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  • Author or Editor: Carl E. Sams x
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Mature apples (Malus domestica Borkh. cv. Golden Delicious) were immersed for 2 min in 0, 0.14, 0.27, or 0.41 mol·L−1 (0, 2%, 4%, or 6%, respectively) aqueous solutions (w/v) of CaCl2 at 0 or 68.95 kPa, and were stored at 0 °C. Histological samples of peel/cortex were taken at harvest and at four monthly intervals in storage. Paraffin sections were stained with an aqueous mixture of alcian blue 8GX, safaranin 0 and Bismark brown Y, or with the periodic acid-Schiff (PAS) reaction. No histological difference was observed in fruit treated with 2% CaCl2 compared with those pressure-infiltrated with greater amounts of Ca. Fruits pressure-infiltrated with 6% CaCl2 exhibited the greatest amount of flattened epidermal cells and hypodermal cavities. Cuticles were also affected at the higher CaCl2 treatment levels (with regard to staining with Bismark brown), becoming more condensed and uniform. Cuticle and hypodermis were stained differentially with PAS in the 6% CaCl2 treatment. All tissues, including the cuticle, were stained magenta red, indicating a possible chemical alteration of the cuticle and the underlying tissue by Ca.

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Plants encounter various environmental stress factors that can potentially impact nutritional requirements and fruit quality. Adequate levels of calcium (Ca) in tomato (Solanum lycopersicum) fruit have positive effects on fruit quality, specifically firmness. One of the results of insufficient Ca uptake and movement in tomato is the physiological disorder blossom-end rot (BER), which is associated with a Ca deficiency in the distal fruit tissue. Previous research has demonstrated that foliar abscisic acid (ABA) applications decreased the incidence of BER and increased the uptake of Ca into fruit tissue. This study examined how root and foliar spray ABA applications, individually and in combination, affect the partitioning of Ca between the leaves and fruit of tomato plants, especially in the distal tissue, and how ABA affects the incidence of BER in the distal tissue of tomato fruit. ‘Mt. Fresh Plus’ tomato were grown in the greenhouse at 25/20 °C (day/night) under a 16-hour photoperiod. Plants were treated with different Ca concentrations in the fertilizer solution. Plants were also treated with foliar spray ABA applications weekly. Calcium was applied through the irrigation lines at 60, 90, or 180 mg·L−1. ABA treatments were applied as a combination of foliar sprays and root applications. Foliar ABA applications, treatments consisted of deionized (DI) water control (0.0 mg ABA/L) or 500 mg ABA/L. For ABA root applications, treatments consisted of a DI water control (0.0 mg ABA/L) or 50 mg ABA/L applied through the irrigation lines. ABA spray treatments were applied once weekly until dripping from the foliage (tops of pots were covered to prevent spray drip into the pot), whereas root applications were applied four times per day through the irrigation system. Fruit tissues were harvested 84 to 90 days after seeding. Fruit tissue was harvested at red ripe maturity and evaluated for yield, BER, and Ca concentrations. Leaves were harvested at the time of fruit and were analyzed for Ca concentrations. The results indicate that a combination of the spray and root applications of ABA resulted in the greatest decrease in BER. The foliar spray application of ABA combined with the Ca treatment of 180 mg·L−1 decreased the incidence of BER. Results also demonstrate that ABA treatments are effective in increasing fruit Ca and preventing BER in the early stages of plant development but are less effective in preventing Ca deficiency in the later stages of growth.

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Calcium has been linked to disease resistance in fruits and vegetables. The effects of calcium nutrition on six hydroponically grown tomato cultivars (`Switch', `Match', `Blitz', `Caruso', `Trust', and `Celebrity') were evaluated in the fall of 1996. Disease resistance and yield were measured for plants grown in either perlite or pine bark mulch. Plants were fertilized with a 5N–11P–26K water-soluble fertilizer solution containing micronutrients and either 60, 120, or 185 mg·L–1 calcium. Disease resistance was determined by measuring disease lesion diameters on mature green harvested fruit 3 to 5 days after inoculating with Botrytis cinerea Pers.: Fr. There was no significant difference in disease when evaluated by medium, cultivar, or calcium treatment. Foliar analysis by Inductively Coupled Argon Plasma Atomic Emission Spectrophotometer (ICAP) indicated that leaf calcium content ranged from 27,000 to 54,000 μg·g–1 dry weight (leaf above fifth flower cluster), but was not significantly different when analyzed by medium, cultivar, or calcium treatment. There was no significant difference in marketable yield due to medium or calcium treatment. Among cultivars, `Trust' had the highest marketable yield at 2.7 kg per plant, which was significantly different from `Celebrity' at 1.6 kg per plant. This experiment suggests that a cheaper medium (pine bark) and lower calcium levels can be utilized in fall tomato production.

