Growth Regulator Treatments Research Articles

Post‐harvest age‐induced seed dormancy of Acer ginnala and its alleviation by growth regulator and low temperature treatments

SUMMARYOne‐month‐old fruits of Acer ginnala with winged pericarp attached gave 44% germination and this was not increased by cold treatment at 4°C for 0, 10, 20, or 30 days, gibberellic acid treatment at 0, 1, 10, 100 or 1000 mg litre‐1, or ethephon treatment at 0, 2, 20, 200 or 2000 mg litre‐1.After 6 months of storage at 20–25 °C, germination of untreated fruits fell to 5% but could be restored to that of 1‐month‐old fruits by incubation at 4 °C for 30 days.After 9 months storage, no germination occurred in untreated fruits. Cold treatment (30 days at 4 °C partially restored germination (26%). Treatment with either gibberellic acid (1000 mg litre‐1) and 30 days at 4 °C (40%) or ethephon (100 mg litre‐] and 30 days at 4 °C improved germination (69%). The combination of all three treatments, i.e. 100 mg litre‐1 gibberellic acid, 100 mg litre‐1 ethephon and 30 days at 4 °C, optimised germination (86%).Thus, dormancy of A. ginnala developed during storage but could be reversed by a combination of treatment with low temperature and growth regulators. The highest germination (86%) was achieved after low temperature and growth regulator treatment of stored fruit.

The Physiology of Epicormic Bud Emergence in Pedunculate Oak (Quercus robur L.) Responses to Partial Notch Girdling in Thinned and Unthinned Stands

The physiology of epicormic bud development in Quercus robur was studied by recording the effect of partial notch girdles applied at different dates, in the spring and summer of 1985, on epicormic shoot emergence in stands of thinned and unthinned trees. The girdles were applied singly or in tandem pairs one above the other. In one experiment they were applied in combination with the synthetic auxin 1-napthaleneacetic acid (NAA) or were replaced by treatment with 2, 3, 5-triiodobenzoic acid (TIBA), an inhibitor of auxin transport. Thinning had no consistent effect on the numbers of epicormic shoots emerging, only on their later vigour, and did not consistently affect the response to girdling or the growth regulator treatments. Epicormic shoot emergence was stimulated only by girdling treatments applied in April and May, and not in June or August, indicating that the epicormic buds enter dormancy early in the season. The pattern of responses to the single and tandem girdles was consistent with a suppression of the buds in the spring by a basipetally-transported inhibitor, from the inhibitory effect of NAA observed, probably auxin. The development of the buds was not controlled by an acropetafly-transported promoter whose supply could be interrupted by the girdling treatments.

Physiological, environmental and genetic variation in apical dominance as determined by decapitation in Triplochiton scleroxylon.

Patterns of lateral shoot growth following decapitation in 1-meter tall, rooted Triplochiton scleroxylon K. Schum. cuttings varied with clone and in response to a range of environmental conditions and growth regulator treatments. Two phases of bud activity were identified, the Sprouting Phase, in which many buds were released from correlative inhibition, and the Dominance Phase (starting 3-4 weeks after decapitation) in which uppermost laterals began to dominate and suppress growth, and sometimes cause apical abscission of lower lateral shoots. Except in non-erect plants, the most distal lateral to elongate became the new leading shoot. During the Sprouting Phase, the proportion of active buds was increased by removing leaves from the upper part of the stem, and by reducing the photoperiod from 13-15 h to 11 h, particularly at 20 degrees C rather than 25 degrees C. Conversely, the proportion of sprouting buds was decreased by injecting plant stems with NAA (250 microg/plant). During the Dominance Phase, suppression of lateral shoot growth was hastened by stem injection with GA(3) (200 microg/plant), especially when applied to the uppermost shoot at the end of the Sprouting Phase. Reimposition of dominance was delayed, however, by (1) high rates of N:P:K fertilization, (2) low temperature (20 versus 25 degrees C) under relatively long days (13 and 15 h), (3) low photon flux density (160 micromol m(-2) s(-1)) and (4) severe defoliation. Plant orientation had no effect on bud activity of decapitated plants, but affected the relative vigor and orientation of new lateral shoots. High temperature (25 versus 20 degrees C) and injection with GA(3) increased the erectness of newly developing lateral shoots.

