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Richard P. Marini, Ross E. Byers, Donald L. Sowers, and Rodney W. Young

Five apple (Malus domestica Borkh.) cultivars were treated with dicamba at concentrations of 0 to 200 mg·liter-1 during 3 years. Although the response varied with cultivar, dose, and year, dicamba always delayed fruit abscission. At similar concentrations, dicamba usually reduced fruit drop more than NAA, but less than fenoprop. Dicamba at 10 mg·liter-1 effectively delayed drop of `Delicious', whereas 20 to 30 mg·liter-1 was required for `Red Yorking', `Rome', `Winesap', and `Stayman'. Dicamba did not influence flesh firmness, soluble solids content, water core, or starch content at harvest or after storage. Chemical names used: naphthaleneacetic acid (NAA); 2-(2,4,5-trichlorophenoxy)propionic acid (fenoprop); 3,6dichloro-2-methoxybenzoic acid (dicamba).

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Uday K. Tirlapur, Guglielmo Costa, Carlo Malossini, Giannina Vizzotto, and Mauro Cresti

`Redhaven' peach (Prunus persica L. Batsch) fruit abscission has been investigated using scanning electron microscopy, computer-assisted video-image analysis, and confocal laser scanning microscopy in conjunction with chlorotetracycline and ethidium bromide as fluorescent probes for membrane Ca2+ and nuclear DNA. This enabled us to document the morphological changes of the cells, distribution patterns of membrane Ca2+ in the constituent cells of the abscission zone, and the nuclear morphology with accompanying changes in nuclear DNA. The digitized images of CTC-fluorescence emissions revealed that the membrane Ca2+ levels in the pre-abscission zone (control) is uniform and similar to that present in the cells of the spongy proximal region of the peduncle and that of the fruit parenchyma. However, with the induction of abscission, 2 days after embryoctomy, there was a significant increase in membrane Ca2+ in the cells of the abscission zone compared to the neighboring cells of the fruit and the peduncle. Thereafter, with the gradual separation of the cells and the concomitant vacuolation, the membrane Ca2+ level decreased substantially. Confocal imaging of EB labeled cells of the abscission zone before induction invariably revealed a well-organized nucleus. However, during cell separation, significant changes in the cellular and nuclear morphology occured, including 1) rounding of cells, 2) reduction in the nuclear volume, and 3) concomitant fragmentation of nuclear DNA. The possible role of Ca2+ during the process of peach fruit abscission and nuclear DNA fragmentation leading to cell death is discussed. Chemical names used: chlorotetracycline (CTC), ethidium bromide (EB).

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Luis Pozo and Jacqueline K. Burns

the harvesting season ( Burns et al., 2005 ; Li et al., 2008 ). Work to register this product for Florida mature citrus fruit abscission is ongoing. In the event that CMNP registration fails or is delayed, other abscission agent options such as

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Derek W. Barchenger, Danise L. Coon, and Paul W. Bosland

initiate abscission of flowers and peduncles of mature inflorescences ( Weis et al., 1991 ). Kahn et al. (1997) evaluated the effect of fall ethephon applications at concentrations of 0, 1000, 2000, 3000, and 4000 ppm to control fruit abscission in paprika

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Martin J. Bukovac, Paolo Sabbatini, Philip G. Schwallier, and Michael Schroeder

The discovery of auxins provided the basis for current chemical fruit thinning of apples. The promotion of postbloom fruit abscission was first reported over 60 years ago ( Davidson et al., 1945 ), and since then, synthetic auxins, NAA and its

Open access

Steven A. Weinbaum and Roy K. Simons

Abstract

Comparisons of seed tissues from persistent and potential drop apple fruit (‘Golden Delicious’) 3 weeks after full bloom suggested that fruit commitment to abscise (determined by a reduced rate of fruit enlargement between 16 and 21 days after full bloom) preceded ultrastructural evidence of degenerative or functional changes in embryo or endosperm tissue. The results do not support the concept of ‘embryo abortion’ as a causal mechanism in natural fruit abscission during post-bloom.

Open access

Mokhles A. Elsysy, Andrew Hubbard, and Todd C. Einhorn

fruitlet diameter. Delayed postbloom chemical thinning poses a considerable risk to growers because chemical stimulation of fruit abscission decreases with fruit development. Higher carbohydrate status of apple trees is purported to reduce susceptibility of

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Keith Yoder, Rongcai Yuan, Leon Combs, Ross Byers, Jim McFerson, and Tory Schmidt

fruit set. These results suggest that LLS + FO applied over the bloom period causes flower or fruit abscission mainly through inhibiting pollen germination, pollen tube growth in the style, and fertilization. This suggestion is supported by the fact that

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Madhumita Dash, Lisa K. Johnson, and Anish Malladi

Shading during early apple fruit development decreases fruit growth and induces fruit abscission and has been used to understand processes that affect thinning ( Byers et al., 1985 , 1990a , 1990b , 1991 ). During early fruit development, active

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Lisa Tang, Sukhdeep Singh, and Tripti Vashisth

of the mechanism that underlies how HLB increases mature fruit abscission can be a key for the development of strategies to mitigate HLB-associated preharvest drop and thereby improve the yields. The increased occurrence of sieve pore plugging and