Salt-sensitive Plants Research Articles

In vitro selection for salt tolerance in crop plants: Theoretical and practical considerations

In recent years attempts have been made to supplement traditional breeding for the production of salt-tolerant plants with variability existing in cell culture. The potential causes suggested as an explanation for the limited success of the in vitro approach include: a) lack, or loss during selection, of regeneration capability; b) the development of epigenetically adapted cells; c) lack of correlation between the mechanisms of tolerance operating in cultured cells and mechanisms that operate in cells in the intact plant; and d) multigenicity of salt tolerance. The recent successful production of healthy, fertile, and genetically stable salt-tolerant regenerants from cells obtained from highly morphogenic explants which are selected early in culture (using one-step or short-term strategies) for salt tolerance, together with the demonstration that salt-sensitive plants can become tolerant by mutations in one or few genes, suggest that some of the potential limitations can be overcome and that some of them may not exist at all.

THE RESPONSE OF PLANTS TO SALINITY: FROM TURGOR ADJUSTMENTS TO GENOME MODIFICATION

The parameters affected by salinity in salt-sensitive plants are reviewed. Turgor is the potential energy which powers extension growth, but is not a parameter which controls the growth process. Cell expansion is affected by phytohormones, and salinity modifies the phytohormonal balance of the plant; one of the major effects of salinity on growth results from a modification of the phytohormonal balance. Exposure to salt of certain plant genotypes, under appropriate conditions, results in an increase in salt resistance, which has been termed adaptation. The capacity to adapt is limited to a precise period of development. The process of adaptation is accelerated by abscisic acid and inhibited by cytokinin. It is a genetic character which is not a property of all genotypes. Adaptation is transmitted to the next generation, which suggests that it involves a modification of the genome. In plants, genome organization and expression are modified during development and under various types of environmental conditions. These changes in DNA are generally transitory, but under defined conditions they can be permanent and hence heritable. Changes in salt tolerance have been reported in the literature in the past but not recognized as adaptation because the authors were not aware of the phenomenon.

Metabolism of Activated Oxygen in Peroxisomes from two Pisum sativum L. Cultivars with Different Sensitivity to Sodium Chloride

The effect of NaCl salinity on the metabolism of activated oxygen was studied in peroxisomes purified from leaves of two cultivars of Pisum sativum L. with different sensitivity to NaCl. Salinity caused a decrease in urate oxidase and hydroxypyruvate reductase activities in peroxisomes from NaCl-sensitive plants, whereas the activity of glycollate oxidase was stimulated by NaCl in salt-tolerant plants. Catalase activity was decreased by NaCl in both cultivars of Pisum sativum L. Xanthine oxidase was the most abundant form of xanthine oxidoreductases in pea leaf peroxisomes. Both xanthine oxidase and xanthine dehydrogenase were differentially influenced by NaCl depending on the pea cultivar, but there was no concomitant increase in the activity of xanthine oxidase, indicating that salinity does not affect the interconversion of xanthine dehydrogenase into xanthine oxidase. In peroxisomal membranes, neither NADH-dependent generation of O2- nor lipid peroxidation was altered by salinity. However, the endogenous concentration of H2O2 in leaf peroxisomes was decreased by NaCl in both salt-tolerant and salt-sensitive plants. Thus, in NaCl-tolerance of Pisum sativum L. both the photorespiratory glycollate pathway and the urate oxidase-catalyzed biosynthesis of allantoin appear to be involved at the peroxisomal level.

Characterization of Na+ exclusion mechanisms of salt-tolerant reed plants in comparison with salt-sensitive rice plants

Characterization of Na+ exclusion mechanisms of salt-tolerant reed plants in comparison with salt-sensitive rice plants

Salt-tolerance in plants. II. In vitro translation of m-RNAs from salt-tolerant and salt-sensitive plants on wheat germ ribosomes. Responses to ions and compatible organic solutes

Salt-tolerance in plants. II. In vitro translation of m-RNAs from salt-tolerant and salt-sensitive plants on wheat germ ribosomes. Responses to ions and compatible organic solutes

La teneur en proline et la résistance des plantes aux sels

Application of sodium chloride to crop plants in the culture medium leads to an increase in their endogenous content of free proline. There is a certain concentration of sodium chloride above which the proline content of the plants strongly rises (critical point). A relationship between endogenous sodium and proline contents could be found. In salt-sensitive plants (wheat) the critical point lies below that of salt-tolerant plants (barley). The critical concentration is not changed by certain alterations of the culture medium. The determination of the critical point by means of measurement of the proline concentration served as a basis for the analysis of the salt tolerance of crop plants.