Influence of growth regulator treatments on dry matter production, fruit abscission, and14C-assimilate partitioning in citrus

Experiments were performed to monitor (1) uptake and translocation of foliar-applied microdroplets of14C hormones and (2) effects of multiple growth regulator sprays on foliar and fruit growth variables and photosynthate partitioning in Valencia orange trees (Citrus sinensis (L.) Osbeck). The uptake of14C-sucrose,14C-paclobutrazol (PP333), and14C-napthaleneacetic acid (NAA) in 6-month-old greenhouse-grown trees exceeded that of14C-abscisic acid (ABA) and14C-benzyladenine (BA) 48 h after microdroplet application.14C-sucrose transport from the application site was much greater than any other source, especially14C-BA. In a second study, 2-year-old Valencia orange trees were maintained under field conditions and were sprayed to foliar runoff (3 × /week for 3 weeks) with BA, NAA, ABA, PP333, and gibberellic acid (GA3) at 100 μM during flowering and early fruit set. Select branches were then briefly exposed to14CO2 and harvested 24 h later. Both GA3 and BA sprays promoted foliar growth. BA also stimulated fruit growth, whereas GA3 sharply increased fruit dry weight while fruit number decreased. BA and GA3 enhanced14C assimilate export by the foliage to the developing fruit, and GA3 was especially active in promoting fruit sink intensity (14C/dry wt). The other compounds (NAA, ABA, PP333) restricted foliar and fruit growth. They also inhibited transport of14C assimilate from the leaves to the fruit. Results indicate that foliar-applied growth regulators can influence source-sink relations in citrus early in reproductive development by manipulating photoassimilate production and partitioning.

Growth and morphogenesis of shoot initials of Douglas fir, Pseudotsuga menziesii (Mirb.) Franco, in vitro.

A method of micropropagation of Douglas fir is described. Differences in morphogenesis and photosynthesis were found in shoot initials that had been isolated from buds in 10 topophysical positions on 2-yr-old trees. These differences were influenced by medium composition and light intensity, and by forcing, topping or growth regulator treatment of the mother trees. Shoots originating from buds in less exposed parts of the tree generally had a higher relative growth rate, max. net photosynthesis and photochemical efficiency and a lower compensation irradiance. Seasonal changes were found in the optima for nitrate and sucrose concn. in the medium and for light intensity. (Abstract retrieved from CAB Abstracts by CABI’s permission)

The effect of paclobutrazol on mineral nutrition of apple seedlings1

Abstract Greenhouse grown ‘Golden Delicious’ apple seedlings were treated with soil drenches of paclobutrazol (PP333) at rates equivalent to 0.1, 0.2, 0.4, 0.8, and 1.6 kg of active ingredient (a.i.) ha.‐1 Eleven weeks after treatment initiation, seedlings were harvested, divided into leaves, stems, and roots, weighed and analyzed for the content of macro‐and microelements. Shoot growth rate, leaf area, and total dry weight showed a decreasing trend with increasing rates of PP333. In contrast, specific leaf weight increased in response to growth regulator treatments. The total amount of N, Zn, and Cu absorbed by seedlings was not affected and that of K, Ca, Mg, and Mn was decreased by PP333 treatments. Concentration of Ca and Mn in leaves, N in roots, and N, Ca, Mg, Mn, Zn, and Cu in stems increased in response to PP333 treatments. The magnitude of these increases were dependent on the rate of growth regulator applied. Potassium was the only element which declined in concentration in leaves and stems; thi...

Organogenesis in pepper tissue cultures

Knowledge concerning in vitro growth and developmental responses of bell and chile peppers (Capsicum annuum L.) has been limited. Shoot and root organogenesis in cultures of seedling explants was restricted to primary cultures or those less than three months old under 12-and 16-h photoperiod at 25°C. Shoot organogenesis was extended to 5 months under continuous light at 25°C, and to 8 months under continuous light at 28.5°C. Murashige and Skoog basal media containing 0.05mg/l each of IAA and BA promoted shoot elongation and rooting of some explant sources, while 0.05-4 mg/l IAA with 10–50 mg/l BA promoted adventitious shoot bud formation. Glucose was superior to sucrose as the carbon source. Leaf discs collected from greenhouse-grown plants regenerated shoots for at least 2 months. Incubation environment, carbon source, explant source, growth regulator treatment and passage number were not independent variables as demonstrated by statistical analysis. The plant regeneration techniques described here have useful but limited applications, not extending to unorganized callus or cell suspension cultures.

