Search Results

You are looking at 1 - 10 of 27 items for

  • Author or Editor: B.W. Wood x
Clear All Modify Search
Author:

Abstract

Pecan [Carya illinoensis (Wang.) Koch] axillary buds of nodal explants from 4- to 12-week-old ‘Stuart’ seedlings were first induced to proliferate shoots and then to elongate on a defined medium. An evaluation of 6-benzylamino purine (BA), isopentenyladenine (2iP), indolebutryric acid (IBA), and indoleactic acid (IAA) for shoot proliferation found a combination of 4 mg/liter BA and 1 mg/liter IBA to be most effective. The synthetic hormones were much more effective at inducing a growth or development response than were their natural counterparts. Gibberellic acid (GA) at 3 mg/liter plus 0.1 mg/liter BA enhanced shoot elongation.

Open Access
Author:

Abstract

‘Schley’ pecan [Carya illinoensis (Wang.) K. Koch] fruit were selectively thinned within one week after treatment with (2-chloroethyl)phosphonic acid (ethephon) without causing leaf abscission. A concentration range of 25, 50, 75, 100, 150, and 200 ppm caused progressive and selective fruit thinning ranging from 25 to 75%, depending upon concentration and fruit age. Fruit treated when at 4-mm diameter (June 15) were more heavily thinned at the same rate than fruit at 12-mm diameter (July 15). Leaf abscission occurred at rates of 300 ppm or greater on each treatment date. Ethephon levels had no effect on return bloom or fruit set.

Open Access
Author:

Abstract

Several gibberellin-like substances were detected by cucumber, dwarf pea, and lettuce bioassays after liquid chromatographic (HPLC) fractionation of liquid endosperm from the developing seed of pecan [Carya illinoensis (Wang.) K. Koch cv. Moneymaker]. The response of bioassays to authentic gibberellin standards and fractions eluted from the HPLC column at the same times as gibberellin A3, A4, and A7 suggests that these 3 gibberellins may be present in the liquid endosperm.

Open Access
Author:

Alternately bearing `Cheyenne' pecan [Carya illinoensis (Wangenh.) K. Koch] trees were studied to assess the temporal aspects of previous season fruit development on several reproductive and vegetative traits of horticultural importance. Action spectra were generated and used to identify the relative sensitivities of these traits to the temporal aspects of fruiting. Based on date of maximum rate of change in sigmoidal models fitted to these action spectra, the relative sensitivity of certain important growth and developmental parameters to fruit removal time was number of distillate flowers per terminal shoot > number of distillate flowers per flower cluster on lateral shoots> length of terminal shoots > percentage of lateral shoots with fruit= catkins per terminal shoot at top of the tree> percentage of terminal shoots with fruit > catkins per standard terminal shoot> shoots produced per l-year-old branch> percentage of l-year-old shoot death. Maximum rates of change for these reproductive and vegetative parameters were typically during the dough stage of ovule development; however, substantial change also occurred for several parameters over a much wider developmental window. No evidence was found for a hormone-like translocatable factor from developing fruit that either promotes or inhibits flowering. Extending the time from nut ripening to leaf drop increased production of staminate and distillate flowers the following year and appeared to increase fruit set.

Free access
Author:

Abstract

Pecan [Carya illinoinensis) (Wangenh.) K. Koch] kernel development was characterized by an initial rapid localized expansion of testa and endosperm, which was closely associated with low levels of free and bound abscisic acid (ABA) and with high levels of gibberllin-like (GL) substances. Rapid cotyledon growth began with the termination of testa and endosperm expansion, which was subsequent to a sharp increase in both free and bound ABA. The rate of change for growth in kernel dry weight was highly correlated with the rate of change in levels of both free ABA (R 2 = 0.86) and bound ABA (R 2 = 0.88). Levels of GL substances (ng/g kernel), as measured by the dwarf pea and cucumber bioassays, were relatively low after the rapid accumulation of kernel dry weight, however, GL substances detected by the barley endosperm bioassay were high during the last 30 days of kernel development. Abscisic acid and GL substances seem to exercise a significant role in seed development.

