Anther and pollen development in the lodgepole pine dwarf mistletoe (Arceuthobium americanum) staminate flower

Author:

Munro Kaitlyn C.1,Jackson Jeffrey R.M.1,Hartling Ivan1,Sumner Michael J.2,Ross Friedman Cynthia M.1

Affiliation:

1. Department of Biological Sciences, Thompson Rivers University, 900 McGill Road, Kamloops, BC V2C 0C8, Canada.

2. Department of Biological Sciences, University of Manitoba, Winnipeg, MB R3T 2N2, Canada.

Abstract

The lodgepole pine dwarf mistletoe, Arceuthobium americanum Nutt. ex Engelm., is a parasitic angiosperm that infects conifers in western Canadian forests. While production of viable pollen in anthers is critical to dwarf mistletoe reproduction, the few existing reports that examine staminate development in Arceuthobium are often incomplete or conflicting. The objective of this work was to investigate the developmental anatomy of anther and pollen of A. americanum using modern microscopy. We found that the microsporangium was toroidal from the outset and gave rise to a central peg-shaped sterile “columella” early in anther development. The endothecium was absent, the epidermis persisted as an “exothecium” fulfilling the role of the endothecium, and a primary parietal layer generated a secretory tapetum and middle layer. Thus, we suggest that a new category of anther wall development, the Arceuthobium type, be created. Microsporogenesis produced tetrahedral microspores via simultaneous cytokinesis and involved callose wall formation. Microgametogenesis resulted in round and atypical generative and vegetative nuclei. Additionally, the heterocolpate, echinate pollen grains, which were shed at the two-celled stage, were seen for the first time in their native state with environmental scanning electron microscopy. This work contributes to the understanding of A. americanum, the genus Arceuthobium, and angiosperms as a whole.

Publisher

Canadian Science Publishing

Subject

Plant Science,Ecology,Ecology, Evolution, Behavior and Systematics

Reference46 articles.

1. The Microsporangium

2. Bhandari, N., and Vohra, C. 1983. Embryology and affinities of Viscaceae. In The biology of mistletoes. Edited by D.M. Calder and P. Bernhardt. Academic Press, New York, USA. pp. 69–86.

3. Bhatnagar, S., and Moitra, A. 1996. Gymnosperms. New Age International, New Delhi, India.

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