TL;DR: The analysis of almost 30,000 twig fragments over the course of 3 years demonstrated at least partial control by the tree of the process of abscission, which supports the widely held belief that cladoptosis is mainly an immediate reaction to drought stress that reduces transpiring leaf area.
TL;DR: The branch-base xylem constriction would appear to facilitate branch abscission, while the associated Huber values show that W. nobilis supplies a relatively large leaf area through a relatively small diameter 'pipe'.
TL;DR: The hypothesis that the changes in shoot and consequently crown architecture that are observed in ageing and declining trees can limit photosynthesis by reducing shoot hydraulic conductance is supported.
TL;DR: When nodal explants from tips of horizontal branches of seedling Agathis australis are cultured in vitro, the distal 3 mm of internode progresses through a series of morphological and anatomical changes, and ultimately detaches.
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.