The apple crop in Brazil is established in acid soils with low pH. This condition leads to high aluminum levels in the soil. The aim of this work was to evaluate the callogenesis and organogenesis of apple rootstock somatic material under aluminum and different auxins concentrations. Internodes of apple rootstock cv. Marubakaido were inoculated in a MS medium containing aluminum (10 mg·L–1), BAP (5.0 mg·L–1), MS vitamins, myo-inositol (100 mg·L–1), sucrose (30 g·L–1), and agar (6.0 g·L–1). Picloram and NAA were tested at (0, 0.5, 1.0, 1.5, and 2.0 μM. Internodes were inoculated in test tubes and the whole material remained in dark for 3 weeks and then to 16-h photoperiod, 25 ± 2°C and 2000 lux. NAA-treated explants performed better than picloram ones. Callus intensity was maximized at 0.5 μM NAA. Although the higher percentage of callus formed (91%) occurred for NAA at 1.0 μM and 82% for picloram at the same concentration. NAA-treated explants responded for 62% of regenerated callus, while picloram presented only 6%. NAA also increased the mean number of shoots (3.54) and buds (11.52) as compared to picloram, which presented 1.40 and 2.78, respectively.
Effects of various combinations of NAA-800 and Retain on fruit retention, yield, and harvest and post-storage fruit quality of `Rome Beauty' and `Delicious' apples were studied over one to three seasons. Retain and NAA-800 often reduced preharvest fruit drop as compared to control. Fruit from trees that received Retain at 123.6 g a.i./ha, or 61.8 g a.i./ha plus NAA-800 showed lower starch degradation pattern (SDP) at harvest and higher firmness. Retain treated fruit had lower evolved ethylene and respiration. Application of Retain at 61.8 g a.i./ha plus NAA-800 delayed fruit maturity, and the effects on fruit quality at harvest was comparable to the effects of this chemical at 123.6 g. a.i./ha. However, after storage, fruits from trees receiving Retain at 123.6 g a.i./ha often were firmer. Split applications of NAA-800 did not show major improvement in delaying fruit maturity over a single application. Application of NAA-800 at 585 mL/ha tended to reduce fruit firmness and increase fruit SDP. These fruits some times tended to have better color. Results on fruit color varied from year to year.
Abstract
Ethephon at 3, 6, and 12 mm induced abscission of mature foliage on pecan [Carya illinoensis (Wangenh) K. Koch] seedlings. This effect was offset to varying degrees using NAA at 3, 6, or 12 mm in which NAA acted as an effective antidote to ethephon and presumably ethylene. Abscission varied with leaf age and with the relative timing of leaf treatment with ethephon and NAA. Leaves treated with NAA 6 days prior to ethephon treatment were much more sensitive to ethephon induced abscission than those treated one day prior to, at time of, or one day after ethephon sprays. There were no abscission response differences among the 3 latter NAA treatment times. Ethephon greatly reduced 14C-IAA transport in leaf midrib tissue and increased the amount of IAA conjugated in leaf tissue without changing free IAA levels. It is suggested that ethephon treatment reduces the amount of IAA transported from the leaf blade to the abscission zone by inhibiting auxin transport in vascular tissue. IAA inactivation by conjugation appears to have no influence on the IAA level reaching the cells of the abscission zone. Chemical names used: (2-chloroethyl)phosphonic acid (ethephon); 1-naphthaleneacetic acid (NAA).
