Ipsophyto

The following glossary is simply a starter in the wierd and wonderful language of horticulture 

Acid soil  One which has a pH of less than 7.0. Degrees of acidity are known. Soils with pH 5.0 or less are recognised as being ‘very acid’Adventitious  Arising casually or in unusual places. A bud or a root, for example, that develops from tissue that would not normally give rise to such an organ.Aeration  The level to which air can penetrate undindered or permeate a dense medium, for example, compost.Allelopathy  The release into the environment by an organism of a chemical substance that acts as a germination or growth inhibitor to another organism. Typical substances include alkaloids, phenolics and terpenoids.Alkaline soils  Ones which have pH above 7.0. Degrees of alkalinity are known. These types of soil can generally have a large proportion of calcium ions in them. Soil pH does not usually get measured much more than 10.0 because of nutrient availability issues.  Soils over 8.5 are recognised as strongly alkaline.Angiosperm  One of two divisions of spermatophyte (seed plants), These are flowering plants that have seeds fully enclosed by a fruit. As opposed the Gymnosperms who bare their seed , naked in a cone. Angiosperms are the more evolved. Anther  The terminal portion of a stamen of a flowering plant;The pollen sacs containing pollen are borne on the anther.Amorphous  Applied to materials that have no regular atomic structure, or in which no extensive portions have a regular structure; but small units, irregularly alligned or stacked, may have a regular structure.Apical Bud  The active bud at the growing tip of a shoot.Axil  The upper angle between a leaf, or leaf stalk, and the stem from which it grows.Axis  The main (or central) stem of a plant or infloresenceAxillary bud  The bud situated in the axil.Basal  At the base or bottom. The basal shoot or root on a plant is the bottom one. The basal cut on a scion or cutting is made at the bottom.Basal or base plate  The flattened or squat conical stem within a bulbBlanching  The exclusion of light from a stem so that its green colouring (Chlorophyll) disappears. Blanching causes rapid stem growth (Etiolation)Bottom heat   The heat (normally applied artificially) under the compost in, for example, a propagator, to encourage the initiation and growth of roots.Bracts. A leaf, usually much reduced or modified, which subtends a flower or inflorescence in its axis.Broadcast sowing  Uniform and even distribution of seeds over a seed bed. As opposed to sowing in ‘drills’.Bud-break  The end of the dormant season, as perceived by a plant, when stems are induced to grow, occurs when temperatures rise above 5 degrees celcius/41F.Bulbs  (See Bulb page)Bulblet  As aboveBulbils  As aboveBushel  A unit of imperial measurement equal to 1.28 cubic feet or the amount of compost that will fit into a box 22in x 10in x 10in without compacting.Callus  The developing protective wound tissue produced by a plant on any damaged surface.Cambium  The simple basic cells making up the actively growing tissue of a stem, root, or leaf from which the various ‘conducting’ tissues develop.Capilliary action  A  process by which water rises above its normal level through a series of very small spaces, for example, through sand. The smaller the spaces the higher the water rises.Chlorophyll  The pigment in plant cells which gives rise to leaves having their green colouring. These are the photosynthetic molecules which conduct the magick of converting light energy into chemical energy by absorbing energy at 438nm and 660-670nm (blue and red-far red.) Very similar in shape, molecularly, as haemoglobin. Chlorophyll contains magnesium whereas we contain iron. Chloroplast  A semi-autonomous organelle within plant cells responsible for photosynthesis by means of its stacked membraneous discs containing chlorophyll pigment.Chlorosis  A symptom of disease or disorder in plants, which involves a reduction in or loss of normal green colouration. Consequently, the plants are typically pale green or even yellow. Chlorosis is caused by conditions that prevent the formation of chlorophyll (eg lack of light or a deficiency in iron or magnesium)Clone  A group of genetically identical plants produced vegetatively or asexually from a single parent.Club root.  A serious disease of cruciferous (cabbage family) plants. Caused by a fungus Plasmodiophora brassicae which can remain in the soil for years even without a host. Symptoms include; wilting plants in bright sunlight, whilst leaves may take on a bluish or reddish colouration. The root shows characteristic ‘gall’ like growth and should be thrown on the fire.Cold frames  Provides basic control over the environment by placing a box with a glass/plastic lid over soil. It helps to increase soil temperatures, reduce temperature fluctuation, maintains humidity and allowing light penetration. Can be used to propagate a wide range of hardy plants. Main disadvantage: excessive air temperatures when conditions are sunny. To alleviate this there are two main choices; opening the lid and/or shading the glass. The former will reduce humidity whereas the latter will reduce photosynthsis. Plastics retain heat / transmit light less efficiently than glass.Compound  Applied to flowers or leaves that have two or more partsContinuum  The idea that vegetation is continuously variable and cannot be classified into discrete entities, since it shows gradual change in response to environmental change.  