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Cactus - (Greek: kaktos = a prickly plant (Spanish artichoke) from Sicily) -
A spiny, succulent, dicotyledonous plant of the family Cactaceae (Linnaeus 1737) native mainly to arid regions of North and South America, although some species are rainforest epiphytes. The fleshy stems and branches are characteristically furnished with tufts of hairs or spines coming from a common areole, a structure unique to this family. Only a few species of cacti have leaves. In the majority of species, photosynthesis is carried out on the green surface of enlarged stems that also serve as water storage organs.
Cactiform - with the growth habit of a dwarf cactus, having a ribbed or tuberculate green stem that is not much taller than wide.
Caducous - falling off early.
Caerulea (-is, -um) - blue.
Caespitose - forming a cluster or clump of stems by repeated branching of the stem above ground, at or near the base of the plant. Of plants that offset freely to form a large clump.
Caffeine - a methyl-xanthine alkaloid occurring naturally in some plants used to make beverages and foods including Coffea arabica berries (coffee), Thea sinensis leaves (Tea), Cola acuminata nuts (Coca Cola), Themobroma cacao beans (chocolate) and added to a wide range of manufactured foods. Caffeine is one of the most widely used mood-altering drugs and has probably been used through the whole of human history.
Calcareous - chalky, derived from limestone, or with an excess of lime.
Calcifuge - a plant unable to stand chalky (limy) soil.
Callus - a tissue composed of large thin-walled cells, usually produced in response to injury.
Calyptra - a hood or covering over the calyx or other part.
Calyx - a small whorl of modified leaves (sepals) at the base of a flower and, where present, enclosing the other parts of the flower in bud. These may occur individually or joined into a cup or tube and may be of any colour, but commonly green.
CAM metabolism - Crassulacean Acid Metabolism - a metabolic adaptation allowing temporary storage of carbon-dioxide as organic acids (e.g. malate) and later release of carbon-dioxide, by decarboxylation of these acids, for fixation into sugars. This allows uptake of carbon-dioxide during the cool nights, when water loss by transpiration is relatively low, while providing a store of carbon-dioxide for photosynthesis during the day. CAM metabolism is typical of Agaves, Cactaceae, Crassulaceae. Tropical grasses use a similar C4 pathway to support high rates of growth under optimum conditions.
Cambium - a layer of tissue giving rise to secondary growth in stems and roots by cell division. Seasonal growth within the cambium produces annual growth rings. The corky bark of the cork oak tree is formed from cambium cells.
Campanulate - bell shaped, applied to the shape of a flower.
Canadensis - from Canada, or sometimes more loosely applied to originating from the northeastern USA.
Canariensis (-e) - from the Canary Islands.
Candida - white.
Cane - a long woody pliable stem arising from the ground.
Canescence - a dense covering of very fine white or gray short hair.
Canopy - the foliage cover of a plant community especially woodland.
Caperatus (-a, -um) - wrinkled.
Capillaceus (-a, -um) - slender, hair-like.
Capillatus (-a, -um) - with hair.
Capitulum - pl. capitula -
i. a dense flat or globular cluster of sessile flowers or foliage e.g. inflorescence of clover, cauliflower, daisy and dandelion, head of lettuce.
ii. a dense fruiting spike of a cereal plant such as corn.
iii. the upper branches and foliage of a tree forming the crown
iv. any part forming a knob-like protruberance.
Capsule - a dry multi-chambered seed pod with many seeds per chamber that splits along several seams to open when dry and ripe.
Carbohydrate - a diverse group of large food storage molecules formed by linking sugar monomers into polysaccharide chains by glycosidic bonds.
Cardinalis (-a, -um) - red.
Carinate - keeled.
Carmine - a precipitate of cochineal (carminic acid) made by adding alum, cream of tartar, stannous chloride, or potassium hydrogen oxalate to a solution of cochineal. Sometimes proteinaceous substances such as egg white, fish glue or gelatine are added before precipitation. Carmine is used as a food dye, to colour alcoholic beverages, as a pigment in microbiology and in crimson ink.
