Microgametophytic plastid nucleoid content and reproductive and life history traits of tribe Trifolieae (Fabaceae)

Microgametophytic plastid nucleoids were quantified for 18 species representing the four core genera of the tribe Trifolieae (Fabaceae), Medicago, Melilotus, Trigonella, and Trifolium. Generative cells of all taxa contained nucleoids, establishing that biparental plastid inheritance is common in the Trifolieae. Nucleoid number and volumes of pollen grains and generative cell nuclei differed among taxa. Nucleoid number was positively correlated with pollen grain and generative cell nuclear volumes, flower size and style length. These relationships disappeared after adjusting nucleoid number for pollen grain and generative cell nuclear volumes. Adjusted nucleoid numbers provided no evidence to support hypotheses that plastid content is associated with ploidy level, mating system, perenniality or size of the reproductive apparatus.