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Bethany A. Galloway, Jonathan R. Schultheis, and David W. Monks

A study was conducted in Fall 1995 at the Horticultural Greenhouse, North Carolina State University, to examine growth of banana (`Banana Supreme'), bell (`Camelot'), and jalapeno (`Mitla') pepper under overhead (OI), ebb and flood (EF), and float (F) irrigation systems. Plant emergence was fastest in the float system, but slowest in the OI system. Irrigation treatment was highly significant for all weekly sampling dates for root and shoot fresh weight, root and shoot dry weight, root length, stem diameter, height, and leaf area. Stem diameter of F plants was greater than both EF and OI. However, EF and OI plants had similar diameter regardless of sampling date. Root fresh weight did not differ among pepper cultivars. By 39 days after planting (DAP), F plants had 33% greater root fresh weight, by 46 DAP they were almost double, and at 53 DAP they were 44% larger compared to the EF treatment. Float plants had greatest root length, but EF and OI plants had denser root mass (visual observation) in the transplant container cell. At 46 and 53 DAP, EF plants were generally taller than OI plants, and by 60 DAP this difference was almost 30%. Float plants were about double the height of the EF and OI plants and this difference continued until the experiment terminated. Bell pepper had the greatest shoot fresh weight at all sampling dates after 25 DAP, while jalapeno was greater than banana only up to 39 DAP. Beyond 39 DAP, banana pepper fresh weight surpassed jalapeno pepper. By 53 DAP, shoot fresh weight of float transplants were almost 3 times greater than EF or OI plants. Float plants reached a satisfactory size (137 mm height) for transplanting by 8 weeks. Height of EF and OI plants at this time was 68 and 48 mm, respectively. This experiment is being repeated in Spring 1996.

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Wayne C. Porter

Black polyethylene, perforated clear polyethylene, double-slitted clear polyethylene, spunbonded polyester, and a bare soil control were evaluated for their effect on the number, size, and distribution of production of sweet potato transplants. The perforated and double-slitted bed covers increased the weight and number of sweet potato transplants compared with the control or with black polyethylene at the first harvest in 1986 and 1987, Seed roots covered with the spunbonded polyester bed cover produced more plants of greater weight than seed roots covered with bare soil at the first harvest in 1986 only. Black polyethylene treatments produced the greatest weight and number of transplants at the second harvest (8 to 12 days later) in both years. There were no significant differences in total weight and number of transplants among black polyethylene, perforated or double-slitted clear polyethylene treatments in 1986. Total transplant number and weight from plots covered with spunbonded polyester were lower than those from plots with any other bed covers.

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Jim E. Wyatt, Marla C. Akridse, and Douglas W. Hamilton

Studies were conducted in plastic foam trays in float tanks to investigate effects of aeration of the nutrient solution, tray management after seeding and addition of KNO3 fertilizer to the substrate media on tomato transplant growth. Aeration of the nutrient solution had no effect on rate of tomato seedling emergence or growth, even though dissolved O2 was higher in aerated tanks than in non-aerated tanks. Placing trays in the tanks immediately after seeding caused faster seedling emergence than either delaying placement in the tanks or stacking trays until emergence began. KNO3 at 20 g·kg dry Pro-Mix” media resulted in delayed initial emergence but no differences were found 7 days after planting. Initial tray treatments or addition of KNO3 to the media had no effects on final tomato transplant size.

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Po-Lung Chia and Chieri Kubota

Plant morphology control is a critical technique in commercial greenhouse transplant production. Light treatment at the end of the day affects a phytochrome-regulated response affecting plant height among other characteristics and has been studied by biologists for many years. Recognizing the need to produce long hypocotyls in vegetable grafting, effects of end-of-day far-red (EOD-FR) light on tomato rootstock hypocotyl elongation were investigated. Two commercial rootstock cultivars, Aloha (Solanum lycopersicum) and Maxifort (S. lycopersicum × S. habrochaites), were used for the experiments examining responses to EOD-FR light quality [red to far-red ratio (R/FR)] and EOD-FR light dose in a greenhouse environment. In the EOD-FR light quality experiment using ‘Aloha’ seedlings, incandescent light (R/FR = 0.47) induced significant hypocotyl elongation (20%) compared with the untreated control. Incandescent light with a spectral cut filter (reducing R/FR to 0.05) induced a greater hypocotyl elongation (44%) than unfiltered light, confirming the importance of use of light with a lower R/FR (or purer FR) light source in EOD-FR treatments. In the experiment on EOD-FR light dose–response, hypocotyl elongation of both ‘Aloha’ and ‘Maxifort’ was increased by increasing FR intensity as well as FR treatment duration at a lower dose range. The dose saturation curve of hypocotyl length was well described using a Michaelis-Menten-type model with FR dose (in mmol·m−2·d−1) as an independent variable. The model-based estimation of 90% saturating FR light dose for ‘Aloha’ and ‘Maxifort’ was 5 to 14 mmol·m−2·d−1 and 8 to 15 mmol·m−2·d−1, respectively, although practical near saturation dose seems to be 2 to 4 mmol·m−2·d−1 for both cultivars. None of the EOD-FR treatments affected plant dry weight, stem diameter, or plastochron index. Hence, elongation was achieved without compromising growth and development. EOD-FR was shown to be an effective non-chemical means allowing transplant propagation industry to produce long hypocotyls for grafting use.

