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Open access

Athanasios P. Papadopoulos and Herman Tiessen

Abstract

Four cultivars of greenhouse tomato (Lycopersicon esculentum Mill.) were grown in the greenhouse and two cultivars were grown in growth chambers in order to study the effects of root and air temperature on the elemental composition (N, P, K, Ca, and Mg) of leaf tissue. Most of the variation observed in the nutrient composition of leaves was due to air temperature and the cultivar used; only few root temperature effects were significant. Low air temperatures (24°/14°C, 24°/8°, 19°/14°; day/night) resulted in higher N concentrations in the leaf tissue, whereas root temperature had little effect on N. Response to air temperature was similar for P or for N. However, response to high root temperature (27° and 24° in the greenhouse and the growth chamber, respectively) was greater for P than for N. Air and root temperatures had little effect on K concentration in tomato leaves. Consistently high Ca and Mg levels resulted with low air temperatures (24°/8°, 19°/14°, 13°/8°), whereas root temperature had no effect on accumulation of these two nutrients. The incidence of blossom-end-rot in the fruit of all cultivars used in the study was associated with low Ca and Mg levels in the leaf tissue.

Open access

Sharon L. Knight and Cary A. Mitchell

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

Mikal E. Saltveit Jr. and Eric Young

Abstract

A method is described for studying the 3-dimensional distribution of roots grown in a medium consisting of small pieces of glass. After growing to a desired size, the plant is sacrificed by evaporating all water from the media with flowing air. To visualize the undisturbed root system, an immersion oil with the same refractive index as the glass is added to the glass container in which the plant was grown.

Open access

Sharon L. Knight and Cary A. Mitchell

Abstract

‘Salad Bowl’ and ‘Waldmann’s Green’ leaf lettuce (Lactuca sativa L.) were exposed to photosynthetic photon flux densities (PPFD) of 444 or 889 µmol s–1m–2 for 20 hours day–1 under a diurnal temperature regime of 25°C days/15° nights or 20° days/15° nights. Leaf dry weight of both cultivars was highest under the high PPFD/warm temperature regime and lowest under the low PPFD/cool temperature regime. ‘Waldmann’s Green’ yielded more than did ‘Salad Bowl’ at 889 µmol s–1m–2 and 25° days/20° nights. Under high PPFD, both cultivars yielded better with 25° days/25° nights than with 25° days/20° nights, although relative growth rates were the same under both temperature regimes.

Open access

B. V. Neilson and G. W. Eaton

Abstract

Plants of everbearing strawberry (Fragaria x ananassa Duch. ‘Quinault’) were grown in solution culture with 0.01, 0.05, 0.25, and 1.25 ppm boron. Fruit developed abnormally on deficient plants, but there was no reduction in fruit weight. Where boron was insufficient, flower number per leaf, fruit set, or fruit enlargement limited yield but where boron was intermediate, leaf numbers limited yield. No single component limited yield at the highest level of boron.

Open access

A. Hagiladi, J. Ben-Jaacov, N. Levav, and N. Zamir

Abstract

The cultivation of a wide range of ornamental plants in a closed hydrosolaric greenhouse was studied. The hydrosolaric greenhouse was composed of a solar energy harvesting system and a hydroponic system. Energy collected by the greenhouse air from the sun during the day was conserved in the growth solution, which released it during the night. This system was able to maintain the air temperature 6 C above the outdoor temperature during the night. Relative humidity ranged between 85 and 100%, thus providing a favorable environment for tropical foliage plants. Philodendron bipinnatifidum Schott, Gardenia jasminoides Ellis, Ficus benjamina L., F. lyrata Warb., Anthurium andreanum Lind and Brassaia actinophylla Endl. produced under this system were of excellent quality.

Open access

R. B. Marlatt and J. J. McRitchie

Abstract

Symptoms of zinc deficiency in hydroponically-grown Chrysalidocarpus lutescens H. Wendl. included plant stunting, uniformly chlorotic foliage and very small leaves bearing stubby, clustered pinnae.

