Abstract
The effects of administering CaCl_2 or Ca(N0_3)_2 solution with high concentration to the roots of lettuce (Lactuca sativa L.) grown hydroponically for 48 hr on the Ca, Cl, and NO_3 contents in the leaves were studied. The Ca content in the outer and inner leaves increased with a rise of Ca concentration in the treatment solution, and a greater part of the Ca content was water-soluble. A high positive correlation was observed between the foliar Ca content and the foliar Cl content in the CaCl_2 treated plants or the foliar NO_3 content in the Ca(NO_3)_2 treated plants. It is considered that Ca(NO_3)_2 was unsuitable in this soaking method because a significant amount of NO3 accumulated in the leaves with the increased Ca. It was found that the Ca content markedly increased without damage or withering if the Ca concentration in the treatment solution was below about 40mM. The Ca content in the leaves treated with 40mM CaCl_2 was 1.92 gkg^<-1> (fresh weight) and was about 2.6 times more than that of the control.
