The effects of calcium salts and concentrations from 25 to 200 mM on the induction of chilling tolerance in cucumber roots were studied using total root growth, electrolyte leakage, lipid peroxidation, and activities of antioxidant enzymes as indicies of chilling injury. Cucumber seeds `Poinsett 76' germinated at 25 °C for 36 h were treated with calcium sulfate, calcium nitrate, and calcium chloride for 2 h at 25 °C. After incubation, treated seedlings were rinsed with distilled H2O and chilled at 2 °C for 72 or 96 h with or without re-warming at 25 °C. Roots of CaSO4-treated cucumber seedlings exhibited less chilling injury at all concentrations, when exposed to 72- or 96-h chilling periods with a 72-h re-warming period as shown by greater root growth compared to the chilled control. Concentrations of CaCl2 and Ca(NO3)2 above 100 mM resulted in significant root growth inhibition. Electrolyte leakage (EL) was significantly reduced by CaSO4 up to 150 mM under chilling conditions and all calcium salt treatments reduced malondialdehyde (MDA) levels in seedling roots up to 150 mM. However, at 150 mM CaSO4 both EL and MDA values of 72 h chilled and re-warmed roots were at their lowest levels compared to the control and other treatments. Both superoxide dismutase and catalase activities of seedling roots decreased under chilling conditions compared to the nonchilled control, although the reduction was less in the presence of CaSO4. Peroxidase and glutathione reductase activities increased under chilling conditions and were generally reduced in the presence of calcium salts compared to the chilled control.
Mustafa Ozden and Paul H. Jennings
Robert C. Ebel
, flooding, and salt injury. Hurricane Katrina is an example of the impact that hurricanes can have as evidenced by its devastating impact of the Satsuma industry from Louisiana to Alabama. Development of the industry will also require concomitant development
Anthony S. Aiello and Robert J. Joly
Redbud (Cercis canadensis) is known to be very susceptible to injury by road de-icing salts. The purpose of these experiments was to measure the effects of sodium chloride on net CO2 assimilation (A), conductance (g), transpiration (E), and leaf area expansion (LAE) of hydroponically grown redbud seedlings. Eight week-old seedlings were exposed to 0, 4500, and 9000ppm NaCl in the hydroponic growth solution. A, g, E, and LAE were measured for seven consecutive days during treatment application.
A, g, E, an LAE all decreased with increased salt stress. By the seventh day, growth in NaCl at 4500 and 9000 ppm resulted in reductions in A from that that of the control by 34% and 63%, respectively. For the medium treatment, g and E had decreased by 70% over control rates, and by 85% over control for the high treatment. For the 0, 4500, and 9000ppm treatments, total leaf area increased by 68%, 46% and 28%, respectively, over the seven days of the experiment.
Further experiments will examine the effect of treatments on whole plant transpiration, water potential and osmotic potential and will measure the ability of seedlings to recover from treatments of various duration.
Ningping Lu and J.H. Edwards
A greenhouse pot study was conducted with a Wynnville sandy loam surface soil to determine the influence of application rates of poultry litter (PL) on growth and nutrient uptake of collard (Brassica oleracea, Acephata Group L., cv. Champion), and the residual effects of PL on growth and nutrient uptake of cabbage (Brassica oleracea, Capitata Group L., cv. Rio Verde). PL at 0, 13, 26, 53, and 106 g·kg–1 was incorporated into limed (pH 6.5) and nonlimed (pH 5.2) soil. Collard plants were grown for 52 days. The residual effects of PL were evaluated by growing three successive crops of cabbage without further application of PL (total 218 days). Collard plants were severely damaged or killed within 7 days after transplanting when the application rate of PL exceeded 26 g·kg–1 soil. Maximum dry matter yield of cabbage shifted from 26 to 106 g PL/kg soil during three successive crops. After four successive growth periods, 6% to 37% of N, 3% to 62% of Ca, 20% to 120% of K, 5% to 60% of Mg, and 3% to 25% of P added through PL was removed by plants. The decrease in water-extractable K accounted for the decrease in the soil salinity. Our results suggest that application rates of PL ≥ 53 g·kg–1 soil can result in elevated levels of salts and NH3 in soil, which can produce severe salt stress and seedling injury.
N.M. El-Hout, C.A. Sanchez, and S. Swanson
Potassium is often considered the nutrient element most limiting to crop production on organic soils. On Histosols in southern Florida, K2SO4, rather than KCl, is often used for lettuce (Lactuca sativa L.) production to minimize the risk of salt injury. However, recent soil-test calibration research suggests that current K fertilizer recommendations for lettuce may be too high. Four field studies were conducted from 1989 to 1991 to evaluate the response of five lettuce types to K rate and source. The five lettuce types evaluated were leaf, bibb, boston, romaine (cos), and crisphead. Two sources of fertilizer K (K2SO4 and KCl) were evaluated at rates ranging from 0 to 600 kg K ha-1. Lettuce showed a minimal or no response to K fertilization. Potassium chloride had detrimental effects on lettuce only when applied at rates in excess of those required for optimal production. These studies showed that K fertilizer recommendations for lettuce produced on Histosols in Florida can be reduced. Furthermore, KCl, a more economical source, is suitable when the K is applied at appropriate rates.
