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Cyrus A. Smith, James L. Walworth, Mary J. Comeau, Richard J. Heerema, Joshua D. Sherman, and Randall Norton

plants use Na and Cl to maintain turgor pressure in leaves, the plant may need to develop a balance between these ions to avoid ion toxicity. It is unclear which of the ions in saline water or soil cause salt injury in pecans. Faruque (1968 ) treated

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Moo R. Huh, Beyoung H. Kwack, and Leonard P. Perry

Salt injury was induced by 5% (w/v) NaCl drenching on Hibiscus hamabo Sieb. & Zucc. and H. syriacus L. seedlings. Total chlorophyll content of H. hamabo was higher than that of H. syriacus. Uniconazole (0.0, 0.5, 1.0, and 5.0 mg·liter–1) treatment increased and 25- or 50-mg·liter–1 GA3 treatment decreased chlorophyll content of H. hamabo. Total chlorophyll content of H. syriacus was not affected by uniconazole or GA3. Total carbohydrate content of H. syriacus was more accumulated than that of H. homabo. Total carbohydrate content of H. hamabo was more decreased than that of H. syriacus by Ca (13.35 or 133.5 mM), uniconazole, or GA3 in relation to total carbohydrate contents. Protein contents of H. hamabo were higher than those of H. syriacus. Uniconazole or GA3 increased those of H. hamabo and decreased those of H. syriacus. Peroxidase activity of H. hamabo was higher than that of H. syriacus. Uniconazole decreased that of H. hamabo and increased that of H. syriacus. GA3 or Ca (13.35 mM) treatment increased that of both species. ATPase activity of H. hamabo was higher than that of H. syriacus. Uniconazole (5 mg·liter–1), GA3, or Ca decreased that of H. hamabo increased that of H. syriacus.

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Moo R. Huh, Beyoung H. Kwack, and Leonard P. Perry

Shoot length, leaf length and width, root length, and crown diameter were affected by 0.0-, 0.5-, 1.0-, and 5.0-mg·liter–1 uniconazole drench and 25- or 50-mg·liter–1 GA3 spray but not significantly by 0.0%, 2.5%, and 5.0% NaCl. Leaf width of H. syriacus Sieb. & Zucc. was not affected and that of H. syriacus L. significantly decreased, as NaCl concentration increased. Effect of NaCl on H. syriacus leaf width was offset by treatment with uniconazole but not by GA3 treatment. With 2.5% NaCl, dry weight of H. hamabo treated with uniconazole or GA3 increased and that of treated H. syriacus decreased. With 5.0% NaCl, dry weight of both species decreased with uniconazole or GA3. Calcium at 13.35 or 133.5 mM decreased the reduction of dry weight by NaCl treatment. The dry: fresh weight ratio of H. hamabo and H. syriacus treated with NaCl plus uniconazole was higher than that only treated with NaCl. GA3 treatment with NaCl did not affect the dry: fresh weight ratio for either species

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Steven F. Berkheimer, Eric J. Hanson, Jason K. Potter, and Jeffrey A. Andresen

Some highbush blueberry (Vaccinium corymbosum) fields adjacent to Michigan roads exhibit abnormally high levels of winter fl ower bud mortality and twig dieback, even following relatively mild winters. This work was conducted to determine if this injury was caused by deicing salts (primarily sodium chloride) that are applied to adjacent roads and blown by the wind onto bushes. Flower bud mortality was recorded in the spring at several locations within six farms adjacent to divided highways treated with deicing salts. Four farms were east of highways (downwind of prevailing wind direction) and two were west (upwind) of highways. Each May for 3 years, the numbers of live and dead fl ower buds were counted on plants located varying distances from the highway. Bush position and distance from the highway were determined with global positioning system (GPS) equipment. Bud health was also assessed monthly during the winter. In fields located downwind of highways, bud mortality was consistently greatest close to the road and decreased with distance. Salt had an apparent effect on mortality 60 to 120 m from the highway, depending on the year. In fields west or upwind of highways, bud mortality was not consistently related to distance from the highway. Flower bud injury was evident by mid-January, and increased throughout the winter. Results indicated that wind-blown salt spray can cause considerable injury in blueberry fields close to salted roads.

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Jeff Million, Tom Yeager, and Claudia Larsen

-leach conditions of this experiment, OVR in combination with N rates of 1.5 lb/yard 3 or higher resulted in PT substrate EC levels higher than 4 dS·m −1 during most of the experiment ( Fig. 2 ). Because PT EC levels higher than 2 dS·m −1 may cause salt injury to

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Sanjit K. Deb, Parmodh Sharma, Manoj K. Shukla, Theodore W. Sammis, and Jamshid Ashigh

pecan seedlings with scorched leaves resulting from salt injury, it appeared that leaf chloride (Cl – ) was significantly higher compared with the control treatment, indicating that Cl – ions were readily translocated to the leaves ( Fig. 6B ). Even at

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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.

