ISHS Acta Horticulturae 179: V International Symposium on Growth Regulators in Fruit Production
LONG-TERM EFFECTS OF PACLOBUTRAZOL (CULTAR) ON APPLE-TREE SHOOT GROWTH, CROPPING AND FRUIT-LEAF RELATIONS |
| Authors: | D.C. Elfving, J.T.A. Proctor |
| Abstract:
Paclobutrazol (Cultar) was applied as foliar or soil treatments to 6-year-old 'Summerland McIntosh'/MM.106 or 12-year-old 'Spartan'/M.26 trees in spring, 1983. No effects on growth or yield were observed in 1983. Bloom, fruit-set and trunk growth in 1984 were similarly unaffected. Paclobutrazol treatments in 1983 produced reductions in shoot number rather than length in 1984. Lateral-shoot development was preferentially inhibited over terminal-shoot growth. Yield in 1984 was either unaffected or decreased in treated trees. Mean fruit weight decreased only when shoot growth was reduced to less than 50% of control. Crop load, leaf-fruit relations and photosynthesis could not account for reduction in mean fruit weight. Fruit length-diameter ratio and pedicel length in 1984 proved particularly sensitive to 1983 paclobutrazol treatments. Significant shortening and thickening of pedicels and flattening of fruit occurred at 1983 paclobutrazol doses producing modest reductions in 1984 shoot growth. | |
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