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- Author or Editor: Daniel J. Cantliffe x
Phosphorus applied at frequent rates via the flotation irrigation system affected growth of both roots and shoots of lettuce transplants grown with a flotation irrigation system. After an initial P addition of 15 mg·L–1, further P additions up to 90 mg·L–1 P resulted in a minimal growth response. Transplants produced with 0 P had similar poor growth, regardless of the amount of N applied. Nitrogen at 100 mg·L–1 improved the response of shoot growth to any level of P, but adversely affected root growth compared to N at 60 mg·L–1. Quality transplants had a root to shoot ratio of ≈0.25, total root lengths between 276 and 306 cm, and total root area between 26 and 30 cm2 in a 10.9-cm3 cell volume. Only 30% of the plants produced with 0 P could be pulled from the transplant flats, compared to ≈90% pulling success with added P. All pretransplant P treatments had a similar effect of increasing head mass at harvest time, and in reducing time to maturity regardless of production season. At transplanting, plants produced with transplant P were larger than those produced with no transplant P. Thus, at least 15 mg·L–1, supplied every 2 days via flotation irrigation, is recommended for production of high quality lettuce transplants in a peat+vermiculite media containing low concentrations of water extractable P.
Plant formation from somatic embryos in response to BAP, NAA, and sucrose was studied in sweetpotato [Ipomoea batatas (L.) Lam.]. A maximum of 15% embryos at the torpedo stage of development formed plants of agar-solidified basal medium containing 3% sucrose and no growth regulators. The percentage of embryos forming shoots was increased to 53% by 4 μm BAP, but BAP reduced whole plant formation and promoted callusing at the root axis end of embryos. The frequency of plant development was increased to 38% by adding 0.1 μm NAA to the basal medium. Reducing sucrose concentration to 1.6% in basal medium increased the frequency of plant development to 32%. Chemical names used: 6-benzylaminopurine (BAP; α-naphthaleneacetic acid (NAA).
The demand for plug transplants by the Florida winter strawberry (Fragaria ×ananassa Duch.) industry may increase as water conservation during plant establishment becomes more important and the loss of methyl bromide fumigant makes the production of bare-root transplants more problematic. A study was conducted during the 1995-96 and 1996-97 seasons to determine the effect of container size and temperature conditioning on the plant growth and early season fruit yield of `Sweet Charlie' strawberry plants. Plants in containers of three sizes (75, 150, and 300 cm3) were grown in one of two temperature-controlled greenhouses (35 °C day/25 °C night or 25 °C day/15 °C night) for the 2 weeks just prior to transplanting into a fruiting field at Dover, Fla. Plants exposed to the 25/15 °C treatment had significantly higher average root dry weights at planting in 1995 and 1996 than did plants exposed to the 35/25 °C treatment. Plants exposed to the 25/15 °C treatment also had higher average fruit yields than the plants exposed to the 35/25 °C treatment (48% and 18% higher in 1995-96 and 1996-97, respectively). The effect of container size on plant growth and yield was variable. Plants propagated in the 150- and 300-cm3 containers tended to be larger (at planting) than the plants propagated in the 75-cm3 containers, but the larger container sizes did not result in consistently higher yields.
Bare-root strawberry transplants have been conventionally used for establishment of strawberry fruiting fields. These bare-root transplants have variability in vegetative vigor that results in irregular flowering patterns. We have been experimenting with a containerized transplant system to produce uniform transplants. Increasing transplant container volume by increasing perimeter, rather than depth, has resulted in increased plant size, but also increases transplant production costs. This study evaluated three container perimeters (17, 25, 32 cm) and three container shapes (circular, elliptical, and biconvex) such that different cell perimeters had the same greatest diameter. All containers had a depth of 3.5 cm. Root imaging analysis (MacRHIZOTM) was used to measure root growth in the container as well as root growth 3 and 6 weeks after transplanting. Increasing container perimeter led to increased plant growth before and after transplanting, but did not affect fruit production. Transplant container shape did not significantly alter plant growth or fruit production. Biconvex and elliptical containers required 25% and 15% less surface area, respectively. Therefore, a biconvex shaped container can be used to increase plant density during transplant propagation, decreasing surface area needed and reducing production costs.
Abstract
Eight accessions of muskmelon (Cucumis melo L.) possessing one of 3 growth habits, vine, short-internode, and birdsnest, were germinated at 15°C. All 3 birdsnest lines had at least 85% germination after 12 days incubation, whereas all vine and short-internode lines tested had 0% germination. Various seed pretreatments, including presoaking in aerated water for 24 hours, had beneficial effects on germination of birdsnest types at this temperature.
