Development of Proteoid Roots in Hakea obliqua R.br. (Proteaceae) Grown in Water Culture

Proteoid roots of Hakea obliqua seedlings grow rapidly at 20°C in water culture. The surface area of an average developing proteoid root increases 1500 mm2 per day, which finally represents a 25-fold increase over that of the parent root. The epidermis and interior tissues of the rootlets are derived from the pericycle but the root cap cells originate from the endodermis of the parent root. The root cap cells of the rootlets secrete a considerable amount of mucilage both before and after emergence from the parent root.