⁻¹ GA₃. In a second experiment, the plants were sprayed with 100, 250, 500 or 1000 mg L⁻¹ or drenched with 0.25, 0.5, 1 or 2 mg L⁻¹ paclobutrazol. Other plants were sprayed with 250, 500, 1000 or 1500 mg L⁻¹ or drenched with 100, 250, 375 or 550 mg L⁻¹ chlormequat. In each experiment, the control treatment consisted of untreated plants. Results indicated that the tallest plants (37.3 cm) in the GA₃ experiment were those sprayed with 250 mg L⁻¹. The most rapid flowering (160 days after planting) occurred when a 375 mg L⁻¹ GA₃ spray was used, whereas flowering was delayed to 200 days using 1 mg L⁻¹ GA₃ drench. Drenching with 1 mg L⁻¹ GA₃ increased height of the flower stalk by 7 cm compared to the control. Though relatively slow to flower, plants drenched with 1 mg L⁻¹ GA₃ had long and rigid stalks, which were suitable as cut flowers. Number and characteristics of the sprouts were not affected by GA₃. All paclobutrazol sprays resulted in leaf falcation. A 500 or 1000 mg L⁻¹ paclobutrazol spray resulted in severe and undesirable control of plant height, drastic reduction in stalk height and weight, and delayed flowering. Plants drenched with 0.25 or 1 mg L⁻¹ paclobutrazol were suitable as pot plants. Chlormequat reduced plant height only at the highest drench concentration, which also reduced flowering to 70%. No leaf falcation was observed with GA₃ or chlormequat. Chemical names: ( ± )-(R*,R*)-beta-((4-chlorophenyl)methyl)-alpha-(1,1,-dimethylethyl)-1H-1,2,4,-triazol-1-ethanol (paclobutrazol); (2-chloroethyl) trimethylammonium chloride (chlormequat).     

The influence of gibberellic acid, 2,4-dichlorophenoxyacetic acid and 6-benzylaminopurine on fruit-set of Clementine mandarin

A study was made of the influences of gibberellic acid (GA₃), 2,4-dichlorophenoxyacetic acid (2,4-D) and 6-benzylaminopurine (BA) on leafy inflorescences — and of GA₃ on entire trees — on fruit-set and fruit-weight of Clementine mandarin (Citrus reticulata Blanco).Applying GA₃ to inflorescences of cultivar ‘Fino’ (seedless Clementine) between anthesis and 14 days after anthesis increased fruit-set and weight of the fruits at harvest. No significant differences in effects were observed between the application to leaves, to flowers or to leaves and flowers simultaneously. GA₃ induced the development of parthenocarpic fruits of cultivar ‘Monreal’ (Clementine with seeds) and a fruit-set similar to that obtained with self-pollination. Spraying GA₃ (5–200 mg/l) to entire trees of cultivar ‘Fino’ increased the number of fruits per tree and decreased the average weight of the fruits. However, the commercial yield per tree increased with the concentration of GA₃ employed.The application of 2,4-D and BA to inflorescences of cultivar ‘Fino’ increased fruit-setting and weight of the fruits, although not as efficiently as GA₃, both the concentration and the time of application being more critical.     

Modification of episodic growth in Skimmia japonica ‘Rubella’ by gibberellic acid treatment

Applications of GA₃ in May/June, when the first flush of growth was maturing, induced an extra flush of vegetative growth and initiated lateral bud break. Flower initiation was delayed and flower size reduced by the GA₃. These responses were only slightly modified by additional sprays with BAP and TIBA. GA₄₊₇ was ineffective in promoting either extra extension growth or lateral bud break, but it did reduce flower size.     

Response of Dendranthema grandiflora (Ramat) to three plant growth regulators in container paint mix applications

The effectiveness of plant growth regulators (PGRs) when applied in a paint mix to the inside of containers was evaluated. Two kinds of paint (regular flat latex and SpinOut^®) were evaluated for their respective effectiveness with three separate plant growth regulators (paclobutrazol, uniconazole, and ancymidol) on the growth of Dendranthema grandiflora (Ramat) (cv. Fina and Pelee) plants. Chrysanthemums grown in containers were subjected to three different application methods: interior surfaces covered by a mixture of paint and plant growth regulator (PGR) and soil drench or spray treatments according to label recommendations. The effect of composted pine bark on the effectiveness of two methods of application (paint and drench) was also compared. Paint alone had no effect on growth and development. None of the plants given treatments with paint with or without PGR, showed any sign of phytotoxicity. Plants exposed to PGRs appeared greener and were shorter than control plants. Both the regular flat latex and SpinOut paints were effective carriers of PGRs, although plants grown in containers coated with PGR/SpinOut paint were taller than plants grown with latex/PGR-coated containers. Composted pine bark slightly reduced the effectiveness of ancymidol on plant growth. This reduction in effectiveness was smaller when ancymidol was carried by latex paint but was greater when carried by SpinOut paint. These results indicate that the paint/PGR method may not represent any real advantage over the drench method to overcome the effect of composted pine bark in the growing mixes on the effectiveness of ancymidol. Chemical names used: β-((4-chlorophenyl)methyl)--(1,1-dimethyl)-1H-1,2,4,-triazole-1-ethanol (paclobutrazol); (E)-(+)-(S)-1-(4chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-pent-1-ene-3ol (uniconazole-P); -cyclopropyl-(p-methoxyphenyl)-5 pyrimidinemethanol (ancymidol).     

