Marcescence is the withering and persistence of plant organs that normally are shed, and is a term most commonly applied to plant leaves. [1] [2] The underlying physiological mechanism is that 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. [3] 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. [4] Marcescence is most obvious in deciduous trees that retain leaves through the winter. Several trees normally have marcescent leaves such as oak (Quercus), [5] beech (Fagus) and hornbeam (Carpinus), or marcescent stipules as in some but not all species of willows ( Salix ). [6] All oak trees may display foliage marcescence, even species that are known to fully drop leaves when the tree is mature. [7] Marcescent leaves of pin oak (Quercus palustris) complete development of their abscission layer in the spring. [8] 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.
Marcescent leaves may be retained indefinitely and do not break off until mechanical forces (wind for instance) cause the dry and brittle petioles to snap. [9] The evolutionary reasons for marcescence are not clear, theories include: protection of leaf buds from winter desiccation, and as a delayed source of nutrients or moisture-conserving mulch when the leaves finally fall and decompose in spring. [10]
Many palms form a skirt-like or shuttlecock-like crown of marcescent leaves under new growth that may persist for years before being shed. [11] [12] In some species only juveniles retain dead leaves [13] and marcescence in palms is considered a primitive trait. [14]
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. [15] Genus Marasmius is well known for this feature, which was considered taxonomically important by Elias Magnus Fries in his 1838 classification of the fungi. [16]
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. [17] They are also more noisy when browsed, thereby potentially deterring browsers. [18]
Species that display marcescence, such as beech and oak, have adapted to retaining their leaves for prolonged periods to thrive in difficult growing media. When growth is most vulnerable in the early stages of spring, they benefit from the compost provided by the newly dropped and decomposing leaves, allowing them to outcompete species that have already dropped theirs. It is suggested that such variations can significantly impact their success in such conditions. [19]
Some experimentation on plant litter from marcescent trees indicates that keeping the leaves above ground may increase the amount of photodegradation the leaves are exposed to. Because some marcescent species' leaves do not decompose well, the increased photodegradation may allow them to decompose better once they finally fall off the tree. [20]
Others theorize that leaves which remain on a tree due to marcescence allow the tree to trap snow during the winter months. By using their dead leaves to collect additional snow, trees are able to provide themselves more water in spring when the snow begins to melt. [21]
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. [22] [23]
The litter-trapping marcescent leaf crowns of Dypsis palms accumulate detritus thereby enhancing their nutrient supply, [24] but in trapping nutrient-rich detritus, palms with marcescent leaf bases are also more likely to allow the germination of epiphytic figs in the marcescent leaves, with the figs possibly subsequently strangling the palms. [25] Palm genera with taxa having marcescent leaf bases and attracting epiphytic fig growth include Attalea , Butia , Caryota , Copernicia , Elaeis , Hyphaene , Livistona , Phoenix , Sabal , and Syagrus . [25]
Marcescence in various species.
Marcescent species are found in the following (incomplete) list of plant families and genera:
The Fagales are an order of flowering plants, including some of the best-known trees. The order name is derived from genus Fagus, beeches. They belong among the rosid group of dicotyledons. The families and genera currently included are as follows:
An oak is a hardwood tree or shrub in the genus Quercus of the beech family. They have spirally arranged leaves, often with lobed edges, and a nut called an acorn, borne within a cup. The genus is widely distributed in the Northern Hemisphere; it includes some 500 species, both deciduous and evergreen. Fossil oaks date back to the Middle Eocene. Molecular phylogeny shows that the genus is divided into Old World and New World clades, but many oak species hybridise freely, making the genus's history difficult to resolve.
In the fields of horticulture and botany, the term deciduous means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, after flowering; and to the shedding of ripe fruit. The antonym of deciduous in the botanical sense is evergreen.
The Fagaceae are a family of flowering plants that includes beeches, chestnuts and oaks, and comprises eight genera with about 927 species. Fagaceae in temperate regions are mostly deciduous, whereas in the tropics, many species occur as evergreen trees and shrubs. They are characterized by alternate simple leaves with pinnate venation, unisexual flowers in the form of catkins, and fruit in the form of cup-like (cupule) nuts. Their leaves are often lobed, and both petioles and stipules are generally present. Their fruits lack endosperm and lie in a scaly or spiny husk that may or may not enclose the entire nut, which may consist of one to seven seeds. In the oaks, genus Quercus, the fruit is a non-valved nut called an acorn. The husk of the acorn in most oaks only forms a cup in which the nut sits. Other members of the family have fully enclosed nuts. Fagaceae is one of the most ecologically important woody plant families in the Northern Hemisphere, as oaks form the backbone of temperate forest in North America, Europe, and Asia, and are one of the most significant sources of wildlife food.
