ISHS Acta Horticulturae 644: International Symposium on Growing Media and Hydroponics
EFFECTS OF SODIUM SULFATE, SODIUM BICARBONATE AND SUPPLEMENTAL CALCIUM ON THE GROWTH OF LETTUCE |
| Authors: | Z. Bie, T. Ito, Y. Shinohara |
| Keywords: | salinity, gas exchange, mineral composition, Lactuca sativa L. |
| Abstract:
Butterhead lettuce (Lactuca sativa L. cv. L-2) plants were subjected to 0, 20, 40 and 60 mM Na2SO4 or 0, 2.5, 5 and 7.5 mM NaHCO3, and 0, 2 and 4 mM supplemental Ca2+ in nutrient solution culture in the greenhouse. In Na2SO4 experiment, leaf chlorophyll increased whereas shoot dry weight decreased with increasing Na2SO4 concentration. Concentration of Ca, Mg, K, N and P decreased whereas Na increased as Na2SO4 concentration increased. Supplemental Ca2+ improved shoot growth, increased Ca but decreased Na concentration. In NaHCO3 experiment, shoot dry weight decreased with increasing NaHCO3 concentration, chlorosis appeared on the leaves of plants subjected to 5 and 7.5 mM NaHCO3 treatments. Supplemental Ca2+ did not improve shoot growth under NaHCO3 salinity although it increased shoot Ca and diminished Na concentration. Photosynthetic rate, transpiration rate and stomatal conductance decreased with increasing Na2SO4 or NaHCO3 concentration, and supplemental Ca2+ improved gas exchange only in Na2SO4 experiment. This study indicated that lettuce growth was more sensitive to NaHCO3 salinity. The more severe depression of shoot growth in NaHCO3 experiment was not likely caused by excessive accumulation of Na+, but may be due to the specific toxicity of HCO3-. | |
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