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Wasabi japonica plantlets were acclimatized in a hydroponic system to determine effective procedures. The plantlets were cultured on solid Murashige-Skoog medium with 3% sucrose. Shoots that formed roots were transplanted into hydroponic systems: 1) acclimatization in ebb-and-flow (EBB) for subirrigation (medium: granulated rockwool and coir); and 2) acclimatization in deep flow technique (DFT). The plantlets were acclimatized for 5 weeks under two irradiance treatments, 50 and 300 mmol·m-2·s-1. Photosynthetic capacity in high PPF was higher than that in low PPF during acclimatization. Electron transport rate from PS II (ETR) and biomass production increased significantly with increased light availability. The fresh weight, dry weight, and leaf area of plantlets in high PPF were higher than those in low PPF. In particular, the dry weight and ETR of the plantlets grown in high PPF increased more than twice as much as those in low PPF. At 50 mmol·m-2·s-1 PPF, growth indexes, such as number of leaves, leaf length, leaf width, leaf area, fresh weight, and dry weight, were higher in EBB (granulated rockwool) > EBB (coir culture) > DFT. At 300 mmol·m-2·s-1 PPF, those indexes were higher in DFT > EBB (granulated rockwool) > EBB (coir). The Wasabi japonica plantlets acclimatized in a hydroponic system also had a superior performance when they were transferred to the field.

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In growing greenhouse tomato (Lycopersicon esculentum Mill.) using the nutrient film technique (NFT), HNO3 or H3PO4 is usually added to offset the increase in pH of the recirculating solution. For economic and environmental reasons, HCl would be a possible substitute for either HNO3 or H3PO4. Therefore, experiments were initiated to evaluate HCl as an alternative acid in controlling the pH of the recirculating solution in NFT-grown greenhouse tomato. The effects of HNO3, H3PO4, and HCl on the growth, fruit yield, and fruit quality were quantified. In 1995, these effects were tested using `Trust' and `BST 7804' at a recirculating solution pH of 5.5, 6.0, or 6.5; in 1996, only `Trust' was grown at a recirculating solution pH of 6.2. In the 1995 experiment, genotypic differences in marketable fruit yield tended to be smaller when HCl was used to control the recirculating solution pH at 6.0 than when either H3PO4 or HNO3 was used. In `Trust', at a pH of 5.5 under the HCl treatment, fruit quality tended to be higher than in other treatment combinations. In 1996, over a 45-day period, the concentration of Cl that accumulated in the recirculating solution from added HCl was 313 mg·L−1 (313 ppm). There were no significant effects of the treatments on the growth, fruit quality, or yield of the crop. The total marketable yield was better when HCl had been used, likely due to high fruit production at the early part of the harvesting period. Potential savings for the season can be achieved if HCl is substituted for H3PO4 to regulate the nutrient solution pH in NFT-based greenhouse tomato production.

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Abstract

Static solution culture systems are widely used in plant research and for teaching demonstrations of plant nutrient deficiency symptoms. Numerous systems have been described (1,2) including one (3) constructed of readily available materials. Reported here is another design for a static solution culture system built of readily available components. This system is characterized by a) low cost, b) simplicity, c) easy assembly, d) potential for variable spacing of culture vessels, e) identical aeration rate for each vessel without individual air flow valves, and f) aeration from the top of the culture vessel rather than the bottom, eliminating drainage through aeration lines should the air supply fail.

Open Access

Abstract

Many different hydroponic systems and methods have been used for growing plants. This report describes an outdoor sand-nutrient culture system that has been used for more than 10 years to study the response of vegetables to inorganic nutrition under natural outdoor conditions and with controlled rooting conditions. The system is simple, dependable, and provides abundant aeration for plant roots.

Open Access

concentrations in hydroponics solutions. Plants were maintained under these conditions until the first flowers were present (4–8 weeks, depending on the cultivar), at which time plants were harvested. Tissue from each cultivar was collected on the same day

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Indoor vertical farms that grow lettuce commonly encounter tipburn, which is an environmental disorder caused by calcium (Ca) deficiency during the late head-forming stages of lettuce. Characterized by marginal leaf necrosis of young expanding leaves, tipburn reduces marketable yield because of the appearance of these necrotic lesions. Lowering the daily light integral (DLI) to slow the plant growth rate has been a widely practiced approach to avoid tipburn in lettuce, but it largely reduces the final yield. We assessed the effect of lowering the DLI only during the end of production, which is a critical time because it is when tipburn is typically observed. Lettuce plants of tipburn-sensitive cultivars Klee and Rex were grown under a tipburn-inducing condition in growth chambers. Sixteen days after transplanting, the DLI was varied to 100% (L100), 85% (L85), 70% (L70), or 55% (L55) of the original 17.4 mol⋅m−2⋅d−1 to grow the final 12 d. At harvest, tipburn severity was reduced by lowering the DLI, but the magnitude of reduction was cultivar-specific. For ‘Klee’, the lowest tipburn severity was found at L55 (8% ± 2.1% of leaves), but the severity was similar for all other DLI levels (33% ± 3.5% of leaves). For ‘Rex’, tipburn severity was highest in the control (L100; 14% ± 2.8% of leaves) but similar for all other DLI levels (2% ± 0.9% of leaves). Reducing the end-of-production DLI to 55% resulted in a linear decrease in yield by up to 22% and 26% for ‘Klee’ and ‘Rex’, respectively. When the increase in marketable yields and decrease in the electricity cost were considered, decreasing the end-of-production DLI yielded a profitable contribution only for ‘Klee’ (L55). For moderately tipburn-sensitive ‘Rex’, revenue losses attributable to the yield decrease were too large to justify this approach of end-of-production reduced DLI.

