Differential Salt‐Oxygen Levels Influence Plant Growth1

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Abstract
Two salt‐oxygen‐plant growth experiments, one a solution culture, the other involving soil, were conducted in a greenhouse using tomato plants (Lycopersicon esculentum Rutgers) as the test plant. Plant growth as measured by eight growth indices was shown to be adversely affected by decreasing the oxygen content of the aerating gas from 21% or by increasing the salt level of the growth media from 20 meq/liter. Simultaneous changes in both the oxygen and salt levels generally produced significantly greater changes than could be accounted for by considering the effects brought about by the salt and oxygen levels considered independently.Tomato plants affected by high salt or low oxygen levels had similar characteristics of stunting and small, somewhat cup‐shaped, wrinkled, dark green leaves. Severity of the symptoms increased as either the salt level increased or the oxygen level decreased. Severe symptoms appeared at combinations of oxygen and salt levels which individually did not cause the symptoms to appear.Reducing the oxygen level from 21% had a significantly adverse effect on growth at all salt levels, while increasing the salt level from 20 meq/liter caused varying amounts of growth reduction depending on the oxygen level. At any given level of one treatment, increasing the stress of the other treatment generally resulted in a considerable reduction in growth, although where growth was already markedly decreased, applying a more severe treatment produced smaller additional detrimental effects.In both the solution and soil experiments the salt effect was greatest under conditions of adequate oxygen. Under low or inadequate oxygen levels the salt effect appeared but to a much smaller extent.

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