Cotyleden  A seed leaf that is borne on a plant embryo. For monocotyledons only 1 seed leaf is present whilst dicotyledons usually have 2. There are always exceptions to rules and you can be sure this one is no different.Cross-breeding  The breeding of two genetically unrelated individuals. In plants this can entail the transfer of pollen from one individual to the stigma of another genotype.Crown  The part of a plant at or above ground level that normally produces stems. Herbaceous plants and occasionally woody shrubs that tend to grow densely are often referred to as having crowns.Cutting  A  separated piece of root, stem or leaf that has been prepared solely to propagate a new plant.Dessicate  To lose water, to dry out; to wilt.DEFRA  Department of environment, farming, and rural affairs.Dichotomous branching  A repeated division into two parts.Dibber  A tool used to make a hole in which to plant a cutting, seedling or small plant. Dibbers are available in various sizes that are related to the required size of the hole.Diffusion  The movement of molecules from a region of higher to one of lower solute concentration as a result of their random thermal movement.Differentiate  The process of changing from one or more simple plant cells, eg in the cambium, into a particular specialised organ or tissue, such as roots.Dioecious  Possessing male and female sexual organs or flowers on separate, unisexual, individual plants. As opposed to monoecious.Dominant  The effect of one plant organ on another, usually with regard their position. For example, on a stem there is apical dominance over other lower buds. Dormant  Asleep! A dormant seed or plant is one in a temporary resting state while it survives adverse climatic conditions.Endosperm.  A tissue within the seed, usually used as food storage reserves for the developing seedling.Ephemeral  A term given to species that with favourable conditions, complete their life cycle quickly, and a number of times over the course of a year. Many weeds are ephemeral species, as re many desert species.Epidermis  The outer most layer or layers of cells on a plant or animal. On plants it is one cell thick.Etiolation  The state of plants that have been grown in the dark: not green, little or no chlorophyll, extended internodes and rudimentary leaf growth. These features associated with etiolation, ensure, in natural conditions that the shoot is carried toward the light as rapidly as possible.Eutrophication  The process of nutrient enrichment in aquatic ecosystems. It happens naturally over geological time, but is accelerated by human activities eg sewage disposal and land drainage. The rapid increase in nutrient levels results in algal bloom. On death, bacterial decomposition of the excess algae may seriously deplete oxygen levels. This can lead to death of fish, further accelerating the death cycle.Eye  A bud.F1   The first filial generation of plants or animals produced by the crossing of two parental lines.Foliar  Of the leaf. Fungicide  A substance that will kill fungi.Flower  In angiosperms, the structure is for sexual reproduction, consisting of the androecium (male organs) and gynoecium (female organs) commonly surrounded by a corolla, (petals) and calyx (sepals). The male and female parts may be in the same flower or different flowers. In many plants the term flower is popularly applied to an inflorescence that in fact comprises many small flowers (florets) grouped togetherFriable  Applied to the consistency or handling properties of soil, meaning that the soil crumbles easilyFruit  Strictly, the ripened ovary of a plant and its contents. More loosely, the term is extended to the ripened ovary and seeds together with any structure with which they are combined eg the apple (a pome) in which the true fruit (core) is surrounded by flesh derived from the floral receptacle.Gaian hypothesis  A hypothesis formed by James Lovelock and Lynn margulis, that the prescence of living organisms on a planet leads to major modifications of the physical and chemical conditions pertaining on the planet, and that subsequent to the establishment of life, the climate and major bio-geochemical cycles are mediated by the organisms themselves.Gaseous exchange  The transfer of gasses between an organisms and its environment; it may occur in both photosynthesis and respirationGene  The fundamental physical unit of hereditry. It occupies a fixed chromosomal position, and when ‘transcribed’ has a specific effect on the ‘phenotype’. A gene comprises a segment of D.N.A coding for one function or several related functions. The D.N.A is usually situated in a thread-like chromosome together with protein within the cell nucleus.Gene pool  The total number of genes, or the amount of genetic information that is possesed by all the reproductive members of a population of sexually reproducing organisms.Genotype  The genetic constitution of an organism, as opposed to its physical appearance (phenotype).Germination Technically, the point of appearance of the radicle (baby root) through the seed coat. In practice in the garden, we say a seed is germinated when its cotyledens (seed leavs) are fully opened. Usually after period of dormancy, given suitable environmental conditions most importantly warmth and moisture. Please refer to germination page.Girdling  In propagation, the act of removing a ring of bark from a stem during preperation for air layering. Cutting through the phloem directly under the bark prevents sap transport. On full grown trees girdling around the trunk results in death.Grafting  A technique of bringing two parts of different plants together in such a way as they unite and grow as one plant. Usually, a scion (a stem) of one plant is grafted  onto a root sysytem (rootstock). All the various techniques of joining plants are called grafting, however, when buds only are joined to the rootstock it is sometimes called budding.Gourd  A curcurbit, eg pumpkin, Squash etc.Greenhouse effect  The effect of heat retention in the lower atmosphere as a result of absorption and re-radiation of long wave terrestrial radiation by clouds and gasses (eg water vapour and carbon dioxide). The analogy with greenhouses is not strict because the heat build up in a glasshouse is due to reduced air movement. The atmospheric effect is to alter the balance of incoming and outgoing radiation in the Earth’s energy budget. Marked increases in atmospheric carbon dioxide, generated by burning fossil fuels is resulting in global increases in atmospheric temperatures. Please refer to Kartoon Kate’s ‘Funy weather’ book! A link is available at ipsophyto.co.ukGrowth  The increase in size of a cell, organ or organism. This may occur by cell enlargement, or cell division.Growth-form  The morphology of a plant, especially as it reflects physiological adaptation to the environmentGymnosperm  A seed plant in which the ovules are carried naked on the cone scales, in contrast to the angiosperms, in which they are enclosed by an ovary. They were the dominant vegetation in prehistoric times. Superceded by angiosperms through evolution.Habitat   The living place of an organism or a community, characterised by its biotic or physical properties.Harden off  Weaning a seedling off the protected conditions it hitherto experienced, enabling the young plant to be planted out without checking growth. Achieved by gradually introducing a seedling to the vagories of natural climate.Hardpan  A hardened soil horizon, usually found in the middle to lower parts of the profile that may be ‘cemented’ by a number of possible cementing materials.Hardwood cutting  Taken during the dormant season from fully mature stems of trees and shrubs. One of the easiest techniques of vegetative propagation.Haricot bean  A lesser-used name in the UK for Phaseolus species (Runner bean).Heterosis  The increased vigour of growth, survival and fertility of hybrids resulting from the cross of 2 genetically distinct, highly inbred linesHeel in  Storing plant material in the open ground. Plants, stems or cuttings are placed together upright or inclined in a trench, which is then back-filled with soil and firmed. This technique is employed especially with bare rooted trees awaiting planting.Herbicide  A chemical that will kill plants.Homologous  Applied to both organs and chromosomes. Evolutionary embryonic corresspondances. Chromosomes are homologous when they contain; pairing, identical linear gene sequences. Each homologue is therefore a duplicate of one of the chromosomes contributed by one of the parents; and each pair of homologous chromosomes is normally identical in shape and size.Hormone  A regulatory substance present throughout the plant’s life cycle, and available in different cells, active at low concentrations. The effects can be in distant cells or those all over the organism. It is conveyed via tissue fluids. Humidity  The amount of water vapour in the atmosphere. Relative humidity is the amount of water in the atmosphere, relative to it being saturated, at a particular temperature ( Warm air will hold more water than cold air).Humus  Decomposed organic matter of soils that are aerobic for part of a year. It is dark brown and amorphous, having lost all trace of the structure and composition of the vegetable and animal matter from which it was derived. Husbandry  The understanding and care of plants.Hybrid  An individual plant produced by cross-pollinating