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.     

Cold treatments enhance responsiveness to gibberellin in stock (Matthiola incana (L.) R. Br.)

Summary

Endogenous GAs have been suggested as regulators of stem elongation and flowering of cold-requiring plants. Here, the relationship between temperature conditions and responsiveness to GA₄ on stem elongation and flowering of stock (Matthiola incana) was investigated. The optimum temperature for induction of flower bud initiation was 10°C, and the minimum duration was 20 d in the late flowering cv. Banrei; the type of cold treatment effect on flowering was classified as a “direct effect”. Stem elongation was markedly promoted by cold treatment regardless of flower bud initiation. The cold treatment amplified the stem elongation response to GA₄. The GA₄ level necessary for flower bud initiation was lower in the 10°C treatment than in the 15°C treatment, and it became lower at longer durations of cold treatment. These results indicate that the cold treatments enhance responsiveness to GA₄ not only in the stem elongation process but also in the flower bud initiation process and that the development of responsiveness to GA₄ may correlate with the temperature and duration of cold treatment.     

Regulation of gibberellin biosynthesis and stem elongation by low temperature in Eustoma grandiflorum

Summary

Heat-induced rosetted Eustoma grandiflorum requires low temperature for induction of stem elongation and flowering. Although heat-induced rosetting is associated with a reduction of gibberellin A₁ (GA₁) content, how thermo-induction affects GA biosynthesis is unclear. Thus, we examined levels of GA, precursors including that of ent-kaurene which is the first committed step in GA biosynthesis. We used uniconazole, an ent-kaurene oxidase inhibitor to estimate the ent-kaurene biosynthesis activity. The accumulation level of ent-kaurene in stems of the cold-treated seedlings was approximately 1.8 times that of the non-cold-treated seedlings, whereas no difference was observed in the leaves. No change was observed in endogenous levels of GA₁ and GA₂₀ in stems of the heat-induced rosetted plants during the cold treatment, whereas their levels increased with stem elongation after transfer to warm conditions. In contrast to the levels of GA₁ and GA₂₀, endogenous levels of ent-kaurene, ent-kaurenoic acid, GA₅₃, GA₄₄ and GA₁₉ in the stems markedly increased at the end of cold treatment. These results indicate that ent-kaurene biosynthesis and its metabolism early in the GA biosynthetic pathway are stimulated by low temperature and, later, the stimulation leads to an increment of endogenous levels of GA₁ which is essential for stem elongation of the heat-induced rosetted E. grandiflorum.     

The effect of gibberellic acid on lignification and peroxidase activity in dwarf bean

Treatment of dwarf bean plants (Phaseolus vulgaris L.) with gibberellic acid (GA₃) produced a characteristic stem elongation accompanied by an increase in lignification of meta and secondary xylem and a decrease in peroxidase activity. Increasing concentrations of GA₃ and time after treatment led to increases in stem elongation and lignification, but to a decrease in peroxidase activity.     

Reduction of low temperature breakdown in apples with gibberellic acid

Gibberellic acid (GA₃) was found effective in reducing low temperature breakdown in stored apples when it was applied as a dip in aqueous or ethanolic solution or in wax emulsion. The levels of GA ₃ examined, which ranged from 2 to 80 µmole/fruit, all reduced breakdown to the same extent.     

Effects of bud scales and gibberellins on dormancy of in vitro cultured Japanese pear leaf buds

Leaf buds of Japanese pear were collected in early June and early November and regarded as summer and winter dormant buds, respectively. Bud explants with and without scales were prepared from each of them, and cultured in vitro for 75 days at 25°C with 14 h photoperiod, on a medium either without growth regulators, or supplied with BA and GAs (GA₃ and GA₄₊₇), singly or in combination.When either BA or GA₄₊₇ was contained in the medium, bud expansion occurred. Thereafter, summer dormant buds grew into shoots in the presence of BA, while winter dormant buds, although they swelled profusely, remained in a rosette. In the presence of BA, GA₄₊₇ markedly stimulated shoot elongation of summer dormant buds, but GA₃ did not. In winter dormant buds, GA₄₊₇ not only failed to stimulate shoot elongation, but also interfered with the BA-induced swelling described above.The presence of bud scales delayed expansion of summer dormant buds, while it had little effect on winter dormant buds. The delaying effect of scales on expansion of summer buds was effectively removed by application of GA₄₊₇ to the medium.     

