Lithophytes are

plants Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclude ...

that grow in or on

rocks In geology, rock (or stone) is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its chemical composition, and the way in which it is formed. Rocks form the Earth's o ...

. They can be classified as either epilithic (or epipetric) or endolithic; epilithic lithophytes grow on the surfaces of rocks, while endolithic lithophytes grow in the crevices of rocks (and are also referred to as chasmophytes). Lithophytes can also be classified as being either obligate or facultative. Obligate lithophytes grow solely on rocks, while facultative lithophytes will grow partially on a rock and on another substrate simultaneously.

Nutrients

Lithophytes that grow on land feed off nutrients from rain water and nearby decaying plants, including their own dead tissue. It is easier for Chasmophytes to acquire nutrients because they grow in fissures in rocks where soil or organic matter has accumulated. For most Lithophytes, nitrogen is only available through interactions with the atmosphere. The most readily available form of nitrogen in the atmosphere is the gaseous state of ammonia (NH3). Lithophytes consume atmospheric ammonia through a concentration gradient that allows the compound to traverse the plants' apoplast. Once free in the apoplast, gaseous ammonia is absorbed into metabolic cells by the enzyme glutamine synthetase. To be able to absorb the few nutrients available on rocks or rocky substrates efficiently, Lithophytes have evolved certain adaptations. They possess decreased numbers of root hairs and larger root diameters in comparison to other plant species. To add to this nutrient uptake efficiency, lithophytic plants have increased their relationship with arbuscular mycorrhizal fungi and dark septate endophyte fungi. These two types of fungi live inter- and intracellularly with the roots of Lithophytes and a wide variety of other plant species. They increase the uptake of nutrients and water and have been found in greater concentrations in Lithophytes.

Walls colonised as artificial cliffs by lithophytes

Asarina procumbens cascading down wall beside Paxton church gatepost

Walls, and other exposed stonework, are colonised by plants in a similar way to the colonisation of
cliff In geography and geology, a cliff is an area of rock which has a general angle defined by the vertical, or nearly vertical. Cliffs are formed by the processes of weathering and erosion, with the effect of gravity. Cliffs are common on coa ...
s and
scree Scree is a collection of broken rock fragments at the base of a cliff or other steep rocky mass that has accumulated through periodic rockfall. Landforms associated with these materials are often called talus deposits. Talus deposits typically h ...
. These natural features are uncommon, especially in the lowlands, so walls are important for the conservation of plants which might otherwise be very isolated. Some wall plants even have ‘wall’ or ‘muralis’ as part of their common or scientific name such as Wall-flower ('' Erysimum cheiri'') or Ivy-leaved toadflax (''
Cymbalaria muralis ''Cymbalaria muralis'', commonly called ivy-leaved toadflax or Kenilworth ivy, is a low, spreading, viney plant with small purple flowers, native to southern Europe. It belongs to the plantain family (Plantaginaceae), and is introduced in North A ...
''), which shows their long established relationship with these man-made structures.

English Heritage
''Landscape Advice Note: Vegetation on Walls''

Examples

Examples of lithophytes include many orchids such as '' Dendrobium'' and ''

Paphiopedilum ''Paphiopedilum'', often called the Venus slipper, is a genus of the lady slipper orchid subfamily ''Cypripedioideae'' of the flowering plant family Orchidaceae. The genus comprises some 80 accepted taxa including several natural hybrids. The g ...

'',

bromeliads The Bromeliaceae (the bromeliads) are a family of monocot flowering plants of about 80 genera and 3700 known species, native mainly to the tropical Americas, with several species found in the American subtropics and one in tropical west Africa, ...

such as '' Tillandsia'', as well as many ferns,

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthesis, photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from u ...

and

liverwort The Marchantiophyta () are a division of non-vascular land plants commonly referred to as hepatics or liverworts. Like mosses and hornworts, they have a gametophyte-dominant life cycle, in which cells of the plant carry only a single set of ge ...

s. Lithophytes have also been found in many other plant families, such as, Liliaceae, Amaryllidaceae, Begoniaceae, Caprifoliaceae, Crassulaceae, Piperaceae and Selaginellaceae.

Carnivorous plants

As nutrients tend to be rarely available to lithophytes or chasmophytes, many species of

carnivorous plants Carnivorous plants are plants that derive some or most of their Plant nutrition, nutrients from trapping and consuming animals or protozoans, typically insects and other arthropods. Carnivorous plants still generate some of their energy from ph ...

can be viewed as being

pre-adapted Exaptation and the related term co-option describe a shift in the function of a trait during evolution. For example, a trait can evolve because it served one particular function, but subsequently it may come to serve another. Exaptations are common ...

to life on rocks. By consuming prey, these plants can gather more nutrients than non-carnivorous lithophytes.McPherson, S.R. (2010). ''Carnivorous Plants and their Habitats. Volume 1.'' Redfern Natural History Productions, Poole. pp. 176–180. Examples include the pitcher plants '' Nepenthes campanulata'' and '' Heliamphora exappendiculata'', many ''

Pinguicula ''Pinguicula'', commonly known as the butterworts, is a genus of carnivorous flowering plants in the family Lentibulariaceae. They use sticky, glandular leaves to lure, trap, and digest insects in order to supplement the poor mineral nutrition t ...

'' and several ''

Utricularia ''Utricularia'', commonly and collectively called the bladderworts, is a genus of carnivorous plants consisting of approximately 233 species (precise counts differ based on classification opinions; a 2001 publication lists 215 species).Salmon, Br ...

'' species.

Tennyson poem inspired by lithophyte

In the year 1863,

Alfred, Lord Tennyson Alfred Tennyson, 1st Baron Tennyson (6 August 1809 – 6 October 1892) was an English poet. He was the Poet Laureate during much of Queen Victoria's reign. In 1829, Tennyson was awarded the Chancellor's Gold Medal at Cambridge for one of his ...

was moved to write his short and pithy poem of metaphysical speculation Flower in the Crannied Wall upon contemplating an unnamed lithophyte growing out of the masonry of the wishing well at Waggoners Wells. National_Trust_wishing_well_sign,_Waggoners_Wells,_Grayshott

National_Trust_wishing_well_sign,_Waggoners_Wells,_Grayshott

Flower in the crannied wall, I pluck you out of the crannies, I hold you here, root and all, in my hand, Little flower—but if I could understand What you are, root and all, and all in all, I should know what God and man is.''Poems of Alfred Lord Tennyson.'' Eugene Parsons (Introduction). New York: Thomas Y. Crowell Company, 1900.

Gallery

File:Erinus alpinus plant in flower.jpg, '' Erinus alpinus'', the fairy foxglove, growing out of a crack in the mortar of a stone wall File:Lithophytes at Chatswood West.jpg, Rock Felt Fern, Elkhorn fern, Birds Nest Fern and moss growing on

Hawkesbury Sandstone Sydney sandstone is the common name for Sydney Basin Hawkesbury Sandstone, one variety of which is historically known as Yellowblock, and also as "yellow gold" a sedimentary rock named after the Hawkesbury River north of Sydney, where thi ...

at Chatswood West, Australia

References

Plant morphology {{Botany-stub he:מורפולוגיה של הצמח - מונחים#צורות חיים ושלבי חיים של צמחים