Open access

R. B. Marlatt

Abstract

Boron deficiency symptoms of hydroponically-grown Ficus elastica Roxb. ‘Decora’ included plant stunting, deformation of immature leaves and necrosis of terminal bud. Excessive boron caused the undersides of mature leaves to have brown, circular lesions with chlorotic halos, starting at leaf margins. Affected leaves abscised prematurely. Boron deficiency symptoms of hydroponically-grown Chrysalidocarpus lutescens Wendl. included stunted growth, chlorotic mottling and streaking of leaflets and eventual death of immature leaves and terminal bud. Inflorescences bore necrotic fruits and died prematurely. Toxicity symptoms included leaflet mottle chlorosis and premature death and tip-bum of all leaves.

Free access

Jonathan M. Frantz, Gregory E. Welbaum, Zhengxing Shen, and Ron Morse

“Float-bed” (FB) is a simple hydroponic system used by the tobacco industry for transplant production. “Ebb-and-flood” (EF) is a modified FB system with periodic draining of the bed to limit water availability and control plant growth. Field-bed cabbage (Brassica oleracea L. gp. Capitata) transplant production was compared with FB, EF, and overhead-irrigated plug-tray greenhouse systems. Plants were produced in May and June and transplanted in a field near Blacksburg, Va., in June and July of 1994 and 1995, respectively. Beds for FB and EF production consisted of galvanized metal troughs (3.3 × 0.8 × 0.3 m) lined with a double layer of 0.075-mm-thick black plastic film. In 1994, both EF and FB seedlings were not hardened before transplanting, were severely stressed after transplanting, and had higher seedling mortality compared with plants from other systems. Plug-tray transplants showed the greatest increase in leaf area following transplanting and matured earlier than seedlings produced in other systems. In 1995, EF- and FB-grown cabbage plants were hardened by withholding water before transplanting, and seedlings had greater fresh mass and leaf area than plug-tray or field-bed seedlings 3.5 weeks after transplanting. Less succulent cabbage transplants were grown in EF and FB systems containing 66 mg·L-1 N (40% by nitrate) and 83 mg·L-1 K. Compared with the FB system, the EF system allowed control of water availability, which slowed plant growth, and increased oxygen concentration in the root zone. Both EF and FB systems are suitable for cabbage transplant production.

Free access

Gregory E. Welbaum, Jonathan M. Frantz, Malkanthi K. Gunatilaka, and Zhengxing Shen

Sweet corn (Zea mays L.) cultivars containing the shrunken-2 (sh2 ) gene have superior kernel quality but often germinate poorly and display poor seedling vigor. The transplanting of sh2 sweet corn was investigated as a method to improve stand establishment and hasten maturity. Three-week-old plants (sh2 cv. Krispy King) were raised in 200-cell polystyrene trays in either plug-trays (PT), float beds (FB), or ebb-and-flood (EF) production systems and compared with direct-seeded (DS) controls for transplant quality, successful establishment, and early harvest. In 1994, when plants were established in early June, PT plants matured 1 week earlier than DS and FB plants, which had similar mean times to harvest. In 1995, when field planting occurred in July, all plants flowered prematurely when only 60 cm tall. In 1996, the experiment was begun in early May, and survival of all transplants was >85% vs. 54% for DS plants. In 1996, transplants matured 10 to 13 days earlier than DS plants, however, >90% of DS plants produced marketable ears vs. 63%, 49%, and 44% of EF, FB, and PT plants, respectively. The DS plants were also taller with better root development than transplants in all years. Transplants produced smaller, lower-quality ears than did DS plants, thus nullifying the benefits of greater plant populations and earlier maturity. The EF system produced high-quality seedlings because of the greater control of water availability during seedling development. In some areas, the increased value of early sh2 sweet corn may be worth the additional cost of transplanting and greater percentage of unmarketable ears.