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`Golden Delicious' apples were pressure-infiltrated (34 kPa) at harvest with 0, 20, 35, or 50 g·L–1 solutions of CaCl2 followed without and with a water rinse, a wax or shellac emulsion treatment, or a shrink-wrap packaging, and stored at 0°C. The CaCl2 treatments delayed senescent breakdown, but also caused superficial injury to the fruit. A water rinse in combination with a wax- or shellac-based coating or shrink wrap packaging reduced the appearance of superficial injury in fruit treated with 35 or 50 g·L–1 solutions of CaCl2 and eliminated it in fruit treated with a 20 g·L–1 solution of CaCl2. While reducing the risk of calcium-related injury to the fruit, the coating and film treatments maintained the beneficial effects of calcium on apples and reduced weight loss of the fruit during cold storage.

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Due to the declining availability of fungicides for use in commercial tomato production, there is a need to investigate alternative disease control methods. Several theories of disease resistance are associated with an increase in plant tissue calcium content, which has increased resistance of tomato seedlings to bacterial wilt and other diseases. Three tomato cultivars (`Mountain Supreme', `Sunrise', and `Celebrity') were grown in a greenhouse hydroponic system to study the role of Ca in reducing decay of fruit by Botrytis cinerea. Calcium treatments of 20, 200, or 1000 ppm were applied in a modified Hoagland's solution. A 3 × 3 factorial randomized complete-block design was used. Mature whole leaves were collected from immediately below the third flower clusters and the calcium content analyzed by inductively coupled plasma emission spectrophotometry. Harvested fruit were inoculated with a 5 × 105 spore/ml conidial suspension of B. cinerea and the decay lesion diameter measured once daily for 7 days. This was repeated for 8 consecutive weeks. Leaf Ca content significantly increased (P < 0.01) as the Ca treatments increased from low to medium (310%) and from medium to high (150%). The medium and high Ca treatments significantly reduced the area of decay caused by gray mold rot (P < 0.01). There were no differences in Ca content or decay among cultivars, and the Ca × cultivar interaction was not significant. It appears that leaf Ca content is negatively associated with resistance of greenhouse-grown tomatoes to gray mold rot, strengthening the hypothesized role of calcium in promoting disease resistance.

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An experiment was conducted to investigate the effect of Ca nutrition on yield and incidence of blossom-end rot (BER) in tomato. Three levels of Ca (low = 20 ppm, medium = 200 ppm, and high = 1,000 ppm; selected to represent very deficient, normal, and very high levels of calcium) were applied to three cultivars of tomatoes (`Mountain Supreme', `Celebrity', and `Sunrise'; selected to represent genetic differences in susceptibility to BER) grown in modified Hoagland solutions using a greenhouse hydroponic system. The experiment was constructed in a randomized complete-block design with three blocks, two replications, three cultivars, and three calcium treatments. The source of basic nutrients was a 5–11–26 soluble fertilizer containing micronutrients. The ratio of N–P–K was adjusted to 1.0–1.3–3.0 by adding NH4NO3 (34% N). Calcium was added as CaCl2. Nitrogen concentrations were maintained at 30 (first month), 60 (second month), and 90 ppm (during fruit growth), while the concentration of other nutrients followed proportionally. Cultivars differed significantly in yield and average fruit weight but not in incidence of BER or leaf Ca concentration. There was no cultiva × calcium treatment interaction. Leaf Ca content across cultivars was increased by 34% and 44%, respectively, by the medium and high Ca treatments. Average fruit weight and total yield per plant were not significantly different between the low and medium Ca treatments, however, both were reduced by the high Ca treatment. Incidence of BER was 95% higher in the low rather than in the medium Ca treatment. There was no significant difference in BER between the medium and high Ca treatments.

