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- Author or Editor: D. A. Williamson x
Abstract
The cover depicts a cross-sectional photomicrograph of a root from peach treated with a soil application of paclobutrazol. The 14-μm section was taken about 2 mm from the root apex. The tissue was fixed and embedded by conventional methods similar to those described by Sass (8), then doublestained with safranin and fast green. Photomicrographs were taken at × 180 with Ektachrome film (Kodak) using a Leitz Dialux 20 research microscope equipped with an Orthomat automatic microscope camera.
Abstract
Seed of snap bean, Phaseolus vulgaris L. cv. Avalanche were separated into 3 length or 3 diameter groups and then each group separated into 3 classes based on aerodynamic properties. The grading procedure resulted in seed grades having large differences in physical characteristics, growth and yield responses. Yield response potential of snap bean was determined primarily by seed weight. A grading method utilizing size grading based on seed diameter followed by aspiration in a vertical air column was the most effective method of eliminating seed with low yield potential.
Abstract
Root growth of cucumber (Cucumis sativus L.) was not greatly restricted by soil strength less than 500 kPa (5 bars). Root growth was inhibited 80% at a soil strength of 850 kPa. Mechanical compaction produced by a tractor wheel resulted in a 50% reduction of tissue NO3 at comparable soil NO3 levels, a 25 to 35% yield reduction, and a decrease in fruit length/diameter ratio. The effects of soil compaction could be partially alleviated by increasing the rate of nitrogen fertilization; however, a 3-fold increase in N fertilization did not completely counteract the effect of compaction on cucumber yield. A system for cucumber seedbed preparation which reduces soil compaction is presented.
Abstract
Removal of 20% of the seed of a commercial ‘Poinsett’ seed lot in a vertical air column increased the mean thickness and weight of the remaining seed. Fruit yield was increased by use of thicker, heavier seed when yield potential was not limited by high soil strengths. Seed grading effect on cucumber yield was less when either soil compaction or climactic conditions reduced yield potential. A combination of both yield limiting factors eliminated seed grading effect. Yield response to source of nitrogen was different when cucumbers were grown on compacted and noncompacted seedbeds. An interaction of seed grade, nitrogen source and seedbed compaction on marketable fruit yield was found.
Abstract
Plant and root growth and root distribution of ‘Dixie’ squash (Cucurbita maxima Duch.) were reduced by mechanical soil compaction of a Tifton loamy sand soil. Soil atmospheric O2 and CO2 concentrations were not affected by soil compaction. Marketable fruit yield was reduced 46 to 58% by increased soil strength produced by tractor wheel traffic. Nitrogen from Ca(NO3)2 produced greater yields in non-compacted plots and smaller yields in compacted plots than NH4NO3.
Abstract
Seed of 11 cultivars of snap bean, Phaseolus vulgaris L., were separated by aerodynamic properties in a vertical air column. Seed physical characteristics associated with air column separation were weight, density, volume, diameter, and length. The separation technique did not affect seed germination, seedling emergence, or plant survival at full expansion of the first trifoliate leaf growth stage. However, seed remaining in the air column after aspiration produced fewer weak plants and fewer plants with root rot at the first trifoliate leaf. These seed produced a greater plant stand, a greater pod weight per plant, a more uniform pod size distribution, and a greater yield at harvest than the seed removed. Yield from seed remaining after air column aspiration was 21% greater than from non-graded seed.
Planting treatments were evaluated for their influence on shoot development and root distribution of own-rooted `Redhaven' peach [Prunus persica (L.) Batsch] trees planted to high density (5000 trees/ha). Planting in fabric-lined trenches (FLT) or narrow herbicide strips (NHS) reduced the diameter and length of primary shoots, the number and combined length of second-order shoots, and the total length of shoots. Flower density, the number of flowers per node, and the percentage of nodes containing one or more flowers were increased for FLT trees but not for NHS trees when compared with controls. The length of primary shoots increased quadratically for all treatments with increasing limb cross-sectional area (LCA). The total length of shoots increased more with increasing LCA for controls than for FLT trees. The number of flowers per shoot increased linearly for all treatments with increasing LCA values. Root concentration decreased with increasing soil depth and distance from tree rows for all treatments. Reduced widths of weed-free herbicide strips had little effect on root distribution. Roots of FLT trees were reduced in number and restricted vertically and laterally when compared with other planting treatments. The FLT treatment modified shoot development by reducing the length of total shoots and length of primary shoots across LCA values measured when compared with NHS and control-treatments.
Three southern highbush blueberry cultivars (Vaccinium corymbosum hybrids) were mechanically harvested (MH) or hand-harvested (HH) and commercially packed before storage for 14 days at 1 °C in two successive years. MH fruit were softer, had lower ratings for overall appearance, and lost up to 20% more fresh weight than HH fruit after 14 days storage. MH ‘Meadowlark’ had fewer soft fruit (<35%) during storage than either ‘Sweetcrisp’ or ‘Farthing’; however, the latter two cultivars had lower incidences of shrivel and weight loss. Fruit in the 2010 season were more susceptible to bruising than those from the 2009 season; however, soluble solids content (SSC), total titratable acidity (TTA), and ascorbic acid concentration remained constant during storage and between seasons. ‘Meadowlark’ had the highest sugar to acid ratio (25.0). Successful implementation of MH of southern highbush blueberries for fresh market will only be commercially feasible if harvest impacts are further reduced.
Abstract
Ethylene is produced by cucumber fruits (Cucumis sativus L.), at a rate which is size dependent. Small fruits (<2.6 cm diam) produced substantially more ethylene/kg fruit than did large fruits (2.6-3.8 and 3.8-5.1 cm diameter). Respiration was similarly affected. Mechanically harvested fruits produced 2 to 3 times more ethylene than did hand-harvested fruits. Texture profile analysis (TPA) of cross-sections of fruits treated 48 hr with 0, 0.1, 0.5, 1.0, 5.0 and 10.0 µl/liter ethylene indicated little change in textural parameters at concentrations below 10.0 µl/liter. Ethylene treatment, especially high concentrations, decreased fruit chlorophyll content. Greatest chlorophyll loss was at the stem-end of the fruit. Ambient concentrations of ethylene in well-ventilated trucks of cucumbers were not great enough to present a quality problem for processing cucumbers.
The Y locus of peach [Prunus persica (L.) Batsch] controls whether a tree will produce fruit with white or yellow flesh. Flesh color has implications for consumer acceptance and nutritional quality, and improved cultivars of both flesh types are actively sought. This paper focuses on evidence that the flesh color locus also controls senescent leaf color (easily observed in the fall) and hypanthium color. In two progeny populations totaling 115 progeny plus their parents, the three traits co-segregated completely. Trees carrying the dominant allele for white flesh had yellow senescent leaves and yellow hypanthia, while homozygous recessive yellow-fleshed types exhibited orange senescent leaves and orange hypanthia. Senescent leaf color was also measured quantitatively, with major colorimetric differences observed between white-fleshed and yellow-fleshed progeny. Senescent leaf hue angle and reflected light wavelengths of 500 to 560 nm were the parameters most affected by the flesh color locus. Results were verified with 10 white-fleshed and 10 yellow-fleshed cultivars. The findings show that the Y locus in peach controls the type and concentration of carotenoids in multiple organs, including fruit, leaves, and flowers. The ability to discriminate between white and yellow flesh color using a simple visual method, applicable in plants not yet at reproductive maturity, is valuable to breeders wanting to save time, growing space, and money.