Effect of salinity of nutrient solution on growth, translocation and accumulation of 45Ca in butterhead lettuce

The possible causes of tipburn in butterhead lettuce 'Omega' were investigated by measuring the uptake of water, growth, translocation and accumulation of Ca-45 within the leaf position. Salinity levels were controlled at EC 1.5, 4.5 and 9.0 dS m(-1) by addition of NaCl. Amount of water uptake and growth of butterhead lettuce decreased significantly with increasing EC. At 9.0 dS m(-1), amount of water uptake or growth of the plants reduced to 55% or 71% compared to that of plants grown at 1.5 dS m(-1), respectively. Decreased amount of water uptake resulted in the decrease in leaf number and fresh weight. The translocation and accumulation of Ca-45 in the leaves, measured by the bioimaging analyzer decreased with elevated EC. The values of photo-stimulated luminescence of the 3rd leaf from the apex showed high in vein and low in leaf blade regardless of salinity treatment. The difference in Ca-45 ion content in the leaves with increased EC level strongly indicated that calcium translocation might be independent of the root pressure flow. These data suggest that the incidence of tipburn in butterhead lettuce may be related to the reduced water uptake, growth, translocation and accumulation of Ca. Incidence of tipburn in butterhead lettuce was affected by root pressure flow, when plants were grown in salinity condition.