A very efficient adventitious regeneration (shoot organogenesis) system for cranberry (Vaccinium macrocarpon Ait.) leaves was developed. A basal medium consisting of Anderson's rhododendron salts and Murashige and Skoog's (MS) organics, supplemented with 10.0 μm thidiazuron (TDZ) and 5.0 μm 2ip, was effective for adventitious regeneration from leaves for the five cranberry cultivars tested: `Early Black', `Pilgrim', `Stevens', `Ben Lear', and `No. 35'. Parameters examined included: 1) varying combinations of three plant growth regulators (TDZ, 2ip, and NAA); 2) explant orientation (adaxial vs. abaxial side in contact with the medium); and 3) leaf position relative to the apical meristem from the source plant. Cultivars varied in regeneration frequency, but cultivar × growth regulator interaction was nonsignificant. With optimal treatment conditions, regeneration occurred on more than 95% of the explants, with `Early Black' and `Pilgrim' producing as many as 100 shoot meristems per explant. At all concentrations tested, NAA (as low as 0.1 μm) increased callus formation and significantly reduced regeneration. Emerging adventitious shoots were always observed on the adaxial side of the leaves regardless of explant orientation on the medium. Regeneration was much greater when the abaxial side was in contact with the medium, and was not related to leaf position on the source plants. Elongation of adventitious shoots began ≈2 weeks after transfer to the basal medium without growth regulators. Cuttings of elongated shoots rooted 100% both in vitro in the basal medium and ex vitro in shredded sphagnum moss. The high regeneration efficiency achieved by using this system will be very useful in the application of techniques, such as Agrobacterium- and particle bombardment-mediated transformation. Chemical names used: 1-phenyl-3-(1,2,3-thiadiazol-5-yl) urea (thidiazuron, TDZ); N6-(γ-γ-dimethyallylamino) purine (2ip); α-naphthaleneacetic acid (NAA).
Six trials were conducted to determine whether lower spray volumes or inclusion of different surfactants would permit adequate thinning of mandarin hybrids (Citrus reticulata hybrids) at a much lower cost per hectare. Sprays were applied using a commercial airblast orchard sprayer during physiological drop when fruitlets averaged 8 to 16 mm in diameter. Surfactant was always included at 0.05% v/v. NAA always reduced fruit per tree, increased fruit size, and decreased production of smallest size fruit. However, in only three experiments, contrast of all NAA treatments vs. controls indicated increased production of the largest (80–100 fruit per carton) and most valuable fruit. In four of five experiments, comparison of spray volumes of 600 (only examined in three of four experiments), 1200, or 2300 L·ha–1 demonstrated significant fruit size enhancement from all NAA applications. Most individual NAA treatments resulted in fewer fruit per tree, but there were no statistically significant differences between NAA treatments at different spray volumes. In only one of the four experiments, there was a marked linear relationship between spray volume and fruit per tree, yield, mean fruit size, and production of largest fruit sizes. The effects of surfactants (Activator, a nonionic, Silwet L-77, and LI-700) on NAA thinning were tested in both `Murcott' and `Sunburst'. In comparisons between Silwet L-77 and Activator surfactant, one experiment with `Murcott' showed greater fruit per tree and yield reduction from using Silwet, but with a smaller increase in production of largest fruit sizes, whereas in another `Murcott' experiment, Silwet L-77 reduced numbers of smaller fruit size with no increase in production of larger fruit. Based on these findings, current recommendations for NAA thinning of Fla. mandarins are use of spray volume of ≈1100–1400 L·ha–1 on mature trees with proportionally lower volume on smaller trees. These data appear to support use of a nonionic surfactant rather than other tested surfactants in NAA thinning of Florida mandarins. Because experience with NAA thinning of Florida citrus is limited, it is only recommended where the disadvantages of overcropping are perceived to substantially outweigh the potential losses from overthinning.
Thinning with BA reportedly increases size of 'Empire' fruit more than does thinning with NAA because of enhancement of cell division by BA. This study was conducted to determine the phenological stage at which BA application provides maximum fruit weight relative to degree of cropload reduction. In all years, treatments were applied at a range of timings: petal fall (PF), 5-, 10-, or 15-mm king fruitlet diameter (KFD). For each thinner, the same concentration was used throughout the study. In 1994, only Accel® at 75 mg·L-1 was evaluated. In 1995, NAA (7.5 mg·L-1) + carbaryl (600 mg·L-1), Accel®, and a BA-only formulation were compared, but BA alone was applied only at PF, 10- and 15-mm KFD. In 1996, Accel® and NAA were compared with and without carbaryl at all timings. Most treatments reduced cropload and enhanced fruit weight. When data for all 3 years were combined, Accel® or BA increased cropload-adjusted fruit weight (CAFW) in 8 of 10 treatments made at 10- or 15-mm KFD, PF treatments never increased CAFW, and only one of four applications at 5-mm KFD increased CAFW. In contrast, NAA + carbaryl increased CAFW in four of four treatments applied at PF or 5-mm KFD, but in only one of four treatments at 10- or 15-mm KFD. Accel® was less effective than NAA in reducing fruit clusters to a single fruit per spur in most comparisons, either with or without carbaryl. Return bloom varied greatly across years, but was always influenced by application time and types of thinners. In 1994 and 1996, return bloom was closely related to cropload the previous year. Although return bloom was very low for most treatments in 1995, 10- and 15-mm KFD applications of NAA + carbaryl increased it three-fold in comparison with other treatments (NAA + carbaryl at PF or 5 mm or BA at 10-mm KFD) that had similar effects on cropload. Chemical names used: 6-benzyladenine (BA); naphthaleneacetic acid (NAA).
