Reprinted with permission from: Canadian Journal of Botany. 1999. 77:599-610. Published and copyrighted by: National Research Council of Canada, http://www.nrc.ca/cisti/journals/ Ovule, embryo sac, embryo and endosperm development in leafy spurge (Euphorbia 1 esula L.) JEFFREY S. CARMICHAEL* and SARENA M. SELBO Department of Biology, University of North Dakota, Grand Forks, ND 58202, Phone: (701) 777-4666, Fax: (701) 777- 2623, *Author for correspondence, e-mail:
[email protected]. Abstract: Leafy spurge (Euphorbia esula) is a noxious, invasive weed that domi- nates many agriculturally important regions. While many research efforts are currently aimed at controlling the spread of this plant, relatively little is known about its sexual reproductive biology, especially from a struc- tural perspective. This report describes key features of ovule development, embryogenesis, and endosperm formation in leafy spurge. Ovules are ana- tropous, bitegmic, and form a zigzag micropyle. A distinct elaisome (ca- runcle) and hypostase are formed as ovules mature. Obturators are present and are derived from placental tissue. The embryo sac conforms to the Po- lygonum type. A single embryo is formed in each seed and stores nutrients primarily as globoid protein bodies. Endosperm is persistent and also con- tains protein bodies as its primary nutrient reserve. Preliminary structural evidence is presented that indicates the potential for apomixis. Keywords: Leafy spurge, Euphorbiaceae, Euphorbia, ovule, endosperm, embryo. Introduction Leafy spurge (Euphorbia esula L.) is an herbaceous perennial that has flourished as a noxious weed of economic and ecological significance (Lajeunesse et al. 1995; Lym and Messersmith 1983; Messersmith 1983; Messersmith and Lym 1983a, b).