REPRODUCTIVE RESPONSES TO MYCORRHIZAL COLONIZATION OF ABUTILON-THEOPHRASTI MEDIC PLANTS GROWN FOR 2 GENERATIONS IN THE FIELD

Plants of Abutilon theophrasti Medic. were grown for two consecutive years in the field. First generation (maternal) plants were grown either with or without mycorrhizal inoculation with Glomus intraradices Schenck & Smith. We collected early and late cohorts of seeds which were used to produce second generation (offspring) plants. Offspring plants were grown either with or without mycorrhizal inoculation with G. intraradices. Irrespective of maternal mycorrhizal status, we found that offspring of early cohort seeds had greater percent mycorrhizal colonization early in the growing season, a greater proportion of plants flowering early in the season, and a greater number of capsules per plant at the end of the season compared with offspring of late cohort seeds. These differences were observed despite the fact that shoot N and P concentrations were greater in offspring of late cohort seeds. We found that mycorrhizal colonization of maternal plants decreased the average time to reproductive maturity in offspring plants, but did not significantly influence any other vegetative or reproductive trait in the offspring plants. Mycorrhizal colonization of offspring plants resulted in a greater number of branches per plant and a greater number of mature capsules per branch. Mycorrhizal colonization of offspring plants also resulted in a significant increase in seed P content, but only for seeds that were produced late in the growing season. We conclude that mycorrhizal colonization of the offspring generation was more important than mycorrhizal colonization of the maternal generation in determining offspring reproductive output, but maternal seed cohort is an important interacting factor that influences offspring fecundity.