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I.E. Yates and C.C. Reilly

The influence of stage of fruit development and plant growth regulators on somatic embryogenesis and the relation of cultivar response on somatic embryogenesis and subsequent plant development have been investigated in eight cultivars of pecan [Carya illinoensis (Wangenh.) C. Koch]. Explants from the micropylar region of the ovule were more embryogenic when removed from fruits in the liquid endosperm stage than were intact ovules from less-mature fruits or from cotyledonary segments of more-mature fruits. Explants conditioned on medium containing auxin alone or auxin + cytokinin produced more somatic embryos than medium containing cytokinin alone. Under the conditions of this study, frequency of embryogenesis, as well as the germination of somatic embryos leading to plant development, indicated appreciable variation among cultivars. Plant development was greatest by far from somatic embryos of `Schley' than other cultivars studied.

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Eakhlas U. Ahmed, Takahiro Hayashi, and Susumu Yazawa

The developmental pattern of leaf color distribution during plant development in 10 cultivars of Caladium ×hortulanum Birdsey was investigated. We used the color occupying the largest area in the terminal leaf as the dominant color, and expressed the leaf color stability during plant development by the ratio of the percentage of the dominant color area in the terminal leaf to that of the dominant color area in the initial leaf (leaf color stability index). In some cultivars, leaf color stability index was clearly greater than 1 (leaf-color-unstable cultivar), but in some cultivars it was close to 1 (leaf-color-stable cultivar). In plants regenerated from leaf explants of leaf-color-unstable cultivars, many (21% to 43%) color variants were observed but only a few (0% to 6%) occurred from leaf explants of leaf-color-stable cultivars. Tissue culture appears to be a useful technique for rapid propagation based on leaf color stability in leaf-color-stable and leaf-color-unstable cultivars.

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R.L. Korthals”, S.L. Knight, and L.L. Christianson

Chrysanthemum, wheat, and soybean were grown in a growth chamber to study the effects of airflow direction, velocity, and turbulence on vegetative growth. These three plant species were chosen to examine how plants with different leaf architectures and morphology are influenced by varying air velocity and pattern. A hot wire anemometer accurate to ±0.025 m s-1 and capable of responding to 50 khz turbulent velocity fluctuations was used to characterize the environment in a growth chamber under three different experimental conditions: <0.50 m s-1 horizontal velocity, >1.00 m s-1 horizontal velocity, and <0.50 m s-1 vertical velocity. Plants were grown under the three different treatments for five weeks with plant height, width, stem diameter, and node number, and fresh and dry weights of leaves, stem, and roots determined at three internals throughout each experiment. Tire variation in plant development resulting from the different treatments has practical implications for using ventilation to aid in controlling plant growth and development.

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Fred T. Davies Jr., Sharon A. Duray, Lop Phavaphutanon, and Randy Stahl

The influence of P nutrition on gas exchange, plant development, and nutrient uptake of Capsicum annuum chile ancho `San Luis' and bell pepper `Jupiter' plants was studied. Plants were fertilized weekly using 250 ml of a modified Long-Ashton solution, containing 0, 11, 22, 44, 66 or 88 μg P/ml. Phosphorus stress was evident with both pepper cultivars at 0 and 11 μg P/ml, with reduced plant growth and development: leaf number and area and fruit, leaf, stem, root, shoot, and total plant dry weight. The root: shoot ratio was greatest at 0 μg P/ml, reflecting greater dry matter partitioning to the root system. Greater P stress occurred at 0 μg·ml–1 in `San Luis' compared to `Jupiter' (88% vs. 58% reduction in total plant dry weight compared to optimum P response). `San Luis' was also more sensitive to P stress at 11 μg P/ml than `Jupiter', as indicated by the greater reduction in growth responses. With increasing P nutrition, leaf tissue P increased in both cultivars with maximum leaf tissue P at 88 μg P/ml. In `San Luis', there were no differences in tissue P between plants treated with 0 and 11 μg P/ml, whereas the `Jupiter' plants treated with 0 μg P/ml had the lowest tissue P. Low P plants generally had the highest tissue N and lowest S, Fe, Mn, Zn, B, Mo, and Al. With both cultivars, gas exchange was lowest at 0 μg P/ml, as indicated by low transpiration (E), stomatal conductance (gs), and net photosynthesis (A). Internal CO2 (Cj) and vapor pressure deficit were generally highest at 0 μg P/ml, indicating that Cj was accumulating with lower gs, E, and A in these P-stressed plants. Generally, no P treatments exceeded the gas exchange levels obtained by 44 μg P/ml (full strength LANS) plants.

