Influence of certain fungi on seed germination and seedling survival of four colonizing annuals.
The association between seeds of Abutilon theophrasti, Datura stramonium, Ipomoea hederacea and Polygonum pensylvanicum and their mycoflora was examined. Fungal species on the seed surface differed among the weed species and were mainly host-specific. A more extensive mycoflora occurred within seeds of Polygonum pensylvanicum and D. stramonium than within seeds of I. hederacea and A. theophrasti. Ipomoea hederacea and A. theophrasti seeds showed greater resistance to fungal infection than those of P. pensylvanicum and D. stramonium. Fungi also differed in their ability to penetrate the seeds. Seed germination and seedling development were affected, both quantitatively and qualitatively, by fungal isolates. Polygonum pensylvanicum seedlings were more susceptible to fungal invasion than those of A. theophrasti or I. hederacea. Extracts from all tissues of I. hederacea and from the roots of A. theophrasti showed antifungal activity. Little activity was detected in extracts from P. pensylvanicum. Plant densities of I. hederacea, D. stramonium and P. pensylvanicum remained fairly constant in the field, after seedling emergence, irrespective of density or species diversity. Fungi mainly affected seed germination and the development of young seedlings; at later stages, herbivory became more important in plant survival. From summary.