The Influence of Growth Regulators on Gerbera Daisy

Abstract The effect of 3 growth regulators on the growth and flowering of Gerber jamesonii Hook. f. were evaluated. Two applications of daminozide and ancymidol restricted the height of gerbera, but no response occurred with chlormequat. Ancymidol was more effective than daminozide, especially when applied 6 or 7 weeks after transplanting. Times to visible bud and leaf number were not affected by growth regulator treatments. Plants were more responsive to daminozide when applied 8 weeks after transplanting compared with 5, 6, or 7 weeks.

Micro-grafting shoot-tip culture of citrus on three trifoliolate rootstocks

Simple techniques and growth regulator treatments to improve micro-grafting success of ‘Mexican’ lime, ‘Valencia’ orange and ‘Star Ruby’ grapefruit were studied. Most scion cultivars grafted best on ‘Carrizo’ citrange [ Poncirus trifoliata (L.) Rat. x Citrus sinensis (L.) Osbeck]. Dipping the shoot-tip in 2,4-D or kinetin before grafting doubled the percentage of successful grafts. Highest grafting success occurred when the scion shoot-tip was placed in an inverted-T incision on the epicotyl of the rootstock.

Invertase activity in sinks undergoing cell expansion

During the development of roots, internodes and leaves, closely correlated changes occur in the rates of cell expansion, specific activities of acid invertase and concentrations of hexose sugars and sucrose. Rates of cell growth and acid invertase activities frequently exhibit closely coupled responses to environmental changes and to growth regulator treatments. The possibility is considered that, by controlling the availability of hexose substrates for cellular metabolism, acid invertase may regulate cell growth. Potential mechanisms regulating the in vivo activity of acid invertases are reviewed and attention is drawn to the need for more information on the sub-cellular localization of the enzyme.

Effects of Dormant and Summer Pruning, Disbudding, and Growth Retardants on Growth, Flower Bud Formation, and Fruiting of Young Apple Trees

Abstract Summer pruning, dormant pruning, and growth-regulator treatments were applied for 5 years on newly planted ‘McIntosh’ and ‘Melba’ apple trees (Malus domestica Borkh.) on Alnarp 2 and Mailing 26 rootstocks. All forms of pruning reduced tree growth and yield. Light-to-moderate pruning was the best treatment for forming tree canopies. The reported stimulative effect of summer pruning on flower bud formation was not supported by this research. Pinching shoot tips led to a new secondary growth and inhibited rather than stimulated flower bud formation.

Investigations into the use of plant growth regulators in oil-seed sunflower (Helianthus annuusL.) husbandry

SUMMARYThe effects of some plant growth regulators on the growth and development of two cultivars of oil-seed sunflower (cvs Flambeau and Luciole) were examined in 1977 and 1978. Sunflower is a marginal crop for the United Kingdom, being late maturing and susceptible to infection by grey mould (Botrytis cinerea) during the seed-filling period.An experiment in 1977 indicated that suitable growth regulators might improve sunflower husbandry principally by shortening the stem, allowing late applications of fungicide and insuring against lodging. A mixture of mepiquat chloride and ethephon (BAS 098 OOW) was the most effective stem shortener. Daminozide gave variable effects on yield depending on the rate and time of treatment. The number of seeds per m2 was the major determinant of yield; 1000-seed weights and oil contents were similar for all treatments. The proportion of linoleic acid in the oil was very high in all experiments.In 1978 a second experiment involving daminozide and two sunflower cultivars revealed seasonal and varietal differences in response. The timing of growth regulator application seemed critical to affect seed yield. The third experiment, in 1978, investigated the results of applying BAS 098 OOW to four plant population densities varying from 40000 plants/ha to 160000 plants/ha. High plant population density advanced maturation by 2 weeks, but in these plots the crop lodged in the absence of growth regulator treatment.

Stimulation of celery seed germination and seedling growth with combined ethephon, gibberellin and polyethylene glycol seed treatments

The upper-temperature limit for germination of cv. Celebrity celery seeds incubated in darkness in laboratory tests was slightly raised following a seed soak with a mixture of the gibberellins A4 and A7 + ethephon (G + E) but more so by osmotic priming with polyethylene glycol (PEG). However, the best effects were obtained with a combination of growth regulator and priming treatments. Incorporation of growth regulators into the PEG was more effective than soaking seeds in G + E solutions either before or after osmotic priming. In glasshouse tests, seedling emergence was more rapid, percentage emergence was higher and seedling weight was greater from seeds treated with PEG either alone or in combination with G + E than from untreated seeds, water-soaked seeds or seeds given G + E soaks before or after PEG treatment.

