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). The term oak can be used as part of the common name of any of about 400 species of Trees and Shrubs in the Genus Quercus (from Latin For the babyfood see Beech-Nut. Beech ( Fagus) is a genus of ten Species of Deciduous Trees in the Plants in the genus Carpinus ( Cár-pi-nus) are commonly called Hornbeams. Marcescent leaves of pin oak (Quercus palustris) complete development of their abscission layer in the spring. There is also the community of Pin Oak West Virginia, USA The Pin oak or Swamp Spanish oak ( Quercus palustris) is an The base of the petiole remains alive over the winter.

Oak with marcescent foliage.

Many other trees may have marcescent leaves in seasons where an early freeze kills the leaves before the abscission layer develops or completes development. Abscission (from Latin abscindere from ab- ‘off away’ + scindere ‘to cut’ is the shedding of a body part Diseases or pests can also kill leaves before they can develop an abscission layer.

The term "marcescent" is also used in mycology to describe a mushroom which (unlike most species, described as "putrescent") can dry out, but later revive and continue to disperse spores. Mycology (from the Greek μύκης meaning "fungus" is the branch of Biology concerned with the study of fungi, including their genetic ^[1] Genus Marasmius is well-known for this feature, which was considered taxonomically important by Elias Magnus Fries in his 1838 classification of the fungi. There are about 300 Species of agarics in the genus Marasmius (family Marasmiaceae) of which a few such as Marasmius oreades Elias Magnus Fries ( August 15, 1794 &ndash February 8, 1878) was a Swedish Mycologist and Botanist born ^[2]

Benefits

In plants, 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. Herbivory is a form of Predation in which an Organism, known as a herbivore, consumes principally Autotrophs ref name=Campbell>Campbell A deer is a Ruminant Mammal belonging to the family Cervidae. The moose (North America or elk (Europe Alces alces, is the largest extant Species in the Deer family. Dead, dry leaves make the twigs less nutritious and less palatable.

Espeletia pycnophylla with darker marcescence

Marcescent leaves may protect some species from water stress or temperatures 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. Plant life-form schemes constitute a way of classifying plants alternatively to the ordinary species-genus-family Scientific classification. 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. Espeletia, commonly known as Frailejón or Fraylejón is a Genus of perennial subshrubs in the family Asteraceae. The Andes form the world's longest exposed Mountain range. They lie as a continuous chain of highland along the western coast of South America. ^[3][4]

References

• Earl E. 1931. Marcescent leaves of certain species of Quercus. Botanical Gazette 92: 85-93.
• Hoshaw, R.W. and Guard, A.T. 1949. Abscission of marcescent leaves of Quercus palustris and Q. coccinea. Botanical Gazette 110: 587-593.
• Svendsen, Claus R. Elias Magnus Fries ( August 15, 1794 &ndash February 8, 1878) was a Swedish Mycologist and Botanist born 2001. Effects of marcescent leaves on winter browsing by large herbivores in northern temperate deciduous forests. Alces 37(2): 475-482.