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  • Author or Editor: B. R. Roberts x
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Abstract

A population of 1945 seedlings of Ilex opaca Ait. was observed for a period of seven years after field planting. Sex determinations were obtained for 1930 of the seedlings. In general, the staminate plants flowered at an earlier age than did the pistillate plants. However, staminate and pistillate plants were found to occur with equal frequency (1.03/1.00).

Open Access
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Abstract

Two-year-old containerized seedlings of American sycamore (Platanus occidentals L.) were treated with maleic hydrazide (MH) before, after, or in the absence of sulfur dioxide (S02) fumigation. Exposure to S02 did not reduce the effectiveness of MH in controlling regrowth of this species. A strong negative linear trend was observed between SO2 concentration and sprout growth, either with or without MH treatment. In all instances, exposure to 1.0 ppm S02 resulted in high levels of phytotoxicity.

Open Access

Variations in the levels of volatile constituents during maturation of peaches were determined by means of capillary gas chromatography. C6 aldehydes were the major volatile compounds isolated from immature fruit, however, as the fruit matured, levels of the C6 aldehydes decreased. The final period of peach maturation (120 to 126 days after flowering) showed significant increases in benzaldehyde, linalool, γ- and δ- decalactone; γ- decalactone being the principal volatile compound. The major volatiles, sucrose, quinic acid, and the malic/citric acid ratio, either singly or in combination, appear to be useful indices for estimating maturity of peaches.

Free access

Abstract

An anti-oxidant chemical, EDU, was applied in the greenhouse as a soil drench or by stem injection to 2-year-old containerized seedlings 7 days prior to fumigation with 0.35 or 0.95 ppm ozone (O3) for 3 hr. EDU treatment reduced the appearance of O3-induced symptoms (surface bleaching, bifacial necrosis, and chlorosis) on the foliage of red maple, Acer rubrum L.; honeylocust, Gleditsia triacanthos L.; sweetgum, Liquidambar styraciflua L.; and pin oak, Quercus palustris Muenchh. Stem injection of EDU was significantly more effective than soil drench at the same concentration, although both treatments afforded some protection at the low O3 level (0.35 ppm). About 50 times more EDU was required for comparable levels of O3 protection using soil application as opposed to stem injection. Honeylocust showed the greatest physiological response to EDU as evidenced by changes in root, stem, and leaf dry weight of stem-injected seedlings. All 4 species showed some sensitivity to O3 at 0.95 ppm in the absence of EDU. Chemical name used: N-[2-(2-oxo-1-imidazolidinyl)ethyl]-N’-phenylurea (EDU).

Open Access

Trellising was evaluated for its effects on yields of cucumber (Cucumis sativus L.) cultivars Dasher II, Marketmore 76, and PetoTripleMech at Lane and Wilbutton, Okla. Trellising improved total and marketable yield at both locations compared with ground culture. `PetoTripleMech', evaluated as a fresh-market cultivar, produced yields equal to, or higher than, the other cultivars. Average marketable fruit weight was not affected by trellising but was affected by cultivar at Lane, with `PetoTripleMech' having the heaviest fruit. Economic analysis indicated that trellising is a viable management system for small-scale cucumber production.

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Trellising was investigated for intensive, small-scale, fresh market cucumber (Cucumis sativus L.) production. Economic feasibility of trellising was examined. The cultivars Dasher II, Marketmore 76, and PetoTripleMech were evaluated using trellising and ground culture at two locations in Oklahoma. The cultivar PetoTripleMech is normally grown as a processing cucumber. Here it was evaluated as a fresh market entry. Trellising significantly improved marketable yield of the three cultivars at both locations in comparison to ground culture. PetoTripleMech yields were equal to, or better than, the fresh market standards Dasher II and Marketmore 76. Average marketable fruit weight was not affected by trellising. Economic analysis indicated that trellising is a viable management system for small-scale cucumber production because the gross and net returns to the producer were increased by 20% and 10% respectively.

