Liverworts, hornworts and mosses form a group of simple plants called bryophytes (2). Bryophytes lack many of the more complex structures of the higher plants, such as a vascular system, and flowers. They do not have roots, instead they have structures called 'rhizoids' which absorb water and anchor the plant to the substrate. In liverworts these rhizoids each consist of a single elongated cell (4).
Bryophytes have an interesting life cycle, which consists of two main stages, called the gametophyte and sporophyte generations, the gametophyte generation is dominant. (4). Violet crystalwort produces sporophytes towards the end of summer and into autumn, it has very large spores, and is therefore a poor disperser; spores persist in the mud until conditions become suitable for growth (2).
This liverwort has been recorded from 23 sites in Britain, since 1970, however, it has been found in just 8 sites (2). At present it hangs on at just two reservoirs in East Sussex, and a new population was found in 2001 in South Devon (3). Elsewhere, this liverwort occurs in Europe, where it is classified as Rare, and in eastern Asia (3).
This species is vulnerable to the artificial maintenance of high water levels throughout summer and autumn, for example for fishing interests (2). Nitrate and phosphate pollution may also pose problems, but this is yet to be proven (2). One of the populations in southern England is seriously threatened by the invasive alien plant, New Zealand pygmy weed (Crassula helmsii) (3).
Violet crystalwort is a priority species under the UK Biodiversity Action Plan (UK BAP), and a Species Action Plan has been produced to guide the conservation of this liverwort (5). Plantlife, the wild plant conservation charity, has included this species in its Back From the Brink Programme, and has funded research and survey work on the species (3). Water levels should be lowered during summer and autumn at all sites supporting violet crystalwort (3).
A life cycle stage in plants, which has one set of chromosomes (threads of DNA protein) in the cell nucleus (a condition known as ‘haploid’), which arises from a spore (which is also haploid). Sex cells (gametes) are produced during the gametophyte stage. This is the dominant life-cycle stage in liverworts and mosses.
Species introduced deliberately or unintentionally outside their natural habitats where they have the ability to establish themselves, invade, outcompete natives and take over the new environments.
Thread-like structures that help to anchor the plant to the substrate, and absorb minerals and water. In liverworts they consist of a single cell, in mosses they are multi-cellular.
Microscopic particles involved in both dispersal and reproduction. They comprise a single or group of unspecialised cells and do not contain an embryo, as do seeds.
The stage of a plant life cycle that produces spores (microscopic particles used in dispersal and reproduction). This stage is diploid (in the cell nucleus there are two sets of chromosomes - threads of DNA protein) and is dominant in ‘higher’ plants such as flowering plants.
In plants, the system that allows water and nutrients to move around.
Church, J. M., Hodgetts, N. G., Preston, C. D. and Stewart, N. F. (2001) British Red Data Books: mosses and liverworts. Joint Nature Conservation Committee, Peterborough.
Holyoak, D. T. (2002) Violet crystalwort (Riccia huebeneriana) and beaked beardless moss (Weissia rostellata): report to Plantlife on work carried out in southern England during 2001. Plantlife report number 198. ISBN 1 87261369 1.
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