The influence of timing of application and gibberellic acid on the effects of ancymidol on growth and flowering of Mid-Century Hybrid lily cv. Enchantment

The response of Mid-Century Hybrid lily ‘Enchantment’ to ancymidol has been investigated in two experiments. In the first, three dates of application were employed, the earliest at inflorescence initiation, the second and third 10 and 20 days later, respectively. Application (750 μg/plant as a 15 ppm soil drench) on the second date produced the shortest plants, a result attributed to more extensive uptake by a better-developed root system. Plants subjected to treatment on the third date were, by then, too tall for the maximum dwarfing effect to occur. Flower number was unaffected by treatment, but ancymidol delayed anthesis by between 4 and 6 days and promoted earlier senescence of basal leaves.In the second experiment, interactions between gibberellic acid (GA₃) and ancymidol were demonstrated. Increasing amounts of GA₃ (20, 200 and 2 000 μg/plant as aqueous applications to the shoot tip) progressively counteracted the dwarfing effect of ancymidol (500 μg/plant as a 10 ppm soil drench) and, in the absence of ancymidol, 2 000 μg GA₃/plant significantly promoted stem extension. Flower number was slightly decreased by GA₃ in the absence of ancymidol. An ancymidol-induced delay in anthesis of almost 5 days was progressively reduced by increasing levels of GA₃, which, in the absence of ancymidol, did not significantly influence the time of anthesis. Applied separately, neither ancymidol nor GA₃ significantly affected pedicel length of the first flower, but increasing levels of GA₃ progressively promoted pedicel elongation in the presence of ancymidol.     

Gibberellic acid influences the production of malformed and button berries,and fruit yield and quality in strawberry (Fragaria × ananassa Duch.)

Experiments were conducted to observe the effects of foliar application of gibberellic acid on vegetative growth, flowering, fruiting and various disorders in ‘Chandler’ strawberry. GA₃ (75 ppm) was applied to the strawberry plants either during mid-November (at fruit bud differentiation stage), or mid-February (pre-flowering stage) or at both times. Fruit under control were sprayed with tap water only. Observations were recorded on vegetative attributes like crown height, crown spread, petiole length, leaf number, leaf area; flowering and fruit set, fruit size; production of albino, malformed and button berries, total yield and marketable fruit yield and quality parameters, like juice content, TSS, ascorbic acid contents, acidity etc. Results indicated that GA₃ (75 ppm) spray either during mid-November or mid-February or at both times has favourably influenced all vegetative attributes of ‘Chandler’ strawberry over control. Similarly, fruit set was increased, and production of malformed and button berries was reduced, but albinism remained unaffected. Although individual berry weight was reduced slightly, but fruit number, total as well as marketable yield was increased tremendously over control with no adverse effect on fruit quality parameters. In all, spraying GA₃ both during mid-November and mid-February was much more effective in achieving the desirable results than single application of GA₃ either during mid-November or mid-February.     

Responses of day-neutral,June-bearing and everbearing strawberry cultiv ars to gibberellic acid and phthalimide treatments

Field grown day-neutral, June-bearing and everbearing strawberry cultivars responded similarly to GA₃ in most cases. GA₃ stimulated daughter-plant production in ‘Hecker’ (DN) and suppressed it in ‘Guardian’ (June). Fifty mg l^?1 GA₃ increased initial runner production of all cultivars, while both 50 and 100 mg l^?1 GA₃ increased fruit yield the year following treatment. In greenhouse studies, GA₃ initially increased leaf number, petiole length and runner production, but the effects diminished with time. Phthalimide at 1000 mg l^?1 was most effective in increasing leaf number.     

Comparison of shoot induction ability of different explants in herbaceous peony (Paeonia lactiflora Pall.)

