Studies on the salt tolerance of vegetable crops in sand culture. I

On fruit vegetables

Abstract

From 1957 to 1960, vegetable crops were grown in sand culture under glass at various concentrations of NaCl to study their relative salt tolerance, visual symptoms of salt injury, and effect of NaCl on absorption of nutrient elements and carbohydrate content of plants. HOAGLAND's solution was used as the basic solution (control), and 1000, 2000, 4000 8000, or 16000 ppm of NaCl was added to it. The present paper, as a part of the studies, deales with the results of experiments on six fruit vegetables, namely, tomato, pepper, cucumber (the 1000 ppm treatment was omitted), broad bean, snap bean (the 100 and 16000 ppm were omitted), and strawberry.
1. With increasing concentration of NaCl, plants were dwarfed and the emergence of lateral shoots was restricted. Concentrations of NaCl above 8000 ppm in cucumbers, broad beans, and snap beans, and above 4000 ppm in strawberries caused severe dying off of older leaves and finaly death of entire plant. With the increase of NaCl, the fresh weight of tops (vines) was reduced, excpet that tomatoes showed the greatest weight at the 1000 ppm treatment The yield of fruits, however, was reduced in any crop with the increase of NaCl. The concentrations of NaCl in the solution corresponding to a 50 percent reduction in yield of fruits of tomatoes, peppers, cucumbers, broad beans, and strawberries were about 3500, 3000, 3000, 2500, 2000, and 1000 ppm, respec-tively. In tomatoes, and peppers, the reduction in yield of fruits was more significant than that of vines. The dry weight percentage of tops generally decreased in high salt treatments.
2. The number of flowers tended in general to parallel declining vegetative growth as salinity in-creased. The rate of fruit setting was reduced mark-edly in the treatments above 8000 ppm in tomatoes and above 4000 ppm in peppers. In most crops, the dates of first flower opening and of first harvesting were not so remarkably affected by NaCl treatments, but in peppers, severe shedding of early fruits in higher salt treaments retarded the first harvest. No apparently harmful effects of NaCl treatments were observed on the fertility or germination percentage of pollens, and on the seed set.
3. Symptoms of salt injury were as follows: In tomatoes, leaves were dark green from 1000 to 8000 ppm, but were chlorotic at the 16000 ppm. In pep-pers, leaves were chlorotic and leaf margins incurl-ed at the 16000 ppm. In cucumbers, above 8000 ppm, leaf margins incurled and interveinal chlorosis occurred starting from older leaves before the death of the plant. In snap beans, leaves were dark green at the 2000 and 4000 ppm, while at the 8000 ppm older leaves developed severe burn between veins before the death of the plant. In strawberries, severe mar-ginal burn occurred in older leaves and petals were greenish at the 2000 and 4000 ppm. Blossom-end rot occurred to a high degree at the 1000 ppm and above 8000 ppm in tomatoes, and at the 2000 ppm in pep-pers. Broad beans developed no specific symptoms.
4. With increasing concentration of NaCl, the accumulation of Na in leaves increased almost linearly, except in peppers and snap beans, while Cl accumu-lated linearly in any crop. Cl accumulated in leaves in greater equivalent amounts than Na except in broad beans. Antagonistic relations between Na and other cations, i. e. K, Ca, and Mg, varied with ions or vegetables, and the total amount of these four cations in leaves decreased in peppers and snap beans and increased in the others with the increase of NaCl. The variation in the content of N or P was rather slight as compared with cations and was variable with the vegetable species. There was no definite tendency in the contents of carbohydrates.