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Marcescence is the retention of dead plant organs that normally are shed. It is most obvious in deciduous trees that retain leaves through the winter. Several trees normally have marcescent leaves such as oak (Quercus), beech (Fagus) and hornbeam (Carpinus). Marcescent leaves of pin oak (Quercus palustris) complete development of their abscission layer in the spring. The base of the petiole remains alive over the winter.
Many other trees may have marcescent leaves in seasons where an early freeze kills the leaves before the abscission layer develops or completes development. Diseases or pests can also kill leaves before they can develop an abscission layer.
Marcescence is considered a juvenile characteristic because it is more common on younger trees and on the lower, more juvenile, parts of older trees. One possible advantage of marcescent leaves is that may deter feeding of large herbivores, such as deer and moose, which normally eat the twigs and their nutritious buds. Dead, dry leaves make the twigs less nutritious and less palatable.
Marcescent leaves may protect some species from water stress or temperatures stress. In Espeletia schultzii, an evergreen rosette species living high in the Andes, removal of marcescent leaves increased the probability of the plant dying. In Espeletia timotensis marcescent leaves improved plant water balance and protected the plant from cold injury.
Pyrinean Oak (Quercus Pyrenaica)
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Marcescence". A list of authors is available in Wikipedia.|