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  • Author or Editor: Martin J. Bukovac x
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Abstract

I am deeply honored to have been selected to participate in this centennial recognition of the enactment of the Hatch Act signed 100 years ago. I am particularly pleased because my entire educational and professional life has been interwoven with the goals and objectives of this far-reaching concept in agricultural research. Celebrations of this kind, especially centennials, provide opportunities to reflect on accomplishments of the past and to dream of the future.

Open Access

The importance of spray application and the role of spray additives are reviewed in reference to increasing the effectiveness of plant growth regulators (PGR). The spray application process is composed of a number of interrelated components, from formulation of the active ingredient into a sprayable, bioactive solution (emulsion/suspension), to atomization, delivery, retention, and penetration into the plant tissue. Each of these events is critical to performance of the PGR. Also, each can be affected by spray additives, particularly adjuvants, which may be incorporated in the formulation of the active ingredient or added to the spray mixture. The role of the individual components and effects of spray adjuvants, particularly surfactants and fertilizer adjuvants, on the component processes are discussed.

Full access

Abstract

(2-Chloroethyl)phosphonic acid (ethephon) applied as a foliar spray at 250 to 1000 ppm reduced fruit removal force by 30 to 60%, and significantly increased (50 to 300%) the percentage fruit removed by machineharvest in sweet cherry (Prunus avium L.). The response was more pronounced as time between application and harvest increased, with optimum results between 7 and 14 days before harvest. Fruit quality was equal to or better than that of the control, the greatest effect being a reduction in percentage of bruised fruit and fruit with persisting pedicels. The degree of bruising was directly related to the duration of the shaking period. Efficiency of machine-harvest was markedly increased (20 to 30%) by selectively removing the lower branches and heading back long willowy branches around the periphery of the tree. Excessive leaf abscission and gummosis were common at the 1000 ppm rate and occasionally at the lower rates, particularly when trees were under moisture or disease stress.

Open Access

Abstract

The abscission of maturing fruit is an important process which has not been extensively studied. Earlier reports on fruit abscission in the cherry have stressed premature drop associated with failures in fruit-set (2, 20). With the development of various mechanical harvesting devices and the rapid commercial adoption of machine harvesting (14, 15), attention has now been focused on abscission of mature fruit.

Open Access

The effects of CPPU [forchlorfenuron, N-(2-chloro-4-pyridinyl)-N-phenylurea] on berry development of Vitis labrusca and V. labrusca × V. vinifera cultivars was evaluated under field conditions. A concentration response was initially established by spraying clusters of `Himrod' at a mean berry diameter of about 5 mm with 0, 5, 10, or 15 mg·L–1 CPPU. Berry enlargement was monitored (16, 30, 44, and 59 days after treatment) during development. Cluster mass, number of berries per cluster, berry mass and firmness, and °Brix were determined at harvest. Berry mass was dramatically increased (2.3 versus about 3.6 g/berry) at harvest by all concentrations of CPPU. Cluster mass and compactness were also increased and berry firmness was linearly related to CPPU concentration (r 2 = 0.997). There was no significant effect on number of berries per cluster (79 to 86). °Brix, rachis necrosis at harvest, and berry abscission after 30 days of refrigerated storage (1 °C) were significantly reduced. Effect of time of CPPU application (0, 5, and 10 mg·L–1) was established by treatment of clusters at mean berry diameters of about 4, 5, 7, and 9 mm. Response was indexed by following berry enlargement at 14, 28, 42, and 56 (maturity) days after treatment. Maximum berry size for both 5 and 10 mg·L–1 was obtained from applications at 4 to 7 mm berry diameter. Relative response of seedless and seeded cultivars was compared by application of CPPU at 0, 5, 10, or 15 mg·L–1 to clusters (4 to 6 mm berry diameter) of seedless `Vanessa' and `Lakemont' and seeded `Concord' and `Niagara'. Bioresponse was determined by a time course of berry enlargement and berry and cluster mass, number of berries per cluster, and rating cluster compactness at maturity. Except for `Lakemont' at the 5 mg·L–1 concentration, CPPU at all concentrations increased seedless berry diameter significantly from the first measurement at 14 through 56 days after application. Berry and cluster mass and cluster compactness were significantly increased in `Vanessa'. In contrast, the only effect of CPPU on the two seeded cultivars was an increase in berry size in `Concord' and an initial increase in berry size 14 days after application in `Niagara'.

