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.
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.
Abstract
The identification of exceptional genotypes in a breeding program can involve evaluating the responses of large numbers of plants to environmental stress (2). Major hydroponic systems include aerated standing or flowing-nutrient solution, mist, and nutrient film cultures. Flowing solution culture currently provides the most consistent environment for roots, but it is costly and difficult to maintain (1, 3).
Abstract
A 50% increase in total radiation by extending the photoperiod from 16 to 24 hr doubled the weight of all cultivars of loose-leaf lettuce (Lactuca sativa L.) ‘Grand Rapids Forcing’, ‘Waldmanns Green’, ‘Salad Bowl’, and ‘RubyConn’, but not a Butterhead cultivar, ‘Salina’. When total daily radiation (moles of photons) was the same, plants under continuous radiation weighed 30% to 50% more than plants under a 16 hr photoperiod. By using continuous radiation on loose-leaf lettuce, fewer lamp fixtures were required and yield was increased.
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.
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.
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.
The sweetpotato [Ipomoea batatas (L.) Lam] breeding clone TU-82-155 was grown during Spring 1990 and Summer 1991 in standard Tuskegee Univ. (Alabama) growth channels (0.15 × 0.15 × 1.2 m) for 120 days in a greenhouse using a hydroponic (nutrient film) system with a modified half-strength Hoagland nutrient solution. The nutrient solution was changed every 2, 14, or 28 days. Total N, oil, ash, amino acid, vitamin, and mineral concentrations in storage roots generally were higher and dry weight and starch concentration were lower with 2-day solution changes than with those less frequent.
The effects of 0.25, 1.0, 2.5, 10, and 100 mg Mn/liter on sweetpotato [Ipomoea batatas (L.) Lam] were evaluated in a greenhouse during 2 years using the nutrient film technique. Foliage and storage root dry weights declined linearly as Mn concentration increased in either whole plants or fibrous roots. Foliage and storage root dry weights were equally sensitive to Mn concentration in whole plants but 5 to 15 times more sensitive to increased Mn concentration in the fibrous roots. Foliar N, P, K, Ca, and Mg concentrations were adequate and did not appear to limit plant growth. Manganese concentrations in solution had very little effect on Fe, Zn, or B concentration. Manganese concentration was higher in the foliage than in fibrous roots. Plant roots showed browning at the higher (10 or 100 mg Mn/liter) concentrations in solution, which indicated the presence of oxidized Mn. Characteristic toxicity symptoms were observed in plants receiving 2.5 (moderate), 10, or 100 mg Mn/liter in solution.
`Inca Yellow' marigolds (Tagetes erects L.) were planted in polyethylene bags containing coal bottom ash (CBA), pine wood peelings (PWP), a mixture of 1 CBA: 1 PWP (v/v), and loose Grodan rockwool (RW) and grown in a circulating nutriculture system. Three fertigation frequencies of 12, 6, or 4 cycles per 12-hour light period were set with a duration of 5 minutes each. Flower diameters of marigolds grown in CBA, PWP, and CBA-PWP exceeded flower diameters of RW-grown marigolds, and days from planting to harvest were less in CBA and CBA-PWP than in the other two media. There was no interaction between medium and fertigation frequency. Foliar analysis showed no significant differences in plant elemental composition among root media or fertigation frequencies. Postharvest PWP water extracts contained higher P levels than extracts of other media, and CBA-PWP water extracts contained higher K, Ca, and Mg. In the CBA-PWP mixture, decomposition products from PWP may have increased P volubility and solubilized the K, Ca,-and Mg-in CBA.