Marcescence

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.

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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.

Benefits

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.

Examples

Pyrinean Oak (Quercus Pyrenaica)

References

• Earl E. 1931. Marcescent leaves of certain species of Quercus. Botanical Gazette 92: 85-93.
• Goldstein, G. and Meinzer, F.1983. Influence of insulating dead leaves and low temperatures on water balance in an Andean giant rosette plant. Plant, Cell & Environment 6: 649-656.
• Hoshaw, R.W. and Guard, A.T. 1949. Abscission of marcescent leaves of Quercus palustris and Q. coccinea. Botanical Gazette 110: 587-593.
• Smith, Alan P.1979. Function of dead leaves in Espeletia schultzii (Compositae), and Andean caulescent rosette species. Biotropica 11: 43-47.
• Svendsen, Claus R. 2001. Effects of marcescent leaves on winter browsing by large herbivores in northern temperate deciduous forests. Alces 37(2): 475-482.