Light-Induced Effects of Tris on the Ultrastructure of Leaf Tissue

The effects on ultrastructure of tris(hydroxymethyl)aminomethane (Tris), pH 8· 0, were examined in leaf segments of wheat, barley, and maize in both light and dark. Tria in the light induces drastic changes in chloroplast ultrastructure which are not apparent in the dark except in mesophyll cells of maize. Both grana and stroma lamellae are affected and structural changes are apparent after treat-mentwith Tris for 3 hr. Vacuoles appear in the chloroplasts and both grana and stroma lamellae frequently Wldergo coiling. At later stages, disruption of the tonoplast occurs. The action of Tris appears to be specific for chloroplast membranes and the tonoplast, there being no apparent effect on the plasmalemma, or the membranes of mitochondria or microbodies.