Carmine lake - a pigment obtained by adding freshly precipitated alumina to a solution of cochineal (carminic acid).
Carotenoid - Carotene - a class of violet to orange or yellow fat-soluble unsaturated hydrocarbon pigments, usually with 9 conjugated double bonds, found in most higher plants and responsible for the colour of carrots, squashes and sweet potatoes. Carotene assists photosynthesis by transmitting energy from absorbed light to chlorophyll.
Dietary carotene is converted to Vitamin A in the liver of animals, which are unable to synthesise their own, and becomes concentrated in fat and cell membranes where it acts as an antioxidant. Carotene may cause a yellowish colour in people who consume large amounts in their diet. Carotene pigments extracted from plants are used to colour foods such as cheese and margarine.
The oxygenated derivatives of carotenes are known as xanthophylls.
Carpel - female reproductive part of flower including ovary, style and stigma, which may be solitary, grouped or fused.
Caruncle - an outgrowth on a plant or animal such as a fowl's wattle or a protuberance near the hilum of certain seeds.
Caryopsis - a dry, indehiscent seed-like fruit with a thin pericarp adnate to the seed coat, typical of cereal grasses e.g. wheat.
Cataphyll - a poorly developed, often thickened leaf whose primary function is other than photosynthesis. e.g. cotyledon, scale leaf. In Cycads, cataphylls protect the apical meristem and are often produced prior to the emergence of leaves or cones.
Catkin - a cylindrical spike-like inflorescence consisting of a cluster of scaly bracts, often pendulous and unisexual.
See also: corymb, cyme, fascicle, panicle, raceme, spadix, spike, thyrse umbel
Caudex - a swollen base to the stem and upper part of the root system used as a storage organ.
Caudiciform - of plants with a caudex.
Cell - the basic structual unit, which may be capable of replication or differentiation, from which all living tissues are made. Hence adj. cellular made from cells.
Cell wall - the rigid semi-solid layer surrounding a cell, protecting the interior from physical damage and resisting expansion from turgor pressure.Found in plants and many micro-organisms and constructed from a variety of materials:
Plant cell walls are constructed from a matrix of insoluble polysaccharides including cellulose, hemicellulose and pectin.
Algal cell walls contain cellulose and glycoproteins and a variety of other polysaccharides including alginic acid and sulphonated polysaccharides. Diatoms synthesise distinctive crystalline silica cell walls from orthosilicic acid.
Fungal cell walls contain cellulose and chitin.
Bacterial cell walls, especially those of Gram Positive species contain peptidoglycan, a polymer of N-acetyl muramic acid and archebacteria contain pseudopeptidoglycan N-acetyltalosaminuronic acid.
Cellulose - the major constituent of plant cell walls and probably the most abundant organic substance on earth with about 1011 tons synthesised each year. Cellulose consists of beta-D-glucose units linked together with beta-1,4' linkages (compare with starch) into very long, high molecular weight polysaccharide molecules (typically up to several million kDa). Up to 50% of the carbon content of plants may be cellulose.
Central - positioned at or near the centre of an area, as opposed to being peripheral in position. A spine originating in the centre of an areole as opposed to those growing around the edge of the areole.
Cephalium - modified flowering zone of stems of certain species of cactus, often ornamented by copious development of hairs or bristles. In some species (e.g. Melocactus) stem growth ceases once the cephalium is produced. In others, a pseudocephalium is produced while stem growth continues.
Cereus - wax-like, candle-like.
Cereiform - with the growth habit of a cereus, having elongated, cylindrical and usually ribbed green stems.
Chamber - a hollow space. Hence: Chambered - with hollow spaces.
Character - a characteristic trait or feature sufficiently unique to be of value in distinguishing forms and defining relationships.
