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.     

Gibberellic acid and flower bud development in loquat (Eriobotrya japonica Lindl.)

The application of gibberellic acid (GA₃) to the whole loquat tree from mid-May to early June and from early August to the onset of flowering, significantly reduced the number of premature flowering shoots per current shoot and per m³ of canopy, and so reduced the total number of panicles per m³ of canopy. The number of vegetative shoots per m³ of canopy was also significantly reduced by applying GA₃. The response depended on the concentration applied and produced optimal results at 50 mg l⁻¹. Differences in the number of flowers per panicle and leaves per shoot were not significantly modified by the treatment. Nevertheless, GA₃ applied directly to the developing apex near to flower differentiation reduced the number of flowers per panicle by 25–35% and without modifying the morphological characteristics of the panicle. Results suggest that less sprouting of lateral buds was largely responsible for the reduction in flowering intensity caused by GA₃. Best treatments reduced thinning costs (60%, approximately) of premature flowering shoots, slightly increased fruit diameter and significantly improved fruit colour and juice quality, thus advancing harvest date.     

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).     

Germination of Passiflora mollissima (Kunth) L.H.Bailey, Passiflora tricuspis Mast. and Passiflora nov sp. seeds

Passiflora mollissima, Passiflora tricuspis and Passiflora nov sp. are three passion fruit species occurring in Bolivia. Germination percentages and rates were determined for 11 different treatments. Per species, germination of 100 seeds was monitored every 3 days, during 90 days. Germination started after 9 days and 50% of final germination was reached within a month or less. Successful, recommended methods for P. mollissima are removing the basal point of seeds (27% germination) or removing the basal point in combination with pre-soaking seeds for 48 h in 50 ppm GA₃ (18%). Pre-soaking seeds for 24 h in 400 ppm GA₃ (42%) and removal of the basal point in combination with pre-soaking seeds for 48 h in 50 ppm GA₃ (36%) are suggested methods to improve germination of P. nov sp. Removing the apical point of P. tricuspis seeds resulted in maximal germination (57%). No unique treatment gave satisfactory results for the three species tested. Exogenous dormancy, probably a combination of mechanical and chemical dormancy is present in the three species studied. Presence of physical dormancy was found in P. mollissima.     

Gibberellic acid soak treatments for fully-cooled tulips

In attempts to reduce the glasshouse period of fully-cooled 5°C-forced tulips, ‘Apeldoorn’ bulbs were soaked before planting in aerated and non-aerated gibberellic acid (GA₃) solutions for 2–48 h. A 48-h treatment with 250–500 mg l^?1 GA₃ was the most effective, giving a glasshouse period 7–11 days shorter than for untreated bulbs. Soaks for 24 and 48 h caused root emergence, and 48-h soaks caused perianth segment splitting in one experiment. Aerated or non-aerated GA₃ solutions gave similar results. Soaking in water alone gave a smaller increase in earliness. In general, a shortened glasshouse period was associated with shorter whole stem and last internode lengths. In GA₃ treatments, flower losses were lower than for distilled water treated and untreated bulbs. A practical treatment would be a non-aerated soak for 24 h with between 250 and 500 mg l^?1 GA₃.     

