The
Raunkiær system is a system for categorising plants using
life-form categories, devised by
Christen C. Raunkiær. It was first proposed in a talk to the
Danish Botanical Society in 1904 and briefly described in the society's journal
Botanisk Tidsskrift. A fuller account appeared in
French the following year.
Raunkiær elaborated further on the system and published this in
Danish in 1907. The original note and the 1907 paper were much later translated to
English and published with
Raunkiær's collected works.
Raunkiær's life-form scheme has subsequently been revised and modified by various authors, but the main structure has survived.
The subdivisions of the Raunkiær system are based on the location of the plant's growth-point (bud) during seasons with adverse conditions (cold seasons, dry seasons): Phanerophytes : Projecting into the air on stems – normally woody perennials - with resting buds more than 25 cms above soil level, e.g. trees and shrubs, but also epiphytes, which Raunkiær separated out as a special group in later versions of the system. May be further subdivided according to plant height in megaphanerophytes, mesophanerophytes and nanophanerophytes and other characterssuch as duration of leaves (evergreen or deciduous), presence of covering bracts on buds, succulence and epiphytism. Chamaephytes : Buds on persistent shoots near the ground – woody plants with perennating buds borne close to the ground, no more than 25 cms above soil surface, e.g. bilberry and periwinkle. Hemicryptophytes : Buds at or near the soil surface , e.g. daisy, dandelion.
- ; Protohemicryptophytes : only stem leaves
- ; Partial rosette plants : both stem and basal rosette leaves
- ; Rosette plants : only basal rosette leaves Cryptophytes : Below ground or under water - with resting buds lying either beneath the surface of the ground as a rhizome, bulb, corm, etc., or a resting bud submerged under water. Cryptophytes are divided into 3 groups:
- ; Geophytes : Resting in dry ground, e.g. crocus, tulip. May be further subdivided into rhizome, stem-tuber, root-tuber, bulb and root geophytes.
- ; Helophytes : Resting in marshy ground, e.g. reedmace, marsh-marigold.
- ; Hydrophytes : Resting by being submerged under water, e.g. water-lily, frogbit. Therophytes : Annual plants which survive the unfavourable season in the form of seeds and completes its life-cycle during favourable seasons.
Annual species are therophytes. Many desert plants are by necessity therophytes.
Aerophytes : New addition to the Raunkiaer lifeform classification. Plant that obtains moisture (though not through haustorium), and nutrients from the air and rain; usually grows on other plants but not parasitic on it .
References
See also