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Fred T. Davies Jr., Sharon A. Duray, Lop Phavaphutanon, and Randy Stahl

In two separate experiments, the influence of phosphorus nutrition on gas exchange, plant development, and nutrient uptake of Capsicum annuum chile ancho `San Luis' and bell pepper `Jupiter' plants were studied. Plants were fertilized weekly using 250 ml of a modified Long–Ashton solution (LANS) containing 0, 11, 22, 44, 66, or 88 μg P/ml. Phosphorus stress was evident with both pepper cultivars at 0 and 11 μg P/ml, with reduced plant growth and development: leaf number and area, fruit, leaf, stem, root, shoot, and total plant dry weight. The root: shoot ratio was greatest at 0 μg P/ml, reflecting greater dry matter partitioning to the root system. Greater phosphorus stress occurred at 0 μg P/ml in `San Luis' compared to `Jupiter' (88% vs. 58% reduction in total plant dry weight compared to optimum P response). `San Luis' was also more sensitive to phosphorus stress at 11 μg P/ml than `Jupiter' as indicated by the greater reduction in growth responses. With increasing P nutrition, leaf tissue P increased in both cultivars with maximum leaf tissue P at 88 μg P/ml. In `San Luis', there were no differences in tissue P between 0 and 11 μg P/ml plants, whereas 0 μg P/ml `Jupiter' plants had the lowest tissue P. Low P plants generally had the highest tissue N and lowest S, Fe, Mn, Zn B, Mo, and Al. With both cultivars, gas exchange was lowest at 0 μg P/ml, as indicated by low transpiration (E), stomatal conductance (gs), and net photosynthesis (A). Internal CO2 (Ci) and vapor pressure deficit were generally highest at 0 μg P/ml, indicating that Ci was accumulating with lower gs, E, and A in these phosphorus-stressed plants. Generally, no P treatments exceeded the gas exchange levels obtained by 44 μg P/ml (full strength LANS) plants.

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Jim Berry and Aimee Coker

Plant Development Services, Inc. (PDSI), was organized in 1996 for the purpose of research, development and the marketing of new innovative landscape plants. PDSI focuses on discovery, evaluation and production of new clones that are superior in horticultural qualities to current ones in our industry. Some superior horticultural traits that PDSI looks for are disease and insect resistance, heat and cold tolerance, superior foliage, form, or flower, ease of propagation and cultivation, and marketability. All new ornamental plant introductions orginate from small producers, private breeders, or from our own research. PDSI offers new plant discoveries a place and method of evaluation, legal protection services, production and marketing. Our method of evaluation includes propagation and cultivation and can take varying lengths of time to complete. On an average, it can take 3 to 5 years of evaluation before final selections are made. Once we have a high confidence level on a particular variety we enter them into university trials. We also offer public gardens these new plants for public exposure and evaluation. This has given us valuable feedback on the performance of these new cultivars in different areas of the country. This exposure has also turned into promotion. As people notice these new plants established and performing well in landscapes, they become confident to try the plants on their own, often talking about them and sometimes writing about them. If a plant is patented, the patent belongs to the breeder and typically PDSI is the managing partner making decisions on royalties, promotion, production, and licensing. Royalties fund our program and are paid on a per plant basis, not per size.

