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- Author or Editor: Walter J. Kender x
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.
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.
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).
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.
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).
Endogenous concentrations of IAA and ABA in the peel, pulp, seed, and abscission zone of mature `Valencia' oranges [Citrus sinesis (L.) Osbeck] were determined by high-performance liquid chromatography and enzyme-linked immunosorbent assay from early November 1998 to mid-June 1999. Ethylene production of mature `Valencia' oranges during the same period was determined by gas chromatography. IAA concentrations in the pulp and seed were three to five times lower than those in the peel over the 7-month observation period. IAA concentration in the abscission zone and peel was high from late April to mid-May, the period of less responsiveness to abscission chemicals. ABA concentration in the pulp was low over the entire observation period. ABA concentration in the abscission zone and peel was low during the less responsive period. Ethylene production was always low except for a slight increase during late December and early February. The IAA to ABA ratio was high in the fruit abscission zone during the less responsive period. Fruit detachment force of CMN-pyrazole-treated fruit was positively correlated with the ratio of endogenous IAA to ABA or endogenous IAA, but negatively to endogenous ABA in the fruit abscission zone. These data suggest the balance between IAA and ABA in the fruit abscission zone may be an important factor in determining sensitivity and thereby the response of mature `Valencia' orange fruit to abscission chemicals. Chemical names used: abscisic acid (ABA); indole-3-acetic acid (IAA); 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMN-pyrazole).