Free access

Water conductance of the cuticle of mature fruit of apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf., `Golden Delicious' Reinders/`Malling 9' (M.9)], sweet cherry (Prunus avium L., `Sam'/`Alkavo'), grape (Vitis vinifera L.), pepper (Capsicum annuum L. var. annuum Fasciculatum Group, `Jive'), and tomato (Lycopersicon esculentum Mill.) was de ter mined using excised epidermal segments (consisting of epidermis, hypodermis, and some cell layers of parenchyma) and enzymatically isolated cuticular membranes (CM) from the same sample of fruit. Segments or CM were mounted in diffusion cells and transpiration was monitored gravimetrically. Conductance (m·s-1) was calculated by dividing the flux of water per unit segment or CM area (kg·m-2·s-1) by the difference in water vapor concentration (kg·m-3) across segments or CM. Transpiration through segments and through CM increased with time. Conductance of segments was consistently lower than that of newly isolated CM (3 days or less). Conductance decreased with increasing time after isolation for apple, grape, or sweet cherry CM, and for sweet cherry CM with increasing temperature during storage (5 to 33 °C for 4 days). There was no significant effect of duration of storage of CM on conductance in pepper or tomato fruit. Following storage of CM for more than 30 days, differences in conductance between isolated CM and excised segments decreased in apple, grape, and sweet cherry, but not in pepper or tomato. Use of metabolic inhibitors (1 mm NaN3 or 0.1 mm CCCP), or pretreatment of segments by freezing (-19 °C for 18 hours), or vacuum infiltration with water, had no effect on conductance of apple fruit segments. Our results suggest that living cells present on excised segments do not affect conductance and that epidermal segments provide a useful model system for quantifying conductance without the need for isolating the CM. Chemical names used: sodium azide (NaN3); carbonylcyanide m-chlorophenylhydrazone (CCCP).

Free access

Abstract

The development of the embryo sac was followed during the pollination period in ‘Montmorency’ sour cherry (Prunus cerasus L.) and related to fruit set. Twenty five percent to 40% of the embryo sacs were incomplete, degenerating, or contained four nuclei or fewer at anthesis and were considered nonfunctional. The effective pollination period extended for 3 to 5 days in each of two growing seasons, and fruit set ranged from 14% to 26%. The incidence of nonfunctional ovules at anthesis did not appear to be sufficient to fully account for the limited fruit set observed. Other factors, most likely physiological, play a contributing role.

Open Access

Micelles of two nonionic surfactants (Triton X-114 and Neodol 91) were shown by gel filtration chromatography to solubilize nondissociated NAA molecules in aqueous solutions. Micelle solubilization of nonpolar active ingredients in aqueous spray systems alters the distribution of the chemical in the spray solution and may influence chemical deposit formation and penetration characteristics. Chemical names used: 2-(1-naphthyl)acetic acid (NAA), octylphenoxy polyethoxylate-7.5 POE (Triton X-114), linear alcohol (C9-11) polyethoxylate-6 POE (Neodol 91).

Free access

Abstract

Growth and form of numerous fruits are closely related to the number and distribution of developing seeds. The effect of seeds on fruit shape is particularly apparent for the Conference pear, where the length: width ratio is inversely related to seed content (10).

Open Access

Abstract

The presence of abscisic acid (ABA) in both conjugated and free forms was established by thin-layer and gas-liquid chromatography and by combined gas chromatography-mass spectrometry. The concentration of the free acid was greater than that of conjugated ABA early in fruit development (Stages I and II); however, the conjugated form was more prevalent than the free acid during Stage III. The highest concentration of both the free acid and the conjugated ABA was found during periods of most active fruit enlargement and low concentrations during the retarded phase of pericarp growth. The conjugated form represented a significant and, during Stage III, the major portion of the total ABA present.

Open Access