Investigating Developmental Trends in the Male Shoot of \u3cem\u3eArceuthobium americanum\u3c/em\u3e (Lodgepole Pine Dwarf Mistletoe) Using Environmental Scanning Electron Microscopy

The dwarf mistletoes (Arceuthobium) are flowering plants that obligately parasitize conifers. Arceuthobium americanum, known commonly as lodgepole pine dwarf mistletoe, is pathogenic to lodgepole pine (Pinus contorta subsp. latifolia). The parasite develops an endophytic (within-host) system that invades the tree’s vasculature, redirecting the flow of water and nutrients away from the host. After several years, aerial shoots displaying either male or female flowers will emerge from the tree and begin their reproductive cycle. This infestation causes the loss of up to 3.8 million m3 of viable timber per year, estimated to have an economic impact of several billion dollars. The objective of this work is to use environmental scanning electron microscopy to detail the external morphology of preserved male shoots previously collected over the growing season. Branching patterns, anther anatomy/dehiscence, flower opening, and flower bud development are investigated. Gaining a better understanding of the anatomy and developmental morphology as it is linked to the spread of Arceuthobium americanum may allow for better strategies to control the parasite