Effect of some growth regulators on yield and quality of sweetmelon and muskmelon

SUMMARYThis study was carried out at Elminia University farm in two years (1978 and 1980) to evaluate the effect of some growth regulators on the production of sweetmelon and muskmelon. It was found that plants treated with some growth regulators were earlier and yielded better than untreated ones, except that in the first trial (1978), the total yield of plants treated with indole acetic acid (IAA) was less than that of the control. The highest early and total yields of both sweetmelon and muskmelon resulted from spraying ethrel on the foliage. Fruit weight and length and flesh thickness were increased by some growth substances compared with the control for both crops. Also, percentage of total soluble solids and ascorbic acid concentration increased markedly as a result of growth-regulator treatments for sweetmelon and muskmelon. Generally, two sprays of ethrel solution produced the most consistent effects on yield and yield quality in the two trials with both sweetmelon and muskmelon.

Effect of Cultivar, Strain, and Growth Regulator Treatments on Shoot Development and Ethylene Evolution in Apple Trees1

Abstract ‘Miller Sturdeespur Delicious’ apple (Malus domestica Borkh.) trees made less extension growth than ‘Imperial Red Delicious’ (non-spur) under controlled conditions. No differences in extension growth were measured between ‘MacSpur’ and ‘Imperial McIntosh’ (non-spur) trees. Development of the spur-type morphology was determined by the number of lateral buds which grew into spurs during the second growing season. Application of (2-chloroethyl)phosphonic acid (ethephon) alone, or in combination with butanedioic acid mono-(2, 2-dimethylhydrazide) (daminozide) decreased extension growth and increased shoot ethylene evolution in growth chamber studies, and promoted flowering in the field. Application of daminozide plus ethephon was more effective than ethephon alone. Daminozide alone did not affect shoot ethylene. No change in ethylene evolution or shoot development was detected following applications of gibberellin 4/7 (GA) or 2, 3, 5-triiodo benzoic acid (TIBA) to spur or non-spur type trees. Bark scoring had no effect on shoot ethylene. However, this treatment also promoted flowering of young trees in the field. It is suggested that while some manipulations can increase shoot ethylene evolution and also promote flowering, the ethylene evolved following treatment operates indirectly by retarding growth, rather than by directly stimulating flower bud initiation.

Response of Freesia hybrida Corms to Exogenous Growth Regulator Applications1

Abstract Vacuum infusion or soaking of freshly harvested Freesia hybrida Bailey ‘Moya’ corms in solutions of ethephon, gibberellic acid (GA3), abscisic acid (ABA), benzylamino purine (BA) or indoie-acetic acid (I A A), or in solutions with combinations of these growth regulators, did not decrease the time required for shoot emergence. Ethephon delayed shoot emergence and acted synergistically when combined with GA3, or with GA3 and BA, to further delay shoot emergence. Ethephon or ethephon + B A treatments increased the number of shoots produced per corm. Days to flower and flower quality were not influenced by any of the exogenous growth regulator treatments. Presently, there appears to be little horticultural advantage in applying these growth regulators to freesia corms to hasten shoot emergence prior to planting in order to circumvent the need for 10 to 13 week storage treatment at 28°C to remove dormancy and to ensure rapid shoot emergence.

Winter Injury to Apple Cultivars as Affected by Growth Regulators, Weed Control Method, and Rootstocks1

Abstract Effects of cultivars, rootstock, and long-term growth regulator and herbicide treatments on above-ground tree damage from a December 1972 freeze were recorded soon after the freeze and again 7 years later. Ultimate injury was greatest with ‘Jonared’ and least with ‘Golden Delicious’ apple (Malus domestica Borkh.) in the growth regulator plot, while in the herbicide plot it was opposite for the 2 cultivars. There was not a good relationship between injury to specific plant parts (flower buds, spurs, leaders, and lower trunks) observed soon after the freeze, and ultimate tree mortality. Growth regulator treatments significantly increased freeze damage to flowers and spurs, but ultimate tree mortality was reduced by daminozide sprays. Clean cultivation increased flower and spur mortality but did not reduce yield or increase tree mortality compared to the sod treatment. Trees on Mailing (M) 5, M 7 and M 9 rootstocks showed greater initial trunk injury than those on seedling roots, but only those on M 9 showed significantly greater ultimate mortality.

