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  • Author or Editor: D.D. Miller x
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Roots anchor the plant in the soil, absorb and translocate water and nutrients, synthesize and transport growth regulators and other organic compounds, provide a sink for carbohydrates from the shoots, and in some species act as storage organs. Most research on roots has dealt with their role in absorption. Root characteristics that affect the area of absorbing surface are important, i.e., root length density, number and type of root hairs, and mycorrhizal relations. With nutrients that diffuse slowly in the soil, such as P and K, root density is especially important. Factors that reduce root growth may injure the plant by reducing the volume and intensity of soil exploration. Fortunately, plants produce more roots than are needed for normal growth–insurance that the plant can survive stresses, purchased at a cost of the increased photosynthate and other materials required for the extra root production.

Open Access
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Pinto bean plants (Phaseolus vulgaris L. cv. Pinto 111) in the unifoliolate leaf stage were exposed for 3 hours to 0.8 ppm SO2, 0.25 ppm 03, or a mixture of the 2 pollutants at these concentrations at 15, 24, or 32° C. Foliage exposed to O3 alone developed adaxial stipple and leaves exposed to SO2 alone developed interveinal necrosis. The mixture of O3 and SO2 induced O3-type symptoms at 32° and SO2-type symptoms at 15°. Both symptom types were present at 24°. Some abaxial glazing or silvering was also induced by the mixture, and was most common at 15° and 24°. Ozone and SO2 each induced greater foliar injury at 15° or 32°, as compared to 24°. The mixture of O3 and SO2 induced greatest macroscopic foliar injury at 15°. The degree of adaxial vs abaxial leaf surface injury varied with temperature.

Open Access

This study examines the effect of multiple spray applications of Apogee on shoot growth and whole-canopy photosynthesis (WCPn) rate in young, bearing apple trees. Apogee increased fruit numbers and reduced shoot growth and inconsistently reduced leaf area but the reduction in photosynthetic area did not result in reduced WCPn or a detrimental effect on the fruit number:fruit size relationship. Since WCPn was not affected when leaf area was reduced by Apogee treatment, it suggests a greater photosynthetic efficiency of leaves on Apogee treated trees due to reduced shading. The use of Apogee for canopy management may produce a side-effect of increasing fruit set, which may be managed through a crop thinning program.

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Research on silicon nutrition has shown an increase in plant disease resistance to powdery mildew and pythium in some species, such as roses and cucumbers. However, the role of silicon for protecting plants from other stresses e.g., heat, drought, insects, etc., are not known. Two-year-old Sargent Crabapple Malus sargentii seedlings were subjected to 4 continuous days of 100 ml root application of potassium silicate at the rate of 0, 100, 200, and 400 ppm in Aug. 1998. After 3 days post-treatment, three detached leaves were placed in each of three petri dishes along with one adult female Japanese beetle (n = 3/concentrations) for 7 days. Potassium silicate at 100 ppm concentration significantly reduced percent leaf tissue eaten by adult Japanese beetles. There was not any statistical difference between control, 200, and 400 ppm application. The ion leakage of stem tissues of 100 and 200 ppm-treated plants were significantly lower than the control and 400 ppm. These lower ion leakage effects were also observed with red-osier dogwood stem tissues at 100 ppm. In a companion study fall webworm larvae were also exposed to the same above concentrations and treatments. There was not a significant effect of potassium pilicate on percent leaf tissue eaten by fall webworm larvae, suggesting that there may be differences between major groups of leaf-feeding insects. Leaf and root tissue analysis for Ca, K, Mg, Na, and Si will be reported.