two different parental genotypes(species or sub-species) Hybrids may be fertile or sterile.Hybrid vigour (see heterosis) Hypercotyl  The part of a seedling located between the shoot and root system. The area in which root tissues change to shoot tissues and vice-versa.Imbibe  To drink in; absorb water.Infloresence  A flowering structure comprising more than a single flowerInhibit  Suppressing specific growth or particular developmental patterns.Initial  The very first development of new plant organs. For example, a root when only just possible to distinguish it amongst undifferentiated cells. Also used to describe the meristem cells actively dividing.Insecticide  (see pesticide)Internode  The stem between two nodes.Involucre  A whorl of bracts below an infloresence.Isogenic  Applied to grafts involving a scion which is genetically identical to the rootstock.Isotonic  Applied to a cell in which the osmotic pressure is equal to that in the surrounding medium.Juvenile  A young immature plant before it reaches sexual maturity, and therfore, ability to flower.Kranz anatomy  A special structure in the leaves of plants that have a C4 pathway of carbon dioxide fixation.Latent bud  A bud that has been produced normally, which for various reasons will not develop further until stimulated by some unusual circumstance.Lateral  On the side. A lateral bud or root is on the side of a stem or root compared to the top or base.Lamina  A flat, sheet like structure(shaped like the blade of a leaf).Laminate  Flat and broad, shaped like a leaf or comprising layers of material.Labiateae  Old school taxanomic family name for the ‘Mint’ family, which have charactristic flowers with ‘dual lips’. This helps the insects land and pollinate. Lanceolate  Broad, but tapering to a point at both ends, like the blade of a lance.Layer  A stem that is in the process of being layered. Also applied to a rooted plant at the time of and just after seperating from the parent.Leader shoot  The shoot that is dominating growth in a stem system, and is usually uppermost.Loam  A much prized class of soil texture that comprises sand, silt and clay which produces a physical property intermediate between the extremes of the three components. Sought after by Farmers and growers alike.Long-day plant  A plant in which flowering is favoured and influenced by longer days of sunlight, commonly more than 13 hours of daylight and correspondingly, shorter dark periods. Plants are grouped into those which it is an absolute requirement and those in which flowering is hastened. Spinach, lettuces and grasses are all long-day plants as they flower in the summer, here in the UK.Long Tom  A pot about half as deep again as a normal pot.Macronutrient  An organic or inorganic element or compound which is needed in relatively large amounts by living organisms eg Nitrogen, Potassium.Magnesium(Mg) An element which is found in high concentrations in plants. It plays an important role in the chemical structure of chlorophyll and of membranes and is involved in many enzyme reactions. Deficiency results in various symptoms, including chlorosis and the development of other pigments in leaves.Maiden  A tree arising from a seed, or rarely a sucker that has not been coppiced or pollarded.Mature  A plant which can bear flowers, and hence, reproduce sexually.Meristem  A group of plant cells that are able to divide indefinately and whose main function is the production of new growth. They are found at the growing tip of roots and shoots (apical meristem), cambium (lateral meristem) and in grasses, also within the stem and leaf sheaths (intercalary meristem)Micro-climate  The atmospheric characteristics prevailing in a small space, usually in the layer near the ground that is affected by the ground surface. Special influences include…the impact of vegetation cover on humidity (by evapotranspiration) and on temprature and winds.Micronutrient  An organic or inorganic element or compound that is required only in relatively small amounts by a living organism eg Molybdenum (Mo), Manganese(Mn), Zinc(Zn)Micro-organism  Literally, a microscopic organism. The term is usually taken to include to only those organisms studied in microbiology (ie bacteria, fungi, microscopic algae, protazoa and viruses. A wider context allows the inclusion of microscopic worms and other small critters.Mineralisation  The conversion of organic matter into inorganic states as a result of decomposition by soil micro-organisms.Mineral soil  One where soil is composed predominantly of mineral matter and whose characteristics are determined more by the mineral than the organic content.Misting unit  Provides ultimate environmental control in the form of micro-water droplets. Use a mains fed supply of water pushed through at pressure through guaged nozzles. Utilised most efficiently with timer and leaf solenoid to detect moisture within the canopy.Morphology  The form and structure of individual organisms, as distinct from their anatomy (which involves dissection).Mucilage  Any of a variety of complex, gum-like carbohydrate substances that are hard when dry, yet slimy and jelly like when wet. They are produced by many bacteria and plants. In many cases they assist in water retention. Some seeds have a mucilaginous coating that absorbs water and aids germination.Muck  1) Highly decomposed organic matter in which original plant matter cannot be recognised.          