Shoot induction ability of explants of herbaceous peony was investigated in semisolid MS medium containing BA, TDZ and GA₃. Callus was readily induced from stem without node and petiole explants within 2 days of culture but failed to generate shoots. Adventitious shoots were successfully produced from meristematic regions only: bud eyes on nodal stem sections, and junctions of petioles and petiolules. No shoots were induced from internode sections, petiole without junctions, or leaf sections. Nodal sections were the most efficient explants. There were up to 20 shoots in one explant generated within 20 days of culture. TDZ was more effective than BA to induce shoots. The 100% shoot induction rate was obtained in medium containing 0.1–3 mg L⁻¹ of TDZ. However, higher concentrations of TDZ inhibited shoot elongation and only large leaf clusters were produced. Combinations of BA and TDZ failed to increase shoot induction rates but caused shoots shorter. The 2–60-min pretreatment of explants with 20 mg L⁻¹ TDZ solution was very effective to induce adventitious shoots directly, but both shoot number and shoot length tended to decrease as treatment time increased. GA₃ was beneficial for shoot and stem elongation.     

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.     

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.     

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.     

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.     

The physiology of hyacinth bulbs. XI. The effect of gibberellic acid on the growth and flowering of variously chilled bulbs

The effect of gibberellic acid, GA₃, on the growth and flowering of hyacinth cultivars ‘Pink Pearl’, ‘Delft Blue’ and ‘Carnegie’, chilled in a cold room at 5°C or a garden frame for 28, 42 or 81 days, and either rooted or dry, unrooted, was investigated. GA, was applied to the basal plates of the bulbs in a lanolin paste on 10 October 1975.The growth of the inflorescence and leaves of plants originating from dry-chilled bulbs was generally the same as that of those grown from rooted plants. A similar response to GA₃ treatment was observed in all cultivars. Treatment of bulbs with GA₃ decreased the number of days to flowering, stimulated the growth of inflorescences and leaves, and its effect was most pronounced in the plants chilled for shorter periods.     

Effects of photoperiod on shoot elongation and endogenous gibberellins in the glasshouse carnation

Plants of glasshouse carnation were grown in photoperiodic cycles comprising 8 h natural daylight followed by either 16 h of darkness (short-day treatment) or by 16 h of low-intensity lighting from tungsten filament lamps (continuous-light treatment). When plants were transferred from short days to the continuous-light treatment, rates of shoot elongation were increased and flower initiation was promoted. Shoot tips of plants grown in continuous light yielded greater amounts of diffusible gibberellin-like substances than shoot tips of plants grown in short days. Yields of diffusible gibberellins increased with increases in the duration of the continuous light treatment up to 28 days, by which time flower initials were present. Application of GA₃ to the plants resulted in increased rates of shoot elongation, but no effect on flowering was observed.     

Factors affecting the response of tulips to gibberellin

Gibberellic acid (GA₃) treatment of forced tulip crops has potential for producing faster growth to anthesis in the glasshouse, for reducing losses due to floral bud blasting, and for reducing the duration of cold storage needed to obtain satisfactory flowers. Using partly and fully cooled direct-forced tulips, cultivar ‘Apeldoorn’, several factors (relevant to the definition of GA₃ treatments) were studied. Experiments confirmed the previously recorded effects of gibberellins in tulips: GA₃ injections reduced the duration of the glasshouse period, enhanced flower survival and flower length, and reduced stem length at flowering.Following bulb storage at temperatures from ?2 to 20°C, GA₃ reduced the glasshouse period by 15–25% and increased flower length, compared to controls, irrespective of storage temperature. Stem length was also reduced by GA₃, this effect being greater following a storage temperature of 5°C or lower. When GA₃ was applied during the period of 17°C-storage which precedes cool storage, or during or after storage at 5°C, it was found that treatments during or at the end of cool storage were more effective in producing the characteristic effects of GA₃ than were pre-cooling applications. In partly cooled bulbs (but not fully cooled ones), the GA₃-induced earliness of flowering was about doubled when GA₃ injections were given repeatedly at 2-week intervals throughout storage. The responses to GA₃ injections were found to be unmodified by early-lifting and heat-treatment (for earlier forcing), by delaying the start of 5°C storage (for later forcing), by glasshouse temperature (16 and 18°C), and by shading treatments; there was little effect of bulb size.     

