Shoot ontogeny in Arctostaphylos uva-ursi (bearberry): origin and early development of lateral vegetative and floral buds

Abstract

In the course of a general developmental study of Arctostaphylos uva-ursi (L.) Spreng. (bearberry), observations were made on the pattern of lateral bud initiation and development. Three types of foliar organs (foliage leaves, transitional leaves, and bud scales) are initiated by a vegetative shoot apex each year in a predictable sequence. A robust bud, initiated as a detached meristem and delimited by a shell zone, developed in the axil of each foliage leaf. Smaller, poorly developed buds, sometimes arising from tissues of the leaf base, developed in transitional-leaf axils, but they rarely persisted. Although scale axils seldom contained buds, there was evidence to suggest that buds may have started to form but soon became arrested. In the development of an inflorescence, small bracts were initiated by the terminal apex instead of foliage leaves or cataphylls. Flower buds were then initiated in the axils of the bracts and the terminal apex became inactive. The relative roles of shoot apex and subtending leaf primorida in regulating the development of buds are discussed.