2) Farmyard manure (FYM) composed of animal faeces and urine mixed with straw and highly decomposed.Mulch  A loose surface soil horizon, either natural or man made, composed of organic or mineral materials. It protects soil and plant roots from the impact of rain, temperature change or evaporation.Mycorrhiza  A close relationship between a fungus (myco-) and plant roots from which both organisms appear to benefit; a mycorrhizal root takes up nutrients more efficiently than does an uneffected root. A wide array of plants can form mycorrhiza, some estimates suggest 9/10 plants do so in the wild.Nasty  The response of a plant organ to non-directional stimulus (eg, the opening or closing of a flower in response to changes in light intensity or temperature). The plant may respond by changes in cell growth or changes in turgor. For example, epinasty- a result of stress and shock, which commonly follows production of ethylene.Native  Applied to a species that occurs naturally in one area, and therefore one that has not been introduced by humans either accidentally or intentionally. Of plants found in a particular place, the term is applied to those species that occur naturally in the region and at the site.Naturalised  Applied to a species that was originally imported from another country, but that now behaves like a native in that it maintains itself without the need for further human intervention and has invaded native populations.Natural selection ’survival of the fittest’  A complex process in which the total environment determines which members of a species survive to reproduce and so pass on their genes to the next generation. This need not necessarily involve a struggle between organisms.Needle  A linear, commonly aromatic and pungent leaf, mainly spotted on conifers.Node  The place where a leaf joins the plant’s stem and subtends an axillary bud.Nitrogen  A macronutrient needed by plants as an integral part of D.N.A and therefore required by each and every plant cell. N-deficient plants are chlorotic and etiolated, with the older parts becoming affected first.Nitrogen fixation  The reduction of gaseous nitrogen and incorporation of molecular nitrogen into compounds. In nature this occurs after lightening storms, through photochemical fixation in the atmosphere and by the action of nitrogen fixing micro-organisms. Some of these are free living and others form symbiotic relationships with  Symbiotic bacteria include Rhizobium and Bradyrhizobium species which form the characteristic nodules on leguminous plants. The bacteria supply the legume with ammonia and recieve carbohydrates from the legume. Certain non leguminous plants such as Alder and Bog Myrtle, commonly found on nutrient deficient soils, can form N-fixing relationships with Actinomycetes (a type of n-fixing bacteria)Obligate  applied to an organism that can only survive if particular environmental conditions are satisfied.Obovate  A leaf that has the stalk at the narrow end, with the leaf widening toward the tip.Offset  A plantlet that develops laterally on a stem either above or below ground; the stem arises from a crown bud and usually carries no other buds.Opposite  A leaf arrangement in which leaves arise in pairs, one pair at each node.Orbicular  Disk-shaped, circular or globular.Organelle  Within a cell, a persistent structure that has a specialised function; eg mitochondria(respiration)  and chloroplasts (photosynthesis). In most cases, the organelle is seperated from the rest of the cell by selectively permeable membranes.Organic matter  In particular the organic material found in soils, more generally, the organic component of any eco-system.Organic soil  Soil with a high content of organic matter and water. The term tends to refer to peat. The USDA defines an organic soil as one with 20-30% organic matter, depending on the clay content.Ornithophily  Pollination by birds.Orophilous  Applied to plants that grow in sub-alpine habitats.Osmosis  The net movement of water or another solvent from a region of low solute concentration to a region of higher solute concentration, through a semi-permeable membrane.Ovule  A structure in angiosperms and gymnosperms that, after fertilisation develops into a seed. In gymnosperms the ovules are unprotected, whereas in angiosperms they are protected by the megasporophyll (which froms the carpel). One or several ovules may be contained in the carpel and each is attached to the carpel wall by a stalk.Ovum  An unfertilised egg cell.Palmate  Compound leaves with two or