Application of Phyll set (G A3 + NAA) on whole trees of local cultivars of sweet orange (Citrus sinensis Osbeck) and lemon (C. Limon Burmann) at full bloom stage was made during 1988 and 1989 seasons. All concentrations of Phyll set (12, 24 and 48 mg/l) increased fruit set and yield of sweet orange. Lemon yields were increased only at 12 mg/l Phyll set. The use of Phyll set as a new growth regulator for improved fruit quality will be discussed.
Exogenous ethylene could not substitute for NAA to induce adventitious root initiation in juvenile petiole explants of English ivy (Hedera helix L.), indicating that the action of auxin-stimulated root initiation was not directly mediated through ethylene production. Mature petioles did not initiate roots under any auxin or ethylene treatment combination. Ethephon or ACC supplied at 50 or 100 μm was inhibitory to NAA-induced root initiation in juvenile petioles. The pattern of ethylene production stimulated by NAA application was significantly different in juvenile and mature petioles. Ethylene evolution by juvenile petioles declined to near control levels during from 6 to 12 days after NAA application. Reduction in ethylene production was due to reduced availability of ACC in juvenile petioles. Mature petioles continued to produce ethylene at elevated levels throughout the course of the experiment. Ethylene does not appear to play a significant role in the differential root initiation response of juvenile and mature petioles treated with NAA. However, ethylene appeared to have an inhibitory effect during root elongation stages of adventitious root development in juvenile petioles. Chemical names used: 1-aminocyclopropane-1-carboxylic acid (ACC); 1-napthaleneacetic acid (NAA); 2-chloroethylphosphonic acid (ethephon).
A series of greenhouse experiments was conducted with `Shamrock' bell pepper (Capsicum annuum L.) to gain insight into the flower abscission mechanism and to investigate methods to reduce reproductive structure abscission due to low light intensity. Foliar sprays of STS reduced stress-induced abscission. Application of the synthetic auxin NAA to the ovary substituted for pollination to effect fruit set under nonstress conditions, but did not improve fruit set compared to pollinated controls under low-light stress. Ovary treatment with GA3 and BA either alone or combined with NAA had similar results to NAA treatment alone. Foliar sprays of NAA or CPA also did not improve fruit set under low-light stress conditions. Application of NAA in an aqueous paste to the abscission zone prevented abscission but inhibited fruit growth. Taken together, the results indicate that stress-induced abscission is not prevented by auxin application to the ovary or foliage. The interaction of ethylene and auxin in reproductive structure abscission under stress conditions requires further investigation. Chemical names used: 6-benzylaminopurine (BA), p-chlorophenoxy acetic acid (CPA), gibberellic acid (GA,), silver thiosulfate (STS).
We studied the effect on fruit and leaf abscission of application of ethephon (ETP) at 600 mg liter-1 on excised fruit-bearing olive (Olea europaea L.) shoots held under controlled conditions of temperature and relative humidity analogous to field conditions during fall harvest. Fruit removal force (FRF) and percent leaf drop (%LD) were quantified. Raising solution pH did not improve harvest effectiveness. %LD was significantly higher than control at pH 5, but not at pH 3 or pH 7; FRF was not significantly affected by pH. %LD was not significantly higher than control in the time-of-application treatments (pH 3 only); FRF was significantly less than control when applied at 7AM or 12 noon, but not at 5PM or 10PM. Addition of NAA to the ETP solution raised FRF and lowered %LD; BA had the opposite effect. BA accelerated anthocyanin production on fruits. Regardless of treatment, FRF and %LD are highly but negatively correlated (r2 = 0.62). Harvest effectiveness of ETP use on olive can be defined as a convergence of decreasing FRF and increasing %LD. Mean values for all ETP treatments were FRF = 3.0 N and %LD = 15%, acceptable values for effective olive harvest. Chemical names used: (2-chloroethyl)phosphonic acid (ethephon); naphthalene acetic acid (NAA); 6-benzylaminopurine (BA).
Abstract
Spray applications of NAA or NAA ethylester at 1000 ppm acid equivalent (A.E.) reduced axillary bud number by 30% and 21%, and weight by 73% and 52%, respectively, on pinched potted chrysanthemums, Chrysanthemum ×morifolium Ramat. ‘Mountain Snow’ and ‘Mountain Peak’. Diameter of floral sprays and vegetative heights also were reduced with increasing concentrations. Flower number was not affected by the treatments. NAA treatments caused leaf epinasty, but NAA ethylester treatments did not. Chemical names used: 1-naphthaleneacetic acid (NAA).
