EFFECTS OF SODIUM SULFATE, SODIUM BICARBONATE AND SUPPLEMENTAL CALCIUM ON THE GROWTH OF LETTUCE

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^–.

International Symposium on Growing Media and Hydroponics

Z. Bie, T. Ito, Y. Shinohara

salinity, gas exchange, mineral composition, Lactuca sativa L.

https://doi.org/10.17660/ActaHortic.2004.644.57