Recent research demonstrates that biparental inheritance of plastids (BIP) may be more common in the plant kingdom than previously thought. Plastids are inherited biparentally in approximately 20% of angiosperm taxa studied. Various hypotheses have been presented to explain the basis for patterns of plastid inheritance in plants, however, very little is understood regarding the evolutionary significance of these inheritance patterns. Our research with alfalfa (Medicago sativa), which exhibits regular BIP, suggests that there may be fitness effects associated with sporophyte plastid composition (maternal, paternal, or biparental) in this species. Plastids may also provide an energy source for the developing microgametophyte, sperm or the fertilized egg in species with BIP. The research described here would consider these two possible explanations for the existence of the BIP. Using sets of full-sib families with defined constitutions, we propose to measure the effects of 1) plastid composition in sporophytes on basic physiological processes and components of fitness in alfalfa. Measurement would concentrate on physiological traits influenced by plastid-nucleus interaction and whole-plant characteristics that may reflect differences in primary metabolism.
