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D. Bradley Rowe, Stuart L. Warren, and Frank A. Blazich

Catawba rhododendron (Rhododendron catawbiense Michx.) seedlings of two provenances, Johnston County, N.C. (35°45′N, 78°12′W, elevation = 67 m), and Yancey County, N.C. (35°45′N, 82°16′W, elevation = 1954 m), were grown in controlled-environment chambers for 18 weeks with days at 18, 22, 26, or 30C in factorial combination with nights at 14, 18, 22, or 26C. Shoot and root dry weights and total leaf areas of seedlings of the Yancey County provenance (high elevation) exceeded (P ≤ 0.05) those of the Johnston County (low elevation) provenance at all temperature combinations. Leaf area was maximal at 22/22C, 18/26C, and 22/26C and minimal at 30/14C (day/night). Shoot dry weight responded similarly. Root dry weight decreased linearly with increasing day temperature, but showed a quadratic response to night temperature. Leaf weight ratio (leaf dry weight: total plant dry weight) increased, while root weight ratio (root dry weight: total plant dry weight) decreased with increasing day temperature. Leaf weight ratio was consistently higher than either stem or root weight ratios. Day/night cycles of 22 to 26/22C appear optimal for seedling growth.

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Jane E. Lancaster, Julie Farrant, and Martin L. Shaw

Three onion (Allium cepa L.) cultivars, `Southport White Globe', `Grano', and `Pukekohe Longkeeper' were grown at low to high S (at 0.5, 1.8, 3.0 or 4.0 meq·L-1) in hydroponic culture. Differential solvent extractions of bulbs were used to isolate quantitatively cell contents, cell wall proteins, and cell wall residue. The weight of the cell fractions, their S content, and the S content of intact bulbs were determined. Bulb characteristics of fresh weight (FW), firmness, soluble solids concentration (SSC), and soluble sugars were also determined. For all three cultivars, bulb FW increased with S from 0.5 to 4.0 meq·L-1. Sulfur had a significant effect on bulb firmness. Onion bulbs grown with S at 0.5 meq·L-1, the lowest S concentration, were significantly softer than onion bulbs grown at the highest concentration of 4.0 meq·L-1. Varying the S supply had a major effect on dry weight (DW) allocation to the cell wall residue. Bulbs of all three cultivars grown at the lowest S had significantly less DW in the cell walls compared to S at 3.0 or 4.0 meq·L-1. In contrast to the effect of S supply on DW allocation, varying S supply had no effect on total bulb S, free SO4 -2, and on the S content of the cell contents and the cell wall residue and only a minor effect on cell wall proteins. There was no significant effect of S supply on either SSC or soluble sugars. At low S nutrition, which is limiting to the growth of onion bulbs, cell wall deposition is reduced, with a consequent decrease in bulb firmness. The S composition of the cellular components is maintained at the expense of bulb growth.

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D.C. Ferree, D.M. Scurlock, and J.C. Schmid

`Seyval blanc' and `Vidal blanc' grapevines (Vitis sp.) grown in large containers were root-pruned at different severities and/or stages of development and the effects on growth of both cultivars and fruiting of `Seyval blanc' were determined. As the severity of root pruning increased, stomatal conductance (g s) and transpiration (E) decreased and the number of wilted leaves increased in both cultivars. In both cultivars, root pruning reduced net photosynthesis (Pn) and E for as long as 18 to 20 days, as well as total leaf area and dry weight of leaves and petioles plus tendrils. The reductions were proportional to the degree of root pruning. A similar pattern existed for cane and root tissue of `Vidal blanc'. As the severity of root pruning increased, berry and cluster weight, and titratable acidity (TA) of `Seyval blanc' decreased. There was no effect of root pruning on berries per cluster, soluble solids content (SSC), or pH of the juice. No interaction was significant for any factor between time of root pruning and fruiting measured on `Seyval blanc' vines. Root pruning at bloom reduced leaf area, number of leaves, and dry weight of petioles, trunks, and canes. Root pruning at veraison had no effect on any vegetative or fruit parameters. Fruiting `Seyval blanc' vines had less leaf area and smaller petiole and cane dry weights than did nonfruiting vines.

