Photochemical Characteristics of Mesophyll and Bundle Sheath Chloroplasts from C < inf > 4 < /inf > Plants

Abstract

Mesophyll and bundle sheath chloroplasts were isolated by differential grinding from the leaves of two NADP‐ME C4 plants, Setaria italica Beauv. cv. H‐1, Pennisetum typhoides S & H. cv. AKP‐2, and a NAD‐ME C4 species Amaranthus paniculatus L. The mesophyll chloroplasts of C4 plants possessed slightly lower Km for ADP and Pi than those of bundle sheath chloroplasts. The Hill reaction activities and noncyclic photophosphorylation rates of the bundle sheath chloropiasts from S. italica and P. typhoides were less than one‐fifth of those by the mesophyll chloroplasts. But the bundle sheath chloroplasts of A. paniculatus exhibited high rates of Hill reaction, cyclic as well as noncyclic photophosphorylation. The pigment‐ and eyiochrome composition suggested a relative enrichment of PS 1 in bundle sheath chloroplasts of S. italica and P. typhoides. The chain exists in both mesophyll and bundle sheath chloroplasts. As much as 35–52% of leaf chlorophyll was located in the bundle sheath chloroplasts. The photochemical activities of bundle sheath chloroplasts are significant though a major part of leaf photochemical potential is associated with the mesophyll chloroplasts. Copyright © 1978, Wiley Blackwell. All rights reserved