is by cladoptosis of whole shoots, not individual leaves. Cladoptosis is thought to have four possible functions: self-pruning (i.e. programmed
plant senescence), drought response (characteristic of
xerophytes)
liana defence, and in some plant families, normal leaf drop is by shedding small whole shoots, rather than individual leaves. • Self-pruning is the shedding of branches that are shaded or diseased, which are potentially a drain on the resources of the tree. • Drought response is similar to the leaf-fall response of drought-deciduous trees; however, leafy shoots are shed in place of leaves. • In tropical forests, infestation of
tree canopies by woody climbers or
lianas can be a serious problem. Cladoptosis, by giving a clean
bole with no support for climbing plants, may be an adaptation against lianas, as in the case of
Castilla. • In the conifer family
Cupressaceae, most species shed old foliage by cladoptosis, rather than individual leaf drop. Dawn redwood (
Metasequoia glyptostroboides) and western redcedar (
Thuja plicata) provide examples; within the family, the only species that do not use cladoptosis for shedding old foliage are the junipers (
Juniperus) in sections
Juniperus sect.
Caryocedrus and
J. sect.
Juniperus. ==See also==