Photosynthesis, Leaf Anatomy, and Morphology of Progeny from Hybrids between C3 and C3/C4Panicum Species

Species in the Laxa group of Panicum have C(3) or C(3)/C(4) photosynthesis based on leaf anatomical and CO(2) exchange characteristics. Hybrids were previously made between C(3)/C(4) and C(3) species in this group (RH Brown et al. 1985 Plant Physiol 77: 653-658). In this paper, CO(2) exchange, morphological, and leaf anatomical characteristics of F(2) or F(5) progeny from colchicine-induced amphiploids of C(3)/C(4) x C(3) hybrids (Panicum milioides Nees ex Trin. [C(3)/C(4)] x Panicum laxum Mez [C(3)] and Panicum spathellosum Doell [C(3)/C(4)] x Panicum boliviense Hack. [C(3)]) were studied.There were no differences found in morphology or physiology between the amphiploids and the F(1) hybrids from which they were produced. In the segregating progeny, CO(2) compensation concentration and photorespiration values typical of C(3), but not of C(3)/C(4) plants, were recovered. Progeny were found from both crosses which possessed O(2) inhibition of apparent photosynthesis typical of the parents, and in the case of the P. milioides x P. laxum cross, leaf anatomy and overall plant morphology typical of the parents were observed in some progeny. The progeny were found to possess recombinations of various traits associated with reduced photorespiration, so that no correlation existed among O(2) inhibition of apparent photosynthesis, CO(2) compensation concentration, and leaf anatomical traits. One plant was especially noteworthy in possessing leaf anatomy typical of C(3)/C(4) plants, but with CO(2) exchange characteristics of C(3) plants.