Search Results

You are looking at 11 - 20 of 26 items for

  • Author or Editor: D.G. Mortley x
Clear All Modify Search

Growth chamber experiments were conducted to study the physiological and growth response of sweetpotato [Ipomoea batatas (L.) Lam.] to either 50% or 85 % relative humidity (RH). Vine cuttings of T1-155 were grown using the nutrient film technique in a randomized complete-block design with two replications. Temperature regimes of 28/22C were maintained during the light/dark periods with irradiance at canopy level of 600 μmol·m-2·s-1 and a 14/10-hour photoperiod. High RH (85%) increased the number of storage roots per plant and significantly increased storage root fresh and dry weight, but produced lower foliage fresh and dry weight than plants grown at 50% RH. Edible biomass index and linear growth rate (in grams per square meter per day) were significantly higher for plants grown at 85 % than at 50% RH. Leaf photosynthesis and stomatal conductance were higher for plants at 85 % than at 50% RH. Thus, the principal effect of high RH on sweetpotato growth was the production of higher storage root yield, edible biomass, growth rate, and increased photosynthetic and stomatal activity.

Free access

The effects of light intensity on three sweetpotato cultivars [Ipomoea batatas (L.) Lam] were evaluated in growth chambers, as part of NASA's Closed Ecological Life Support Systems (CELSS) program for long duration space missions. Vine cuttings of `TI-155', `GA Jet', and TUJ1 were grown using nutrient film technique (NFT) in a modified half Hoagland's solution with a 1:2.4 N:K ratio in channels (0.15×0.15×1.2 m). Plants were exposed to irradiance levels of 360 or 720 umols m-2s-1 with an 18/6 photoperiod in a randomized complete block design with two replications. Temperature was set at 28:22 lightdark and RH was 70%. Differences in plant response to were more related to cultivars than the effect of light intensity. Storage root number (8) fresh, (786 g/plant) and dry weights (139 g/plant) were highest for `TI-155' while foliage fresh and dry weights were highest for `TUJ1' when averaged across light levels. TI-155' (921 g/plant) and `GA Jet' (538 g/plant) produced greater yields at higher irradiance. `TUJ1' produced a higher yield (438 g/plant at the lower intensity compared to 219 (g/plant) at the higher intensity, suggesting this cultivar could produce storage roots in similar conditions in a CELSS.

Free access

The effect of inoculation with Azospirillum brasilense strain Cd on mineral concentration in sweetpotato, [Ipomeo batatas (L) Lam cv. TI-155] tissue and ionic composition of plant nutrient solution was investigated in a greenhouse study. In the field, inoculation of sweetpotato with Azospirillum spp. has been reported to enhance. sweetpotato yield. In this study, 48-h old broth cultures were used as inoculum at a population density of approx. 1 × 108 cfu/ml. The inoculum (0.20 L) was added to the reservoirs containing 30.4 L of a modified half Hoagland's plant nutrient solution at 28 days after the start of the experiment Results indicate that percent total nitrogen in sweetpotato foliage tended to be higher for the inoculated fibrous mat than in the fibrous mat for non-inoculated plants. The percent total nitrogen in storage roots for the non-inoculated treatment tended to be higher than in storage roots for inoculated plants. Inoculation resulted in a slight increase in foliar phosphorus concentration but had no effect on phosphorus concentration in sweetpotato storage and fibrous root samples. Inoculation tended to reduce foliar calcium concentration. Magnesium concentration in leaf tissue was not influenced by inoculation. Foliar potassium concentration tended to increase slightly. The effect of inoculation on potassium concentration in sweetpotato root tissue was not well-defined; potassium concentration tended to be higher in fibrous root tissue for the inoculated treatment. But in storage root tissue, potassium concentration was higher for the non-inoculated treatment than for the inoculated treatment. Inoculation did not affect foliar concentrations of any of the micronutrients measured. This study indicates no effect of inoculation on ionic strength of nutrients in solution reservoirs.

Free access

The effects of photoperiod and light intensity on two sweetpotato cultivars [Ipomoea batatas (L.) Lam] were evaluated in growth chambers. Vine cuttings of `TI-155' and `GA Jet' were grown using nutrient film technique (NFT) in a modified half Hoaglands solution with a 1:2.4 N:K ratio in channels (0.15×0.15×1.2 m). Plants were exposed to 9:600 or 18:300 umols m-2 s-1 photoperiod:light intensity treatments in a randomized complete block design with two replications. Temperature was set at 28:22 light:dark and RH was 70%. Storage root fresh and dry weights and fibrous root dry weight for both cultivars were significantly higher for plants exposed to longer photoperiod and lower light intensity than for those at a shorter photoperiod and higher light intensity. Foliage fresh weight for TI-155' was higher at 18:300 photoperiod:light intensity but dry weights were similar. Foliage fresh and dry weights for `GA Jet' and number of storagage roots/plant for both cultivars were similar regardless of treatments.