Quercus palustris, also called pin oak, swamp oak, or Spanish oak, is a tree in the red oak section of the genus Quercus. Pin oak is one of the most commonly used landscaping oaks in its native range due to its ease of transplant, relatively fast growth, and pollution tolerance.
Beech (Fagus) is a genus of deciduous trees in the family Fagaceae, native to subtropical and temperate Eurasia and North America. There are 14 accepted species in two distinct subgenera, EnglerianaeDenk & G.W.Grimm and Fagus. The subgenus Englerianae is found only in East Asia, distinctive for its low branches, often made up of several major trunks with yellowish bark. The better known species of subgenus Fagus are native to Europe, western and eastern Asia and eastern North America. They are high-branching trees with tall, stout trunks and smooth silver-grey bark.
Fagus sylvatica, the European beech or common beech, is a large, graceful deciduous tree in the beech family with smooth silvery-gray bark, large leaf area, and a short trunk with low branches.
Fagus grandifolia, the American beech or North American beech, is the only species of beech native to North America. Its current range comprises the eastern United States, isolated pockets of Mexico and southeastern Canada. Prior to the glacial maximum of the Pleistocene epoch, the tree flourished over most of North America, reaching California.
Quercus falcata, also called southern red oak, spanish oak, bottomland red oak or three-lobed red oak is an oak. Native to the southeastern United States, it gets its name the "Spanish Oak" as these are the areas of early Spanish colonies, whilst "southern red oak" comes from both its range and leaf color during late summer and fall. The southern red oak is a deciduous angiosperm, so has leaves that die after each growing period and come back in the next period of growth.
Bickelhaupt Arboretum is a non-profit arboretum located in Clinton, Iowa. It is open dawn to dusk daily without charge.
Abscission is the shedding of various parts of an organism, such as a plant dropping a leaf, fruit, flower, or seed. In zoology, abscission is the intentional shedding of a body part, such as the shedding of a claw, husk, or the autotomy of a tail to evade a predator. In mycology, it is the liberation of a fungal spore. In cell biology, abscission refers to the separation of two daughter cells at the completion of cytokinesis.
In botany, a rosette is a circular arrangement of leaves or of structures resembling leaves.
Quercus faginea, the Portuguese oak, is a species of oak native to the western Mediterranean region in the Iberian Peninsula. Similar trees in the Atlas Mountains of northwest Africa are usually included in this species, or sometimes treated as a distinct species, Quercus tlemcenensis. It occurs in mountains from sea level to 1,900 metres above sea level, and flourishes in a variety of soils and climates. Out of all the oak forests in the Iberian Peninsula, the southern populations of Portuguese oak were found to have the highest diversity and endemism of spider species.
Quercus myrsinifolia is an Asian species of tree in the beech family Fagaceae. It has several common names, including bamboo-leaf oak, Chinese evergreen oak, and Chinese ring-cupped oak. Its Chinese name is 小叶青冈; pinyin: xiǎo yè qīng gāng, which means little leaf ring-cupped oak, in Japan it is called white oak and in Korea it is known as gasinamu (가시나무). It is native to east central and southeast China, Japan, Korea, Laos, northern Thailand, and Vietnam. It is placed in subgenus Cerris, section Cyclobalanopsis.
Quercus aliena, the galcham oak or oriental white oak, is a species of oak in the family Fagaceae, in the white oak section Quercus.
Quercus pyrenaica, also known as Pyrenean oak, or Spanish oak is a tree native to southwestern Europe and northwestern North Africa. Despite its common name, it is rarely found in the Pyrenees Mountains and is more abundant in northern Portugal and north and northwestern Spain.
A Fau de Verzy is either a Dwarf Beech, a dwarf oak tree, or a dwarf chestnut tree. These grow in the forest of Verzy, 25 km south of Reims in France. In this forest are less than a thousand dwarf beeches, some dozen dwarf oaks and some dwarf chestnuts, but this article speaks in the main about dwarf beeches.
Quercus delgadoana is an endangered species of oak in the family Fagaceae, found in eastern Mexico. It was originally misidentified as other members of the genus Quercus, but was determined as a new species in 2011.
marcescent in immature [descriptive of several spp.]
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