Sexual reproduction of Pinus contorta. II. Postdormancy ovule, embryo, and seed development

Abstract

Postdormancy development of the ovule, fertilization, and embryo and seed development of Pinus contorta (Dougl.) are described. Reproductive development in lodgepole pine (P. contorta var. latifolia) growing within and outside its natural range is described in detail and compared with the phenology of shore pine (P. contorta var. contorta) growing within its natural range. The female gametophyte of lodgepole pine overwinters at the free nuclear stage, resumes development in early April, and is mature by mid-June. Fertilization occurs in mid-June and the embryo and seed are mature by early August. Seed cones of lodgepole and shore pines growing in the coastal region resume development in late March, develop more slowly at first, then complete each subsequent stage of development about 1 month earlier than lodgepole pine grown in the interior of British Columbia. Stages of the reproductive cycle as they affect potential seed production are discussed.