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Dennis R. Decoteau, Michael J. Kasperbauer, and Patrick G. Hunt

Mulch surface color affected the growth of bell pepper (Capsicum annuum L.) plants, the amount and quality of upwardly reflected light, and the soil temperatures under the mulch. Of the surface colors evaluated (black, red, yellow, and white), plants grown over red mulch were the tallest. The darker (black and red) mulches reflected less total light and more far-red (FR) relative-to-red (R) light, and soil temperatures recorded in the afternoon and evening were warmer than under the yellow and white mulches. Plant growth responses to mulch surface color were also observed when soil temperature differences among the mulch color treatments were minimized by placing insulation boards between the mulch surface and the soil. Sensitivity of young pepper plants to a high or low FR: R light ratio was demonstrated by exposing plants to 15 minutes of FR or 15 minutes of R light at the end of the photosynthetic period each day for 14 consecutive days in a controlled environment. Plants that received the FR (high FR: R ratio) were 51% taller than plants exposed to R (low FR: R ratio) light treatments. The similar responses of pepper plants to differences in FR: R ratios associated with mulch color and end-of-day light treatments provide evidence that pepper plant growth is affected by relatively small changes in light environment induced by the surface color of the mulch.

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Dharmalingam S. Pitchay and Paul V. Nelson

It is a common practice in greenhouses to apply fertilizers with a high proportion of N in the NO3 form to achieve short, compact shoots and a moderate (25% or greater) proportion of NH4 or urea for large shoots. However, this practice is not substantiated in the scientific literature. Two experiments were conducted in a greenhouse to assess effects of N form on development. In the first, Petunia hybrida `Mid-night Dreams' was treated with five ratios of NH4:NO3 or urea:NO3 in a factorial arrangement with three concentrations of N (50-low, 100-adequate, and 200-high mg/L at each irrigation). In the second experiment six species of bedding plants were treated in a factorial arrangement of five ratios of NH4:NO3 and two pH levels (acceptably low, 5.4-5.8, and unacceptably low, 4.6-5.2). In all comparisons, height and dry weight of shoots grown with 100% NO3 were equal or larger than the plants grown with combinations of N. There was a general trend for plants to be shorter and lighter at higher NH4 or urea proportions. These results refute the hypothesis that shoot size is under the control of N form. Depth of green foliar color correlated positively with proportion of NH4 or urea. Reputed NH4 toxicity symptoms of chlorosis, necrosis, and curling of older leaves occurred only at adversely low pH levels below 5.2 in experiment 2. Resistance of plants to this disorder under conditions of pH levels in the range of 5.4 to 5.8, high N application rates, and applications of 100% NH4 indicates that bedding plants during commercial production are fairly resistant to this disorder.

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Eva Bacaicoa and Jose María García-Mina

size. The whole experiment was carried out twice and representative results are presented. Parameters evaluated in the experiments The effect of Fe deficiency on plant development was evaluated through the analysis of the following parameters

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F.M. del Amor, V. Martinez, and A. Cerdá

In order to simulate the usage of brackish irrigation water in greenhouse tomato (Lycopersicum esculentum Mill. cv. Daniela) culture in perlite, plants were supplied with nutrient solutions containing 0, 20, 40, and 60 mm NaCl. The three highest salinity treatments were applied at three different plant growth stages, during early vegetative growth [16 days after transplanting, (DAT)], beginning of flowering (36 DAT), and starting fruit development (66 DAT). Salt tolerance of tomato plants increased when the application of salinity was delayed. Salinity significantly decreased size and number of marketable fruits, but increased fruit quality by increasing total soluble solids and sugar content. Leaf and fruit calcium and potassium concentrations were decreased significantly by increasing salinity levels. This was compensated for the accumulation of sodium. Anion accumulation was increased by increasing chloride concentration. These results indicate that it is feasible to use brackish water for growing tomato with minimum yield losses if salt concentration and duration of exposure are carefully monitored.