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The Raunkiær system is a system for categorizing plants using life-form categories, devised by Danish
botanist Botany, also called plant science, is the branch of natural science and biology studying plants, especially Plant anatomy, their anatomy, Plant taxonomy, taxonomy, and Plant ecology, ecology. A botanist or plant scientist is a scientist who s ...
Christen C. Raunkiær and later extended by various authors.


History

It was first proposed in a talk to the ''Danish Botanical Society'' in 1904 as can be inferred from the printed discussion of that talk, but not the talk itself, nor its title. The journal, '' Botanisk Tidsskrift'', published brief comments on the talk by M.P. Porsild, with replies by Raunkiær. A fuller account appeared in French the following year. Raunkiær elaborated further on the system and published this in Danish in 1907.Ch. 2 in Raunkiær (1934): The life-forms of plants and their bearings on geography, p. 2-104. The original note and the 1907 paper were much later translated to English and published with Raunkiær's collected works.Ch. 1 in Raunkiær (1934): Biological types with reference to the adaption of plants to survive the unfavourable season, p. 1.


Modernization

Raunkiær's life-form scheme has subsequently been revised and modified by various authors, but the main structure has survived. Raunkiær's life-form system may be useful in researching the transformations of biotas and the genesis of some groups of phytophagous animals.


Subdivisions

The subdivisions of the Raunkiær system are premised on the location of the bud of a plant during seasons with adverse conditions, i. e. cold seasons and dry seasons:


Phanerophytes

These plants, normally woody
perennial In horticulture, the term perennial ('' per-'' + '' -ennial'', "through the year") is used to differentiate a plant from shorter-lived annuals and biennials. It has thus been defined as a plant that lives more than 2 years. The term is also ...
s, grow stems into the air, with their resting buds being more than 50 cm above the soil surface, e.g.
tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, e.g., including only woody plants with secondary growth, only ...
s and
shrub A shrub or bush is a small to medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees by their multiple ...
s, and also
epiphytes An epiphyte is a plant or plant-like organism that grows on the surface of another plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it. The plants on which epiphyt ...
, which Raunkiær later separated as a distinct class (see below). Raunkiær further divided the phanerophytes according to height as *Megaphanerophytes, *Mesophanerophytes, *Microphanerophytes, and *Nanophanerophytes. Further division was premised on the characters of duration of foliage, i. e. evergreen or deciduous, and presence of covering bracts on buds, for 12 classes. Three further divisions were made to increase the total of classes to 15: *Phanerophytic stem succulents, *Phanerophytic epiphytes, and *Phanerophytic herbs.


Epiphytes

Epiphyte An epiphyte is a plant or plant-like organism that grows on the surface of another plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it. The plants on which epiphyt ...
s were originally included in the phanerophytes (see above) but then separated because they do not grow in soil, so the soil location is irrelevant in classifying them. They form characteristic communities of moist climatic conditions.


Chamaephytes

These plants have buds on persistent shoots near the soil surface; woody plants with perennating buds borne close to the soil surface, a maximum of 25 cm above the soil surface, e.g.,
bilberry Bilberries () are Eurasian low-growing shrubs in the genus ''Vaccinium'' in the flowering plant family Ericaceae that bear edible, dark blue berries. They resemble but are distinct from North American blueberries. The species most often referre ...
and periwinkle.


Hemicryptophytes

These plants have buds at or near the soil surface, e.g. common daisy and dandelion, and are divided into: *Protohemicryptophytes: only cauline foliage; *Partial rosette plants: both cauline and basal rosette foliage; and *Rosette plants: only basal rosette foliage.


Cryptophytes

These plants have subterranean or under water resting buds, and are divided into: *Geophytes: rest in dry soil as a
rhizome In botany and dendrology, a rhizome ( ) is a modified subterranean plant stem that sends out roots and Shoot (botany), shoots from its Node (botany), nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from ...
,
bulb In botany, a bulb is a short underground stem with fleshy leaves or leaf basesBell, A.D. 1997. ''Plant form: an illustrated guide to flowering plant morphology''. Oxford University Press, Oxford, U.K. that function as food storage organs duri ...
,
corm Corm, bulbo-tuber, or bulbotuber is a short, vertical, swollen, underground plant stem that serves as a storage organ that some plants use to survive winter or other adverse conditions such as summer drought and heat (perennation). The word ''c ...
, et cetera, e.g.
crocus ''Crocus'' (; plural: crocuses or croci) is a genus of seasonal flowering plants in the family Iridaceae (iris family) comprising about 100 species of perennial plant, perennials growing from corms. They are low growing plants, whose flower stem ...
and
tulip Tulips are spring-blooming perennial herbaceous bulbiferous geophytes in the ''Tulipa'' genus. Their flowers are usually large, showy, and brightly coloured, generally red, orange, pink, yellow, or white. They often have a different colour ...
, and are subdivided into: **Rhizome geophytes, **Stem-tuber geophytes, **Root-tuber geophytes, **Bulb geophytes, and **Root geophytes. *Helophytes: rest in marshy or wet soil, e.g. reedmace and marsh-marigold; and *Hydrophytes: rest submerged under water, e.g. water lily and frogbit.


Therophytes

These are
annual plant An annual plant is a plant that completes its life cycle, from germination to the production of seeds, within one growing season, and then dies. Globally, 6% of all plant species and 15% of herbaceous plants (excluding trees and shrubs) are ...
s that complete their lives rapidly in favorable conditions and survive the unfavorable cold or dry season in the form of seeds. About 6% of plants are therophytes but their proportion is much higher in region with hot-dry summer.


Aerophytes

Aerophytes were a later addition to the system. These are plants that obtain moisture and nutrients from the air and rain. They usually grow on other plants yet are not parasitic on them. These are
perennial plant In horticulture, the term perennial (''wikt:per-#Prefix, per-'' + ''wikt:-ennial#Suffix, -ennial'', "through the year") is used to differentiate a plant from shorter-lived annual plant, annuals and biennial plant, biennials. It has thus been d ...
s and are like epiphytes but whose root system have been reduced. They occur in communities that inhabit exclusively hyper-arid areas with abundant fog. Like epiphytes and hemicryptophytes, their buds are near the soil surface. Some ''
Tillandsia ''Tillandsia'' is a genus of around 650 species of evergreen, perennial plant, perennial flowering plants in the family (biology), family Bromeliaceae, native to the forests, mountains and deserts of the Neotropical realm, Neotropics, from northe ...
'' species are classified as aerophytes.


Popular references

Farley Mowat, in his book, '' Never Cry Wolf'', described using a Raunkiær's Circle in making a "cover degree" study to determine the ratios of various plants one to the other. He spoke of it as "a device designed in hell."


References

{{DEFAULTSORT:Raunkier plant life-form Plant life-forms Botanical nomenclature Ecology de:Lebensform (Botanik)