Relation Between Salt Tolerance and Long-Distance Transport of Sodium and Chloride in Various Crop Species

Abstract

The effect of NaCl concentrations up to 100 mM in the nutrient solution upon dry matter production and mineral composition of seven plant species was studied in a pot culture experiment. The plants could be arranged into three groups according to the depression in dry matter production at 100 mM NaCl: tolerant (sugar beet; maize, cv. Velox); moderately tolerant (cress; sunflower; safflower; maize, cv. DC 790); and sensitive (pepper; bean, cv. Saxa and Contender). In all plant species, the chloride content increased more than the sodium content in the shoots with an increasing supply of NaCl. Differences between plant species were much higher in sodium content than in chloride content. In most plant species, a supply of NaCl decreased the potassium content much less than the calcium content. Application of labelled sodium (22Na) and chloride (36Cl) to the leaves of plants without supplying NaCl to the roots revealed great differences between the species with regards to sodium and chloride retranslocation. No correlation could be found, however, between the retranslocation rates of chloride and sodium respectively within a particular plant species. Part of the retranslocated 22Na and 36Cl had been lost through efflux from the roots. The efflux of 36Cl was low in all plant species. The efflux of 22Na was generally higher and differed considerably between the plant species, ranging from zero in sugar beet to 14% in bean. A significant positive correlation exists between this efflux of 22Na in the various plant species and the corresponding growth depression caused by an increasing supply of NaCl.