In 1994, benzyladenine (BA, formulated as Accel, containing 1.8% BA and 0.18% GA4+7) was evaluated as an apple fruit-thinning agent. Naphthaleneacetic acid (NAA, 10 ppm) and carbaryl (60 g·liter–1) were also used, as well as combinations of these chemicals with BA. Whole trees were treated with either an airblast sprayer or a hand gun, BA being used at 15–20 g/acre. Good responses to BA were obtained in one of two trials, with both `Empire' and `Gala', but `Jonagold' and `Jonathan' were not responsive (one trial each). In general, response to NAA and carbaryl was more consistent. In only one orchard (`Gala') did BA appear to increase fruit size without reducing crop load. Combinations of BA with NAA or carbaryl were generally no more effective than one chemical alone, but such combinations overthinned in one experiment with `Empire'.
Martin J. Bukovac, Jorge B. Retamales, Xu Shao-ying, and Hiroyuki Matsui
Parthenocarpic fruit development was induced in ‘Montmorency’ sour cherry (Prunus cerasus L.) with AC 94377. The biological activity of AC 94377 was increased significantly by NAA. The development (Stages I, II, III, “June drop”, ripening) of parthenocarpic fruit was similar to that of open pollinated controls except for smaller fruit size. Ovules enlarged during Stage I in AC 94377-induced parthenocarpic fruit, but lacked embryos; all ovules aborted during Stage II or III of fruit development. The primary action of NAA appeared to reduce abscission of AC 94377-treated ovaries with no significant effect on fruit size. Chemical names used: 1-naphthaleneacetic acid (NAA); N-(phenylmethyl)-1H-purin-6-amine (6-BA); 1-(3-chlorophthalimido)-cy-clohexanecarboximide (AC 94377); polyoxyethylene sorbitan monooleate (Atlox BI).
S. B. Boswell, B. O. Bergh, R. H. Whitsell, and J. Kumamoto
Naphthaleneacetic acid (NAA) ethyl ester was applied as 0.5% aqueous spray 7 cm below the grafts of 9-month-old avocado (Persea Americana Mill.) prior to graft growth. No growth occurred on the grafts and plants were dead 4 months after treatment. Volatilization of ethyl ester of NAA applied as 0.3% to 1.0% aqueous spray, 7 cm below grafts that had grown out 12 cm, caused the new growth to wilt for 36 hours. The 0.4% spray caused slight bark burn of the seedling trunk. The higher the concentration the greater the burn. Sprays of 0.3 or 0.4% sodium salt NAA did not cause wilting or bark burn. Both formulations of 0.3 and 0.4% gave good control of sprouts on the seedlings trunks. The 0.3 and 0.4% ethyl ester treatments reduced total graft growth.
Ed Stover, Scott Ciliento, and Monty Myers
In spring 1999, a commercial NAA (1-naphthaleneacetic acid) preparation for trunk sprout inhibition was compared with a corrugated plastic trunk wrap, aluminum foil wrap, bimonthly hand removal of sprouts, use of NAA preparation plus bimonthly hand removal when sprouts appeared, and a nontreated control. Three recently planted groves on three different rootstocks [`Midsweet' orange (Citrus sinensis)] on Swingle citrumelo (Citrus paradisi × Poncirus trifoliata), `Valencia' orange on Volkamer lemon (Volk, Citrus limon), and `Minneola' tangelo (Citrus paradisi × C. reticulata) on Smooth Flat Seville (SFS, Citrus hybrid) received each of the treatments in a randomized complete block experimental design with trees blocked by initial height and circumference. Every 2 months, sprouts were counted on each tree and removed from the hand removal treatments. After 1 year, all sprouts were removed and counted and height and circumference of trees was determined. Across all experiments, 82% to 100% of nontreated trees produced trunk sprouts and all sprout control methods significantly reduced sprouts per tree. NAA treatments were never significantly less effective at sprout suppression than the wraps at the P = 0.05 level, although in two experiments, wraps were more effective than NAA at P = 0.10. Time of sprout appearance varied between the three experimental blocks. Plastic and foil trunk wraps enhanced development of trunk circumference compared with nontreated controls in `Midsweet'/Swingle and `Valencia'/Volk. Greater trunk circumference resulted from use of wraps versus NAA in all three experiments, which appeared unrelated to differential sprout suppression. In these experiments, it appears that either wraps enhanced tree development beyond the suppression of sprouts or NAA influence on tree metabolism somewhat reduced trunk growth. The economics of the sprout suppression methods are also discussed.
G. W. Schneider
Pre-June drop sprays of naphthaleneacetic acid (NAA) applied to apple trees increased the radial pedicel-xylem ratio, the % tracheary cells that were lignified, and the number of mature treacheary cells on the 7th day following treatment No significant response for these characters were obtained with sprays of 1-naphthyl methyl carbamate (Sevin). Both NAA- and Sevin-treated pedicels had a higher percentage of sclereids that contained nuclei. Neither material affected pedicel diameter, width of phloem or xylem, size of newest lignified tracheary cells, number of immature secondary tracheary cells, or the radial xylem-phloem and pedicel-phloem ratios.
S. B. Boswell, B. O. Bergh, and R. H. Whitsell
A 1% ethyl ester or sodium salt formulation of naphthaleneacetic acid (NAA) in 30% aqueous solution of white latex paint sprayed below the grafts effectively controlled trunk sprouts in topworked avocados (Persea americana Mill). Regrowth was suppressed over a 7-month growing period with no adverse effects on the grafts.
Robert L. Geneve, Wesley P. Hackett, and Bert T. Swanson
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).
Makki A. Al-Khafaji and M. M. Musalat
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.
Raymond Chée and Robert M. Pool
We previously reported a method for shoot tip micropropagation of the Vitis hybrid ‘Remaily Seedless’ (1, 2). In preliminary trials, rooting of subcultured shoots was erratic and shoots deteriorated after 2 weeks in culture. Herein we report the effects of sucrose and naphthaleneacetic acid (NAA) concentrations on the physical condition of subcultured shoots and subsequent root production in an attempt to increase the efficiency of grape micropropagation.
R. E. Lyons and P. Meyers
As the concentration of the exogenously applied gibberellin GA4+7 increased from 1 to 100 ppm, 3 significant correlations were observed: 1) the number of days to first flowering decreased; 2) the peduncle length of the first flower increased; and 3) the number of visible peduncles on the primary phyllomorph increased. A subsequent application of 10 ppm naphthaleneacetic acid (NAA) generally had no effect on these results.