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Several levels of P were supplied via floatation irrigation to `South Bay' lettuce (Lactuca sativa L.) transplants to determine the optimum P concentration necessary. Plants were propagated by floating flats (ebb and flow system) in a nutrient solution containing P at either 0, 15, 30, 45, or 60 mg·L^-1 in summer and fall experiments, and either 0, 15, 30, 60, or 90 mg·L^-1 P in a factorial combination with 60 or 100 mg·L^-1 N in a winter experiment. Adding more than 15 mg·L^-1 P had minimal effect on growth. Transplants produced with 0 P grew poorly, regardless of the level 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 with N applied at 60 mg·L^-1. In general, relative growth rate was improved, while net assimilation rate was reduced at all levels of P. High-quality transplants had a root to shoot ratio of about 0.25, total root lengths between 276 and 306 cm, and total root area between 26 and 30 cm³ in a 10.9-cm³ cell volume. Only 30% of the plants produced without P could be pulled from the transplant flats, whereas 90% could be pulled when P was added. Pretransplant P hastened maturity and increased lettuce head weight at harvest in the field. This work suggested that at least 15 mg·L^-1 P, supplied via floatation irrigation to a peat + vermiculite mix, was required to produce a transplant with sufficient roots for ease of pulling, rapid field establishment, and earlier harvest.

Although floatation irrigation has numerous advantages for vegetable transplant production, including improved seedling health, lettuce (Lactuca sativa L.) transplants grown with floatation (ebb and flow) irrigation can have poor root systems. Floatation fertigation of `South Bay' transplants with K at 15, 30, 45, or 60 mg·L^-1 K applied every 2 to 4 days, increased fresh and dry root weight at 28 days. Higher K (24 mg·kg^-1) in the medium did not affect root weight. Fresh and dry shoot weight, leaf area, relative shoot ratio (RSR), relative growth rate (RGR), leaf weight ratio (LMR), and root weight ratio (RMR) were unaffected by applied K, regardless of the initial K concentration in the medium. Available K in a vermiculite-containing medium may have supplied all the K required. When 60 was compared with 100 mg·L^-1 N at various levels of K, the applied K again did not influence dry root weight; however, at 100 mg·L^-1 N, root weight was reduced as compared with 60 mg·L^-1 N, regardless of the level of applied K. In a field experiment, pretransplant K had no effect on growth. Transplants grown with no added K in a peat + vermiculite mix with at least 24 mg·L^-1 water-extractable K produced yields equivalent to transplants supplied with 15, 30, 45, or 60 mg·L^-1 K via floatation irrigation.

Embryo abortion and empty seeds after self-pollination occur in some transgenic (ACO antisense) `Galia' male parental lines. An embryo-rescue system in this melon was developed to save potential viable embryos. To obtain the best and reliable embryo-rescue technique, several parameters were used including an improved (five new supplements) nutrient medium (named E-21) from the E-20A basic medium (Sauton and Dumax de Vaulx, 1987), an inoculation system (removing the embryo from the seed or intact seed), and the use of different fruit harvesting dates of the wild type and a transgenic `Galia' male parental line. Fruits of wild type (WT) and transgenic (ACO gene in antisense orientation) `Galia' male parental line were harvested at 4, 10, 17, 24, and 30 days after pollination (DAP). Fruits were surface sterilized by dipping in a 20% commercial bleach solution for 30 minutes. Subsequently, seeds were removed from fruit under sterile conditions. These seeds were either used to dissect the embryos or placed directly with the hilum facing E-20A or E-21 medium. Seedlings from all treatments were transferred to E-21 elongation medium, incubated 4 weeks, and transferred to soil to evaluate growth. The efficiency of this technique was greater when the time after pollination (4, 10, 17, 24, and 30 DAP) to rescue the embryos was increased. Thus, 30 DAP was the best time to rescue the embryos. The number of rescued embryos using E-21 medium was greater than with E-20A. We did not find any significant differences in survival efficiency rate between WT and transgenic embryos. We have obtained a competent embryo-rescue technique for WT and transgenic `Galia' male parental line, which can be applied to rescue valuable GMO hybrid-melon embryos.