Effects of Depulping, Stratification, and Growth Regulators on Seed Germination of Liriope muscari1

Abstract Depulped seeds of Liriope muscari (Decne.) L. H. Bailey pretreated with GA3 and/or kinetin and placed at 21°C for warm stratification, showed increased germination over unpulped seeds. Germination rates ranged from 87 to 100%. Identical growth regulator treatments resulted in no germination when the depulped seeds were cold stratified (5°C). Unpulped seed, pre-soaked in water for 24 hours or not soaked and given warm stratification germinated 38 and 25%, respectively. This suggested that the inhibition in unpulped seed is influenced by a water soluble inhibitor in the fruit wall.

Improvement of Sugarbeet Seed Emergence with Dilute Acid and Growth Regulator Treatments

Poor emergence of sugarbeet seedling under moisture, temperature, and impedance stress conditions can limit satisfactory stand establishment. The objective of this study was to permeate seeds with dilute acid, growth regulators, and other chemicals, alone and in combinations, and to determine the effect of these treatments on emergence under favorable and unfavorable conditions. Commercially processed seed was treated with 1.0 N hydrochloric acid, propylene, ethylene, 10 and 100 ppm gibberillic acid (GA3), 10 and 100 ppm kinetin, 10 and 100 ppm 6‐benzyl‐aminopurine (6‐BA), 1% sodium hypochlorite, 0.01 M pH 6.7 and 11.4 phosphate buffers, and fermentation, alone and in combination.Effects of treatments on emergence of ‘GWH 58’ were evaluated in laboratory tests with combinations of moisture, temperature, and impedance stress and in field trials in 1977, 1978, and 1979. Laboratory tests showed that the acid treatment stimulates emergence under moisture and temperature, but not impedance stress conditions. The growth regulators ‐ GA3, kinetin, ethylene, and propylene stimulated emergence under combined moisture, temperature, and impedance stress. Under these conditions, acid and growth regulator treatment effects were additive.In field tests, the growth regulator seed treatments stimulated emergence only in combination with acid pretreatment. The acid + 100 ppm GA3 treatment gave the most consistent positive results (significant at 0.05 in 69% of trials) and greatest average improvement in emergence (9.3% of seeds planted) over the control. Significant improvements in field emergence were also obtained with acid + 10 ppm GA3, acid + 10 and 100 ppm kinetin, acid + 10 and 100 ppm 6‐BA, and acid + 100% propylene. Combinations of growth regulators gave no improvement in emergence over that of the individual growth regulators. The acid seed treatment improved emergence only under moisture stress conditions. Cultivars differed in their response to acid + 100 ppm GA, and acid + I00 ppm kinetin treatments in laboratory and field emergence trials conducted in 1980.

Promotion of flowering in the Pinaceae by gibberellins

AbstractSignificant female flowering of 6‐ to 11‐year‐old seedlings and grafted ramets of sexually mature scions of lodgepole pine (Pinus contorta Dougl.) was promoted by both topical and spray applications of a gibberellin (GA) A4/7 mixture (1.6 to c. 5 mg per plant in total) during that period (June to September) when sexual differentiation of lateral primordia would be expected to take place. Girdling was used in most experiments to enhance the GA4/7 effect, as was the auxin, naphthaleneacetic acid (NAA). Average frequency of flowering branches on treated plants over all experiments ranged from 27 to 59% (control ranged from 0 to 36%) and average number of female strobili was increased from 2‐ to 6‐fold by growth regulator treatment, relative to controls. Within an experiment, clonal or family frequency of flowering for treated plants ranged from 11 to 67% (controls were 0 to 28%), and number of female strobili was increased from 2‐ to 14‐fold by growth regulator treatment, relative to controls. Movement of the flowering stimulus from the point of application was apparent in several experiments, the response in adjacent branches being correlated positively with increasing dosage of GA4/7. Significant male flowering occurred only in one experiment, girdling and GA4/7 treatment being promotive factors. The use of spray applications of GA4/7+ NAA is warranted to induce early and enhanced flowering in lodgepole pine seedlings and vegetative propagules for genetic improvement programs.