more leaflets arising from the top a stalk and spreading, like the fingers of a hand.Pandurate  Fiddle-shaped.Peat  An organic soil or deposit. Peat formation occurs when decomposition is slow due to anaerobic conditions associated with waterlogging. Fen and bog peats differ widely.Peat podzol   A soil consisting of distinctive, surface peaty humus up to a maximum thickness of 30cm with an iron pan at the top of the sub-horizon.Ped  A unit of soil structure (eg crumb, aggregate, granule or prism) that is formed naturally.Peltate  Shield shaped, having a central rather than lateral stalk.Petiole  A leaf stalk.Pericarp  The wall of a fruit.Permanent wilting point(PWP)  the point at which a leaf will fail to regain turgidity should unfavourable conditions persist.Pesticide  A chemical which kills insect pests.Perennation  The survival of vegetative plant parts during the dormant season.Perennial  A plant that normally lives for more than two seasons and after an initial period, produces flowers annually.Petal  In a flower, one of the inner floral leaves, usually brightly covered and borne in a tight spiral, or whorled.Phenotype  The observable manifestations of a specific genotype, ie those properties of an organism, produced by the genotype in conjunction with the environment, that are observable. Organisms with the same genotype may have different phenotypes because of the effects of the environment and of gene interaction. Conversely, organisms may have the same phenotype but different genotypes, as a result of incomplete dominance.Phloem  A tissue found in all vascular plants comprising many specialist cells, which transport solutes, synthesised in leaves, to all other parts of the plant. Located directly under the bark of a tree or other woody species.Photosynthesis  The reduction of atmospheric carbon dioxide to carbohydrates occuring within spcecialised plant cells which use light as an energy source and chlorophyll as a catalyst.Photoperiod  The relative lengths of the periods of daylight and darkness associated with day and night.Photoperiodism  The response of an organism to periodic, often rhythmic changes in either the intensity of light or, more usually, the relative length of day.Plumule  The primitive shoot apex in a plant embryo.Polarity  The state of having two poles, one at the top and one at the bottom.Phyllosphere  The micro-environment on and below the surface of a leaf.Phyllotaxis  In a plant, the arrangement of leaves on the stem (opposite pairs, alternate, whorled etc).Pigment  A colouration compound that produces colour in the tissues of living organisms.Pinnate  A compound leaf comprising leaflets displayed on eithr side of a stalk.Pith  A central stem tissue.Plaggen  A man-made soil horizon, more than 50cm deep, resulting from long continued manuring. Often enriched with phosphate.Plicate  Folded or wrinkled.Pollard  To behead a tree at a convenient height, usually about 2metres above ground level, in order to produce a crown of small poles, suitable for firewood, fencing etc. This allows the production of small material out of reach of deer and farm livestock.Pollen  Collectively, the mass of pollen grains or micro-spores produced within the anthers of a flowering plant (angiosperm) or the male cones of a gymnosperm.Pollination  The transfer of pollen grains from the anther (male reproductive organ) to the stigma (female reproductive organ) of a flowering plant. This process facilitates contact between male ‘gametes’ and the female ovum, leading to fertilisation, development of seed and eventually a new plant.Polyploidy  The condition whereby an individual posseses one or more sets of ‘homologous’ chromosomes in excess of the normal 2 sets found in diploid organisms. Cultivated strwberry and Yarrow are two common plants which are polyploids. The difference in numbers of chromosomes can result in totally different chemical profiles or chemotypes. It is caused by the replication within a nucleus of complete chromosome sets without subsequent nuclear division. Examples are triploidy (3n), tetraploidy(4n), hexaploidy (6n),and octaploidy (8n) – (where ‘n’ is one set of chromosomes).Potassium  An element that is vital for healthy plant growth. Deficiency leads to reduced growth and to dark or blue green colouration in the leaves, which can also develop a purple-brown pigment.Profile  A vertical section through all the constituent horizons of soil, from the surface to the relatively unaltered parent material.Pugioniform  Shaped like a dagger.Puddled or Poached soil  Soil in which the structure has been destroyed by the physical impact of rain drops, by tillage when wet, or by trampling by animals.Pulvinate  Cushion-shaped; swollen or convex.Punctate  Applied to any structure that is marked by pores, or by very small point-like depressions.