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S.A. Weinbaum, F.J.A. Niederholzer, S. Ponchner, R.C. Rosecrance, R.M. Carlson, A.C. Whittlesey, and T.T. Muraoka

Four adjacent heavily cropping 12-year-old `Petite d'Agen' prune (Prunus domestica L.) trees were selected, and two of the trees were defruited in late spring (28 May) after the spring growth flush and full leaf expansion. Trees received K daily through the drip-irrigation system, and 15N-depleted (NH4)2SO4 was applied twice between the dates of defruiting and fruit maturation. Trees were excavated at the time of fruit maturity (28 July) and fractionated into their component parts. The following determinations were made after tree excavation and sample processing: tree dry weight, dry weight distribution among the various tree fractions (fruit, leaves, roots, trunk, and branches), tree nutrient contents, within-tree nutrient distribution, total nonstructural carbohydrates (TNCs), and recovery of labeled N. Trees only recovered ≈3% of the isotopically labeled fertilizer N over the 6-week experimental period. Heavily cropping trees absorbed ≈9 g more K per tree (17% of total tree K content) during the 2-month period of stage III fruit growth than defruited trees. The enhanced K uptake in heavily cropping trees was apparently conditioned by the large fruit K demand and occurred despite greatly reduced levels of starch and TNCs relative to defruited trees. Fruit K accumulation in heavily cropping trees was accompanied by K depletion from leaves and perennial tree parts. Except for K, fruited and defruited trees did not differ in nutrient content.

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Pauline P. David, Audrey A. Trotman, and Desmond G. Mortley

One of the major objective of growth analysis data is to provide a basic understanding of some of the mechanisms that affect plant growth. This study was initiated to evaluate the effects on several growth parameters when plants are grown in an NFT system. Vine cuttings (15 cm length) of the sweetpotato cultivar ``Georgia Jet” was grown in a closed NFT system for a period of 120 days. Nutrient was supplied in a modified half-strength Hoagland's solution with a N:K ratio of 1:2.4. Destructive harvesting of plants occurred at 14 day intervals at which time plants were separated into their various component parts and analyzed for dry weight accumulation, leaf area index, crop growth rate, relative growth rate and net assimilation rate. Results showed dry weight distribution within the plant had a linear response for all component part evaluated. Greatest contributors to total plant dry weight was stem followed by leaves, fibrous roots, buds and flowers. However, once storage root production occurred it contributed the largest percentage to total plant dry weight. LAI was optimum at 80 days after planting (DAP) while CGR and RGR fluctuated throughout the growing season. Initially NAR was higher in foliage than storage roots but declined once storage root enlargement began, suggesting a translocation of assimilates to storage root.

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Joel L. Shuman and Todd C. Wehner

Production of pickling cucumber (Cucumis sativus L.) requires a significant expenditure of labor and money. Those resources could be better managed if both yield and harvest date could be predicted for a given planting date and production area. The objective of this experiment was to develop a model to simulate growth and yield of pickling cucumbers under field conditions in North Carolina. Detailed measurements of leaf area, branching habit, flowering, fruiting, and dry weight distribution were obtained for the cultigens `Calypso', M 21, `Wis. SMR 18', and WI 2757 for 10 planting dates. Light interception, air temperature, and rainfall were also recorded. There were differences among cultigens and planting dates for time needed to reach certain growth stages. Number of days to reach a given stage generally decreased with later planting dates. Addition of nodes over time to the main stem was linear and the interaction of planting date by cultigen was significant. Number of staminate and pistillate flowers was affected by both cultigen and planting date.

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Hala G. Zahreddine, Daniel K. Struve, and Salma N. Talhouk

cabinet making. There is some confusion regarding its taxonomy. The purpose of this study was to determine the effects of two fertilizer rates on growth, dry weight distribution, mineral nutrient content and distribution, and mineral nutrient uptake

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Bielinski M. Santos

. Sci. Publ., Univ. of Florida Gainesville, FL Kogbe, J.O.S. 1983 Effects of spacing on the yield of local and exotic species of eggplant Acta Hort. 123 291 297 Hancock, J.F. Moon, J.W. Flore, J.A. 1984 Within-row spacing and dry weight distribution in

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Patrick Conner

a potassium deficiency. Unlike some tree species that alter relative dry weight distribution between roots and stems with N fertigation ( Larimer and Struve, 2002 ), relative weights of pecan seedling roots and stems remained remarkably stable at all

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Janni Bjerregaard Lund, Theo J. Blom, and Jesper Mazanti Aaslyng

in the simulated twilight, whereas total dry weight, dry weight distribution, number of lateral breaks and internodes, leaf area on the main stem, and stem diameter were unaffected after the 3 weeks of EOD lighting. Leaf area on the lateral breaks