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- Author or Editor: Walter J. Kender x
Mature grapevines (Vitis labrusca L. cv. Concord) in a factorial experiment testing effects of nitrogen fertilization, rootstock, flower cluster thinning, weed control, and pruning severity were evaluated for oxidant injury in 1971, 1972, and 1973. Nitrogen at 56 and at 112 kg/ha, own-rooted vines, and flower-cluster thinning reduced the incidence of oxidant stipple over no nitrogen, vines grafted on Couderc 3309 rootstock, and no thinning, respectively. In 1971, a relatively dry growing season, vines in clean-cultivated plots showed less oxidant injury than vines in sod plots. Pruning severity and training system had no influence on oxidant stipple development. Total N concentration of tissue was negatively correlated to oxidant stipple severity. The interactions between flower cluster thinning and weed control, rootstock, and N fertilization were significant, where thinning moderated the deleterious effects of these factors.
Calcium arsenate has been used to control the maggot in the lowbush blueberry fields of Maine since the late 1920's (6). The ability of arsenic to accumulate in the soil from repeated use to crops is known and has been reported by various researchers (1, 2, 3).
2-Chloroethylphosphonic acid (Ethrel), applied to grapevines as an aqueous spray at 100, 200, or 400 ppm, induced hard seed formation in 6 of 13 seedless cultivars studied. Viable seeds were produced in 2 of these cultivars.
Ethrel also promoted femaleness in the staminate flowers of the SO4 rootstock, resulting in fruit and hard seeds in this normally fruitless cultivar.
Orchard and greenhouse experiments were conducted to determine the influence of foliar applications of 6-benzylamino purine (BA) on branching of young apple trees. BA at 100 and 500 ppm, applied to actively growing shoots stimulated lateral bud growth on these shoots during the current season. The presence of fruit, termination of shoot growth, and the localization and non-persistence of BA reduced its effectiveness in breaking apical dominance. For optimum response to BA, multiple spray applications to actively growing shoots in a non-fruiting condition were required. Spray applications of BA failed to induce lateral bud growth on previous season’s wood.
The respiratory rates for eight stages of development of highbush and lowbush blueberry fruits ranging from immature green to senescence are presented. Based on these data, the blueberry exhibits a typical climacteric respiration curve. An increase in temperature from 15.5°C to 25.5°C resulted in an increase in the respiration rate.
The seasonal abscission response of mature `Valencia' oranges [Citrus sinensis (L.)Osb.] to 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMN-Pyrazole) was examined in relation to young fruit, shoot, and root growth. CMN-Pyrazole dramatically increased ethylene production in fruit and effectively reduced the fruit detachment force (FDF), except in a period of reduced response to CMN-Pyrazole in early May. Root growth was inhibited by trunk girdling, in combination with removal of spring vegetative flushes and flowers, but not by their removal alone. During the responsive period, there was no difference in both ethylene production and FDF of CMN-Pyrazole-treated mature oranges between 1) the unmanipulated trees and those manipulated by either 2) girdling, removal of spring flushes and flowers, or 3) removal of flushes and flowers alone. However, during the less-responsive period, ethylene production in CMN-Pyrazole-treated mature oranges was significantly lower while the FDF was higher from non-manipulated trees than from trees treated by either girdling and removal of flush, or only removal of flush. There was no difference in either ethylene production or FDF of CMN-Pyrazole-treated mature oranges between trees manipulated by girdling and removal of flush, and those by removal of flush alone. Flush growth terminated at least 2 weeks before the onset of the less responsive period. This suggests that the hormones from rapidly growing young fruit may be responsible for the less responsive period.
Effects of NAA, TIBA, ethephon, and CMN-Pyrazole on fruit detachment force (FDF) of mature `Valencia' and `Hamlin' orange [Citrus sinensis (L.) Osb.] fruit were examined in 2000 and 2001. NAA effectively inhibited the reduction in FDF or fruit abscission caused by ethephon when applied to the abscission zone 24 hours before ethephon application, but had no significant effect when applied to the fruit without contacting the abscission zone, or to the peduncle ≈4 cm above the abscission zone. TIBA, an auxin transport inhibitor, decreased FDF of mature fruit and promoted fruit abscission when applied alone as a spray to the canopy or directly to the fruit peduncle. This response was dependent on TIBA concentration. TIBA was more effective when applied in combination with ethephon or CMN-Pyrazole than alone. These results are consistent with our previous data that endogenous auxin concentration in the abscission zone of mature `Valencia' orange fruit is one of the factors controlling the sensitivity and thus the responsiveness of the abscission zone of mature fruit to abscission chemicals. Chemical names used: 5-chloro-3-methyl-4-nitro-pyrazole (CMN-Pyrazole); 2-chloroethylphosphonic acid (ethephon); naphthalene acetic acid (NAA); 2,3,5-triiodobenzoic acid (TIBA).