Commercial Plant Growth Regulators Research Articles

Peanut (Arachis hypogaea L.) Response to the Hormonal Plant Growth Regulator Early Harvest®

Abstract Experiments were conducted from 1996 through 2001 in Georgia, North Carolina, and Texas to determine peanut response to the commercial plant growth regulator Early Harvest® (a commercial mixture of cytokinin, gibberellic acid, and indole butyric acid). Early Harvest (applied in the seed furrow) or Early Harvest TST (applied as a dry seed treatment) followed by four foliar applications (four-leaf peanut, initial pegging, 14 d after initial pegging, and pod fill), was compared to non-treated peanut in five, 13, and three experiments in these respective states. Early Harvest did not affect pod yield or gross economic value of peanut regardless of location, cultivar, or edaphic and environmental conditions. These data suggest that a spray program consisting of Early Harvest most likely will not improve pod yield or gross economic value of peanut.

A History of Commercial Plant Growth Regulators in Apple Production

DNA breakdown (Miller et al., 1955). Kinetin was significantly more active than adenine in the tobacco tissue culture bioassay. The use of the plant cell culture bioassay was a key to the eventual isolation of zeatin from corn by Letham (1963). ETHYLENE. The growth regulating properties of ethylene were first recognized by the Russian scientist Nejebulov in 1901 (Beyer et al., 1984). His experiments showed that illuminating gas could cause leaf abscission and epinasty. The fruit physiologist Crocker developed the Alaskan pea bioassay that used the triple response of shortening and thickening of the hypocotyl, agravitropic growth, and maintained hypocotyl hook (Reid and Howell, 1995) to assess ethylene levels. He was the first to suggest that ethylene was an endogenous plant hormone. However, few scientist at the time agreed with Crocker since it was difficult to visualize that a gas could act as an endogenous regulating substance. It was not until the 1960s when gas chromatography was used to quantify endogenous ethylene that the significance of ethylene was recognized and acknowledged as an endogenous hormone. ABSCISIC ACID.While researchers had long speculated that a hormone which affected abscission, dormancy, and stress reduction existed, it was not until the 1950s that work on the isolation and identification of this compound began. In 1953 Bennet-Clark and Kefford discovered an acid fraction of plant extracts that was a potent growth inhibitor. In 1955 Osborne reported on the diffusion of a senescence factor from older leaves that could speed the abscission of bean petioles. By 1963, Addicott s group studying cotton fruit abscission in California had identified and characterized abscisin II. At the same time, Wareing s group in Wales identified the dormin as a compound that promoted dormancy in woody plants. In 1968, these groups formally redesignated abscisin II and dormin as abscisic acid (Milborrow, 1984).

Effects of fruit thinning agents on apple tree canopy photosynthesis and dark respiration

Effects on photosynthesis of the fruit thinning agents naphthaleneaceticacid (NAA) and three commercial plant growth regulator formulations,naphthaleneacetic acid ('Rhodofix') and naphthaleneacetamide('Amidthin') and 2-chloroethylphosphonic acid('Ethrel')were evaluated with respect to the stress they impose on the fruit tree, usingthe alternate-bearing sensitive apple cv. 'Elstar'. This work wasbased on the hypothesis that plant stress in the form of large reductions inleaf photosynthesis are a pre-requisite for successful fruit thinning. A newtechnology was employed for continuous recording of tree canopyphotosynthesis, dark respiration and carbon balance of apple trees. This wasbased on six canopy chambers, which enclosed apple trees under naturalconditions in the field, with on-line measurements and continuous analysis ofCO2 exchange and automated data acquisition. All employed thinningagents reduced whole tree canopy photosynthesis consistently by3–34% on the five days following their application, withphotosynthesis still declining thereafter in the case of the NAA and'Amid-thin' application. The reduction after application of either'Rhodofix' or 'Ethrel', declined within five days, suchthat most of the original photosynthetic potential was restored, indicatingacceptable phytotoxicity of these three plant growth regulators at theconcentrations used. The effects on dark respiration differed markedly. NAA and'Ethrel' increased dark respirationover-proportionally by up to 106%, whereas 'Amid-thin' and'Rhodofix' decreased it by up to 46%inthe first night after application, thereby drastically affecting the carbonbalance of the tree in opposite ways. These results are integrated into ahypothesis linking basipetal auxin transport, phloem loading, translocation anddeficiency of photoassimilates.

