Cotyledon greening in hypogeal seeds of Citrus fruits.

In four different citrus fruit species (Citrus limon, Citrus sinensis, Citrus deliciosa, Fortunella margarita), all with hypogeal seeds, the behavior of the cotyledon plastids was studied during germination. Our surveys have shown that, in addition to the expected storage function, these hypogeal cotyledons also develop a definite photosynthetic function supported by well-organized chloroplasts. The initial presence of chloroplasts with rather large thylakoid stacks in the quiescent cotyledons of two species does not appear to represent an advantage fro them over the two other species, where the white quiescent cotyledons have plastids without thylakoid stacks. It seems that the ability of hypogeal cotyledons to become photosynthetically functional in light might be a common feature of citrus fruits. © 1988.