Abstract
Effects of the surfactants Pace, Regulaid and Tween 20 were determined on foliar penetration of NAA and on NAA-induced ethylene production by cowpea [Vigna unguiculata (L.) Walp. subsp. unguiculata cv. Dixielee]. All three surfactants decreased surface tension of NAA solutions, causing a marked increase in wetting and in droplet : leaf interface area. The greatest increase in NAA penetration was obtained with Regulaid followed by Pace and Tween 20. The surfactant effect was most pronounced during the droplet drying phase, but penetration continued to take place from the deposit after drying. The mode of action of surfactants in enhancing NAA penetration is complex. Regulaid-enhanced penetration closely paralleled the increase in interface area, but similar relationships were not found for Pace or Tween 20, particularly at concentrations above the critical micelle concentration. Surfactant-enhanced NAA penetration caused an increase in NAA-induced ethylene production. There was a strong correlation (r = 0.82) between NAA penetration and ethylene production for doses of 0.5 to 2.5 μg/disk. Above 2.5 μg/disk, ethylene production increased at a decreasing rate. The potential for using auxin-induced ethylene production as an index for quantifying auxin penetration is discussed. Chemical names used: l-naphthaleneacetic acid (NAA), polyoxyethylene polypropoxypropanol dihydroxypropane (Regulaid), polyoxyethylene (20) sorbitan monolaurate (Tween 20), surfactant blend in paraffin base petroleum oil (Pace).
). Increased abscission of young apple fruit caused by the chemical thinner naphthaleneacetic acid (NAA) is linked with increased ethylene production; hence, NAA may act in part through ethylene signaling ( Curry, 1991 ; Zhu et al., 2008 ). The pathway of
retained on cuttings and any remaining leaves were removed. Retained leaves were bisected to reduce water loss. The basal 5 cm of cuttings were dipped for 10 s in 1030 ppm IBA (0.1%) and 660 ppm (0.066%) NAA dissolved in 9.8% isopropyl alcohol (Woods
(NAA) combined with 6-benzylaminopurine (BAP) ( Tokuhara and Mii, 1993 ), thidiazuron (TDZ) ( Ernst, 1994 ), and zeatin ( Park et al., 2003 ). Most of the studies performed to date involve the production of shoots through the formation of protocorm
tips of strawberry cv. Camarosa was investigated. Two types of auxins, IBA and naphthaleneacetic acid (NAA), in different concentrations, were assessed for root induction. ‘Camarosa’ strawberry is a cultivar that is popularly grown in Cameron Highlands
Abstract
Conjugation of 14C-1-naphthaleneacetic acid (NAA) was followed in leaf discs of apple, apricot, grape, orange, peach and pear. NAA was metabolized by all crops studied. Free NAA and 2 metabolites that chromatographed with naphthylacety1-β-D-glucose (NAG) and naphthylacetylaspartic acid (NAAsp) constituted 90% of the radioactivity recovered, NAG was the major metabolite (45-90%) followed by NAAsp (5-30%) and NAA (2-22%). Conjugation was most complete in orange (98%), intermediate in apple, apricot, peach and pear and least in grape (68%).
NAA at 0.25% to 1.0% applied in late May on the basal portion of thornless blackberry (Rubus, subgenus Eubatus) primocanes inhibited lateral shoot growth in the treated area and reduced the number of primocanes. However, regrowth occurred near or below ground from axillary buds not contacted by NAA. Rates of (0.25% and 0.12570 NAA did not affect the terminal or lateral growth above the treated area. The reduced number of basal lateral shoots facilitated machine harvesting. Chemical name used: napthaleneacetic acid (NAA).
Abstract
Consistent sprout control was obtained with peach trees (Prunus persica (L.) Batsch cv. Sungold) when 0.25, 0.5, 0.75 or 1% naphthaleneacetic acid (NAA) was applied to pruning cuts during 2 years with sprout control generally proportionate to concentration. NAA treatments induced gummosis around the pruning cuts with the degree of gummosis related to concentration.
Experiments were carried out in the southeastern United States between 1998 and 2006 to evaluate the potential for applications of NAA, Ethrel, or both, in the on-year of a biennial bearing cycle to increase return bloom in apple. Four bi-weekly applications of 5 ppm NAA beginning in mid June (summer NAA) increased return bloom, measured as the percentage of floral spurs in the year after treatment. The level of return bloom on trees receiving a summer NAA program was more than 2-fold higher than on untreated control trees, averaged across seven different experiments. Four applications of 5 ppm NAA at weekly intervals leading up to harvest (August/September) increased return bloom also. Combining 150 ppm Ethrel with summer NAA sprays resulted in an additive effect on return bloom compared to NAA or Ethrel alone. The effect of flower cluster density on return bloom the following year was more negative on control trees than it was on trees sprayed with Ethrel in the previous year. Treatment effects on fruit maturity at harvest were generally neutral, although flesh firmness was reduced in some experiments. NAA or Ethrel sprays in the on-year of a biennial bearing cycle may provide a strategy for achieving more consistent flowering and cropping in apple.
Post-bloom fruit thinning of spur-type `Delicious' with NAA may occasionally result in excessive small fruit (50 - 67 mm) not correlated with crop load. We evaluated the effect of carrier volume and time of application on incidence of small fruit over three growing seasons. A constant dose of NAA (30 g·ha-1) was applied in 230 to 2100 liter·ha-1 at about 10 mm king fruit diameter (KFD). Amount of NAA-induced small fruit differed from year to year, but there was no significant effect of carrier volume in any given year. NAA (15 mg·liter-1) was applied as a dilute spray at 5 to 22 mm KFD. Time of application influenced fruit size distribution at harvest in only one of three years. The incidence of small fruit appeared more closely related to temperature during spray application than to carrier volume or time of application. The effect of NAA on growth rate of king fruit with minimal competition (branches hand thinned, no lateral fruit) was determined over the first month after thinning. There was no pronounced effect of NAA on post-treatment growth rate. In a related study, NAA caused a significant decrease in fruit size when two or more fruit were competing on the same spur, while fruit size in the absence of intra-spur competition was not significantly reduced.