Effect of GA3, CCC defoliation and quantum flux density on growth and flowering in Pelargonium × hortorum

In vegetatively propagated Pelargonium × hortorum plants, formation of axillary shoots and initiation of inflorescences and leaves were promoted by an increase in quantum flux density, whereas application of GA₃ had a negative effect. Application of CCC caused an increase in number of axillary shoots and consequently an increase in number of inflorescences and leaves per plant.Dry weight increase was promoted by an increase in quantum flux density, unaffected by GA₃ treatment, but inhibited by CCC treatment. Moreover, continuous removal of the oldest leaves reduced the number of inflorescences, leaves, axillary shoots and dry weight. The changes in inflorescence and leaf initiation could not be definitely correlated to the changes in dry weight increase.     

Effects of dose and time of application of GA4+7 on russeting,fruit set and shape of ‘Golden Delicious’ apples

GA₄₊₇ concentrations, treatment date, number and frequency of treatments were factorially combined to determine their effects in preventing russeting of ‘Golden Delicious’ apples.The greatest reduction of russet was obtained by treating fruitlets 8 or 15 days after full bloom.Optimum timing and number of treatments provided better control of russet than high concentrations of gibberellins, although in some cases, higher doses improved russet control.Length of pedicel and ratio of longitudinal to transversal diameter were greater where russeting was reduced, and significant correlations were observed between fruit and pedicel length, and russeting. GA₄₊₇ treatments also affected setting, and in many cases caused parthenocarpy.     

The effects of GA3, CCC and B-9 upon growth,development and organic compounds in Primula obconica

GA₃ induced stem elongation and had no effect on leaf area, whereas CCC and B-9 reduced those characteristics. All 3 growth substances increased leaf formation. GA₃ and CCC accelerated the beginning and duration of blooming, but B-9 exhibited the opposite trend. Inflorescence formation was promoted by CCC and B-9 and decreased by GA₃. Stalk length of inflorescences was elongated only by GA₃ and dwarfed by CCC and B-9. Carbohydrate fractions and content of anthocyanin in flowers were promoted by CCC and B-9.     

The influence of ancymidol,chlormequat and daminozide on the growth and development of forced dahlia variabilis willd

Ancymidol, chlormequat, and daminozide were evaluated as growth retardants on forced dahlias. Only ancymidol was effective in reducing plant height, and at 0.25 to 2.0 mg per plant it did not affect the date of flowering, flower size, or the number of shoots produced from the tuberous roots. Treatment by soil drench was more effective than a foliar spray. The most consistent effects were obtained when ancymidol was applied 2 weeks after planting. Dahlia cultivars differed in the degree of response to ancymidol. Optimum rates must be determined for the cultivars which are suitable for pot plant forcing for spring marketing.     

On the senescence of ovules in cherries

The longevity of ovules in sweet and sour cherries has been studied in vivo, using a fluorescence—microscopic method which enables one to determine the viability of ovules at a very early stage. It was found that ovules which were not fertilized became progressively senescent 4 to 5 days after anthesis, and about a week after flower opening a rather high percentage of the ovules was non-viable.Applied growth regulators usually enhanced senescence of the ovules, especially GA₃. Even those that delayed senescence of the external flower parts, e.g. 2,4-D, benzyladenine and kinetin, accelerated the ageing of ovules in most instances. No substance was found which extended the longevity of ovules in cherries.     

Effects of ethephon,GA3 and nutrient elements on sex expression of Chinese chestnut

The effects of ethephon or GA₃ on sex expression of Chinese chestnut (Castanea mollissima BL.) were opposite to the effects of these plant growth regulators on cucumber, pumpkin and Chinese white-flowered gourd. Ethephon at 100–500 mg 1^?1 inhibited the development of female flowers and promoted that of male flowers. GA₃ at 50–500 mg 1^?1 caused a significantly lower number of male inflorescences, but increased the number of female flowers. Urea applications decreased the number of male inflorescences and increased the number of female flowers. For plants grown on phosphorous-deficient soils, fertilizing with superphosphate also increased the number of female flowers. Spraying trees with GA₃, urea or a mixture of both increased the number of female flowers. Therefore, it is proposed that such applications should be employed at the onset of differentiation of flower primordia of Chinese chestnut to increase the ratio of female to male flowers.     

The effect of gibberellic acid on sprouting and flowering of some tulip cultivars

The effect of gibberellic acid, GA₃, on breaking of dormancy, sprouting and flowering of 9 cultivars of tulips was investigated, using 4 cultivars recommended for forcing and 5 not suitable for forcing. GA₃ was applied to the basal plates of the bulbs in a lanolin paste before planting, or was injected into the bulbs prior to rooting or after 38 or 64 days of cold treatment. The application of GA₃ stimulated sprouting, growth of floral stalks and flowering in all investigated cultivars. Injection of GA₃ was more effective than topical application. The effect of GA₃ on sprouting and flowering of plants was especially effective after 38 or 64 days of cold treatment. The possibility of applying GA₃ in commercial horticulture is considered.