The response of partly cooled tulips to vacuum infiltration with gibberellins

Partly cooled (5°C) tulip ‘Apeldoorn’ were treated with gibberellins GA₃ and GA_{4 + 7} by vacuùm infiltration, with a view to defining conditions suitable for exploiting the effects of GA on forced tulips (faster flowering, control of stem extension, reduction of floral bud blasting).The first experiment showed that GA₃ and GA_{4 + 7} were equally effective in reducing the glasshouse period following 6 or more weeks cold storage; with less than 6 weeks cold storage, effects were less marked. Stem length at flowering was reduced by GA treatments, particularly by GA₃ and following more than 6 weeks cold storage. However, the vacuum infiltration method used (30 min at 10 torr) resulted in serious flower losses.Next, the effect of GA₃ concentration (up to 1500 mg 1^?1) was studied using vacuum infiltration treatments for 1–15 min at 20–510 torr, which resulted in fewer flower losses. Following 4 weeks cold storage, reducing pressure or increasing GA₃ concentration reduced both glasshouse period and stem length, with no effect of duration of treatment; GA₃ concentration was the only factor affecting flower length, which was increased. Following 8 weeks cold storage, increasing GA₃ concentration, vacuum or duration reduced glasshouse period. With all 3 factors at their maximum levels, 16 days earliness was obtained compared with controls. With maximum earliness, stem length was reduced to about 23 cm, compared to about 26 cm for treatments giving about 1 week's earliness, and 32 cm for untreated controls. Increasing vacuum appeared the most economical way of obtaining earliness, 20 torr giving 7 days earliness even at only 250 mg GA₃ 1^?1. Treatments giving earlier flowering also gave larger flowers. For comparison, there was little effect of soaking bulbs at atmospheric pressure even at 500 mg GA₃ 1^?1 for up to 20 h.Further experiments, conducted with vacuum infiltration at 260 torr for 15 min, confirmed these GA effects using formulated GA₃ (as “Berelex”) and GA_{4 + 7} (as “Regulex”). Effects of GA on stem length at flowering had disappeared by the time stems reached their final length. Comparisons with bulb injection of GA showed that this method required less GA than vacuum infiltration for similar effects, and that the greater effectiveness of GA_{4 + 7} compared with GA₃ was less marked using vacuum infiltration.     

A role for carbohydrate levels in the control of flowering in citrus

Girdling in October of small or large fruitless branches increased 2–3-fold both starch content of leaves and flower numbers as compared with ungirdled ‘Murcott’ mandarin trees. Autumn girdling and GA₃ treatments were both effective and additive in increasing starch contents of leaves and twigs of ‘Shamouti’ orange trees. GA₃, however, had the expected effect of depressing the reproductive inflorescences in both girdled and ungirdled branches, while girdling had the opposite effect. Girdling and fruit removal in October also additively and dramatically increased flower production in ‘Murcott’. Lowtemperature regimes in a phytotron caused young ‘Minneola’ budlings to flower earlier in the season and more profusely, while having no effect on starch content of leaves and twigs. The interactions of increased carbohydrate content and gibberellin in the control of flower formation in citrus are discussed.     

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.     

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.     

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.     

Horticultural factors regulating effectiveness of GA3 inhibiting flowering in peaches and nectarines (Prunus persica L. Batsch)

The application of gibberellic acid during the flower bud induction period significantly reduced flowering in peaches and nectarines. The magnitude of the response significantly depended on the total amount of active material applied per tree. Results show, for cultivars tested, a higher sensitivity of peach to GA₃ in comparison with nectarine. Concentrations of 0.5 or 1.0 g tree⁻¹ of gibberellic acid reduce flowering by about 50% in both, peaches and nectarines, respectively, and it gives rise to a reduction of costs of hand thinning by 50%, approximately, without affecting the yield. Fruit colour advanced, total soluble solids concentration increased and fruit firmness increased as a consequence of treatments. The effect was higher in the basal part of the shoots and reduced from the base to the apical part.     

Effect of fruit load on 9,10-ketol-octadecadienoic acid (KODA), GA and jasmonic acid concentrations in apple buds

The relationship between 9,10-ketol-octadecadienoic acid (KODA), GAs and jasmonic acid (JA) and flower bud formation influenced by fruit load in apples (Malus domestica Borkh.) was investigated. The endogenous KODA and JA concentrations in apical buds in plants subjected to flower thinning treatment (FTT), under which all flowers were removed were higher than those in plants subjected to heavy crop treatment (HCT), under which the number of leaves per fruit was adjusted to 20 from 60 to 120 days after full bloom (DAFB). In contrast, the gibberellic acid concentrations [total of gibberellin A₁ (GA₁) and gibberellin A₄ (GA₄)] in FTT plants were low compared with those in HCT plants. The result suggests that KODA and JA in contrast to GAs may have opposite effects on flower bud formation which is significantly influenced by fruit load in apples and that KODA and JA may also be associated with flower bud formation in apples.     

