In vitroabscission of kauri (Agathis australis) branches

Abstract

When nodal explants from tips of horizontal branches of seedling Agathis australis (Araucariaceae) are cultured in vitro, the distal 3 mm of internode progresses through a series of morphological and anatomical changes, and ultimately detaches. Changes include: desiccation; regional chlorosis; internode swelling associated with proliferation and radial expansion of cortical parenchyma; interruption of vascular contiguity by invading vascular parenchyma; necrosis and separation. Explains from material older than one growth flush, and those from orthotropic axes, do not exhibit this syndrome. Second-generation explants show internode abscission, regardless of age of parent material. The technique may be a useful experimental system for studying branch cladoptosis in woody species.