The uninterrupted supply of high quality colored peppers to the U.S. is mainly from imports of greenhouse-grown fruits. Average year-round wholesale market price of these imports was $4.80/kg when U.S. field-grown fruit price was $1.60/kg for colored and $0.91/kg for green. High market prices and a suitable environment for growing colored peppers in inexpensive protected structures led to construction of 25 ha of greenhouses currently growing peppers in Florida. Greater demand for specialty vegetable crops, loss of methyl bromide, and an increase in urban sprawl and price of arable land may result in growers considering greenhouses to produce high value peppers. We estimated the profitability of a greenhouse enterprise with a budget analysis and calculated the returns to capital and management. We assumed use of current technology applied in commercial greenhouse crops in Florida, and in experimental crops at the Univ. of Florida. Revenues per square meter were estimated from current yields and historical fruit price data. Plants were grown in perlite in a high-roof polyethylene-covered greenhouse (0.78 ha) located in north central Florida. Transplanting occurred in August and fruits were harvested from November to May for a yield of 13 kg·m^-2 with a total cost of production of $41.09 and an estimated return of $17.89. The return on investment was 17%. Only yields greater than 7.8 kg·m^-2 generated positive returns using the average wholesale fruit price during the season ($5.29/kg). For this price, a range of possible yields (5–17 kg·m^-2) led to returns ranging from $–9.52 to $30.84, respectively. The estimates indicated that production of greenhouse-grown peppers could represent a viable production alternative for Florida vegetable growers.

The increase in U.S. demand for colored bell peppers (Capsicum annuum) has been satisfied with increased supplies from imports and increased domestic production. Greenhouse-grown peppers of red, orange, and yellow colors were imported during the period 1993–2002 at wholesale fruit market prices that were three to five times greater than field-grown fruits. With high market prices and a suitable environment for growing colored peppers under inexpensive greenhouse structures [<$40/m² ($3.7/ft²)], up to 14 ha (34.6 acres) of greenhouses produced bell peppers in Florida in the year 2002. To estimate the profitability of a bell pepper greenhouse enterprise, a budget analysis was used to calculate the returns to capital and management. Production costs of greenhouse-grown peppers were estimated assuming the use of current technology applied in commercial greenhouse crops in Florida and in experimental crops at the University of Florida. Production assumptions included a crop of nonpruned plants grown in soilless media in a highroof polyethylene-covered greenhouse [0.78 ha (1.927 acres)] located in north-central Florida. For a fruit yield of 13 kg·m^–2 (2.7 lb/ft²), the total cost of production was $41.09/m² ($3.82/ft²), the estimated return was $17.89/m² ($1.66/ft²), and the return over investment was 17.1%. A sensitivity analysis indicated that fruit yields should be greater than 7.8 kg·m^–2 (1.60 lb/ft²) in order to generate positive returns based on a season average wholesale fruit price of $5.29/kg ($2.40/lb). For this price, a range of possible fruit yields [5–17 kg·m^–2 (1.0–3.5 lb/ft²)] led to returns ranging from –$9.52 to 30.84/m² (–$0.88 to 2.87/ft²), respectively. The estimates indicate that production of greenhouse-grown peppers could represent a viable vegetable production alternative for Florida growers.

Pollen germination timing has a paramount role in fertilization of a flower. Rapid germination and outgrowth of a pollen tube that penetrates the stigma is required. Physical and biological factors can affect pollen germination timing. The objective of this study was to determine if ACC oxidase antisense gene expression could influence in vitro pollen germination and in vitro pollen tube length growth. A transgenic (ACC oxidase antisense) `Galia' male parental line had a reduced fruit set compared to its wild type. Likewise, embryo abortion and empty seeds after self-pollination in a `Galia' male parental line were observed. Wild type and transgenic `Galia' male parental line melon plants were grown in a greenhouse according to the practices of Rodriguez (2003). Male flowers were collected from these plants between 10 to 12 am; pollen was obtained by dipping the anther in germination medium (10.25% sucrose, 0.031% calcium nitrate, 0.015% boric acid, 0.0075% KNO<sub>3</sub>, and 0.016% MgSO<sub>4</sub>) at 25 °C and analyzed immediately, either for total percentage of germination after 5 minutes of incubation or to measure pollen tube growth rate every 5 minutes during 1 hour. Each flower provided an average of 250 pollen grains. Assays were conducted by using the “Hanging Drop Method” (Okay and Ayfer, 1994). Percentage of pollen germination in WT `Galia' male parental line was greater than the transgenic line. Likewise, in vitro pollen tube growth in wild type `Galia' melon was greater than pollen from the transgenic line. Possibly the ACC oxidase antisense gene expression in `Galia' male parental line may have had an influence on the reduced fruit set observed.