Open Access
Author:

Abstract

The dynamics of indoleacetic acid (IAA), cis-trans abscisic acid (c,t-ABA), and gibberellin (GA)- and cytokinin-like compounds were measured in pecan [Carya illinoensis (Wang) K. Koch; cv. Desirable] buds following their release from imposed dormancy. Both bound and free ABA levels in apical and basal primary buds and in secondary buds declined 27 days prior to budbreak until the time of budbreak, with the exception of a steady rise in free ABA in secondary buds. During this period IAA initially dropped sharply, remained low, and finally increased again at budbreak. Cytokinin-like substances peaked after the drop in IAA but prior to the peak in gibberellin-like substances which occurred during bud swelling. The findings raise the possibility of a key regulatory role for IAA, possibly through its influence on regulation of bud cytokinin and gibberellin levels via their metabolism in roots. Growth regulator dynamics during pecan budbreak are discussed in relation to the hormonal theory versus tissue sensitivity to growth regulators.

Open Access
Authors: and

Semi-parasitic evergreen mistletoe (Phoradendron flavescens Nutt.) is an increasingly serious weed causing loss of nut yield and tree vigor in pecan [Carya illinoinensis (Wangenh.) K. Koch] orchards of the southeastern United States. Several herbicides and growth regulators were evaluated for efficacy against mistletoe. The dimethylamine salt of 2,4-D proved to be an effective control agent. Ethephon, glyphosate, paraquat dichloride, and polyborate exhibited little or no long-term efficacy. The dimethylamine salt of dicamba also killed mistletoe, but exhibited potential for harming host trees. Dormant season treatment of mistletoe clusters with 2,4-D reduced photosynthesis by about one-third soon after treatment, and by ≈90% from 6 to 16 weeks posttreatment, but clusters did not die until ≈4 months posttreatment. Host limbs, less than ≈3 cm in diameter at the site of mistletoe attachment, usually died within 12 months of 2,4-D treatment of the associated mistletoe cluster. Treatment of entire host trees with 2,4-D did not harm trees if applied prior to ≈1 week of budbreak. Spot treatment of mistletoe clusters, with 2,4-D at 1.2 to 2.4 g·L-1 a.i. (plus 2% crop oil), ≈2 to 3 weeks before budbreak, gave effective long-term control of mistletoe. The inclusion of a crop-oil in the 2,4-D spray greatly increased efficacy. Chemical names used: (2-chloroethyl) phosphonic acid (ethephon).

Free access
Authors: and

Abstract

Immature embryos were excised during kernel development from fruits of the pecan [Carya illinoensis (Wangenh.) C. Koch] cultivars Desirable and Stuart. The cotyledons were removed and the main embryo axes were used as explants. Explants were cultured in vitro on media containing various levels of cytokinins and auxins. Morphogenesis in ‘Stuart’ preceded that of ‘Desirable’ by 1 to 2 weeks. In both cultivars, the percentage of embryo axes forming shoots only or both shoots and roots increased until ≈4 to 6 weeks before nut maturity, as judged by shuck dehiscence. After this time, developmental responses declined. Production of normal plants was highest on a medium containing IBA, BA, and kinetin at 0.5, 4.4, and 9.3 μM, respectively. Shoots only were obtained on a medium containing cytokinin without auxin and roots only on a medium containing auxin with no cytokinin. Axillary shoots elongated from embryo axes of both cultivars. This response was greatest on a medium containing cytokinin as the only hormone for ‘Desirable’, but with both auxin and cytokinin for ‘Stuart’. Chemical names: indole-3-butyric acid (IBA); N-(phenylmethyl)-1H purin-6-amine (BA); N-(2-furanylmethyl)-1H-purin-6-amine (kinetin).

Open Access
Authors: and

Abstract

Twenty-one days of foliar feeding in late spring by the blackmargined aphid [Monellia caryella (Fitch)] on a mature ‘Stuart’ pecan tree [Carya illinoensis (Wang.) K. Koch] reduced soluble sugars and starch in leaves to 82% and 79%, respectively, of the aphid-free control. Chlorophyll levels were unaffected. Sugars were reduced to 75% of the control in both 1- and 2-year-old branches. Starch in 1-year-old branches was reduced to 71%, but was unchanged in 2-year-old branches.

Open Access
Authors: and

Abstract

The early-spring mechanical removal of various combinations of buds from one-year-old branches of pecan [Carya illinoensis (Wang.) K. Koch, cv. Desirable] increased the number of lateral shoots and indicated the potential for development of both pistillate and staminate flowers and mature nuts from primary, secondary, and tertiary buds from nodes throughout the length of one-year-old branches. ‘Desirable’ was found to possess strong apical dominance; thus, bud removal and pruning treatments did not greatly increase the development of greater than normal numbers of lateral shoots. Methods that could block apical dominance and allow continued development of young shoots that normally abort appear to have potential of greatly increasing crop productivity.

Open Access