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  • Author or Editor: D. R. Davis x
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Abstract

Seedlings of 3 birch species were exposed to either 0.3, 0.6, 0.9, or 1.2 ppm SO2 for 1, 2, 3, or 4 hours. Stomatal conductance rate measurements of 10 plants were taken prior to and immediately following each exposure. The percentage of leaf tissue injured by SO2 was estimated 72 hours after exposure. Stomatal conductance rates of European white birch (Betula pendula Roth.) and yellow birch (B. lutea Michx. f.) increased after exposure to 0.3 ppm SO2 for 1 and 2 hours, and decreased in response to all other doses of SO2. Stomatal conductance rates of gray birch (B. populifolia Marsh.) increased only after exposure to 0.6 ppm SO2 for 1 and 3 hours and decreased in response to all other dosages. European white birch was slightly more susceptible to SO2than gray birch, whereas yellow birch was tolerant.

Open Access

Abstract

CO2 enrichment (1200 μl CO2/liter of air) during rooting increased the number of roots per cutting from 7.4 to 12.0 in Peperomia glabella A. Dietr. ‘Variegata’. CO2 enrichment increased length and dry weight of root systems and fresh and dry weights of whole cuttings in P. glabella, Fuchsia magellanica Lam., Peperomia nivalis Miq., Hemigraphis alternata T. Anderson, and Begonia × argenteo-guttata V. Lemoine but not in Osmanthus heterophyllus P.S. Green ‘Rotundifolius’, Ficus pumila L., and Pelargonium × hortorum L.H. Bailey ‘Sprinter Scarlet’. After 4 weeks of growth at 330 μl CO2/liter, only P. nivalis retained the size differential due to CO2 enrichment.

Open Access

Abstract

Storage of Rhododendron catawbiense Michx. ‘Roseum Elegans’ cuttings in moist burlap bags at 21° or 2°C for 21 days did not consistently reduce the percentage of rooting or rootball size. During storage, leaf water potential (ψw) of the cuttings increased from −0.47 MPa initially to −0.27 MPa after 14 days, regardless of storage temperature. Carbohydrate concentrations in the bases of the cuttings changed with time and storage temperature, but apparently neither these changes nor changes in ψw were large enough to influence subsequent rooting.

Open Access

Abstract

Root formation on leafy cuttings of Pisum sativum L. ‘Alaska’ was reduced by about 50% when net photosynthesis was adjusted to the compensation point by reducing the light intensity, reducing the CO2 concentration, or by blocking CO2 exchange with an antitranspirant. Rooting was also reduced by 50% when cuttings were given only enough photoperiod at saturating light to maintain a carbon balance similar to that of the treatments which reduced net photosynthesis to the compensation point. In addition to decreasing rooting, these treatments lowered sucrose and glucose levels in the basal portion of the cuttings compared to controls. Our photosynthesis and carbohydrate data indicate that the supply of current photosynthate to the base of pea cuttings is important to rooting.

Open Access

Abstract

Leafy cuttings of Rhododendron catawbiense Michx. ‘Roseum Elegans’ were rooted under 0%, 55%, or 95% shade in a greenhouse. Compared to the low-light treatment, higher light induced high photosynthetic rates, high sucrose and starch levels, and low leaf water potential, but these differences only persisted for the initial part of the 23-week rooting period and did not influence subsequent rooting percentage. However, in cuttings receiving 95% shade, dry weights of leaves and stems and rootball size were relatively small after 23 weeks, suggesting that growth was reduced by lack of photosynthate. The reduced size of cuttings rooted under 95% shade apparently did not affect vigor because the size of the above-ground portion of all plants was equal after 2 months of growth in a greenhouse.

Open Access

Abstract

Potted plants of ‘Merit’ tomato (Lycopersicon esculentum Mill.) were grown from seed to maturity in controlled-environment chambers and exposed to charcoal-filtered air or 288-314 μgm-3 (0.11-0.12 ppm) SO2 during weeks 1-5, 6-10, or 1-10 beginning about one week after transplanting. Red ripe fruit harvested from plants exposed to SO2 exhibited a slight but significant decrease in ascorbic acid expressed on a dry-weight basis. SO2 induced significantly greater levels of foliar sulfur, but did not increase sulfur content of the fruit. Exposure of plants to SO2 did not affect fruit yield or quality factors including soluble solids, total solids, or ascorbic acid on fresh-weight basis. A multiple regression model revealed low but significant R2 values, indicating a weak and indirect, yet significant, association between plant sulfur content and fruit ascorbic acid.