Robert A. Saftner, William S. Conway, and Carl E. Sams
Changes in tissue water relations, cell wall calcium (Ca) levels and physical properties of Ca-treated and untreated `Golden Delicious' apples (Malus×domestica Borkh.) were monitored for up to 8 months after harvest. Pressure infiltration of fruit with CaCl2 solutions at concentrations up to 0.34 mol·L-1 reduced both fruit softening and air space volume of fruit in a concentration-dependent manner. Turgor potential-related stress within the fruit persisted during storage and was higher in Ca-treated than in untreated fruit. Fruit that were pressure infiltrated with CaCl2 solutions between 0.14 and 0.20 mol·L-1 and then waxed to reduce water loss during storage showed no peel injury. Calcium efflux patterns from apple tissue disks indicated two distinct Ca compartments having efflux kinetics consistent with those for cell wall Donnan-phase bound and water free space soluble Ca. At Ca concentrations up to 0.20 mol·L-1, cell wall bound Ca approached saturation whereas soluble Ca showed a linear dependence. At higher external Ca concentrations, only soluble Ca in the tissue increased. During 8 months of cold storage, cell wall Ca-binding capacity increased up to 48%. The osmotic potential of apples harvested over three seasons ranged between-1.32 and -2.33 MPa. In tissue disks, turgor potential changes caused by adjusting the osmolality of the incubation solution with CaCl2 or sorbitol were accompanied by changes in the osmotic and water potentials of the tissue. In CaCl2 solutions up to 0.34 mol·L-1, turgor potential was ≥0.6 MPa in tissue incubated in 0.14 or 0.17 mol·L-1 solutions of CaCl2 and was more than 3 times higher than in tissues incubated in low (≤0.03 mol·L-1) or high (≥0.27 mol·L-1) concentrations of CaCl2. At osmotically equivalent concentrations, turgor potential was up to 40% higher in Ca-than in sorbitol-treated tissue. The results suggest that postharvest treatment with 0.14 to 0.20 mol·L-1 solutions of CaCl2 are best for maintaining fruit water relations and storage life of `Golden Delicious' apples while minimizing the risk of salt-related injuries to the fruit. While higher concentrations of CaCl2 may better maintain firmness, these treatments adversely affect fruit water relations and increase the risk of fruit injury.
Shanshan Sun, Mengying An, Liebao Han, and Shuxia Yin
a series of oxidative damage and lead to the accumulation of MDA. MDA as the indicator of lipid peroxidation directly reflects the degree of injury suffered in the plant by salt stress ( Athar et al., 2008 ). The levels of MDA and H 2 O 2 content
Longxing Hu, Zehui Huang, Shuqian Liu, and Jinmin Fu
( Hulusi et al., 2007 ). Plant adaptation to salt is a complex phenomenon that may involve growth changes as well as physiological and biochemical processes ( Hare et al., 1997 ). Salinity injury to plants was attributed to lower osmotic potential (ψ S
Peter Nveawiah-Yoho, Jing Zhou, Marsha Palmer, Roger Sauve, Suping Zhou, Kevin J. Howe, Tara Fish, and Theodore W. Thannhauser
Progressive salinization of farmland and diminishing fresh water resources are two major issues affecting sustainability of agricultural crop production. Excess salt (NaCl) content inhibits uptake of essential mineral nutrients and water. Cellular
Elio Jovicich and Daniel J. Cantliffe
A physiological disorder in greenhouse-grown pepper (Capsicum annuum L.) plants was observed in Florida, wherein the base of the main stem becomes swollen below the cotyledonary node level and crack-like wounds develop at the base of the stem's epidermis. The disorder may predispose the plant to a localized rot and result in a sudden plant wilt. The effects of soilless media type, transplant depth, and amount of nutrient solution applied per day were studied to evaluate the development of what was termed “Elephant's Foot” disorder, on a greenhouse-grown bell pepper crop in Gainesville, Fla. The percentage of plants with epidermal wounds at the base of the stem was highest (83%) on plants transplanted at half of the cell height (3.8 cm), compared to plants transplanted to the cotyledonary node level (6%) and the second leaf node (0%). Salts were washed from the surface of basal stem epidermis and electrical conductivity measured in the washing solution was expressed per unit area of epidermal sample (ECA). The ECA in the solutions from plants transplanted at half of the cell height was higher than that from plants transplanted to the cotyledonary node level and to the second leaf node. There was a positive linear relationship (r = 0.81) between the percentage of plants with epidermal wounds and the ECA of the solution obtained from washing the epidermal tissues. Salts deposited on the epidermis beneath the cotyledonary node provoked a tissue injury that may predispose the plant to a Fusarium infection. Simple management practices, such as transplanting deep, using cultivars with lower susceptibility to salt damage, and gradually moving back the emitter from the base of the plant after transplanting (to reduce humid conditions near the base of the stem) would help reduce the appearance of this basal stem disorder in soilless-grown peppers.