Methods to break seed dormancy in Cyclocarya paliurus (Batal)Iljinskaja

Cyclocarya paliurus is native to China and is the sole species in its genus. However, the seeds remain deeply dormant for 2 years in their natural environment. We tested different pretreatments of chemical scarification and exogenous application of gibberellic acid (GA₃) for efficacy in breaking dormancy and speeding germination. In contrast to scarified seeds, non-scarified seed did not germinate, indicating that C. paliurus seeds have hard, impermeable seed coat dormancy. Exogenous application of GA₃ significantly enhanced germination of scarified seeds. Compared with seeds stratified in sand with water, the germination of seeds stratified in sand moistened with 400 ppm GA₃ for 60 days was significantly increased and germination rate was over 90% after 120 days. Analysis of variance indicated that both GA₃ concentration and stratification medium had significant effects on seed germination and final germination percentage. Germination was higher for longer stratification periods, but no significant difference in germination was observed after 90 days. These results suggested that C. paliurus seeds exhibit both exogenous and endogenous dormancy. A combination of chemical scarification and exogenous application of GA₃ alleviated seed dormancy in a relatively short period of time.     

Parthenocarpic fruit production in loquat (Eriobotrya japonica Lindl.) by using gibberellic acid

This study evaluates the effect of gibberellic acid (GA₃) in inducing parthenocarpy in ‘Algerie’ loquat, as well as the optimum treatment conditions and associated techniques, hand thinning and ringing, to produce seedless fruit with high enough quality for fresh consumption. GA₃ applied in the course of the phenological growth stages 504–508 of the BBCH-scale produced seedless fruits, with the magnitude of the response depending on the concentration applied and number of treatments. Percentage of panicles bearing seedless fruitlets significantly increased with increasing GA₃ concentrations up to 100 mg l⁻¹ and significantly and positively correlated with the number of treatments applied. Trees treated three times with 100 mg l⁻¹ developed more than 90% of panicles bearing almost 7 seedless fruits per panicle, which were smaller in size, drier and slightly acid but similar in TSS concentration and skin colour than seeded fruits from untreated trees. Fruit thinning to 3 fruits per panicle did not increase seedless fruit size, but ringing performed at the onset of cell enlargement stage, growth stage 702 of the BBCH-scale, significantly increased fruit size by 12–15%, depending on the year. Trees treated three times with 100 mg l⁻¹ of GA₃ and ringed produced 26 kg, on average, of seeded fruit of suitable commercial quality.     

Effects of gibberellins and benzylandenine on dormancy and flowering of Lilium speciosum

GA_{4 + 7} (1000 mg/l), alone or in combination with BA (100 mg/l), was found to induce shoot emergence and flowering in dormant bulbs of L. speciosum, while GA₃, alone or in combination with BA, had no effect. BA had a significant influence on increasing flower numbers, particularly when combined with GA_{4 + 7}.     

In vitro rescue of immature avocado (Persea americana Mill.) embryos

An in vitro culture protocol was developed as a means of avocado embryo rescue. Different factors including presence of cotyledons, medium texture and cold or gibberellic acid pretreatments, were studied. To better understand the germination process in this recalcitrant species, immature zygotic embryos at different stages were used in these experiments. Optimum results were dependant on the embryo developmental stage. Whereas smaller embryos (5 mm long) germinated better in M1 liquid medium, 15 mm long embryos responded better when precultured in B5m medium supplemented with 1 mg l⁻¹ GA₃, and fully mature embryos were capable of germinating directly in solid M1 medium. Our results suggest the existence of two types of dormancy in avocado embryos: an embryo-dormancy caused by cotyledons, and another type of dormancy, mainly occurring in 35 mm long embryos and revealed by the formation of dwarfing rosette seedlings, that can be released by a GA₃ pretreatment.     

