Liana

Liana

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A liana is any of various long-stemmed
Plant stem
A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , conifer cones, roots, other stems etc. The internodes distance one node from another...

, woody
Woody plant
A woody plant is a plant that uses wood as its structural tissue. These are typically perennial plants whose stems and larger roots are reinforced with wood produced adjacent to the vascular tissues. The main stem, larger branches, and roots of these plants are usually covered by a layer of...

 vine
Vine
A vine in the narrowest sense is the grapevine , but more generally it can refer to any plant with a growth habit of trailing or scandent, that is to say climbing, stems or runners...

s that are root
Root
In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating . Furthermore, a stem normally occurring below ground is not exceptional either...

ed in the soil at ground level and use trees, as well as other means of vertical support, to climb up to the canopy to get access to well-lit areas of the forest. Lianas are especially characteristic of tropical moist deciduous forests
Tropical and subtropical moist broadleaf forests
Tropical and subtropical moist broadleaf forests , also known as tropical moist forests, are a tropical and subtropical forest biome....

 and rainforest
Tropical rainforest
A tropical rainforest is an ecosystem type that occurs roughly within the latitudes 28 degrees north or south of the equator . This ecosystem experiences high average temperatures and a significant amount of rainfall...

s. These climbers often form bridges between the forest canopy, connect the entire forest and provide arboreal
Arboreal locomotion
Arboreal locomotion is the locomotion of animals in trees. In every habitat in which trees are present, animals have evolved to move in them. Some animals may only scale trees occasionally, while others are exclusively arboreal. These habitats pose numerous mechanical challenges to animals...

 animals with paths across the forest. These bridges also protect weaker trees from strong winds. They also compete with forest trees for sunlight and soil resources (water and nutrients). There are also temperate
Temperate
In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...

 lianas, however, for example the members of the genera Clematis
Clematis
Clematis is a genus of about 300 species within the buttercup family Ranunculaceae. Their garden hybrids have been popular among gardeners beginning with Clematis × jackmanii, a garden standby since 1862; more hybrid cultivars are being produced constantly. They are mainly of Chinese and Japanese...

or Vitis
Vitis
Vitis is a genus of about 60 species of vining plants in the flowering plant family Vitaceae. The genus is made up of species predominantly from the Northern hemisphere. It is economically important as the source of grapes, both for direct consumption of the fruit and for fermentation to produce...

(wild grape). Well-known lianas include monkey ladder (Entada gigas
Entada gigas
Entada gigas, commonly known as the Cœur de la Mer or Sea Heart, is a species of flowering liana in the pea family, Fabaceae, that is native to Central America, the Caribbean, northern South America, and Africa. It is notable for having the family's largest seedpods, which measure across and can...

), water vine (Cissus hypoglauca
Cissus hypoglauca
Cissus hypoglauca, commonly known as Jungle Grape, Water Vine or Five leaf Water Vine, is a common Australian Vine. It is one of the better known climbing plants of the genus Cissus in the grape family...

or members of the genus Doliocarpus), but not pothos (Epipremnum aureum
Epipremnum aureum
Epipremnum aureum, also known as the Pothos , Money Plant, Silver Vine, Centipede tongavine, Devil's Ivy and Solomon Islands' Ivy, is an aroid native to southeastern Asia and New Guinea...

), which is classified as an epiphyte
Epiphyte
An epiphyte is a plant that grows upon another plant non-parasitically or sometimes upon some other object , derives its moisture and nutrients from the air and rain and sometimes from debris accumulating around it, and is found in the temperate zone and in the...

 or herbaceous vine.

Note that "liana" is not a taxonomic
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

 grouping, but rather a description of the way the plant grows, and lianas may be found in many different plant families
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

. One way of distinguishing lianas from tree
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

s and shrub
Shrub
A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...

s is based on the stiffness
Stiffness
Stiffness is the resistance of an elastic body to deformation by an applied force along a given degree of freedom when a set of loading points and boundary conditions are prescribed on the elastic body.-Calculations:...

 (specifically, the Young's modulus
Young's modulus
Young's modulus is a measure of the stiffness of an elastic material and is a quantity used to characterize materials. It is defined as the ratio of the uniaxial stress over the uniaxial strain in the range of stress in which Hooke's Law holds. In solid mechanics, the slope of the stress-strain...

) of various parts of the stem. Trees and shrubs have young twigs and smaller branches which are quite flexible and older growth (trunks
Trunk (botany)
In botany, trunk refers to the main wooden axis of a tree that supports the branches and is supported by and directly attached to the roots. The trunk is covered by the bark, which is an important diagnostic feature in tree identification, and which often differs markedly from the bottom of the...

 and large branches) which are stiffer, whereas a liana often has stiff young growths and older growth, at the base of the stem, which is more flexible.

Ecology


Lianas compete intensely with trees, greatly reducing tree growth and tree reproduction, greatly increasing tree mortality, preventing tree seedlings from establishing, and altering the course of regeneration in forests. Lianas also provide access routes in the forest canopy for many arboreal
Arboreal locomotion
Arboreal locomotion is the locomotion of animals in trees. In every habitat in which trees are present, animals have evolved to move in them. Some animals may only scale trees occasionally, while others are exclusively arboreal. These habitats pose numerous mechanical challenges to animals...

 animals, including ants and many other invertebrates, lizards, rodents, sloths, monkeys, and lemur
Lemur
Lemurs are a clade of strepsirrhine primates endemic to the island of Madagascar. They are named after the lemures of Roman mythology due to the ghostly vocalizations, reflective eyes, and the nocturnal habits of some species...

s. For example, in the Eastern rainforests
Tropical and subtropical moist broadleaf forests
Tropical and subtropical moist broadleaf forests , also known as tropical moist forests, are a tropical and subtropical forest biome....

 of Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...

, many prosimian
Prosimian
Prosimians are a grouping of mammals defined as being primates, but not monkeys or apes. They include, among others, lemurs, bushbabies, and tarsiers. They are considered to have characteristics that are more primitive than those of monkeys and apes. Prosimians are the only primates native to...

s achieve higher mobility from the web of lianas draped amongst the vertical tree species. Many lemurs prefer trees with lianas for their roost sites. Lianas also provide support for trees when strong winds blow. However, they may be destructive in that when one tree falls, the connections made by the lianas may cause many other trees to fall.

As noted by Charles Darwin
Charles Darwin
Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...

, because lianas are supported by other plants, they may conserve resources that other plants must allocate to the development of structure and use them instead for growth and reproduction. In general, lianas are detrimental to the trees that support them: growth rates are lower for trees with lianas, they directly damage hosts by mechanical abrasion and strangulation, render hosts more susceptible to ice and wind damage, and increase the probability that the host tree falls. Lianas also make the canopy of trees more accessible to animals which eat leaves. Because of these negative effects, trees which remain free of lianas are at an advantage; some species have evolved characteristics which help them avoid or shed lianas.