Free access

Two sweetpotato [Ipomoea batatas (L.) Lam] genotypes (`Georgia Jet' and the breeding clone TI-155) were grown at 12-, 15-, 18-, and 21-h light/12-, 9-, 6-, 3-h dark cycles, respectively, to evaluate their growth and elemental concentration responses to duration and amount of daily lighting. Vine cuttings (15 cm long) of both genotypes were grown in rectangular nutrient film technique channels for 120 days. Conditions were as follows: photosynthetic photon flux (PPF) mean 427 μmol·m–2·s–1, 28C day/22C night air cycle, and 70% ± 5% relative humidity. The nutrient solution used was a modified half-strength Hoagland's solution. Storage root count per plant and per unit area, yield (in grams per square meters per day), and harvest index increased, while production efficiency (in grams per mole) decreased with increased daily PPF. Stomatal conductance for both genotypes declined with increased daily PPF. Leaves were smallest for both genotypes at the 21-h light period, while storage root yield declined as leaf area index increased. Except for a linear decrease in leaf N and K with increased light period, elemental concentration was not significantly influenced.

Free access

Growth chamber experiments were conducted to study the physiological and growth response of peanut (Arachis hypogaea L.) to 50% and 85% relative humidity (RH). The objective was to determine the effects of RH on pod and seed yield, harvest index, and flowering of peanut grown by the nutrient film technique (NFT). `Georgia Red' peanut plants (14 days old) were planted into growth channels (0.15 × 0.15 × 1.2 m). Plants were spaced 25 cm apart with 15 cm between channels. A modified half-Hoagland solution with an additional 2 mm Ca was used. Solution pH was maintained between 6.4 and 6.7, and electrical conductivity (EC) ranged between 1100 and 1200 μS·cm–1. Temperature regimes of 28/22 °C were maintained during the light/dark periods (12 hours each) with photosynthetic photon flux (PPF) at canopy level of 500 μmol·m–2·s–1. Foliage and pod fresh and dry weights, total seed yield, harvest index (HI), and seed maturity were greater at high than at low RH. Plants grown at 85% RH had greater total and individual leaflet area and stomatal conductance, flowered 3 days earlier and had a greater number of flowers reaching anthesis. Gynophores grew more rapidly at 85% than at 50% RH.

Free access

Dietary intake of a variety of vegetables is very important for disease prevention and may help in the treatment of certain maladies. Experiments were conducted to evaluate yield and the content of antioxidants and phenolics of vegetable Amaranth (Amaranthus hybridus), Celosia (Celosia argentea), Gboma (Solanum macrocarpon), and Long Bean (Vigna unguiculata) in response to poultry litter (PL) and a hydrolyzed fish fertilizer [Megabloom (MB)]. The experiments were conducted as a randomized complete block design with a four × three factorial treatment and four replications. The treatments were applied based on soil test recommendations in a single band 15 to 20 cm away from the plants 1 week after transplanting. Plants were harvested sequentially during the season as foliage and fruits became physiologically mature and once over at the end of the season. Species were analyzed for vitamin C content, total phenolics, and β-carotene content as well as antioxidant capacity. Organic amendments did not significantly influence biomass production, whereas species impacted fresh and dry biomass. Amaranth, Celosia, and Long Bean produced greater fresh and dry biomass than did Gboma. Vitamin C content was highest among Amaranth and Celosia plants receiving nitrogen–phosphorus–potassium (NPK) compared with the other two treatments, whereas that of Gboma was higher among plants receiving MB.

Free access

The effects of altering, nutrient solution N:K ratio on growth of `TI-155' sweetpotato [Ipomoea batatas (L.) Lam] was evaluated in a greenhouse, as part of NASA's Closed Ecological Life Support Systems (CELSS) program for long duration space missions. Vine cuttings of `TI-155', were grown using nutrient film technique (NFT) in a modified half Hoagland's solution in channels (0.15×0.15×1.2 m). Plants were grown for 42 days in a culture solution in which N was doubled (6 mM) in order to accelerate foliage growth after which treatment N:K ratios of 1:2.4, (control) 1:4.8, and 1:7.2 were initiated. A randomized complete block design with 4 replications was used. The number of storage roots/plant increased linearly as K was increased in the solution. Storage root fresh and dry weights, growth rate (g m-2 d-1), fibrous root dry weight, foliage fresh and dry weights, and edible biomass index (root mass/total plant mass), though not significant all increased as K was increased in the nutrient solution. Nutrient solution analyses showed that K uptake was greatest in plants at the highest K level, while nitrate uptake was steady over the duration of crop growth regardless of treatments.

Free access

Studies were conducted in a greenhouse to determine the effects of harvesting sweetpotato (Ipomea batatas L. (Lam.) cv. “TI-82-155”) shoot tips (top 10 cm) at biweekly intervals beginning 42 days after transplanting on yield of storage root and nutrient content of harvested shoot tips. Plants were grown hydroponically from vine cuttings of 15 cm length, planted in 0.15 × 0.15 × 0.12 m growth channels using a closed NFT system. Nutrient was supplied in a modified half-strength Hoagland's solution with a N:K ratio of 1:2.4. Final harvest was at 120 days when shoot biomass and yield of storage roots were measured. Biweekly topping did not affect storage root yield or shoot biomass. However, harvesting time had a significant effect on dry matter and nutrient content of shoot tips.

Free access