growth and quality in various crops ( Shannon and Grieve, 1999 ). Most salinity research in horticulture has focused on NaCl. However, CaCl 2 is also prevalent in many sources of irrigation water, as well as soils, soilless substrates, fertilizers, and
Carolyn F. Scagel, David R. Bryla, and Jungmin Lee
Weiling Yuan, Shangyong Yuan, Zhixiong Liu, Leifu Chen, and Zhengming Qiu
in the shoots ( Collier and Tibbitts, 1984 ; Schlagnhaufer et al., 1987 ). The aim of the present study was to determine the effect of the foliar application of CaCl 2 on lettuce growth and calcium concentrations with organic and conventional
Daniela Borgognone, Mariateresa Cardarelli, Luigi Lucini, and Giuseppe Colla
production in cardoon leaves at the expense of the biomass yield, whereas the use of a solution enriched with 30 m m of CaCl 2 enhanced the biomass quality only in the long term without a detrimental effect on biomass yield ( Borgognone et al., 2013 ). The
Deformed or damaged berries reduce the grade of frozen highbush blueberries (Vaccinium corymbosum L.). Before berries are frozen, immature fruit are commonly removed by density sorting in water tanks. Three studies were conducted to determine if the firmness or quality of highbush blueberries could be improved by the addition of CaCl2 to sorting tank water. `Bluecrop' and `Jersey' berries were dipped in CaCl2 solutions (0.0-4.0%) for periods of 0.5-8.0 minutes. The effect of rinsing the fruit after treatment was also studied. Berries were held at 2C for several days before evaluation. A 61.5 cm length of PVC pipe (4.0 cm. I.D.) was filled to a depth of 50 cm. with berries and dropped 4 times on to a hard surface from a height of 10 cm. The compression of the column of berries was measured and berries were removed and visually sorted according to the degree of damage. The amount of compression and number of damaged berries were inversely related to the CaCl2 concentration. Rinsing berries immediately after dips negated the effects of CaCl2. Treatment with CaCl2 may result in objectionable flavors.
Jeanne Bernardin, Claude Willemot, and Clement K. Sankat
The effect of Ca on breadfruit (Artocarpus altilis) postharvest storage was investigated. Mature-green breadfruits were hand-harvested in Blanchisseuse, Trinidad, dipped in 0%, 2%, 5%, and 10% CaCl2-2H2O solutions for 0.5, 1.0, 3.0, 6.0, and 12.0 hours, and stored at 16C for 9 days. Calcium content was shown to increase in both peel and pulp with increasing concentration and length of treatment. The 5% and 10% Ca treatment had a detrimental effect on color and texture as determined by sensory evaluation. The 2% treatment delayed fruit softening, particularly for 3-, 6-, and 12-hour dips. At the end of storage, total soluble solids content was affected little by the treatments, while pectin solubilization was delayed. Breadfruit shelf life was extended from 4 to 9 days with 2% treatments. Peel browning remains the limiting factor for storage.
Linchun Mao* and Donald J. Huber
Having been hold in 10 μL·L-1 1-MCP or air for 18 h, seedless watermelon (Citrullus lanatus Matsum and Nakai, cv. Millionaire) fruits were cut to obtain tissue cylinders which were rinsed with 2% CaCl2 or deionized water. Respiration rate, ethylene production, firmness, electrolyte leakage, total soluble solids, titratable acidity, microbial growth rates (aerobic bacteria and yeast counts), and activities of ACS, ACO, PLC, PLD, LOX were determined during 7 days at 10°C to investigate the effects of 1-MCP and CaCl2. Ethylene was not detected in cylinders, while wound-induced respiration rates increased over time. Although 1-MCP stimulated ACS activity, it completely inhibited ACO activity and lowered respiration rate. CaCl2 had little effect on ACS activity, but stimulated ACO activity and maintained tissue firmness throughout storage. 1-MCP abolished the effect of CaCl2 in retaining or stimulating PLC, PLD and LOX activities, but inhibited aerobic bacteria synergically with CaCl2. Results suggest that 2% CaCl2 stimulated activities of PLC, PLD and LOX, which are key enzymes catalyzing phospholipid degradation. Results also provide evidence indicating that 1-MCP counteracts CaCl2 in aspect of lipolytic enzymes through unknown mechanisms. Furthermore, we provide results that 1-MCP and CaCl2 have a synergic effect in inhibiting the growth of aerobic bacteria. We suggest that CaCl2 may be applied together with 1-MCP as a complex treatment to extend shelf life of fresh-cut products.