Modern fertilization recommendations must optimize crop yield and quality and minimize chances of negative environmental effects due to overfertilization. Data from fertilizer studies can be fitted to several mathematical models to help determine optimum fertilizer rates, but resulting recommendations can vary depending on the model chosen. In this research, lettuce (Lactuca sativa L.) was used as a case study vegetable crop to compare models for estimating fertilizer N requirements. Greenhouse studies were conducted with `South Bay' and `Sierra' cultivars of crisphead lettuce to measure yield response to applied N. Individual plants were grown in pots and received six rates of N (0.0, 0.2,0.4,0.6,0.8, and 1.0 g/plant) as ammonium nitrate in split applications. Data for plant fresh mass and N uptake were recorded. The logistic model described the data for both cultivars quite well, with correlation coefficients of 0.98 and above. The logistic model was also applied to field data for average head mass of `South Bay' lettuce following application of N at 0,56,112,168,224, and 280 kg·ha^-1. Logistic, linear-plateau, and quadratic models were compared for the field data. Coefficients for the linear-plateau model were derived from the logistic model. All three models for lettuce production were compared graphically and analytically. The model coefficients were then used to make improved estimates of fertilizer recommendations for field production of lettuce.

Pepper seedlings can be infested with broad mites prior to transplanting. Transplanted seedlings may not present visible mite damage symptoms and few microscopic mites will be undetected by growers. A rapid increase of the mite population can subsequently result in yield losses in greenhouse-grown crops. Control of broad mites based on biological (N. californicus) and conventional (sulfur) methods were evaluated after infested transplants were introduced into a production greenhouse. Seedlings were artificially infested with two broad mites, 3 days before they were transplanted in mid-September in a passively ventilated greenhouse in Florida. Plants had either two predatory mites released once [4 days after transplanting (DAT)], or twice (4 and 22 DAT), or were sprayed with sulfur (four weekly applications starting 13 DAT when first damage symptoms were noticed). Damage on plants was assessed by an injury scale transformed into percentage values, with 100% being total damage on untreated infested plants. Broad mites were absent in all plants 38 DAT but the damage caused to the plants at this time was negatively correlated (r= –0.95) with marketable yield at 90 DAT. Plants produced no marketable yield where broad mites were not controlled. One or two releases of predators led to respective damages of 56% and 45%, and fruit yields of 2.0 and 3.0 kg·m^-2. Plants sprayed with sulfur had a damage of 7% after reaching a maximum of 74% at 18 DAT; however, yields were 4.3 kg·m^-2, which was similar to the yield obtained in the uninfested control treatment (4.6 kg·m^-2). Releases of predators prior to transplanting and/or higher predator release densities may be needed under similar conditions and will be evaluated in a subsequent experiment.

Primed, pregerminated, or nontreated `FloraDade' tomato (Lycopersicon esculentum Mill.) seeds in combination with several soil amendments were evaluated in three experiments for stand establishment characteristics and fresh-market fruit yields. Total percent emergence, seedling shoot weight, and marketable fruit yield were not consistently improved by GrowSorb, gel-mix, plug-mix covers, or mixtures with seeds as compared with a control (soil cover). However, rate of emergence was generally faster for plots containing primed or pregerminated seeds with soil amendments than for plots with a soil cover. Primed or pregerminated seeds emerged faster, and had higher total percent emergence and heavier seedling shoot weights than nontreated seeds, but there was little difference in response between primed and pregerminated seeds. Plants from the primed or pregerminated plots produced earlier (first harvest) marketable fruit than did plants from nontreated seed plots in one of three experiments. Priming or pregermination of tomato seeds resulted in a more consistently improved stand establishment than soil amendments.

Primed, pregerminated, or nontreated tomato (Lycopersicon esculentum Mill.) seeds were field-sown with several soil amendments to assess stand establishment at high temperatures. Soil amendments did not consistently improve tomato stand establishment. However, covering seeds with a fine-textured calcined montmorillonite clay (Growsorb) resulted in similar or improved total percent emergence, emergence rate, and seedling shoot dry weight as compared to the soil cover (control) for nontreated, primed, or pregerminated seeds. Plug-mix (a peat-vermiculite medium) or gel-mix [a 1:1 mixture (v/v) of plug-mix and gel, starch-acrylate copolymer, or polyacrylate polymer], covered over or mixed with nontreated, primed, or pregerminated seeds, did not consistently improve total percent emergence over the soil cover. However, soil amendments generally resulted in faster emergence than the soil cover. Pregerminated seeds imbibed for 60 or 72 hours at 25C generally resulted in reduced stands compared to primed or nontreated seeds. Moisturized seeds imbibed for 48 hours at 25C had faster emergence and heavier seedling shoots than nontreated seeds, regardless of soil amendment. However, primed seeds generally resulted in faster emergence and more plants with heavier seedling shoot weights than nontreated or pregerminated seeds sown at high temperatures.