Charcoal - an amorphous form of carbon produced by partially burning or oxidizing wood or other vegetable material in fires from which air is partially excluded by covering with cut turf, or in large kilns in the absence of air. Uses include drawing material, as a fuel, filter, gas absorbent, etc.
Chartaceous - of or like paper or parchment. Usually not green.
Chartreuse - yellow-green.
Chasmathum (-a,-us) - with wide-open, gaping, flowers. Chemotropism - bending, growth or movement of a part under the influence of a concentration gradient of chemical substances. Aerotropism- special case of a response to oxygen.
See also: Tropism.
Chimera - the combination of tissues of different genetic origin in the same part of a plant. Examples of chimeras include some variegated cultivars of Sansevierias, although there can be many reasons for variegation.
Chinosol - 8-hydroxyquinoline sulphate, used as a fungicide and soil sterilant. This compound may inhibit seed germination and show some toxicity to seedlings.
Chitin - may be the second most abundant polysaccharide in nature, after cellulose to which it is structurally related, but see also lignin. At least 109 tons of chitin are thought to be synthesised each year. Chitin is found in the cell walls of many lower plants such as yeast, mushrooms and other fungi. It also forms a substantial part of the exoskeleton shells of crustaceans, such as crabs shrimps and lobsters, as well as in the exoskeletons of marine zoo-plankton, including coepods, and in corals and jellyfish. Insects, such as butterflies and ladybird beetles, have chitin in their wings.
Chitin mainly consists of the amino-sugar N-acetyl-D-glucosamine linked together with beta-1,4' linkages, which may be partially deacetylated to a form of chitin called chitosan. Chitin is usually found complexed with other polysaccharides and proteins.
Chloranthus - with green flowers.
Chloro - (Greek: chloros = yellowish-green) green, as a prefix.
Chlorophyll - (Greek: chloros = yellowish-green) the green metallo-pigment in plants concerned with harvesting energy from light and transmitting the energy to an ordered chain of enzymes, ultimately responsible for the production of sugars. Each chlorophyll molecule contains a central magnesium atom chelated by four nitrogens from a large porphyrin ring and the two forms may be distinguished by substitution of a methyl group in chlorophyll a for an aldehyde in chlorophyll b. Structure of chlorophyll
Chloroplast - a specialised cytoplasmic organelle containing chlorophyll, characteristic of plants, and responsible for using energy captured from visible light to fix carbon from carbon-dioxide and synthesise carbohydrates as energy storage molecules. Like mitochondria, chloroplasts contain a small amount of DNA which encodes genes for a few chloroplast proteins.
Chlorosis - yellowing of plant tissue caused by many factors, often nutitional imbalance or poor illumination.
Cholla - any member of the genus Opuntia with short cylindrical-stems.
Chromoplast - a specialised cytoplasmic organelle containing pigments other than chlorophyll including yellow or orange carotenoid pigments.
Chromosome - tiny condensed X or Y-shaped sub-cellular bodies seen at the time of cell division, containing the genetic material (DNA) in the cell nucleus in association with packaging proteins such as histones. The number of chromosomes is usually constant for a particular species and species with different numbers of chromosomes may have difficulty hybridising.
Chrysantha (-us,-um) - golden.
Chrysocentrus - with a golden center.
Ciliate - fringed with very fine hair-like filaments.
Cincinnus - a branching stem in which the daughter axes are alternatively to the right and left. e.g. a raceme in which the flower stalks (pedicels) are alternatively to one side or the other.
Cinerea (-us,-um) - smoky gray, ashen gray.
Citrina - yellow.
Clade - A group of organisms with common ancestors, therefore sharing similar characteristics.
Cladistics - a method of classification of organisms based on their common ancestry and exploring their relationships within the branching evolutionary family tree or cladogram.
Cladogram - a graphical representations of the evolutionary divergence of species or related groups of species (clades) from common ancestors.
