Enzyme Levels in Pea Seedlings Grown on Highly Salinized Media

Abstract

The levels of 18 enzymes were determined in leaves, stems, and roots of 11-day-old pea seedlings grown in a liquid medium or in the same medium containing, in addition, 5 atmospheres of either NaCl, KCI, Na2SO4, or K2SO4. Though the plants grown in saline media were stunted, the specific activities of the enzymes were the same in the given tissues of all plants. Also, the electrophoretic pattern of isozymes of malate dehydrogenase was not altered by growth of the plants in a saline medium. However, the isozyme pattern of peroxidase from roots of salt-grown plants was altered in that two of the five detectable isozymes migrated a little more slowly than those in extracts from nonsaline plant tissues.Morphologically, the most typical symptom of saline injury to a plant is retarded growth, resulting in a stunted plant. For instance, in beans and radishes the surface area of a leaf from a plant growing in 3 atm of NaCl is approximately 50% less than that from a plant not subjected to salt insult (Ref. 18, and Nieman, R., personal communication 16-hr photoperiod; daytime temperature of 27 to 28 C and night temperature of 25 C; and light intensities of 3.8 X 104 lux at plant height. Light was provided by a bank of fluorescent plus tungsten bulbs.After 24 hr of growth in 1 atm of salt, salinity was increased to 2 atm. Subsequently, salt was added to the media in 1-atm increments at 12-hr intervals to a maximum of 5 atm. This concentration was selected as the maximal amount because plants growing in 5 atm of NaCl were roughly one-half the height of control plants. The salt concentrations were increased stepwise in order to minimize the effect of osmotic shock. In calculating the amount of salt needed to increase the osmotic pressure of each medium to the desired level, the contribution by the basic medium (one-half Hoagland's solution) of 0.4 atm is ignored. After the seedlings had been growing for 3 days in liquid media, one-half of each medium was replaced with an equivalent volume of a fresh solution of the same composition and osmotic strength. In another 3 days the plants were harvested. The pH of the media throughout the entire 6-day period was maintained between 5 and 6. In the above media, the osmotic pressure refers to the concentration of the added salt. The osmotic pressure contributed by the basic medium (one-half Hoagland's solution) is ignored.Both control plants and saline-grown plants had produced 3 to 4 nodes in the 11-day growth period; thus, the plants were assumed to be of nearly the same physiological age as well as chronological age. Except for differences in plant height and size of leaves, the plants grown under the several saline environments appeared healthy.On

Salt Responses of Enzymes from Species Differing in Salt Tolerance

“…Furthermore, growth of Phaseolus and Atriplex in saline cultures failed to alter the specific activity, or NaCl sensitivity, of the enzymes studied. These data thus support and extend the observations of Weimberg (20,21). Weimberg found that different isozymes of malate dehydrogenase, isolated from various plant species, responded similarly to NaCl (20).…”

“…Weimberg found that different isozymes of malate dehydrogenase, isolated from various plant species, responded similarly to NaCl (20). Moreover, Weimberg (21) showed that a variety of salinity treatments failed to alter the specific activity of many enzymes and the isoenzyme patterns of malate dehydrogenase in pea leaf, stem, and root. The data conflict with those of Porath and Poljakoff-Mayber (6,16,17), who reported that two of the in specific activity to NaCl and Na2SO, salinity in pea root.…”

“…However, in the experiments reported here and in those of Weimberg (21), whole roots were used, whereas Porath and Poljakoff-Mayber used only the root tips (16,17).…”

Changes in Activities of Enzymes of Nitrogen Metabolism in Seedcoats and Cotyledons during Embryo Development in Pea Seeds

“…The action of asparaginase yields NH4' and aspartate, which together with imported aspartate could provide the C4 unit for export as a number of C4-dicarboxylic acids (24). The maximal activities of both aspartate and alanine aminotransferases in seedcoat cells (Table I) are the highest of any tissue of the pea plant (8,27).…”

Effect of Salinity on Growth and Genetic Diversity of Broad Bean (Vicia faba L.) Cultivars

“…Salinity damages soil structure and decreases the productivity of most crops as plant growth is affected in several aspects of its metabolism. These include photosynthesis (Nieman and Clark, 1976), osmotic adjustment (Bernstein, 1963), nutritional imbalance and specific ion toxicity (Cordovilla et al, 1994;Gunes and Alpaslan, 1996;Jacoby, 1999), ion uptake (Greenway et al, 1966), enzyme activities (Weimberg, 1970), protein and nucleic acid synthesis (Nieman, 1965), photosynthesis (Downton, 1977), and hormonal balance (Itai et al, 1968). Salinity also reduces growth rate by reducing the uptake of water by plants (Munns, 1993;Munns, 2002).…”