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Rapid cycling brassica (RCB) plants, because of their short life cycle and ease of growth under laboratory conditions, offer a valuable tool for studying Brassica nutrition. We have been particularly interested in B nutrition in Brassica and, therefore, a hydroponic system was developed to accurately deliver micronutrient concentrations to RCB plants. RCB plants were supported in predrilled holes in the lids of brown 1-L plastic containers. Nutrients were supplied by spraying a modified Hoagland's solution onto the plant roots as they developed inside the containers. This system provided adequate solution aeration for plant growth and allowed analysis of both plant shoots and roots. RCB seeds were pregerminated for radicle emergence, then placed in the holes in the plastic container lids. The effect of B nutrient concentration on B uptake was examined using nutrient solutions containing 0.08, 0.02 and 0.00 ppm added B. Leaf B contents were 139.5, 26.1, and 7.1 g·g–1 for plants grown in 0.08, 0.02 and 0.00 ppm added B, respectively. Effects of drought stress on B uptake and distribution were studied by adjusting nutrient solution osmotic potential using polyethylene glycol (PEG) 8000. PEG-induced drought, (osmotic potential –0.1 MPa) reduced leaf and root B content ≈50% compared to plants grown in nutrient solution only (–0.05 MPa). Boron content in the shoots and pods, however, was not affected by PEG-induced drought stress. These results suggest that this system provides a reliable tool for studying nutrition and drought stress effects using RCB plants.

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Abstract

Six accessions of edible amaranths (Amaranthus spp. L.) of varied geographic and genotypic origin were grown in a soil enriched with 0, 50, or 100 kg·ha–1N. Leaves were harvested at 25, 35, 45, 55, and 65 days after germination (DAG) and analyzed for crude protein (CP), neutral detergent fiber (NDF), and NO3 N. In grain-bearing accessions, leaf CP content increased with N application but declined linearly over harvest dates. In vegetable types, leaf CP levels tended to fluctuate over time. In both types, NDF content declined with N application, whereas response to harvest date varied. Leaf NO3 increased two-fold in plants from fertilized plots compared to plants from unfertilized plots, but declined rapidly with time. Leaf content of NO3 did not exceed 239 mmol·kg–1 dry weight with any N fertilization treatment. Edible amaranth appeared to be adapted to soils and climate of the southeastern United States. A. tricolor was most susceptible to disease among the accessions evaluated.

Open Access

Trials were conducted in 2004 to compare the effects of soybean oil formulations and concentrations on flowering and fruit thinning of rabbiteye and southern highbush blueberries. Mature `Climax' bushes near Spring City, Tenn., were sprayed to runoff on 10 Feb. with water, or 9% soybean oil in the formulations TNsoy11, TNsoy12, TNsoy13, TNsoy14, or Golden Natur'l (GN). In a second trial, 3-year-old `Legacy' southern highbush plants at Spring Hill, Tenn., were sprayed on 11 Feb. with 0%, 6%, 9%, 12%, and 15% GN. A similar trial was sprayed on 5 Mar. at Fletcher, N.C., using young plants of various Southern highbush cultivars. Each formulation of soybean oil (9%) delayed bud development and flower anthesis of `Climax' bushes. Bloom opening on `Legacy' bushes was delayed by 2 to 6 days with sprays of ≥9% GN, with higher concentrations causing more delay. However, flower bud mortality of `Legacy' plants was greater when sprayed with the higher oil concentrations. `Legacy' plants sprayed with 0%, 6%, and ≥9% oil had 0%, 30% and ≥70% bud mortality, respectively, at 36 days after treatment. `Legacy' plants sprayed with 12% and 15% oil sprays had an estimated 24% and 13%, respectively, of a crop load compared to the estimated 100% crop load on control plants. Flower bud development, flower bud mortality, crop load and berry size (across cultivars) of Southern highbush cultivars at Fletcher were not affected by oil treatments. Results were variable among trials, perhaps due to factors such as cultivars, timing of application (date), maturity of plants, environmental conditions, etc. There is potential for soybean oil formulations to be used as a chemical thinner as well as to delay blooming.

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