Photosynthesis, Leaf Anatomy, and Morphology of Progeny from Hybrids between C(3) and C(3)/C(4)Panicum Species

Species in the Laxa group of Panicum have C₃ or C₃/C₄ photosynthesis based on leaf anatomical and CO₂ exchange characteristics. Hybrids were previously made between C₃/C₄ and C₃ species in this group (RH Brown et al. 1985 Plant Physiol 77: 653-658). In this paper, CO₂ exchange, morphological, and leaf anatomical characteristics of F₂ or F₅ progeny from colchicine-induced amphiploids of C₃/C₄ × C₃ hybrids (Panicum milioides Nees ex Trin. [C₃/C₄] × Panicum laxum Mez [C₃] and Panicum spathellosum Doell [C₃/C₄] × Panicum boliviense Hack. [C₃]) were studied.

There were no differences found in morphology or physiology between the amphiploids and the F₁ hybrids from which they were produced. In the segregating progeny, CO₂ compensation concentration and photorespiration values typical of C₃, but not of C₃/C₄ plants, were recovered. Progeny were found from both crosses which possessed O₂ inhibition of apparent photosynthesis typical of the parents, and in the case of the P. milioides × 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 O₂ inhibition of apparent photosynthesis, CO₂ compensation concentration, and leaf anatomical traits. One plant was especially noteworthy in possessing leaf anatomy typical of C₃/C₄ plants, but with CO₂ exchange characteristics of C₃ plants.