a: Mitochondria from a young sieve tube of a Helianthus annuus (sunflower) shoot. The inner membrane is folded into numerous cristae that run through the inner part of the mitochondrion, the matrix (grey). The cristae greatly enlarge the inner surface and thus also the working space of the mitochondrion.
(Ch. GLOCKMANN, R. KOLLMANN, 1985);
b: Mitochondria in a haustorial cell of dodder (Cuscuta odorata). Here, too, the cristae formed by the inner mitochondrial membrane are clearly recognizable (Ch. GLOCKMANN, R. KOLLMANN, 1979)