Fidanka Trajkova, Nicolas Papadantonakis, and Dimitrios Savvas
The objective of this study was to discriminate among Na, Cl, and Ca salinity effects on cucumber (Cucumis sativus L.). Cucumber plants grown in perlite were exposed for 134 days to low and moderate levels of salinity induced by the addition of either NaCl or CaCl2 at equal rates (on a chemical equivalent basis) to a standard nutrient solution for cucumber up to two target electrical conductivity (EC) levels (3.0 and 5.0 dS·m–1). The experimental treatments included also a control, which was irrigated with the standard nutrient solution without additional salt. The mean EC values in the drainage solution were 2.35, 3.94, 4.2, 6.31, and 6.35 dS·m–1 for the control, low NaCl, low CaCl2, high NaCl, and high CaCl2 treatments, respectively. The fresh and dry weights of stems and leaves were reduced only under conditions of high NaCl salinity, whereas root mass was not affected. Fruit yield decreased in proportion to the increase in NaCl salinity, while CaCl2 salinity reduced yield only at the high EC, to a level that corresponded to the low NaCl salinity. The suppression of yield with increasing salinity resulted mainly from a decrease in fruit size, while the number of fruit per plant was reduced to a lesser extent. These changes caused a reduction in the number of Class I fruit and an increase in nonmarketable produce. Both salinity sources enhanced the total soluble solids and the fruit chlorophyll concentration. NaCl salinity appreciably raised the concentrations of Na and Cl in young and old leaves, and suppressed the K concentration. CaCl2 salinity increased leaf Cl and Ca levels and diminished Mg and K. It is concluded that cucumber is more susceptible to NaCl salinity than to equal EC levels of CaCl2 salinity.
W.F. Campbell, J.L. Anderson, and D.R. Walker
Calcium chloride (CaCl2) enhances turgidity and quality of postharvest sour cherry, Prunus cerasus L., fruit. Mechanisms by which plasma membrane (PM) ATPase maintains the electrochemical gradient in cell turgor were studied in isolated PM vesicles isolated from tapwater-, CaCl2- and chelated amino acid-calcium-treated Montmorency sour cherry fruit. Electron microscopy and periodic-chromicphosphotungstic acid staining indicated 85-90% closed PM vesicles. Protein activity associated with the PM was four times higher in both Ca treatments than in untreated cherries. ATPase activity was insensitive to NO3 and NaN3, but inhibited by vanadate, indicating absence or low levels of tonoplast and mitochondrial ATPases. PM vesicles exhibited a pH jump in the presence of acridine orange (A493-530nm). Cherry fruit appeared to have a PM ATPase similar to that of other plant species. Generation of a positive membrane potential across the PM was dependent upon ATP.
R. Thomas Fernandez and James A. Flore
Fruit of sweet cherry (Prunus avium L.) crack during or after rain due, in part, to absorption of water through the fruit surface driven by the water potential gradient. In 1972, J. Vittrup-Christensen suggested that overhead misting of calcium salts during precipitation may be an effective way to prevent cherry cracking by reducing the water potential gradient. We tested this hypothesis by designing a computer-controlled irrigation system to intermittently spray a 10% CaCl2 solution on trees during rain events. Spray emitters were placed in the middle and at the top of the canopy. The program turned the system on for 90 s at each 0.3 mm of rain and monitored daily rainfall and accumulated mist times. Two `Emperor Francis' and two `Ulster' were treated with equal number of controls. Intact and cracked cherries were counted on four branches per tree at three times when cherries were susceptible to cracking. Overall, cracking was reduced from 33% to 11% by the CaCl2 spray at the end of the experiment. Treated `Ulster' had 9% cracked fruit, while control had 43% cracked fruit. Differences for `Emperor Francis' were not significant. Phytotoxicity was estimated at about 15 % of leaf area. This system will be reevaluated in 1995 with the added objective of quantifying and reducing phytotoxicity.
F. Chéour, C. Willemot, J. Arul, J. Makhlouf, and Y. Desjardins
The objective of this study was to compare the effects of the foliar application of CaCl2 on the shelf life and Ca content of the fruit of the strawberry (Fragaria × ananassa) cultivars Kent and Glooscap, which differ in fruit firmness. Calcium was applied repeatedly, 3 days, 3 and 6 days, or 3, 6, and 9 days before harvest at 0, 10, or 20 kg·ha-1. Calcium treatment influenced amounts of free sugars and organic acids, color, texture, and disease development during storage in air at 4C. Calcium application had more effect on the fruit of the softer `Glooscap', which contained relatively low levels of Ca at the time of treatment. Calcium content of the fruit appeared to depend mainly on the ability of the plant to accumulate and distribute Ca.