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Fumiomi Takeda Takeda, Stan Hokanson*, John Enns, Penelope Perkins-Veazie, and Harry Swartz

`Chandler' strawberry plants were propagated in tissue culture and grown from April to August in a protected environment to produce stolons. July-harvested daughter plants were stuck in cell packs with rooting media and placed under mist sprinklers, or cold stored at 2 °C for 42 days. Among the July transplants, some were kept in the greenhouse until field planting (14 Sept.) and others were moved into a cold room on 14 August. Daughter plant size and position on the stolon affected rooting and quality of transplants. July-harvested daughter plants that were plugged and misted after being cold stored for 42 days developed fewer roots than daughter plants plugged immediately after detaching from mother plants in July or August. In the field, transplants produced from daughter plants harvested in July and cold stored for 42 days developed more stolons than transplants from July- and August-harvested daughters that were not exposed to cold storage treatments. Larger daughter plants produced more branch crowns than did smaller daughter plants during the fall. All transplants from daughter plants harvested in July and propagated without cold treatment bloomed by November. Fruit production ranged from 521 to 703 g per plant. `Chandler' plants from daughter plants that weighed 10 g produced 10% greater yield than those that weighed <1.0 g. Plants generated from daughter plants plugged in July produced 26% more fruit than those plants plugged in August. Greenhouse soilless systems can be used to grow `Chandler' mother plants for generating runner tips and transplants for the annual plasticulture in colder climates. `Chandler' plants produced in July can yield a late fall crop under high tunnels and more fruit in the spring than August-plugged transplants

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M.M. Gaye and A.R. Maurer

Field studies were conducted to determine the effects of row covers (no row cover or Agryl P-17), seeding date, and seeding method (seeding in a furrow or into a smooth soil surface) on the development, harvest date, and yield of brussels sprouts [Brassica oleracea L. (Gemmifera Group)] grown in southwestern British Columbia. The treatments were applied to the plants in the seedbed after which the plants were transplanted in the field and grown to horticultural maturity. In both years, row covers increased soil temperatures and advanced seedling development and transplanting dates compared with uncovered treatments. Leaf weight ratio (LWR) decreased, specific leaf area (SLA) increased, and leaf area ratio (LAR) was unaffected by the application of row covers. Early seeding also promoted early transplanting. In 1987, plots were harvested when plants reached horticultural maturity. There was a linear effect of seeding date on harvest date, early seeding promoted an early harvest, and row covers advanced the sprout harvest of plants seeded earliest (24 Mar). In 1988 all treatments were harvested from 17 to 19 Oct. and marketable yield was improved by early seeding and by row covers. Seeding method did not influence plant growth or yield.

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A. Liptay and S. Nicholls

Tomato transplant (Lycopersicon esculentum Mill.) root growth in the field was directly related to N level supplied to the transplants as seedlings in the greenhouse. Root growth in the field increased exponentially when N was applied at 50 to 350 mg·liter-1. Transplant growth in multicelled trays increased in a sigmoidal fashion with N, up to 200 mg-liter'. The optimal N range for maximum survival, growth, and early yield in the field was from 100 to 200 mg-liter'. Strength of the seedling stem increased with N level curvilinearly. Seedling survival in the field was highly correlated with seedling stem strength.

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Jean Masson, Nicolas Tremblay, and André Gosselin

This experiment was initiated to determine the effects of supplementary lighting of 100 μmol·s-1·m-2 (PAR) in combination with four N rates (100, 200, 300, and 400 mg N/liter) on growth of celery (Apium graveolens L.), lettuce (Luctuca sativa L.), broccoli (Brassica oleracea italica L.), and tomato (Lycopersicon esculentum Mill.) transplants in multicellular trays. Supplementary lighting, as compared with natural light alone, increased shoot dry weight of celery, lettuce, broccoli, and tomato transplants by 22%, 40%, 19%, and 24%, and root dry weight by 97%, 42%, 38%, and 21%, respectively. It also increased the percentage of shoot dry matter of broccoli and tomato, leaf area of lettuce and broccoli, and root: shoot dry weight ratio (RSDWR) of celery and broccoli. Compared with 100 mg N/liter, a N rate of 400 mg·liter-1 increased the shoot dry weight of celery, lettuce, broccoli, and tomato transplants by 37%, 38%, 61%, and 38%, respectively. High N fertilization accelerated shoot growth at the expense of root growth, except for tomato where a 16% increase of root dry weight was observed. High N also reduced percentage of shoot dry matter. Supplementary lighting appears to be a promising technique when used in combination with high N rates to improve the production of high quality transplants, particularly those sown early.