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Abstract

American elm (Ulmus americana L.) and American sycamore (Platanus occidentalis L.) trees were injected in May or June 1974 and 1975 with water solutions of 1,2-dihydro-3,6-pyridazinedione (Maleic hydrazide, MH) and butanedioic acid mono-(2,2-dimethylhydrazide (daminozide). Measurements in 1977 showed sprout length to be significantly reduced by both chemicals applied in 1974. Of the 1975 treatments, only MH-treated sycamore still showed significant sprout length reduction 3 growing seasons after injection. Between April and June 1977, MH and the sodium sait of 2,3:4,6-bis-0-(1-methylethylidene)-α-L-xylo-2-hexulofuranosonic acid (dikegulac) were injected into the trunks of previously topped American sycamore, silver maple (Acer saccharinum L.), red oak (Querem rubra L.), shamel ash (Fraxinus uhdei (Wenz.)Lingelsh), and eucalyptus (Eucalyptus globulus Labill.). Both chemicals significantly reduced regrowth, but high concentrations were generally more effective than were low concentrations of the same chemical. However, high concentrations of dikegulac were likely to cause unfavorable foliar appearance, including leaf distortion and dieback. Regrowth control was generally similar for a species treated with the same chemical at different geographical locations. Average injection cost for a single treatment is estimated at $2 to $3 per tree.

Open Access

Despite efforts to optimize water and nutrient inputs to Florida's vegetable and fruit crops, the sandy soils, shallow water table, and tropical climate of Florida result in nutrient leaching losses that are unavoidable. Water quantity and quality management strategies that can reduce these nutrient losses from Florida's horticultural crops were reviewed and research needs for quantifying their effectiveness were identified. The water quantity management strategies included water table management for irrigation, drainage management, detention of runoff and drainage, and summer flooding. In addition to the expected water quality benefits of these practices, potential effects on crop production and farm economics were also discussed. Watershed-scale adoption of stormwater harvesting has the potential to not only reduce the nutrient loadings but also become a source of additional income for landowners through water trading. The water quality practices included structural and managerial practices (e.g., vegetative filter strips and ditch cleaning). Key research needs for reducing the unavoidable nutrient discharges included the development of a crop-specific drainage management tool; quantification of farm and watershed-scale benefits of stormwater detention and its reuse with regards to nutrient loadings, water supply, crop production, and farm income; enhancement of hydraulic efficiency of detention areas; and effects of summer flooding and ditch maintenance and cleaning on nutrient discharges.

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Abstract

Topped 1- and 2-year-old seedlings of silver maple (Acer saccharinum L.), American sycamore (Platanus occidentalis L.), cottonwood (Populus deltoides Marsh.) and American elm (Ulmus americana L.) were treated with each of 10 growth regulating chemicals in the greenhouse by chemical injection. Daminozide [butanedioic acid mono (2,2-dimethylhydrazide], maleic hydrazide [l,2-dihydro-3,6 pyridazinedione] and the soldium salt of dikegulac [2,3:4,6-bis-0-(l-methyl-ethylidene)-L-xylo-2-hexulofuranosonic acid] controlled regrowth at appropriate concentrations without causing unacceptable phytotoxicity.

Open Access

Pawpaw (Asimina triloba) is an under-exploited small tree with commercial potential as a fruit crop, ornamental tree, and source of secondary products with insecticidal and medicinal properties. It is most often propagated from seeds that are recalcitrant and must be stored moist at a chilling temperature. Seeds display combinational (morphophysiological) dormancy. Endogenous, physiological dormancy is broken by about 100 days of chilling stratification followed by a period of warm moist conditions where the small embryo develops prior to seedling emergence about 45 days after the warm period begins. Pawpaw cultivars with superior fruit characteristics are propagated by grafting onto seedling understocks. The most common practice is chip budding. Other methods of clonal propagation have proven problematic. Pawpaw can be propagated from cuttings, but only in very young seedling stock plants. Micropropagation from mature sources is not yet possible, but shoot proliferation has been accomplished from seedling explants and explants rejuvenated by induction of shoots from root cuttings of mature plants. However, rooting of microcuttings and subsequent acclimatization has not been successful.

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