The tolerance of sesame to NaCl salinity was studied first during germination (72 hours), and later during plant growth up to maturity. Germination was conducted in the laboratory at 25C. Sesame plants were tested for response to salinity using nutrient solution cultures with sodium chloride added when test plants were approximately 10 cm tall. Experiments were continued until mature seed pod formation. The data showed a high tolerance during germination but sensitivity at later growth stages.Although seed yield was strongly reduced, the seed oil content and its fatty acids were not changed. Analyses of leaf blades at different growth stages did not reveal changes in Ca, Mg, K, P, and N indicative of a nutrient deficiency(s). Chlorides, however, accumulated to levels considered toxic. The chloride absorption isotherm showed a marked increase at all growth stages for the same substrate NaCl concentration. This increase was coincident with severe leaf injury and growth reduction. The Na levels in the leaf blades were very low relative to Cl. For example, Na and Cl levels of plants under the highest NaCl treatment at 6 weeks were 0.20% Na and 5.13% Cl. Growth was reduced approximately 50% by this NaCl treatment. The 0.20% Na level is not high enough to indicate Na toxicity.
A solution culture boron experiment was conducted with sesame (Sesamum indicum L.) to show the effects of excessive B. The boron content of leaf blades, petioles, and stems was highly correlated with substrate boron. The leaf blades contained the highest amount of boron, and the stems the least. Concentrations of 5 mg B/liter or higher inhibited growth, seed production, and resulted in a leaf necrosis and premature leaf drop. Foliage of plants receiving excess B contained > 700 µg B/g on a dry weight basis.An exchangeable sodium experiment using clay soil with and without a synthetic soil conditioner showed that yields were sharply reduced at an ESP level of 15 or greater. Leaf blade sodium was higher for the treatments without the soil conditioner but in both series (± conditioner), 50% growth depression was associated with leaf values of about 0.4% Na. Potassium and Mg in the leaf blades did not vary significantly, and although calcium was decreased 50% with increasing ESP, no visual deficiency symptoms were detected. The oil content of the seed was decreased slightly with ESP levels of about 25.
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