Open Access

Southernpeas are an important crop to Arkansas processors, market gardeners and home gardeners. While the bulk of the acreage produced in the state is pinkeye purple hull types, there is a demand for other horticultural types. At present some processors consider `White Acre' to be the standard of cream pea quality, but under Arkansas conditions, `White Acre' produces excessive vine growth, is very late to mature and is susceptible to bacterial blight. For these reasons, the Arkansas Agricultural Experiment Station announces the release of `Early Acre'. `Early Acre' has been widely tested under the designation Arkansas 84-154 and produces a very compact bush plant that has seed similar in size and shape to `White Acre', but matures 8-10 days earlier under Arkansas conditions. Although the plant type is well suited to narrow row spacing, `Early Acre' has produced yields similar to `White Acre' when both are planted at conventional row spacings. Samples have been canned by the Dept. of Food Science at the University of Arkansas and the samples have been rated equal to `White Acre' in processed quality. “Early Acre' has exhibited high levels of resistance to bacterial blight in replicated yield trials under field epidemics in both Arkansas and Texas.

Free access

A study was conducted to evaluate the possibility of producing and processing immature cowpea (Vigna unguiculata) green pods by using the same technology used for green beans (Phaseolus vulgaris). The cowpea cultivar Bettersnap developed for green pod production and the green bean cultivars Benton and OSU-5402 were produced under the same cultural conditions. `Bettersnap' yielded less than 0.5 ton/ha, while `Benton' and `OSU-5402' produced about 2.5 ton/ha in once-over simulated mechanical harvest. `Bettersnap' had long vines and dense foliage, which resulted in plants with more width and less erectness than `Benton', the predominant green bean cultivar. Uneven pod setting and long pods (23.8 cm) in `Bettersnap' constitute potential problem for mechanical harvest. Canned cowpea pods of sieves 2 and 3 had darker green color, smaller seeds, and higher shear value, fiber content, and sloughing than green bean pods. Our study indicates that there is a need to develop cultivars with high yield potential and concentrated pod setting adapted to mechanical harvest with pods containing less fiber and less tendency to sloughing.

Free access

Pigeonpea, a subtropical legume, was successfully grown in a high-latitude (≈45°N) environment. Four short-season pigeonpea accessions from the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) were subjected to three cycles of pedigree selection. Performance trials (175,000 plants/ha) were conducted on loamy sand with dryland and irrigated sites in 1991 and 1992. Thirty-eight S3-derived lines from ICRISAT ICPL 83004 were used in both years and seven S3-derived lines from ICRISAT P 2125 and ICRISAT ICPL 85010 were added the second year. Differences (P ≤ 0.05) in seed yield (kg·ha–1) were observed among the S3 lines, with a maximum yield of 1468 kg·ha–1. The lines also differed (P ≤ 0.05) for harvest index (HI), calculated as the ratio of seed yield to shoot total dry matter (TDM) with a maximum of 0.48 (line MF-26). Dryland seed yield was strongly correlated with TDM (r 2 = 0.98), HI (r 2 = 0.92), and early bloom (r 2 = 0.76). In a time-of-planting comparison of seven lines in 1992, seed yield was highest (754 kg·ha–1) at the earliest (29 Apr.) planting date and declined progressively to 178 kg·ha–1 at the latest (2 June) planting date, while HI decreased from 0.42 to 0.12. Plants were shorter at maturity in the earliest planting date.

Free access

Abstract

Growth responses of ‘sour orange’ (Citrus aurantium L.), ‘Swingle citrumelo’ [C. paradisi Macf. x Poncirus trifoliata (L.) Raf.], ‘Cleopatra mandarin’ (C. reticulata Blanco), ‘Volkamer lemon’ (C. volkameriana Pasq.), and ‘Troyer citrange’ [C. sinensis (L.) Osbeck x P. trifoliata], infected by the mycorrhizal fungi Glomus etunicatum Becker and Gerd., G. microcarpum (Tul. and Tul.) Tul. and Tul., or 2 isolates of G. fasciculatum (Thaxter) Gerd. and Trappe, were compared. Overall, G. fasciculatum 92 caused the greatest growth responses and G. microcarpum the least. ‘Cleopatra mandarin’, the slowest growing cultivar, was the most mycorrhizal dependent cultivar while ‘sour orange’ and ‘Volkamer lemon’, which exhibited the greatest growth, were the least dependent. The greatest growth responses were usually associated with high concentration of phosphorus in leaf tissue, but phosphorus concentrations were not always related to mycorrhizal dependency. Rarely did mycorrhizal species affect different cultivars in dissimilar ways.

Open Access