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The objectives of this 7-year study were to determine the effect of repeated root pruning and irrigation on peach (Prunus persica L. Batsch) tree growth and soil water use. Root pruning began in the year of planting. Peach trees trained to a freestanding “Y” were root-pruned at flowering for 4 years (1985 to 1988) and subsequently at flowering and monthly through July for 3 years (1989 to 1991). Irrigation was withheld or applied the full season or only during stage 3 of fruit growth on root-pruned and non-root-pruned trees. Root pruning limited soil water availability throughout most of the growing season when irrigation was withheld; however, when irrigation was applied, there was no difference in soil water availability. The root length density of peach roots was greatest in the 0 to 30-cm depth, was promoted by irrigation, and was reduced by root pruning in the 0 to 90-cm root zone. Full-season irrigation increased vegetative growth over the nonirrigated treatments. Root pruning had no effect on vegetative growth measured as fresh pruned material. The treatments had no effect on leaf nutrient content, except that root pruning reduced Zn in five consecutive years. Fruit yield was reduced 1 in 5 years by root pruning, and full-season irrigation reduced yield in 3 of 5 years. Repeated root pruning restricted the lateral spread of the root zone and the use of soil resources, yet on the deep soil of this site, restricting the lateral extent of the root zone did not reduce vegetative tree growth.

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There is a need for Universities to encourage the continuing development of administrative skills among faculty in order to meet the challenges of the future. National and university initiatives have been developed to recognize this need. This sabbatic leave was developed to provide a significant, active, and meaningful administrative experience in the Office of the Dean at the University of Rhode Island.

This paper presents information on the structure, activities and involvement; and benefits to the participating faculty member, administrator, and institutions. The case study presented was both worthwhile and enriching for the participants, and strengthening for the sponsoring institutions.

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Rabbiteye blueberry [Vaccinium ashei (Reade)] production is increasing rapidly and growers of large plantings are converting rapidly from hand harvesting to machine harvesting. In three tests conducted during 1985, machine-harvested ‘Climax’ and ‘Woodard’ blueberries were softer and had higher moisture loss and decay than handpicked fruit after 1, 2, or 3 weeks of storage at 3°C. For both cultivars, berry firmness remained relatively constant during storage, whereas decay and weight loss increased. Berries of ‘Climax’ were firmer, less acidic, and developed less decay than ‘Woodard’. These results will assist in identifying the best fresh-market berries for export from the United States to Western Europe.

Open Access

Abstract

The purpose of this study was to determine if over-the-row mechanical shake-catch harvesting affected root development, leaf water stress, and yield of young ‘Golden Delicious’/M.7A and ‘Law Rome’/MM.111 apple (Malus domestica Borkh.) trees. Leaf water potential and temperature differential (canopy-air temperatures) were not significantly altered by mechanical harvesting. A minirhizotron technique did not detect changes in root distribution or root morphology. The fruit yield was unaffected by mechanical harvesting for four harvest years. No deleterious effects were detected as a result of over-the-row shake-catch harvesting.

Open Access

Abstract

No significant differences in bean seed yield of field grown ‘Dark Red Kidney’ beans were observed in plants treated at the green or white bud stage or in full bloom with (2-chloroethyl)phosphonic acid (ethephon) at concentrations ranging from 300 to 2400 ppm. Plants treated with 300 and 600 ppm ethephon produced and retained more flowers and matured 7-10 days earlier than untreated plants. Treatment with 1200 and 2400 ppm reduced flower production and delayed pod maturity.

Open Access

This study evaluated the total and marketable yield of three peach cultivars [Prunus persica (L.) Batsch. `Autumnglo', `Harvester', and `Redhaven'] when mechanical pruning and harvesting systems were used and trees were grown under three irrigation regimes. All cultivars were trunk-shaken using an experimental inertial shaker on an over-the-row (OTR) shake–catch harvester. `Autumnglo' also was hand-harvested at all irrigation regimes. Fruit damage was not significantly affected by irrigation. A significant source of fruit damage was pruning debris that remained in the canopy after hedging and became lodged in the fruit-conveying system, resulting in cultivar effects on fruit damage. Total yield of firm-ripe fruit was similar among cultivars in 1987 and 1988. However, `Autumnglo' trees had a higher percentage of marketable fruit than `Redhaven' or `Harvester' in 1987 and 1991. Mechanical harvesting appeared to accelerate the decline of `Autumnglo' as shown by tree deaths and greater symptom expression of Prunus necrotic ringspot virus. The potential for a single mechanical harvest of peaches is limited because of the difficulty in managing the ripening window, the high potential for fruit damage, and the possibility of accelerated tree decline for disease-susceptible cultivars.

Free access