Abstract
Naphthalenacetic acid ethyl ester (NAA ethyl ester) applied to actively growing rootsuckers on ‘Oregon Spur Delicious’ apple trees (Malus domestica Borkh.) at 0.5 and 1.0% provided effective sucker suppression 70 days after treatment. Combination sprays of NAA and N-butyl-N-ethyl-a,a,a-trifluro-2,6-dinitro-p-toluidine (benefin) or NAA and straight chain fatty alcohols (Off-Shoot-T85) gave good control of rootsuckers. Lower rates of NAA and NAA plus Off-Shoot-T85 were equally effective when a paraffin based petroleum oil spray adjuvant (Agicide Activator) was added. NAA at 1.0% was the only treatment to provide effective rootsucker supression in the season following treatment.
Abstract
The effects of pH and temperature were determined on NAA sorption by enzymatically isolated tomato (Lycopersicon esculentum Mill. cv. Sprinter) fruit cuticles. Both cuticular membranes (CM) and dewaxed CM (DCM) sorbed more NAA at pH 2.2 than at pH 6.2. At each pH, increasing temperature (15° to 35°C) decreased NAA sorption by both CM and DCM. The same qualitative temperature (5° to 25°) response was observed with 2,4-D for CM at low (0.8) pH. Chemical names used: 2-(1-naphthyl)acetic acid (NAA); (2,4-dichlorophenoxy)acetic acid (2,4-D).
Polymeric formulations of plant growth regulators (PGR) are high-molecular weight systems in which the PGR unit can be slowly released providing prolonged action and effectiveness in a wide range of concentrations. In this study, Achimene explants were used for testing the biological activity of polymeric derivatives of NAA and 2,4-D. Shoots of Achimenes `Bella', obtained from leaf segments cultured in vitro, were transferred for 8 weeks on Murashige and Skoog (MS) medium supplemented with different levels of conventional or polymeric NAA (0, 0.01, 0.05, 0.1, 0.5, 1.0, 1.5, 2.0, 2.5 mg·liter–1) and 2.4-D (0, 0.01, 0.05, 0.1, 0.5, 1.0, 1.5 mg·liter–1), each combined with three levels of BAP (0, 0.1, 0.5 mg·liter–1). Compared to conventional NAA, twice as many shoots proliferated with higher dry weight, at 0.5 0.1, 1.0, or 1.5 mg·liter–1 polymeric NAA with 0.5 mg·liter–1 BAP. In another trial, the combination of 0.05 or 0.1 mg·liter–1 polymeric 2,4-D with 0.1 BAP gave more shoot and vigorous growth without callus formation, compared to conventional 2.4-D These results suggest that the polymeric derivatives of auxins used in this study enhance regeneration and growth of Achimenes in vitro more effectively than conventional formulations, at greater concentrations, without causing toxic or inhibitory effects.
Abstract
Summer pruning significantly restricted radial growth of trunks, shoot growth, and root growth of young trees of ‘Delicious’ apple (Malus domestica Borkh.) the year of treatment. Summer pruning early in the season was most devitalizing. Application of naphthaleneacetic acid (NAA) to the pruning cut after summer pruning had inconsistent effects on dry weight accumulation, but usually reduced regrowth. Growth of summer-pruned trees was generally similar to growth of comparably dormant-pruned trees the year following treatment.