Effects of Simulated Acid Rain on Chloroplast Ultrastructure of Primary Leaves of Phaseolus Vulgaris

Abstract

The ultrastructure of chloroplasts in the primary leaf of 10-d-old bean plants (Phaseolus vulgaris L., cv. Cheren Starozagorski) was studied 3, 5, 24, 48, 72 and 168 h after a single treatment with simulated acid rain (pH 2.4, 2.2, 2.0 and 1.8). Different changes in chloroplast structure till full destruction of organelles were traced. A determining factor for these changes was the histological localization of chloroplasts. In the chloroplasts of palisade parenchyma different degrees of expansion of thylakoids (3, 5, and 24 h after the single treatment), and conformational changes of the inner membrane system (48, 72 and 168 h) were observed. The chloroplasts of spongy parenchyma showed a significantly higher degree of structure resistance. The expansion of thylakoids was weak and did not depend on the duration of treatment. The ultrastructural changes of chloroplasts confirmed relative resistance of this species till pH 2.0.