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  • Author or Editor: J.A. Flore x
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Objectives of this experiment are: 1) to compare crop quality and yield, and insect disease populations between orchard systems that employ integrated crop management technologies with conventional systems, and 2) to monitor soil and fruit chemical residues to determine the effectiveness of these systems. In 1990, 6 one-acre plots were established at the Southwest Michigan Research and Extension center, with 1/3 acre of peaches planted in the center of each plot. Plots were separated by at least 200 m. Conventional culture (clean cultivation, ground application of fertilizer, scheduled pesticide application, dormant pruning) and Integrated Crop Management plots (use of fertigation or manure for N, pesticide application based on trap counts, endophytic rye, pheromone disruption of oriental fruit moth and mulch for weed control) were established. In phase I of the project (1990), insects and diseases, as well as crop growth (Reproductive and Vegetative) were monitored. In phase II (1991), soil and fruit pesticide residues will be determined and compared for the three different strategies. This paper is intended to stimulate discussion and only limited data will be presented for the 1st year results.

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Abstract

To determine if the net CO2 assimilation and water use efficiency (WUE) of highbush blueberry under high temperature can be improved genetically, gas exchange determinations were made for a selection of Vaccinium darrowi Camp (Florida 4B), a highbush cultivar (Bluecrop) (V. corymbosum L.), their F1 hybrid (US75), and two crosses of the F1 hybrid to another improved genotype (US239 and US245). All genotypes responded parabolically to increasing temperature at vapor pressure deficits <1 kPa. Maximum CO2 assimilation of US75 (15 µmol·s–1·m–2) was 30% to 40% higher than either parent. Carbon dioxide assimilation of US75 and Florida 4B was optimum at 30°C and that of ‘Bluecrop’ at 20°. The optimum for US239 was similar to ‘Bluecrop’, and that of US245 to Florida 4B. Florida 4B had higher WUEs than ‘Bluecrop’ at both 20° (5.64 µmol CO2/mmol H2O to 4.01) and 30° (3.73 to 2.53). US239 and US245 had significantly (P < 0.05) higher WUEs at 30° than did ‘Bluecrop’. Residual conductance to CO2 (gr) decreased in ‘Bluecrop’ when temperature was raised from 20° to 30°, but increased in all other genotypes. Due to the favorable gas exchange properties of US75 and US245 at 30°, we suggest that the high temperature tolerance of V. darrowi may be heritable and that US245 may be used to improve the heat tolerance of highbush blueberry.

Open Access

Abstract

Chrysanthemum morifolium Ramat. ‘Bright Golden Anne’ cuttings were grown in a controlled environment at 50, 325, or 600 µmol·s–1·m–2 for 5 weeks at a 10-hr photoperiod. Photosynthetic rates were determined on individual leaves with an open gas analysis system at a range of photosynthetic photon flux (PPF) levels. Plants grown at low PPF (50 µmol·s–1·m–2) had a maximum net photosynthetic rate (Pn) that was about 39% of that for plants grown at 325 µmol·s–1·m–2. Pn of plants grown at 325 or 600 µmol·s–1·m–2 did not differ significantly.

Open Access

Chambers were constructed to measure gas exchange of entire potted grapevines (Vitis vinifera L.). The plant enclosures were constructed from Mylar film, which is nearly transparent to photosynthetically active radiation. Maintaining a slight, positive, internal pressure allowed the Mylar chambers to inflate like balloons and required no other means of support. The whole-plant, gas-exchange chamber design and construction were simple and inexpensive. They were assembled easily, equilibrated quickly, and did not require cooling. They allowed for the measurement of many plants in a relatively short period. This system would enable the researcher to make replicated comparisons of treatment influences on whole-plant CO2 assimilation throughout the growing season. While CO2 measurement was the focus of this project, it would be possible to measure whole-plant transpiration with this system.

Free access

Abstract

Shade treatments giving 36% full sun or less reduced both hardiness and shoot cross-sectional area of one-year-old sour cherry (Prunus cerasus L. cv. Montmorency) and peach [Prunus persica (L.) Batsch cv. Redhaven]. Shade significantly reduced soluble carbohydrate in ‘Redhaven’.

