<P> 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 as the autumn season begins , these veins 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 . </P>
<P> 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 as the autumn season begins , these veins 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 . </P>
what types of trees keep their leaves in the winter
what types of trees keep their leaves in the winter
deciduous trees
deciduous trees