• Flowering Phenology and Outcrossing in Tetraploid Grindelia camporum Green

      Schuck, Susan M.; McLaughlin, Steven P.; University of Arizona (University of Arizona (Tucson, AZ), 1988)
      Several reproductive processes of tetraploid Grindelia camporum were investigated. This plant is a potential resin crop for the southwestern United States. Field observations of 100 flower heads from unopened buds through 100% achene dispersal were made. It was found that individual flower heads are available for pollination for approximately 5 days but all disc florets are open for only 1 day. On average, achenes mature in 22 days and are dispersed 53 days after flowering. Fourteen-hundred hand-pollinations were also made on plants from 6 wild populations of G. camporum grown in a greenhouse and shade house. Estimates of fertility and crossability of populations were made based on achene number and achene weight data from these crosses. All populations studied were interfertile and no evidence of outbreeding depression in between -population crosses was found. It is shown that tetraploid G. camporum is self-incompatible and requires manipulation for achene set.