Cladophyll - Cladode - A leaf-like flattened photosynthetic stem or branch that resembles and functions as a leaf. Typical of epiphytic cacti e.g. Epiphyllum, Zygocactus
Class - a taxonomic group containing one or more Orders, ranking below Phylum or in botany, Division.
Clavate - club shaped. Elongated, with a gradual increase in diameter or increasing abruptly near the top.
Cleistogamous - of flowers that do not open, but nevertheless set seed by self-pollination.
Cloche - a glazed structure used to protect delicate plants from rain, wind and cold.
Clone - a plant which is genetically identical to its parent, produced vegetatively by offsetting, bulbils, cuttings or by in vitro propagation from meristem tissue.
Coalescent - growing together.
Coccineus (-a) - scarlet.
Cochineal - a red anthroquinone dye (carminic acid) made from a domesticated scale insect ( Dactylopius coccus) and related species that live on prickly pear cacti (Opuntia species). Carminic acid is produced by the scale insect as an effective repellent for other insects such as ants. This dyestuff was used in pre-Hispanic Mexico for dying textiles. Although superceded by synthetic aniline dyes such as alizarin from the 1870's onwards, cochineal is still an important food colourant and used for dying textiles in folk art. Carmine is a precipitated form of cochineal.
Structure of carminic acid Cochineal bottle
Coelestina (-us, -um) - pale (sky) blue.
Colliculate - covered with small, rounded or hill-like elevations ( colliculae) e.g. surface of seeds.
Coloratus - coloured, usually with a reddish tint.
Colpa - traditional Irish measure, originally a unit of livestock equal to one cow or horse or 6 sheep. Later adapted to specify a quantity of land which can support a horse or a cow for a year, approximately equal to an Irish acre of good land.
Colpus - an elongated aperture or groove with a length/breadth ratio > 2 in the wall of pollen grains. Hence: colpate = grooved.
Coma a tuft of hair, usually terminal, especially on a seed tip. A tuft of leaves or bracts.
Commensal - literally "eating at the same table"- an organism that lives on or with another without harming it. See also parasite, plantglossaryl.html
Compacta compacted, compressed.
Complete - with all parts - of a flower with sepals, petals, stamens and pistils
Composite - a flower head composed of many small flowers, characteristic of Asteraceae.
Compost decomposed vegetation, used to improve the soil in gardens.
Compound - with two or more like parts. Of leaves with several similar parts or lobes forming the whole. Of a flower head with outer ray florets forming "petals" surrounding the inner disc flowers, as in Asteraceae.
Compound leaves - leaves divided into two or more leaflets.
Compressa - flattened or pressed together.
Concolourous - coloured uniformly throughout, the same colour on both sides. .
Conical - shaped like a cone.
Confluent - blending together or coalescing.
Connate - of similar parts growing from one base, joined or united to a single structure.
Connivent - coming close together or touching without joining.
Contact pesticide - a chemical that injures or kills insects which come into contact with it and does not have to be ingested to be harmful.
Copal - a resinous substance exuded from some species of tropical trees and hardening in air into a glassy solid ranging in colour from red to yellow or brown.
Cordate - heart-shaped, with the point away from the stem and the petiole at the broader, notched end.
Cork - (periderm) specifically the soft, low density bark of the cork oak tree, composed of cambium cells. Cork contains a natural wax, suberin, which protects the tree from water loss. The stems of many succulent plants harden and go brown with age and are often referred to as "corky".
Corm - a flattened fleshy underground stem, often acting as a dormant resting stage, capable of producing stems from the base and top and leaves and flower stems from the top.
Corolla - the collective group of petals which may occur separately or fused into a cup, tube or other structure.
i. outgrowth of the perianth e.g. trumpet of a daffodil
ii. a ring of raised fleshy tissue on the corolla around but not adnate to the base of the stamens.