Abstract
Excised flower buds of Nicotiana affinis were grown to maturity in media in which growth regulators were added to evaluate their effects on growth and development. As the concentration of naphthaleneacetic acid (NAA) was increased from 10-7 to 10-4 m, the number of days required for the buds to open decreased, and the number of days required for the corolla tubes to turn brown increased. Indoleacetic acid (IAA) and indolebutyric acid (IBA) did not affect the rate of bud opening. As the concentration of IBA was increased, however, the days required for the corolla tubes to turn brown increased, but not as much as for buds in media with NAA. IAA had no effect on browning of corolla tubes. At high concentrations of NAA and kinetin the corolla tubes were shortened. Kinetin did not affect the rate of bud opening or days till the corolla tubes turned brown.
Abstract
Excised embryos and explants from 2-week-old and 4-month-old seedlings of Mugo pine (Pinus mugo Turra var. mugo) were cultured in vitro on nutrient media containing BA and NAA. Shoot development on intact embryos occurred primarily via adventitious bud formation that was greatest On a medium containing 44.4 μM BA and 0.05 μM NAA. Subsequent shoot elongation was improved by transferring buds to a growth regulator-free medium containing 1 g/liter activated charcoal (AC). After removal from culture, shoots rooted in response to treatment with 0.8% IBA. Chemical names used: N-(phenylmethyl)-1H-purin-6-amine (BA); 1-naphthaleneacetic acid (NAA); and 1H-indole-3-butanoic acid (IBA).
Abstract
Pot roses (Rosa hyb. cvs. Pink and Orange Margo Koster and Red Garnette) were sprayed with naphthaleneacetic acid (NAA) or 6-(benzylamino)-9-(2-tetrahydropyranyl)-9H-purine (PBA) prior to simulated truck shipment which lasted 5 or 6 days to study the effect on flower bud and leaf abscision and on leaf senescence. “Shipment” under refrigerated conditions (1-3°C) prevented bud and leaf abscission. ‘Red Garnette’ and ‘Orange Margo Koster’ had little or no bud and leaf abscission even at a warm “shipping” temperature (20-22°C); however, ‘Pink Margo Koster’ was severely affected. Observations under “home conditions” for 10 days after this warm “shipping temperature” revealed that all 3 cultivars had severe leaf senescence. NAA spray (15 and 30 ppm) severely accelerated leaf abscission and senescence. NAA prevented bud drop, but the buds did not open. PBA (50 ppm) greatly reduced leaf abscission both during “shipment” and in “home conditions”. PBA also prevented bud drop and flowers subsequently opened normally.
Abstract
Growth regulators were applied in early autumn to evaluate their effects on induction of cold hardiness in 2-year-old apple shoots, as determined by the conductivity test. Mid-October applications of 500 ppm (2-chloroethyl)phosphonic acid (ethephon), followed 11 days later by 100 ppm of naphthaleneacetic acid (NAA), increased cold hardiness up to 5°C by early November in 1974 and to a lesser extent in 1976. Two annual sprays of succinic acid-2,2-dimethylhydrazide (daminozide, SADH) in June increased cold hardiness slightly (2 to 3°C) in late fall of 1974, 1975, and 1976. However, in 1974 treated trees were no hardier than the controls later in the winter and fruit set on ethephon-treated trees was severely reduced. In most cases, the combined content of fructose, glucose, sucrose, and sorbitol in the 2-year-old wood was slightly higher in treatments that induced cold hardiness in November or December, 1974 than in the controls. Techniques are described for screening growth regulators for induction of cold hardiness and estimating relative cold protection.
Five apple (Malus domestica Borkh.) cultivars were treated with dicamba at concentrations of 0 to 200 mg·liter-1 during 3 years. Although the response varied with cultivar, dose, and year, dicamba always delayed fruit abscission. At similar concentrations, dicamba usually reduced fruit drop more than NAA, but less than fenoprop. Dicamba at 10 mg·liter-1 effectively delayed drop of `Delicious', whereas 20 to 30 mg·liter-1 was required for `Red Yorking', `Rome', `Winesap', and `Stayman'. Dicamba did not influence flesh firmness, soluble solids content, water core, or starch content at harvest or after storage. Chemical names used: naphthaleneacetic acid (NAA); 2-(2,4,5-trichlorophenoxy)propionic acid (fenoprop); 3,6dichloro-2-methoxybenzoic acid (dicamba).