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Jim Syvertsen and Yoseph Levy

Multiple stresses almost always have synergistic effects on plants. In citrus, there are direct and indirect interactions between salinity and other physical abiotic stresses like poor soil drainage, drought, irradiance, leaf temperature, and atmospheric evaporative demand. In addition, salinity interacts with biotic pests and diseases including root rot (Phytophthora spp.), nematodes, and mycorrhizae. Improving tree water relations through optimum irrigation/drainage management, maintaining nutrient balances, and decreasing evaporative demand can alleviate salt injury and decrease toxic ion accumulation. Irrigation with high salinity water not only can have direct effects on root pathogens, but salinity can also predispose citrus rootstocks to attack by root rot and nematodes. Rootstocks known to be tolerant to root rot and nematode pests can become more susceptible when irrigated with high salinity water. In addition, nematodes and mycorrhizae can affect the salt tolerance of citrus roots and may increase chloride (Cl-) uptake. Not all effects of salinity are negative, however, as moderate salinity stress can reduce physiological activity and growth, allowing citrus seedlings to survive cold stress, and can even enhance flowering after the salinity stress is relieved.

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Raul I. Cabrera*

The azalea hybrids `Delaware Valley White' (`DVW') and `Hershey Red' (`HR') were grown in 7-L containers filled with a 4 sphagnum peat: 2 pine bark: 1 sand medium (v/v) and fertigated for 15 weeks with a complete nutrient solution supplemented with 0, 6 and 12 mm NaCl-CaCl2 (2:1 molar ratio). Regardless of salinity stress, `DVW' plants had dry weights and leaf areas significantly higher (by 24.7% and 10.2%, respectively) than in `HR' plants. Salinity, however, caused differential growth and quality responses between the hybrids. Growth in `DVW' plants decreased with salinity increases, with 22.6% and 32.4% reductions in total dry weight and leaf area, respectively, observed at 12 mm salt compared to controls. Conversely, `HR' plants exposed to 12 mm salt showed no differences in yield parameters with respect to the controls, whereas plants receiving 6 mm salt showed increases of 14.0% and 7.1% in total dry weight and leaf area, respectively, with respect to the controls. Plant quality, as assessed by visual symptoms of salt injury (“salt burn”), was significantly reduced by salinity increases in `DVW' plants, but was not affected in `HR' plants. While unaffected by salinity, leaf K status in `HR' plants was significantly lower than in `DVW', which showed increases in K concentration with salinity increases. Leaf Ca, Cl and Na concentrations increased with added salinity in both hybrids. The `DVW' plants, however, accumulated exceedingly higher Cl and Na concentrations (up to 3.33% and 5,650 mg·L-1 respectively) than in `HR' plants (up to 1.31% and 463 mg·L-1, respectively). Only the yield and quality of `DVW' plants were negatively and significantly correlated to increases in leaf Cl and Na concentrations.

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Raul I. Cabrera

Yield, quality, and nutrient status of `Bridal Pink' (on R. manetti rootstock) roses were evaluated under increasing NaCl salinity and mixed NO3 /NH4 + nutrition. Container-grown plants were irrigated over eight flushes of growth and flowering with nutrient solutions having 100 NO3 - : 0 NH4 +, 75 NO3 : 25 NH4 +, and 50 NO3 : 50 NH4 + ratios in combination with three NaCl concentrations. During the first four flowering flushes, NaCl was supplemented at 0, 5, and 10 mm, but these concentrations were increased to 0, 15, and 30 mm during the last four flushes. Interestingly, NO3 : NH4 + ratios and NaCl concentration had no main effects over any flower yield or quality component evaluated over the 13-month experimental period. Furthermore, visual symptoms of apparent salt injury were just observed during the last three flowering cycles, and mostly on the oldest foliage of plants receiving the highest salt concentrations (30 mm). Leaf N and Na concentrations were not significantly affected by the treatments over the course of the experiment, averaging 3.34% and 45 mg·kg–1, respectively. Leaf Cl concentrations were significantly increased by salt additions, ranging from 1000 to 15,000 mg·kg–1 [0.1% to 1.5% dry weight (DW)]. Correlation analyses revealed that relative dry weight yields increased with leaf Cl concentrations up to 3000 mg·kg–1 (0.3% DW) but were significantly depressed at higher concentrations. These results confirm recent reports suggesting that roses are more tolerant to salinity than their typical classification of sensitive. Furthermore, this is the first known study to report an apparent positive effect of moderate leaf Cl concentrations on rose biomass yields.