154 Suppressing Purple Passion (Gynura aurantiaca) Flowering Using Selected Plant Growth Regulators

Gynura aurantiaca is a colorful foliage plant with creeping stems and velvety purple hairs that cover the green leaves. It grows rapidly, but is cultivated primarily for those attractive purple leaves. Annually during the spring, this plant produces prominent flowers both in appearance and smell, gaudy and malodorous. Flowering coupled with acquiring an over-grown leggy appearance have been key limitations in its production and use in interiorscaping. This study was undertaken to determine if an available commercial plant growth regulator could inhibit flowering. A-Rest (ancymidol), B-Nine (daminozide), Bonzi (paclobutrazol), cycocel (chlormequat chloride) and florel (ethephon) each diluted to three different concentrations were sprayed in two applications in early spring at 2-week intervals. Flowering and bud numbers and plant growth (number of lateral shoots, vine lengths and internode lengths) were recorded. Results indicated that applications of A-Rest, B-Nine, Bonzi and Cycocel, regardless of treatment concentrations, were ineffective in suppressing the flowering of this plant; whereas, florel completely suppressed flowering at the three concentrations used. The florel-treated plants also grew more lateral shoots, which produced a compact and dense bush-look, indicating that appropriate concentrations of florel application not only will stop flowering of purple passion but can also improve and prolong its aesthetic value as a potted or hanging-basket interior plant.

ReTain Effects on Fruit Size, Maturity, and Storage Quality of' Jonagold' Apples

ReTain™, a commercial plant growth regulator containing aminoethoxyvinylglycine, an inhibitor of ethylene production, was applied 4 weeks before normal harvest to `Jonagold' trees and the effects on fruit maturity and quality at harvest, and quality after air and controlled atmosphere storage was investigated. When fruit were harvested from 3 to 6 weeks after treatment, fruit ripening was inhibited as indicated by lower internal ethylene concentrations, delayed starch hydrolysis, and lower levels of skin greasiness. A number of factors indicated that other aspects of fruit metabolism were affected by the compound. Treated fruit were softer than nontreated fruit at the first harvest, and the benefits of ReTain on firmness appeared only at the later harvests. Also, at each harvest date, average fruit weight of ReTain-treated fruit was lower than nontreated fruit. We have investigated the possibility the ReTain and/or the accompanying surfactant, Silwet, inhibited leaf photosynthesis, thereby leading to altered carbon metabolism. Trees were unsprayed, or sprayed with surfactant, and ReTain plus surfactant. No treatment effects on photosynthesis were detected. However, leaf photosynthesis rates were generally low and quite variable. Measurements of fruit diameter confirmed that the increase in fruit volume following treatment was ≈2% less on the ReTain plus surfactant-treated fruit than nontreated fruit. The increase in fruit volume for the Silwet treatment was ≈1.5% less than in untreated fruit. The data indicates a rapid change in fruit volume as fruit changed in color. Inhibition of ethylene by ReTain may be an important factor influencing fruit size.