Open Access

Greenhouse experiments were conducted in 2005 and 2006 near Live Oak, FL, to develop fertilization programs for fresh-cut ‘Nufar’ basil (Ocimum basilicum) and spearmint (Mentha spicata) in troughs with soilless media using inputs compliant with the U.S. Department of Agriculture's National Organic Program (NOP). Four NOP-compliant fertilizer treatments were evaluated in comparison with a conventional control. Treatments and their analyses in nitrogen (N), phosphorus (P), and potassium (K) contents are as follows: conventional hydroponic nutrient solution [HNS (150 ppm N, 50 ppm P, and 200 ppm K)], granular poultry (GP) litter (4N–0.9P–2.5K), granular composite [GC (4N–0.9P–3.3K)], granular meal [GM (8N–2.2P–4.1K)], and GM plus a sidedress application of 5N–0.9P–1.7K fish emulsion (GM + FE). Electrical conductivity (EC) of the media, fresh petiole sap nitrate (NO3-N) and K concentrations, dried whole leaf NO3-N, P, and K concentrations, and yield and postharvest quality of harvested herbs were evaluated in response to the treatments. Basil yield was similar with HNS (340 g/plant) and GP (325 g/plant) in 2005 and greatest with HNS (417 g/plant) in 2006. Spearmint yield was similar with all treatments in 2005. In 2006, spearmint yields were similar with the HNS and GP yields (172 and 189 g/plant, respectively) and greater than the yields with the remaining treatments. In both years and crops, media EC values were generally greater with the GC than with the GP, GM, and GM + FE treatments but not in all cases and ranged from 1.77 to 0.55 dS·m−1 during the experiments. Furthermore, HNS media EC values were consistently equal to or lower than the GP media EC values except with EC measurements on 106 days after transplanting in both crops in 2005. Petiole NO3-N and K results were variable among crops and years, but provided valuable insight into the EC and yield data. We expected EC, petiole NO3-N, and petiole K to be consistently higher with HNS than with organic treatments, but they were not, indicating a reasonable synchrony of nutrient availability and crop demand among the organic treatments. The postharvest quality of both basil and spearmint was excellent with all treatments with few exceptions.

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Abstract

Several levels of photosynthetic photon flux density (PPFD) were tested for effects on growth of 4 cultivars of lettuce (Lactuca sativa L.) under controlled-environment conditions. Growth of ‘Salad Bowl’, ‘Bibb’, and ‘Ruby’ was greater at 932 µmol s -1m-2 than at ≤ 644 µmol s-1m-2 under a 16-hour photoperiod. Thirty mM NO3 - or 5 mM NH4 + + 25 mM NO3 - increased leaf dry weight while reducing leaf chlorosis in ‘Salad Bowl’ and ‘Grand Rapids’ relative to that with 15 mM NO3 -, and reduced leaf purpling in ‘Bibb’ and ‘Ruby’ with little or no effect on yield. Continuous illumination with 455 or 918 µmol s-1 m-2 stimulated yield of ‘Salad Bowl’ and ‘Bibb’ when 30 mM N as NH4 + + NO3 - was used relative to that with 15 mM NO3 -.

Open Access

Abstract

Cultivars of greenhouse tomato (Lycopersicon esculentum Mill.) were grown in the greenhouse and in growth chambers to study the effects of root and air temperature on flowering and yield. A low air temperature of 19° (day)/14°C (night), during the fall crop, caused no reduction in yield when compared with the commonly used 22°/17° air temperature. A 13°/8° air temperature during the spring crop drastically reduced yield compared with the 19°/14°C air temperature. Flowering of ‘Ohio MR-13’ in growth chambers was delayed significantly at air temperatures of 24°/8° compared to 24°/17°, but the flowering of ‘Vendor’ was unaffected by air temperature treatments. Marketable yield of ‘Vendor’ was significantly higher at 24°/8° compared to the 24°/17° treatment, while the marketable yield of ‘Ohio MR-13’ was unaffected. At a constant, day air temperature of 24°, the amount of small fruit decreased as night air temperature was lowered from 17° to 8° and maturity was delayed as night air temperature was lowered from 14° to 8°. The effect of low air temperature on flowering and yield of tomatoes was large and could not be offset by increasing root temperatures. At air temperatures of 24°/17°, 24°/14°, and 24°/8°, marketable yields were affected adversely by the absence of root thermoperiodicity (day to night root temperature variation).

Open Access