• 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.
    • Dalea - Horticulturally Promising Legumes for Desert Landscapes

      Starr, Greg; Starr Nursery (University of Arizona (Tucson, AZ), 1988)
      Dalea is a member of the family Leguminosae which includes many commonly cultivated plants used in southwestern desert landscapes. With 166 described species, it is surprising to learn that until recently Dalea has largely been neglected horticulturally. In this paper I discuss seven promising species that have been tested in landscape situations for five years. These include six shrubs and one spreading groundcover. All except the groundcover are extremely showy when at the peak of flowering. Each species is unique and all are highly recommended for landscaping in arid regions of the world.
    • Geomorphology and the Distributional Ecology of Fremont Cottonwood (Populus fremontii) in a Desert Riparian Canyon

      Asplund, Kenneth K.; Gooch, Michael T.; Prescott College (University of Arizona (Tucson, AZ), 1988)
      DBH data were taken from Fremont Cottonwood (Populus fremontii) in a desert riparian canyon in west -central Arizona. Recruitment was found to depend on geomorphologic features and flood "refugia" rather than on the absence of grazing. Populus fremontii is specifically a "strandline," streamside species, particularly of braided aggradations and their associated secondary channels, a microhabitat that ultimately depends on upstream and upslope erosion. The concept of flood -subclimax succession explains virtually nothing of the ecology of obligate riparian trees. Riparian classification based upon geomorphology and hydrology are apt to have significant meaning for biogeography and management.
    • The Theory Behind the Clump-Flatting Procedure in Cactus Propagation

      Crosswhite, F. S.; Crosswhite, C. D. (University of Arizona (Tucson, AZ), 1988)
    • Desert Plants, Volume 9, Number 1 (1988)

      University of Arizona (Tucson, AZ), 1988