-Pyriform  Pear-shaped.Raceme  An infloresence where the axil continues to grow extending upwards so that the youngest flower(s) is displayed at the apical tip.Radicle  A rudimentary root in an embryo.Reaction  The degree of acidity or alkalinity in some soil or compost. Reaction is measured on the pH scale, on which pH 7.0 is neutral. Lower figures indicate increasing acidity, whereas higher figures equal increasing alkalinity.Regeneration  Initiation and growth of any missing parts on propagated material (for example, roots on a stem cutting) to make a complete plant.Renewable resource A resource produced as part of  the functioning of natural systems at rates comparable with its rate of consumption, eg food production by photosynthesis. It has been suggested that limits to renewable resources are determined by a ‘flow rate’ and such resources can provide a sustained yield.Relative Humidity (See humidity)Respiration, The liberation of energy by cells to help fuel growth and meet its current demands.Rhizosphere The immediate soil root-zone occupied by and affected through the action of roots and their exudates, growth, exhange of nutrients and respiration. It is a region of high soil-organism and micro-organism activity.Riparian   Pertaining to the bank of a river or shore of a lake.Root  The lower part of the plant, traditionally anchored in soil, providng water and nutrients to the organism.Root cap  A sheath of cells at the tip of the root which are displaced as the root extends into the soil and are rapidly decomposed, releasing nutrients, as well as amino-acids alongside other compounds into the soil.Root Hair  A single cellular hair protruding from the side of the root, increasing the surface area of the root thereby aiding absorption of nutrients and water.Root nodule  The gall-like growths observable on the roots of certain plants, most identifaible on legumes. The nodules develop from sites of infection and are caused by the bacteria rhizodium and bradyrhizobium; two specialist bacteria which fix atmospheric nitrogen as their chief source of energy, and happily, symbiotically, co-exist with plants. Much of the bacterial nitrogen becomes available to other plants.Rosette plants.  Plants like the Daisy whose growth form is one of laterally extending from the crown giving rise to a rosette. Generally found in low lying habitats and sparse ground where they have competitive advantage as they avoid being grazed.Rust  A plant disease caused by a fungus in the class of Urediniomycetes. The characteristic symptom is the development of spots, and  powdery spores, which are usually rust covered, yellow or brown. Infected plants may also show distortions or ‘gall-like’ swellingsRunner  An overground stem, aka stolon, sent generally from a crown of herbaceous plants with only a terminal bud. Strawberry plants and couch grass are two plants which have runners.Sap The exudate from the wounded tissue of vascular plants. Ranging from rubber to mayple syrup.Sapling A young tree, from seed or sucker, not yet of economic importance.Sapwood The heart of the active xylem cells which are next to the dead cells. This is easily distinguished in by the darker colour.Scale leaf A leaf modified to form a scale on an underground stem.Scion wood  The portion ( a single bud or stem) grafted on to a rootstock. Once established,it becemomes the major part of the stem system on the new plant.Seed lot.  A collection of seeds from a particular source of plant or plants.Semi-hard wood  A term for semi ripe wood cuttingSoftwood cutting  A term applied to cuttings from growth of a woody plant which is generally taken early in the growing season when green and full of spring growth. Has highest capacity for regeneration, most difficult to keep alive due to water loss issues. Can be forced at late summer if grown in controlled environment and warmth and extra light are given.Station sowing  The individual sowing of seeds at a predetermined spacing in the site in which they will grow until pricking out or harvesting.Strike off  To remove excess compost above the rim of a pot or seed tray, using a presser-board, a piece of wood, edge of the palm or fingers.Sub-terminal shoot  A shoot immediately behind a leader shoot that usually grows actively but not quite as vigorously as a leader shoot.Succulent  This condition seems to have developed as a response to a lack of water in the arid zones that this type of plant tends to populate. A succulent is capable of storing up relatively large quantities of water, as well as fixing carbon dioxide at night in contrast to the majority of other plants which assimilate carbon as they photosynthsise.Sucker  A shoot growing either from a stem or a root, at or about the ground level.Terminal bud  The bud that terminates growth at the top of a stem, resting throughout the dormant season.Transpiration  The process by which the plant moves water from the soil through its tissues and out of the tiny (stomata) holes in the leaf. Approximately 93% of all water a plant takes up through its roots will be transpired through the leaves.Tuber  A swollen modified underground