Marcescence is the retention of dead plant organs that normally are shed. Trees transfer water and sap from the roots to the leaves through their vascular cells, but in some trees as autumn begins, the veins carrying the sap slowly close until a layer of cells called the abscission layer completely closes off the vein allowing the tree to rid itself of the leaf. Leaf marcescence is most often seen on juvenile plants and may disappear as the tree matures. It also may not affect the entire tree; sometimes leaves persist only on scattered branches. Marcescence is most obvious in deciduous trees that retain leaves through the winter. Several trees normally have marcescent leaves such as oak (Quercus), Berkley, Earl E. 1931. Marcescent leaves of certain species of Quercus. Botanical Gazette 92: 85-93. beech (Fagus) and hornbeam (Carpinus), or marcescent stipules as in some but not all species of willows (Salix). All oak trees may display foliage marcescence, even species that are known to fully drop leaves when the tree is mature. Marcescent leaves of pin oak (Quercus palustris) complete development of their abscission layer in the spring. Hoshaw, R.W. and Guard, A.T. 1949. "Abscission of marcescent leaves of Quercus palustris and Q. coccinea". Botanical Gazette 110: 587–593. 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. Advantages One possible advantage of marcescent leaves is that they 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. Svendsen, Claus R. 2001. "Effects of marcescent leaves on winter browsing by large herbivores in northern temperate deciduous forests". Alces 37(2): 475–482. They are also more noisy when browsed, thereby potentially deterring browsers. Marcescent leaves may protect some species from water stress or temperature stress. For example, in tropical alpine environments a wide variety of plants in different plant families and different parts of the world have evolved a growth form known as the caulescent rosette, characterized by evergreen rosettes growing above marcescent leaves. Examples of plants for which the marcescent leaves have been confirmed to improve survival, help water balance, or protect the plant from cold injury are Espeletia schultzii and Espeletia timotensis, both from the Andes .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.Smith, Alan P.1979. Function of dead leaves in Espeletia schultzii (Compositae), and Andean caulescent rosette species. Biotropica 11: 43-47 .
Marcescence is the retention of dead plant organs that normally are shed. Trees transfer water and sap from the roots to the leaves through their vascular cells, but in some trees as autumn begins, the veins carrying the sap slowly close until a layer of cells called the abscission layer completely closes off the vein allowing the tree to rid itself of the leaf. Leaf marcescence is most often seen on juvenile plants and may disappear as the tree matures. It also may not affect the entire tree; sometimes leaves persist only on scattered branches. Marcescence 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), or marcescent stipules as in some but not all species of willows (Salix). All oak trees may display foliage marcescence, even species that are known to fully drop leaves when the tree is mature. 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. Advantages One possible advantage of marcescent leaves is that they 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. They are also more noisy when browsed, thereby potentially deterring browsers. Marcescent leaves may protect some species from water stress or temperature stress. For example, in tropical alpine environments a wide variety of plants in different plant families and different parts of the world have evolved a growth form known as the caulescent rosette, characterized by evergreen rosettes growing above marcescent leaves. Examples of plants for which the marcescent leaves have been confirmed to improve survival, help water balance, or protect the plant from cold injury are Espeletia schultzii and Espeletia timotensis, both from the Andes .
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Berkley, Earl E. 1931. Marcescent leaves of certain species of Quercus. Botanical Gazette 92: 85-93.
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Hoshaw, R.W. and Guard, A.T. 1949. "Abscission of marcescent leaves of Quercus palustris and Q. coccinea". Botanical Gazette 110: 587–593.
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Svendsen, Claus R. 2001. "Effects of marcescent leaves on winter browsing by large herbivores in northern temperate deciduous forests". Alces 37(2): 475–482.
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.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
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Environment 6: 649-656.Smith, Alan P.1979. Function of dead leaves in Espeletia schultzii (Compositae), and Andean caulescent rosette species. Biotropica 11: 43-47