To alleviate high-temperature-induced reductions in seed germination, emergence, and seedling uniformity in celery (Apium graveolens L.), seeds were primed via solid matrix priming (SMP); 0.5 g celery seeds was incubated at 15C with 10 g calcined clay and 2 ml water. After 2 days, 1, 2, 3, or 4 ml water or 1% NaOCl solution was added and seeds were kept for 2, 4, 6, 8, 10, 12, and 14 additional days. The germination percentage and coefficient of germination velocity (COV) were calculated for each treatment at 15 and 30C. The seeds primed with NaOCl gained significantly less moisture after 8 days of priming than those treated with water, regardless of the volume added. Germination of nonprimed seeds was 83% and 2% at 15 and 30C, respectively. Final germination at 30C increased to >80% when seeds were primed with 3 or 4 ml NaOCl solution or 3 ml water for >10 days. SMP treatment significantly reduced the negative effect of high temperature on celery seed germination.
Containerized strawberry transplants offer an alternative to problematic bare-root transplants, which often have variability in flowering and vegetative vigor. Containerized transplants were propagated in three different container cell sizes (75, 150, and 300 cm3) and grown at two different temperature regimes for 2 weeks prior to planting (25/15 and 35/25°C day/night). Bare-root transplants from Massachusetts and Florida were graded into small, medium, and large plants based on crown size (8, 12, and 16 mm respectively). Plug transplants grown at 25/15°C had greater root dry weights than transplants grown at 35/25°C. Root imaging analysis (MacRHIZO) showed that the differences in dry weight were due to root area, not root tissue density. Crown dry weight increased with increasing cell size. Plug transplants grown at 25/15°C flowered earlier and had greater production than any other treatment. The 75 cm3 cell size grown at 35/25°C produced greater December strawberry production than larger cell sizes at the same temperature regime; however, the 75 cm3 cell size had decreased January strawberry production while the larger cell sizes had increased production. Larger plug cell sizes had significantly greater production than smaller plugs throughout the season, whereas larger bare-roots had greater production only early in the season. Containerized plug transplants therefore offers a viable alternative to problematic bare-root transplants.
Abstract
Varying the level of added P to a deficient soil from 0, 25, 50, 75, 100, 200 and 400 ppm made it possible to study the influence of deficiency, sub-adequate, adequate and excess amounts of P on its distribution into P fractions within tomato leaves. Plant growth response was obtained at P rates up to 100 ppm. The P fractionation data indicated that inorganic phosphate constituted about one quarter of the total plant P even when the plant is deficient in P. The plant did not accumulate phosphate until it was supplied at rates that exceeded requirements of growth and then it was accumulated mainly as inorganic phosphate while the levels of soluble organic P, RNA-P, DNA-P, phospholipid-P and phosphorprotein-P remained unchanged over the entire range of P rates.
Beit Alpha cucumber (Cucumis sativus) is an exciting new greenhouse crop for production in the southeastern U.S. and Florida. Beit Alpha cucumbers are short, seedless fruit with dark-green skin and an excellent sweet flavor. Beit Alpha-types are the leading cucumber types in the Middle Eastern market and have gained recent popularity in Europe. Beit Alpha cucumbers grown hydroponically under a protected structure have prolific fruit set, yielding more than 60 high-quality fruit per plant during one season. U.S. hydroponic vegetable production is generally associated with structure and irrigation investments which are costly as well as other inputs, such as the media, which must be replaced annually or with each crop. Beit Alpha cucumber `Alexander' was grown in Spring 2001 and 2002 in a passive-ventilated high-roof greenhouse in Gainesville, Fla. Three media types, coarse-grade perlite, medium-grade perlite, and pine bark, were compared for efficiency of growing cucumbers (production and potential costs). During both seasons, fruit yield was the same among media treatments [average of 6 kg (13.2 lb) per plant]. Irrigation requirements were the same for each type of media; however, leachate volume was sometimes greater from pots with pine bark compared to either grade of perlite suggesting a reduced need for irrigation volume when using pine bark. Pine bark is five times less expensive than perlite and was a suitable replacement for perlite in a hydroponic Beit Alpha cucumber production system.
A greenhouse hydroponic system, which uses suspended plastic troughs, was found to be an efficient system for the production of high quality strawberry (Fragaria ×ananassa) plantlets. In this system micropropagated mother plants of `Oso Grande' and `Sweet Charlie' produced an average of 84 and 80 daughters per mother plant, respectively, in 1996, at a plant density of 3 mother plants/ft2 (32 mother plants/m2). Nearly 100% of the plantlets harvested from the system were successfully rooted in plug trays, and showed no symptoms of leaf or crown diseases.