Cortex - a soft layer of tissue between the woody vascular tissue and epidermis, or external layer such as bark. Hence: adj. Cortical.
Corymb - (Greek: korumbos = summit) a flat-topped or convex inflorescence with individual pedicels (flower stalks) branching from various points on the main stem. The outer or lower flowers open first, progressing from the margin inwards, and have the longest stalks so all flowers reach a similar height.
Cosmopolitan - distributed world-wide.
Cotyledon - the first embryonic leaf or leaves in the seed. In some plants the cotyledons remain underground in the seedcoat.
Cotyledonosis - See: Krimpsiekte
Creation - most cultures subscribe to a legend that the earth or universe was created in a relatively short period of time by a supernatural power, together with all existing species (presumably including the Cactaceae and all other succulent plants).
Compare with evolution.
Crenate - with rounded teeth or notched edges.
Crenulate - with shallow-toothed edges.
Crisped - with wavy, curled or crumpled margins.
Crispus (-um) - with wavy, curled or crumpled margins.
Cristate - crest-shaped or crested. An abnormal form of growth resulting from lateral distortion of the growing point.
Crown - the part of a tree above the first branching. The area from which new shoots arise or the point at which the roots meet the stem.
Cruciform - shaped like a cross.
Cryptogam - lower plants reproducing by spores rather than seeds, e.g. ferns, mosses, fungi etc.
Cucurbitacin - a toxic steroid developed by some plants, especially in the Family Cucurbitaceae as a defence against herbivores. Cucurbitacin is one of the most bitter tasting substances known. Some analogues have been shown to be toxic to cancer cells.
Structure of Curcurbitacin
Cultivar - a plant originated or selected artificially. Names of cultivars may be appended after the species name, (e.g. Lithops bromfieldii "Sulphurea") sometimes following the letters "cv."
Cultural requirements - the conditions which provide optimal growth of a plant in cultivation.
Cuneate - wedge-shaped with straight sides converging at the base.
Curcumin - a brightly-coloured yellow polyphenol pigment prepared from the root of turmeric (lili haldi), a member of the Zingiberaceae (Ginger Family). Several related compounds are present in turmeric at lower concentrations. Turmeric is widely used as a food colouring (E100) and is an important constituent of Indian food to which it imparts both flavour and colour. Curcumin is used in Indian Ayurvedic medicine and is said to have some activity against a wide range of medical conditions including arthritis, although little is absorbed from food. Curcumin has anti-oxidant and anti-inflammatory properties probably from inhibition of cyclooxygenases. In the presence of boric acid, Curcumin forms a red pigment (rosocyanine). This colour change is sufficiently sensitive and specific that it has been used as an analytical test for boron ions.
Structure of Curcumin
Curvospina - with curved spines.
Cuticle - a thin wax-like waterproof layer, composed of cutin, covering the epidermis. The outer coat of the seed.
Cutin - a waxy, water-impermeable complex fatty substance impregnating the cell walls and as a separate layer, the cuticle, on the outer surface of the epidermis.
cv. - abbreviation of "cultivar".
Cyathium - the cup-shaped inflorescence of a Euphorbia consisting of a cup-like involucre containing a single pistil (female flower) surrounded by male flowers, each contributing a single stamen. Variations on this occur with all-male or all-female flowers. The cyathium may be surounded by brightly coloured bracts that give the appearance of a large flower.
Cycasin - a toxic glycoside - methylazoxymethanolß-D-glucopyranoside - found only in Cycads.
Structure of Cycasin
Cylindric - with a cylindrical shape.
Cyme - a flat-topped or domed inflorescence in which the central or terminal flower in the cluster opens first.
Cynarrhodium - a fleshy, hollow fruit enclosing achenes, typical of Roses.
Cytokinesis - the process of division of a whole cell, distinct from karyokinesis division of the cell nucleus.
Cytoplasm - the contents of the cell excluding the cell nucleus.