Ultrastructure and biochemistry of two mutants in Hosta (Liliaceae)

In a survey of several plastid chimeras of the genus Hosta two white mutants with C4--type ultrastructure were noted. Mesophyll plastids from the white tissue have an extensive system of peripheral reticula, characteristic of C4 plants, and macrograna or vesiculated thylakoids, characteristic of photosystem I deficient mutants. Microbodies were either absent or in low quantities in these cells. Bundle sheath plastids from the white sectors had a concentration of all organelles, with plastids of typical C4 bundle sheath ultrastructure and numerous, ornate mitochondria. Green restituted sectors of one of these mutants retained the ability to make peripheral reticulum yet had normal Hosta granal formation. Despite these changes the plants show a carbon fractionation like C3 plants. Possible reasons for these ultrastructural modifications are discussed.