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Abstract

Tissue culture techniques now are used to propagate species of brassica, many of which are used as vegetables, forage and fodder, and oilseed (2). Tissue culture has been especially beneficial in the maintenance of self-incompatible parent lines of Brassica oleracea and also in eliminating the reduction of vigor associated with continuous inbreeding of parent lines (4). Although many members of B. oleracea have been propagated by tissue culture techniques, the study of the in vitro growth of kohlrabi has been limited (1). In most cases where in vitro growth has been reported, either no plants were regenerated or the regeneration percentage was extremely low (3, 6, 7). We determined the optimum concentration of plant growth regulators needed to induce shoots and to promote their subsequent rooting.

Open Access

Perennial wildflowers, once established, are a low-maintenance alternative in a flowerbed. However, water stress and poor root development in field soil can be detrimental to young plants at the time of transplanting. A fully expanded hydrogel, HydroSource, was incorporated to replace 0% (control), 7.5%, 15% (recommended rate), and 30% of the volume of a clayey field soil to determine its effect on plant water status. Addition of hydrogel reduced water stress in Asclepias incarnata and Gaillardia grandiflora plants. Plants growing in hydrogel amended soil had: 1) significantly lower stomatal resistance (P < 0.01); and 2) significantly higher leaf water potential (P < 0.01). Gaillardia grandiflora control plants showed considerable wilting (reflected in high stomatal resistance and low water potential readings) on the 3rd day of the drought period while those with 15% and 30% hydrogel were turgid even on the 5th day. Hydrogel-amended soil appeared less compacted, and root growth in Asclepias incarnata increased with the increasing rate of hydrogel added to the soil.

Free access

Low mowing increases ball roll distance on putting greens, but may affect growth and physiological responses to summer heat stress. The objective of this study was to examine whether the effect of mowing heights on turf summer performance was associated with changes in photosynthetic activities and respiration rate for two creeping bentgrass [Agrostis palustris (L.) Huds] cultivars, `Crenshaw' and `Penncross'. Both cultivars were grown under USGA-specification putting green conditions from 1997 to 1998. Grasses were mowed daily at a 3-mm (low mowing) or 4-mm (high mowing) height. Turf quality, net photosynthesis rate (Pn), and leaf photochemical efficiency (Fv/Fm) declined, whereas respiration rate of whole plants, canopy minus air temperature, and soil temperatures increased under low mowing compared to those at the high mowing height. The decline or increase in those parameters under low mowing was more pronounced in summer than in spring or fall months. The results showed that turf quality was better at the 4-mm mowing height, especially during summer months. Better quality at the higher mowing height could be related to the maintenance of higher photosynthetic activities and lower respiration rate. Mowing at the lower height had more adverse effects on turf growth and photosynthetic capacity for `Penncross' than `Crenshaw', particularly during summer months.

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Symbiotic mycorrhizal fungi increase the P uptake of agronomic, horticultural, and forestry crops. Little is known about the real-time dynamics of carbon balance (net gain of biomass resulting from photosynthesis less the respiratory costs) of plants colonized with mycorrhizae. Our objective was to determine the carbon balance of endomycorrhizal (VAM) chile pepper `San Luis' (Capsicum annuum L.) as a model system for predicting plant response to limited P availability under elevated CO2. The increase in atmospheric CO2 is expected to result in increased plant productivity and greater demand for soil P, however, the lack of available soil P may become the most important nutritional problem limiting crop productivity. Under current conditions, the limitation of soil-P availability is an enormous problem that affects 25% of the world's arable lands. We are quantifying the carbon costs paid by the mycorrhizal plant under varying levels of P deficiency over the life cycle of the plant. Preliminary results from this study under ambient CO2 conditions indicate that there is a lower maintenance respiration and higher growth efficiency with mycorrhizal pepper plants under low soil-P conditions.

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Eleven rose cultivars were field planted and evaluated weekly for disease, defoliation, and overall vigor in order to compare natural resistance to blackspot (Diplocarpon rosae). Alternative treatments were also compared for efficacy in low-maintenance disease control. Treatments included a bimonthly application of chlorothalonil, a bimonthly application of a horticultural oil, an application of chlorothalonil based on rain events, and a no-treatment control. Cultivars showed significant differences in disease severity, defoliation, and overall performance, with old garden rose varieties showing more natural disease resistance than modern susceptible varieties included in the study. Chlorothalonil applied on a 14-day spray schedule did provide a significant decrease in blackspot disease severity when compared to other treatments. A significant incidence of secondary disease including Cercospora rosicola and Botrytis cinerea occurred on old garden rose varieties. No treatment differences were found for these diseases. `Belinda's Dream', `The Fairy', and `Red Mediland' ranked highest in overall performance throughout the season.

