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- Author or Editor: L. E. Powell x
- Journal of the American Society for Horticultural Science x
Abstract
Single axillary bud explants of apple (Malus domestica Borkh.) were removed from ‘Antonovka’ seedlings or from ‘Delicious’ trees budded on seedling rootstocks, and cultured aseptically under controlled conditions. Many excised buds grew, even though similar buds on intact resting trees did not. Chilling excised buds of ‘Antonovka’ seedlings for 2 weeks in vitro did not increase the number of bursting buds, but promoted shoot elongation on some dates. Chilling ‘Delicious’ trees for 6 and 8 weeks before excising buds promoted both bud burst and shoot elongation. A substantial number of buds excised from ‘Delicious’ trees chilled for as long as 21 weeks did not burst, suggesting other limiting factors.
Abstract
Studies were conducted to determine the effect that plant hormones such as auxins, gibberellins, and cytokinins might have on the mobilization of 32P in apple seedlings grown in the greenhouse. Prior to the hormone treatments the seedlings were defoliated and the apex removed to avoid competition. Experiments with 32P indicated that auxins, gibberellins, and cytokinins could direct the transport of 32P especially when used in various mixtures. It was found that 32P could be mobilized acropetally, basipetally, and into and out of leaves depending on the area treated with the hormones. Their effect in mobilizing 32P was less evident in seedlings that had ceased growth, with subsequent terminal bud formation, than in growing seedlings. It was also found that 32P was mobilized through the phloem and required the synthesis of protein.
Abstract
Indoleacetic acid (IAA), gibberellins A4 + A7 (GA4&7) and benzyladenine (BA) were applied to apple seedlings to determine their influence on movement or translocation of 14C-sorbitol, 14C-glycine, 14C-naphthaleneacetic acid (14C-NAA), 3H-gibberellin A1 (3H-GA), and 14C-kinetin. The materials mobilized 14C-sorbitol in an acropetal direction, but only after root competition had been eliminated by steam girdling. A mixture of the 3 growth substances brought about mobilization of 14C-glycine acropetally that was greatly enhanced after root competition had been eliminated. 14C-NAA was not mobilized acropetally or basipetally by GA4&7, and/or BA. BA mobilized 3H-GA1 acropetally and mobilization was enhanced by the addition of IAA. A mixture of IAA and BA also mobilized 3H-GA1 basipetally. An acropetal movement of 14C-kinetin was induced only with a mixture of GA4&7 and IAA.
Abstract
Levels of free and hydrolyzable abscisic acid (ABA, H-ABA) in vegetative apple (Malus domestica Borkh.) buds were measured by electron capture gas chromatography. ABA level was high during midsummer both before and after entry into dormancy, increased to a maximum just prior to leaf fall, and decreased to a minimum just prior to bloom. H-ABA level was low during midsummer, increased gradually during fall and winter, reached a maximum during the early stages of bud development, and then decreased very rapidly just prior to full bloom.
Abstract
Abscisic acid (ABA) and its water soluble glucoside diffused from leaves through petioles and along the axes of seedlings of tea crabapple (Malus hupehensis, Rehd.). The apparent mobility of the glucoside was considerably greater than that of free ABA. Concentrations of extractable and diffusible ABA were greatest in growing shoot tips. ABA from mature leaves diffused down the petiole more readily than from younger leaves. The enhanced liberation of inhibitor from older leaves may result in greater quantities of mobile ABA as the season progresses.