Salt Toxicity Research Articles

Leaf analysis for pear: development of standards and the nutritional status of orchards in the Goulburn Valley and Murrumbidgee Irrigation Areas

Leaf composition standards for pear trees were formulated from the literature then evaluated in the Goulburn Valley, Victoria by surveying the leaf composition of high-production orchards for two seasons (1971-72 and 1972-73). Good agreement was found between the standards and orchard leaf composition although the calcium standards required slight amendment. A concurrent survey of orchards showing symptoms of salt toxicity showed that sodium and chloride levels previously considered safe were in fact toxic and the standards were amended accordingly. The revised standards were used to evaluate the nutritional status of young and older pear blocks in the Goulburn Valley and pear blocks in the Murrumbidgee Irrigation Areas (MIA), New South Wales. The findings for Goulburn Valley blocks were confirmed by multiple regression analysis of leaf composition and yield data.

Pathological anatomy of conifer needle necrosis

The pathological anatomy of pine needle necrosis caused by major environmental stresses was investigated to determine if histological responses could provide a diagnostic tool. All stresses studied caused a general hypertrophy of the epithelial tissue of the resin canals, occluding these ducts. Granulation of transfusion and mesophyll parenchyma cells was also a general response to stress. Hypertrophy of the phloem cells and transfusion parenchyma was caused by almost all stresses in some instances but was most consistent for necrosis caused by natural senescence, drought, or fluoride. Collapse of the mesophyll cells best characterized necrosis caused by ozone, sulfur dioxide, salt, or boron toxicity. The greatest value of microscopic examination of the tissues adjacent to the necrotic areas was found to lie in the elimination of certain pathogens, narrowing the possible causal agents. Histological examination could ascertain when certain air pollutants were not responsible for a particular injury; for instance, the absence of mesophyll collapse can definitely eliminate sulfur dioxide as a cause of necrosis. Conversely, though, presence of mesophyll cell collapse, because of its ubiquitous nature, could not establish etiology.

Salt injury to plants with special reference to cations versus anions and ion activities

In contrast with the toxicities of sulfate and chloride salts added to substrates, the anions SO4 and C1 were not injurious when accumulated without leaf burning by cotton and tomato plants from atmospheres enriched with SO2 or HC1 gases. The foregoing results are discussed in terms of cationenzyme interactions which appear to represent at least a major cause of salt toxicity. Although anions are largely unreactive with enzymes it has long been observed that chloride salts in soil solutions are far more toxic than sulfate salts. Five of seven species have shown nearly equal growth repressions on substrates with 100 me/1 of C1 salts versus 200 me of SO4 salts, each added as 50 per cent Na. The ion activities of the two solutions were equal and the sum of cations in the plant saps were similar. The osmotic differentials (average about 10 atm) between the expressed tissue fluids and these substrate solutions were remarkably uniform within species. It is projected that the downward transport of salts via the phloem provides for root concentrations which supply ions to the xylem and thereby control the uptake of substrate salts.

Enhanced salt toxicity in the spontaneously hypertensive rat.

SummaryChronic ingestion of 1% salt solution causes accelerated hypertension leading to death in the SH rat at a more rapid rate than in the normal rat given 1% salt or in the SH rat given tap water.

SALT TOLERANCE OF RUSSIAN WILD RYEGRASS IN RELATION TO TALL WHEATGRASS AND SLENDER WHEATGRASS

Salt tolerance of Russian wild ryegrass was compared with that of tall wheatgrass and slender wheatgrass in controlled germination experiments and in a field trial. There appeared to be specific salt toxicity when Russian wild ryegrass was germinated in saline saturation soil extracts and sodium sulphate solutions. However, the absolute germination of this species was intermediate between that of tall wheatgrass and slender wheatgrass in the osmotic range up to 12.15 atmospheres. In the field it was found that Russian wild ryegrass would establish, persist, and produce well in soil concentrations giving osmotic pressures up to 4.5 atmospheres (12 mmhos/cm. conductivity). Although the salt tolerance of Russian wild ryegrass was not as great as that of tall wheatgrass, it was quite comparable to that of Primar slender wheatgrass and above previously recognized levels.

The Effects of Deficiency of B Vitamins on Salt Toxicity in the Rat

The Effects of Deficiency of B Vitamins on Salt Toxicity in the Rat

Plant-growth relationships on salt-affected soils

It is apparent that heightened interest in salinity and related factors which restrict plant growth in arid or irrigated areas has produced notable contributions to the literature of this field in the past two decades. Quantitative information on the salt tolerance of the most important crop plants has been obtained, and the proximal causes of salt injury have, in some cases, been carefully analyzed. Experimental demonstration of the general occurrence of osmotic effects and the more restricted development of specific ion effects has cleared the way for further advances in understanding the nature of salt injury to plants. Still awaiting clarification is the relative importance of factors which contribute to salt tolerance or sensitivity when osmotic effects predominate. It is obvious that when water availability is restricted by salinity, all the factors which regulate or influence water absorption and water loss by plants contribute in some way to the resultant which is termed “salt tolerance.” Little has, as yet, been done to evaluate these factors in terms of their contribution to salt tolerance. The mechanisms whereby chloride or sodium ions are specifically toxic to sensitive species remain unknown. The similarity of toxic levels of accumulation of these ions in widely diverse species suggests a common mechanism or condition which qualitatively distinguishes these species from non-sensitive species. The mechanism of salt toxicity, and the distinguishing features of salt tolerance, appear to be the major tasks for research on salt tolerance of plants in the decade ahead.