In vitro micropropagation of the ornamental prickly pear cactus Opuntia lanigera Salm–Dyck and effects of sprayed GA3 after transplantation to ex vitro conditions

We established the conditions to micropropagate the ornamental prickly pear cactus Opuntia lanigera Salm–Dyck through axillary shoot development from isolated areoles. For the shoot proliferation stage different explant orientation (vertical and horizontal), type of cytokinin (BA, DAP and K), and concentrations (0, 1.25, 2,5, 5.0 and 7.5 mg/L) were evaluated. Media [Murashige, T., Skoog, F., 1962. A revised medium for rapid growth and bioassays with tobacco cultures. Phys. Plant. 15, 473–497: 50 and 100%], and carbohydrate concentration (0.25, 0.5, 0.75 and 1.0%) were studied to optimize individual shoot growth and elongation. Following micropropagation and plantlet acclimatization, the effects of GA₃ on plant growth were determined by spraying a series of increasing concentrations (0, 150, 300 and 450 ppm). A reliable and efficient protocol of micropropagation was established for this particular plant species. The greatest propagation ratio (shoot proliferation) was obtained when explants were cultured in vertical orientation (4.975 shoots per explant) as compared to horizontal position (3.692 shoots per explant). The addition of BA to the media resulted in increased shoot number per explant (8) in comparison to K and DA, which produced only 2 shoots in average. However, after 42 days of culture, significantly higher shoot length was obtained with DAP (14 mm) compared to K and BA (4 mm). After the shoot proliferation stage, an elongation subculture was performed prior rooting in which shoot growth was enhanced when crowns of shoots were cultured in 50% of basal salt formulation of Murashige and Skoog (1962) and low sucrose concentration (2.5 and 5%). Exogenous application of GA₃ after plantlet acclimatization on glasshouse conditions increased spine-hair (developed from areoles in young plants) length as part of short-term effects. However, significantly higher values were obtained in plantlets treated with 300 ppm of GA₃ when compared with the rest of the treatments. At the end of the study, the most important long-term effect produced by GA₃ was the suppression of total shoot growth. The micropropagation protocol described here and the conditions to grow the plants through fertigation plus the application of GA₃ that induced changes in the phenotype may be used in commercial exploitations to regenerate 12,500 plantelts in average after 12 months of culture and produce healthy plants with better ornamental characteristics and higher commercial value.     

The effect of gibberellic acid (GA3) on some phenolic substances in globe artichoke (Cynara cardunculus var. scolymus (L.) Fiori)

Globe artichoke has important nutritional values related to its high content of phenolic compounds such as cynarin and chlorogenic acid. Cynarin (1,5-dicaffeoylquinic acid) is a derivative of caffeic acid and has effect on hepatobiliary diseases, hyperlipidaemia, dropsy, rheumatism and cholesterol metabolism. The effect of gibberellic acid (GA₃) on the yield of the phenolics, chlorogenic acid and cynarin, both in leaves and in the edible part of the head of globe artichoke, were studied. Plant samples were collected for chemical analyses at the laboratories of the Chair of Vegetable Science, Department for Plant Sciences, Technische Universität München in Freising-Weihenstephan, Germany. GA₃ at 60 ppm was applied either at 4, 6 or 8 weeks after transplanting date (ATD). When transplant were used, application of GA₃ at 4 weeks ATD significantly increased the content of chlorogenic acid in leaves while the level of cynarin was similar to the untreated control. In contrast when plants were direct seeded into the field, GA₃ treatments had no affect on phenolics in leaves compared to the untreated control. Whereas GA₃ reduced the time to flowering, it did not increase the content of chlorogenic acid or cynarin in leaves or in most of the flower receptacles, except when GA₃ was applied at 6 or 8 weeks. On the other hand, cynarin yield in the 3rd–5th harvested flower heads was higher than controls. The timing of GA₃ application is, thus, critical for decreasing time to flower as well as altering the content of cynarin and chlorogenic acid in globe artichoke.     

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.