ReTain Effects on Fruit Size, Maturity, and Storage Quality of' Jonagold' Apples

ReTain™, a commercial plant growth regulator containing aminoethoxyvinylglycine, an inhibitor of ethylene production, was applied 4 weeks before normal harvest to `Jonagold' trees and the effects on fruit maturity and quality at harvest, and quality after air and controlled atmosphere storage was investigated. When fruit were harvested from 3 to 6 weeks after treatment, fruit ripening was inhibited as indicated by lower internal ethylene concentrations, delayed starch hydrolysis, and lower levels of skin greasiness. A number of factors indicated that other aspects of fruit metabolism were affected by the compound. Treated fruit were softer than nontreated fruit at the first harvest, and the benefits of ReTain on firmness appeared only at the later harvests. Also, at each harvest date, average fruit weight of ReTain-treated fruit was lower than nontreated fruit. We have investigated the possibility the ReTain and/or the accompanying surfactant, Silwet, inhibited leaf photosynthesis, thereby leading to altered carbon metabolism. Trees were unsprayed, or sprayed with surfactant, and ReTain plus surfactant. No treatment effects on photosynthesis were detected. However, leaf photosynthesis rates were generally low and quite variable. Measurements of fruit diameter confirmed that the increase in fruit volume following treatment was ≈2% less on the ReTain plus surfactant-treated fruit than nontreated fruit. The increase in fruit volume for the Silwet treatment was ≈1.5% less than in untreated fruit. The data indicates a rapid change in fruit volume as fruit changed in color. Inhibition of ethylene by ReTain may be an important factor influencing fruit size.

Effects of Several Commercial Plant Growth Regulator Formulations on Yield and Allelochemicals of Cotton (Gossypium hirsutum L.)

In recent years, a number of kinetin-based commercial plant growth regulators have been evaluated for their effects on various crop plants. In a study at Mississippi State during 1986-1992, five commercial plant growth regulators and urea were evaluated as foliar sprays on growing cotton (Gossypium hirsutum L.) plants for their effects on yield, agronomic traits, and pest allelochemicals. Of the five tested, the activities of three (Burst, Foliar Triggrr, and Maxon) were attributed by their providers to cytokinins. FPG-5 contained cytokinins, IAA, GA, and several inorganic micronutrients, and PG-IV contained IBA, GA, and micronutrients, but no cytokinins. FPG-5 and Foliar Triggrr caused statistically significant increases in yield, but only in 1992. The foliar application of urea had a consistently negative effect on yield (...)

Effect of a commercial plant growth regulator on the elemental content of tea plants

Response of field grown mature tea to the foliar application of Biozyme Crop Plus, a commercial plant growth regulator, applied at different concentrations ranging from 250 to 1000 ppm was evaluate...

Toxicant-disease-environment interactions associated with suppression of immune system, growth, and reproduction.

The effects of marginal malnourishment , infections, and environmental chemicals on growth and reproductive success in Swiss-Webster white mice and wild deer mice were studied with fractional factorial designs. Interaction effects were discovered. For example, malnourished mice were more sensitive to virus exposure and environmental chemicals (a plant growth regulator or polychlorinated biphenyls). Since several commercial plant growth regulators also appear to suppress the immune system, these results cast doubt on the adequacy of current toxicity testing procedures in which factors are studied individually and not in combination.

Título en español.

Se examinó el comportamiento diurno de la invertasa ácida en plantas de caña de azúcar de 5 y 14 semanas de edad tratadas con Polaris. Este se administró en aspersión foliar acuosa a las 0645 h. Se cosecharon muestras de tallos verdes a intervalos de 2 horas de 0630 n 1830 h el día del tratamiento y durante los dos días siguientes. En las plántulas, Polaris adelanto el tiempo de acción máxima de la invertasa dentro de las 2 horas posteriores a la aplicación, sin retardar la acción de la enzima. Durante el tercer día Polaris retardó persistentemente la invertasa sin alterar el tiempo o la magnitud de fluctuación de la enzima. Efectos similares se produjeron en plantas adultas jóvenes con conductos de transporte alargados y elaborados. Ni las f1uctuaciones naturales ni los cambios producidos por el agente químico fueron acompañados por cambios en el contenido de sacarosa del tejido, reducción de los azúcares o cantidad de proteína soluble. En este contexto se discuten dos sistemas de control para la invertasa ácida, uno que gobierna su síntesis y el otro que gobierna su comportamiento diurno, posiblemente localizado en los tejidos de la hoja, el que el Polaris altera temporalmente.