Tetracaine inhibition of electron transport in pea chloroplasts is coupled to calcium displacement by the local anesthetic.

Chloroplasts isolated from pea seadlings grown on water containing 45Ca2+ were treated with local anesthetic tetracaine. Addition of tetracaine inactivated the electron transport activity of donor side photosystem II. This inhibition was accompanied by 45Ca2+ release from the chloroplast membranes as the whole and destroyed by osmotic shock. No such effect was observed when Tris or hydroxylamine were used to inhibit the donor side photosystem II. Upon thermal inactivation of chloroplasts 45Ca2+ release occurred but at temperatures above 80 degrees. The functional role of Ca2+ in photosystem II is discussed.