Vérification et utilisation d’un test élaboré de préselection des plantes tolérantes aux sels, à partir de la teneur en proline

This paper deals with the verification of a test of crop seedlings for the determination of the salt tolerance. There is a typical concentration of NaCl in the culture medium above which an enhancement of the free proline content is induced (critical point, critical concentration). The determination of this critical concentration in 19 cultivars of crop plants has proved that plants grown in aride areas (i.e. Hordeum, Triticum durum) have a critical concentration that is by about 50 to 80 mmol l-1 of NaCl higher than that of plants grown in more humid regions (i.e. Triticum aestivum). The critical concentration is not influenced by pH changes of the external solution. Calcium application leads to an enhancement of tolerance. The different increases of growth and fresh mass of salt sensitive and salt tolerant plants selected by this test system proved the aptitude of the critical concentration in culture medium for proline augmentation as a test parameter.

Effect of NaCl on the levels of putrescine and related polyamines in plants differing in salt tolerance

The levels of free and bound putrescine, spermidine and spermine were investigated in differentially salt tolerant plants under conditions of increasing salinity. No accumulation of putrescine or spermidine was detected in any plant tested. Free and bound putrescine decreased even in the salt sensitive plant Vicia faba. Bound spermidine diminished in all plants tested. The possible involvement of the reduction of di- and polyamines in the formation of NaCl-induced effects is discussed.

Effect of Sodium Chloride on Expansion Rates and Invertase Activity of Leaves

The rate of expansion and the invertase (�-fructofuranosidase, EC 3.2.1.26) activity of leaves of two relatively salt-sensitive plants, Phaseolus vulgaris and Zea mays, decreased with increasing concentrations of NaCl from 0 to 50 mM in nutrient solutions supplied regularly in a porous growth medium. Sucrose concentrations in the leaves were higher and reducing sugar concentrations were lower at the higher concentrations of NaCl. Growth of leaves, invertase activity, and concentrations of reducing sugar and sucrose changed much less, if at all, with NaCl treatment of Hordeum vulgare, a reasonably salt-tolerant plant. Cellulase activities were not different in bean leaves from plants grown on different NaCl concentrations. The Km values for sucrose for invertase from bean leaves were 5.8, 8.1 and 10.4 mM for plants grown on 0, 20 and 50 mM NaCl respectively. NaCl at concentrations up to 200 mM did not affect the in vitro activity of invertase from barley, bean or maize leaves.

High humidity overcomes lethal levels of salinity in hydroponically grown salt-sensitive plants

Red kidney bean (Phaseolus vulgaris L.) plants were grown at five NaCl levels in continuous 95–100 per cent RH. Plants survived, flowered, and produced normal-sized pods and beans even at the highest NaCl level, 9800 ppm, a level which normally results in death of the plants at lower RH. The results suggest that, because of the dwarfed nature of the plants and the reduced number but normal-sized pods and beans produced, higher planting density could substantially increase the yield per unit growing area in high humidity greenhouses when the water supply is highly saline. re]19740805

Formation of alkali soils by neutral salt solutions

Abstract It has been reported that large tracts of land under irrigation in the western part of United States contain enough soluble salts to depress crop production and thousands of acres have been abandoned because of salinity. In soils commonly called white alkali soils, containing accumulation of neutral salts in the form of chlorides or sulphates, 0.2% of salt will reduce yields of salt sensitive plants and 1.0% will cause marked yield reduction in most crops. If the drainage is poor and water table is maintained near the surface of the soil, evaporaLion will be high and the salt will accumulate. When large amount of soluble salts accumulate at the surface, the soil is termed as saline and has a pH value below 8.5. The soils containing alkali salts such as Na.COa or NaHC03 and having a pH value above 8.5 are called alkali soils or black alkali soils. Misra (1954) has reported that a gradual replacement of calcium ions and a subsequent increase in the exchangeable Na or K in the exchange complex of th...