Effect of cytokinin content of the regeneration media on in vitro rooting ability of adventitious apple shoots

Rooting ability of ‘Royal Gala’ shoots regenerated on media with different cytokinin content (thidiazurone, benzyladenine, benzyladenine-riboside and meta-topolin-riboside) was observed directly after regeneration and compared after subculture on hormone-free medium (A), or on medium with decreased cytokinin content (B), or elevated gibberellic acid (GA₃) content (C) for a week, or after a subculture on proliferation media (1.0 mg l⁻¹ benzyladenine-riboside) for four weeks (treatment D). Rooting and acclimatization of regenerants after directly regeneration was not successful. Subculture of shoots on hormone-free medium did not improve the rooting ability of shoots, while their subculture on B and C media resulted in up to 36% rooting rate depending on regeneration media from which the shoots originated. The best rooting rate (up to 76%) was achieved in shoots regenerated on medium with benzyladenine-riboside after treatment D similarly to rooting ability of micropropagated shoots (80%). The rooting capacity of shoots depended on both the cytokinin content of the regeneration media and different subculture media used. All rooted shoots survived after acclimatization.     

Effects of growth regulators on growth and flowering in Hippeastrum hybridum hort

Soaking of bulbs in 3 concentrations of indoleacetic acid (IAA), gibberellic acid (GA₃), 2-chloroethyltrimethyl ammonium chloride (cycocel) or 2-chloroethylphosphonic acid (ethrel) showed various responses on growth and flowering. IAA increased the weight and number of bulblets, GA₃ increased bulb weight. Cycocel (1000 mg l^?1) increased the number of flowers, while GA₃ increased the diameter of the flowers.Application of IAA at 100 mg l^?1 and GA₃ at 10, 100 or 1000 mg l^?1 twice as foliar spray at an interval of 30 days promoted the number of bulblets on the treated plants, while high concentrations of cycocel and ethrel (1000 mg l^?1) increased the weight of bulblets. All concentrations of IAA, GA₃ and 1000 mg l^?1 cycocel increased the number and size of the flowers.     

GA3对杨梅叶片木质素水平及其相关酶活性和成花的影响

 ‘荸荠种’杨梅小年树花芽孕育初期, 苯丙氨酸解氨酶(PAL) 活性首先达到高峰; 之后多酚氧化酶(PPO) 活性出现高峰。花芽孕育盛期过氧化物酶(POD) 活性达到高峰, 且与木质素积累到最大值相一致。花芽发端期间, POD活性和木质素水平均降低。GA₃处理降低了花芽孕育期间PAL、PPO 和POD 的活性, 导致木质素合成滞缓, 抑制花芽发端和降低成花率。     

Response of evergreen perennial tree crops to gibberellic acid is crop load-dependent. I: GA3 increases the yield of commercially valuable ‘Nules’ Clementine Mandarin fruit only in the off-crop year of an alternate bearing orchard

Worldwide, gibberellic acid (GA₃) is used routinely to increase fruit number and size of seedless mandarins. The efficacy of seven combinations of GA₃ concentrations and application times to maximize total yield and yield of commercially valuable fruit (diameter 57.2–76.2 mm) of ‘Nules’ Clementine mandarin (Citrus reticulata Blanco) was determined in a commercial orchard. GA₃ applied during the period of intense flower abscission failed to reduce the total number of abscised flowers in both the light off- and heavy on-bloom years. No GA₃ treatment reduced fruit abscission when trees were setting the low yield off-crop. However, all trees receiving GA₃ in the high yield on-crop year had fewer abscised fruit than untreated control trees (P = 0.0188) and GA₃ applied 10 days after 75% petal fall and in July increased the number of fruit retained on tagged branches >20% compared to control trees (P = 0.0005). Maximum air temperature was not related to flower or fruit abscission. In the off-crop year (548 fruit per untreated control tree), it was necessary to apply 15 or 25 mg L⁻¹ GA₃ at 60% bloom, 90% bloom, 75% petal fall and 10 days after 75% petal fall to significantly increase the number of fruit per tree and yield of commercially valuable fruit (kilograms and number per tree) (P < 0.0001) above that of control trees, with no reduction in total kilograms per tree. In the following on-crop year, it was better not to apply GA₃: no treatment increased total yield or fruit size and five of seven GA₃ treatments tested reduced total yield as kilograms and number of fruit per tree (P = 0.0003). The results provide strong evidence that GA₃ efficacy is crop load-dependent and dictate that crop load should be considered when using GA₃ to increase fruit set or fruit size of mandarins.