Open Access

Abstract

Needle surface characteristics and NaCl penetration rates were compared and related to deicing salt spray injury for resistant Austrian pine, Pinus nigra Arnold, and susceptible Eastern white pine, Pinus strobus L. Stomata in longitudinal rows separated by parallel ridges characterized needle surfaces of both species; surface fine structure was free of trichomes or other recognizable structures. Pinus nigra in comparison to P. strobus had greater surface area (3.64 cm2/needle vs. 1.87 cm2/needle) and larger quantities of epicuticular wax 183 μg/cm2 vs. 75 μg/cm2). Thin-layer chromatography indicated no distinct differences in epicuticular wax chemistry. Surface wettability, measured by contact angle, was similar. Retention of an aqueous solution was similar when needles were attached to fascicles. Penetration of 36C1 was significantly greater in needles of P. nigra on a surface area basis (P. nigra = 9,839 dpm/cm2, P. strobus = 3,503 dpm/cm2). No differences in penetration occurred when expressed on a fresh weight basis. Electron microprobe analysis substantiated a greater penetration of Na+ and Cl- in needles of P. nigra. Levels of Na+ were higher than Cl in both species. Triphenyl tetrazolium chloride studies indicated greater sensitivity to increasing concentrations of NaCl in needles of P. strobus and in P. nigra. Differences in species sensitivity appears to be related to protoplasmic sensitivity rather than to differences in penetration of Na+ and Cl ions.

Open Access

Auxin induction of ethylene, and fruit growth rates were investigated as early indicators of NAA thinning response for Golden Delicious, Red Delicious, McIntosh, Empire, and Tydeman's Red over a four period. Abscission at the end of the drop period was correlated with ethylene evolution from leaves 24-48 hours after NAA application and with changes in fruit growth at 2-3 day intervals through 10-14 days after application. Variation in ethylene evolution and fruit growth were also associated with environmental conditions prior to and at the time of NAA application to determine which factors have the greatest influence on response. Ethylene was a better predictor of final fruit drop than changes in fruit size for all varieties tested. However both performed very well. The ethylene bioassay requires more equipment, but the response is more-immediate. Bourse, and spur leaves as well as fruit were capable of producing ethylene in response to NAA application. Thinning response was greatest when all leaves and fruit were treated with NAA, followed by the bourse and spur leaves. Little or no response was produced when the fruit alone were treated. Concentration experiments and radioisotope data indicate that ethylene response is directly related to the amount of NAA absorbed. Regression analysis indicates that approximately 60% of the variation in response can be predicted by ethylene evolution

Free access

Abstract

Periderm from the roots of carrot (Daucus carota L.) was isolated enzymatically and analyzed anatomically and chemically during development. The outer transverse walls of the phellem layer formed a continuous, external membrane containing chloroform/methanol-soluble lipids. Separated by thin layer chromatography, these lipids contained at least 6 major chemical groups, the most abundant of which cochromatographed with fatty acids. Scanning electron microscopy revealed the absence of surface fine structure. The periderm membrane decreased in weight with development of the root, attributable to reductions in both chloroform/methanol-soluble and insoluble material per unit area.

Open Access

Abstract

A determinate cherry tomato (Lycopersicon esculentum Mill. cv Farthest North) was used to test whether fruit set involves mobilization of sucrose to the ovary, or whether mobilization occurs only after fruit growth commences. Following auxin treatment, average ovary fresh weight increased 0.4 mg and 3.6 mg during the first 24 and 36 hours, respectively. Radioactivity from foliar-applied 14C-sucrose was not significantly greater in auxin-treated ovaries than in water controls until 48 hours after treatment. Parallel data were obtained following pollination. Labelling with l4CO2 did not alter the response, nor did the time of labelling with 14C-sucrose. Thus, tomato fruit set per se does not appear to involve mobilization.

Open Access

Abstract

Light levels were estimated by hemispherical photography at 4 different times during the growing season, in 4 different peach [Prunus persica (L.) Batsch] hedgerow canopies: oblique fan, canted oblique fan, modified central leader, and open center. Greatest percentage of sky levels occurred in the area from above to 25 cm below the top of the canopy. There was little difference between canopy training systems except 1 m above the ground. Hedging improved the light microclimate in the canopies, but only within the top 25 cm. Spectral distribution determined in an open-center tree did not follow the general trend of total radiation. As shading increased, not all wavelengths were absorbed equally, resulting in a decrease of the visible to infrared ratio.

Open Access