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Five species and 27 cultivars of fine-leaved fescues (Festuca sp.) were evaluated for low-maintenance utility turf in a variety of golf course conditions. Cultivar selection and management techniques varied across six sites in 4 years. Germination, tillering, rapidity of establishment, turf density, and general turfgrass quality were significantly different between both species and cultivars. Annual and seasonal decline and recovery of turf quality was also dependent on both species and cultivar. Greater differences exist within cultivars in some species than between species. Aspect, slope, soil disturbance, shade, seeding date, irrigation, fertility regime, mulch, and mowing influenced establishment and seedling development. Absence of endophytic fungi and development of diseases, insects, weeds, and post-germination disturbance markedly contributed to losses in turf quality, percent living cover, and increased erosion potential. Success and duration of fescue slope plantings are both positively and negatively correlated to various site characteristics and management techniques. Fescues are an appropriate choice in specific circumstances.

Free access

Water scarcity delay the social development in the coastal arid zones of México. In these areas, fresh water can be obtained from the ocean using different methods. In this work, a design of a self-sufficient system for desalting seawater, using the sun and the wind, is applied to irrigate a small horticultural plot. A daily mean water production of 160 l was obtained from a 60 m2 solar desalter, which was supplied with seawater with an aeolian pump. Three varieties of tomatoe were assayed: ACE-55, Cherry, and Saladette. Cherry tomatoe showed the highest yield with a consumption of 45 l/plant per month. A plastic mulch was used to minimize evaporation. The system may represent an economic alternative with low-maintenance requirements for self-supplying vegetables in marginal coastal zones.

Free access

Abstract

Glasshouse microclimate during 3 growth periods in the Southern Piedmont region of the United States was characterized. An increase in density of tomato plants (Lycopersicon esculentum Mill.) by one-third, which doubled radiation interception, was suggested by early observations. Maintenance of clean glass surfaces was found to be particularly important during cloudy weather. There was no significant difference between mean air temperature and mean rooting media temperature in the raised beds used. CO2 concentration was found to be low (240 ppm) when fans were not circulating outside air. CO2 generators, installed to increase greenhouse CO2 levels, were not effective possibly because control was inadequate. The use of CO2 enrichment requires further study under Southeastern conditions. Relative humidity remained below the recommended 90% in the green-house except during cloudy-mild weather. Although inside relative humidity was generally less than outside relative humidity, values ranged from 90 to 100%.

Open Access

Abstract

Effects of several vesicular-arbuscular mycorrhizal (VAM) fungi on shoot growth and mycorrhizal development in ‘Citation’ perennial ryegrass (Lolium perenne L.) were studied as a function of inoculum placement depth. Soil columns were layered with inoculum at 0, 5, 10, or 20 cm prior to seeding. Three inocula were tested: 1) chopped roots and soil from sorghum (Sorghum bicolor L.) plants previously infected with the VAM fungus Glomus macrocarpus Tul. and Tul. var. macrocarpus; 2) a mixed inoculum from plants infected with G. macrocarpus var. macrocarpus; G. mosseae (Nichol. and Gerd.), G. faciculatum (Thaxter) Gerd. and Trappe, Gigaspora margarita Becker and Hall; 3) roots and soil from noninoculated sorghum plants. Shoot growth was greatest when VAM inoculum was placed at the surface, and declined progressively with deeper placement. Greatest mycorrhizal fungal infection of the root system occurred at the site of inoculum placement regardless of depth. The effectiveness of the surface-applied inoculum on enhancing the initial shoot growth (70 days) of perennial ryegrass in this study suggests that inoculation with VAM fungi might prove useful in low maintenance turfgrass culture.

Open Access

The concept of designing and implementing sustainable landscapes for low-income communities grew from collaboration between several community partners and Clemson Univ. It was our desire to research, plan, design, and implement sustainable landscapes for Habitat for Humanity homes. The primary goal of designing for these low-income homes was to design for sustainability. We wanted our plans to promote energy efficiency, water conservation, and low maintenance costs. These implemented principals would help the homeowner drastically cut living costs. The design and implementation of wildlife habitats was also encouraged to promote knowledge and research on environmental issues. In the beginning of our design phase we interviewed our client about her user needs/desires and later presented her with the design. This began the exhibition and education phase of the project. By exhibiting the project we hoped to education the homeowner about the sustainability issues that are pertinent to her case. Our biggest educational outreach program took place during homecoming at Clemson Univ. Partnering with other student organizations and using donated plant material from a local nursery, we constructed gardens and “planted” trees around a Habitat for Humanity house that is built each year during homecoming and later moved by trailer to its final site. We also displayed our designs inside the house and created pamphlets and brochures for visitors to pick up detailing such topics as Butterfly Gardening. Spurred on by the success of this project a web page detailing our community and organizational involvement was created. Our projects have been covered in many newspaper articles, cable TV, and in a video on service learning being produced for national distribution. As a student it has given me and my other student colleagues an opportunity to engage in and acquire valuable hands-on experience in horticulture and environmental education/stewardship all the while providing a much needed public outreach service that assists and partners with community members in order to enhance their personal home environments.

Free access