Abstract

The effects of 30 and 60 mM NaCl on Lettuce (Lactuca sativa L. ‘Eish!’), grown in soilless culture, with additions of 0, 1, 2 and 4 mM Si was evaluated. Height, leaf number, weight, chlorophyll content and elemental analysis of plants were examined. Fresh root and shoot weight significantly increased with additions of 2 mM Si compared to that of the 60 mM NaCl control, with notable increases with Si treatments of 1 and 4 mM. Dry root and shoot weight with additions of 1 mM Si, and in shoot weight with additions of 2 mM Si, significantly increased when compared to the 60 mM NaCl control. Increases in dry root and shoot weight of the other Si additions lead to clear, yet insignificant increases in dry weights. Few differences in Cl content were evident amongst treatments, besides a significant increase in root content and a significant decrease in shoot content with applications of 4 mM Si exposed to 60 mM NaCl. Na shoot content of 1, 2 and 4 mM Si at 60 mM NaCl showed a significant decrease compared to that of the control. Applications of 2 and 4 mM Si showed increased shoot Si when compared to both the 30 and 60 mM NaCl controls. With clear evidence for a reduction in Na content in shoots with applications of Si at higher NaCl concentrations, and further increases in plant weights, it can be stated that applications of Si are of a distinct benefit for the growth of lettuce.

Key words: Lettuce, Si, NaCl, salt, sodium chloride, hydroponics.