stem, adapted into a storage organ. Usually annual the axillary buds point to next years growth. It is these so called eye’s which will ‘chit’ pre-empting their desire to grow. As opposed to tuberous roots.Tuberous roots  Found under perennial herbaceous crowns which act as storage organs for the dormant season. Can be found on annuals also.Tendril  A modified stem that is to be found twining, grasping and twisting its thread-like attachment. Peas, Beans, Passiflora and many others have tendrils. In the plant kingdom the responses from tendrils to touch are analogous to animals. Indeed, the sensitivity of plants to their environment is arguably superior to humans.Turgid  A cellular state, as opposed to flacid. Think tort, rigid or full. These are words to be associated with turgidity. It is brought about by hydrostatic pressure.Thorn A woody projecting structure with a sharp point that is derived from the stem, branch or leaf of the plant and is connected to its vascular system.Tilth  The physical condition of soil that determines its suitability for cultivation.Tissue  A group of cells of similar type working in a co-ordinated manner towards a common metabolic and / or structural function. In plants they are normally bound together by cell walls. Fluids are also considered tissue.Trichome  A single cellular outgrowth, eg a root hair, arising from an epidermal cell.Trifoliate  Applied to leaves with three leaflets.Turbinate Shaped like a spinning top and attached to the point.Unavailable water  Water that is present in the soil, but cannot be absorbed rapidly enough by plants for their needs because it is held too strongly (adsorbed) to soil particles.Union  The union where a rootstock and a scion join in graft to develop and grow as a whole.Urceolate  Flask-shaped.USDA  United States Department of Agriculture.Vagile Applied to a plant that is free to move about. Seeds, pollen grains and spores can travel miles on the wind.Valvate  Applied to a flower where the petal or sepals meet at the edges but do not overlap.Variegation  A phenomena whereby two or more distinct colours are revealed on a leaf; plant names commonly ending ‘variegata’ have this feature. Variegation may be inherited and also as a resut of viral infections.Vascular bundle  Longitudinal strands of xylem and phloem conducting tissue, essential for transport of water and solutes throughout the organism. It also helps structural support within a plant.Vegetative  Applied to a structure or stage that is concerned with feeding and growth rather than with sexual reproduction. Vegetative reproduction is therefore ASEXUAL reproduction.Vein  A vascular bundle or group of vascular bundles lying in close proximity in a leaf. Venation  The arrangement of veins in a leaf.Vernalisation  The process of subjecting seeds and plants to low temperatures in order to break dormancy and trick the plant’s flowering responses. A natural cyclic event for an organism in the UK experiencing the seasonal changes and associated change in daylengthViability  The probability that a fertilised egg will survive into an adult organism, often applied to plant germination.Water table  The upper surface of groundwater or the level below which the material is permanently saturated with water.The region below the water table is termed the vadose zone.Water-stress A variable condition where a plant is losing more water than it is taking on board. Can easily result in ethylene production by the plant which inhibits growth even more than simple water stress.  Weed   A plant opportunistically taking advantage of suitable conditions having been distributed by human intervention. A plant out of place, competing for water, nutrients and light.Whorl  A variable group of three or more flowers or bracts or any other ringed floral stem arrangement.Wounding Techniques to disrupt the epidermal layer, usually knicked, scored or girdled. This encourages the initiation of roots in a cutting with sufficient viability and vigour whilst enables an easier passage for the roots through the tough outer cells of the stem.Wilting  When cells have insufficient water to maintain turgidity. May occur when the rate of transpiration exceeds that of water entering the root cells, in a soil containing ample water, causing the tissues to lose turgidity and droop downwards. This response is designed to get the leaf out of the sunlight. It can also occur when there is not adequate water in the soil. Mulching alleviates this. Curcurbits will limp naturally in the sun. Xylem   A tissue specifically designed to conduct the water and solutes entering the root. Consists of various cells and is distinguishable by presence of vertical systems of dead cells which have thickened lignidfied cell.Yodas power law  A numerical approach to describing the process of self-thinning amongst seedlings. Beyond a certain density of sowing, it is hypothesised that the number of surviving plants is not related to the inititial seed density.