Glossary

Abscisic acid: ABA; Plant hormone that indicates stress (‘stress hormone’), induces stomatal closure and leaf fall (→abscission), inhibits growth, and controls seed dormancy. The carboxylic acid ABA is a breakdown product of →carotenoids and is produced when plant cells lose →turgor. ABA acts antagonistically to →gibberellin.

Abscission: (Latin ‘abscissus’ = to cut off) The shedding of leaves, flowers, fruits or other plant parts, usually following the formation of an abscission zone and preceded by →senescence.

Absorption: (Latin ‘absorbere’ = to swallow) Uptake, e.g. of light photons by leaves or of nutrient ions by roots.

Acid: A substance that dissociates in water, releasing hydrogen ions called protons (H+) and thus causing a relative increase in the concentration of these ions. The most important (organic) acids in grapes are tartaric and malic acids. Acid also means having a →pH in solution of less than 7 due to the presence of more protons than hydroxyl ions (OH-).

Adaptation: An anatomical or physiological trait that has been changed by →evolution, so that it more or less matches a particular set of environmental conditions. Such traits often appear to be ‘designed’ for a specific purpose or environment.

Adsorption: (Latin ‘ad’ = to, at; ‘sorbere’ = to suck) Binding of gaseous or dissolved compounds to the surface of a solid object.

Adventitious root: (Latin ‘adventicius’ = not properly belonging to) →Root that develops from the →cambium of the stem, as in grapevine cuttings.

Aglycon: Organic component of a →glycoside that remains after removal of the sugar.

Allele: One particular version of a →gene that has several different forms. Alleles can be present on the →chromosome pairs of an individual in single dose (→heterozygous) or double dose (→homozygous). Different alleles of the same gene generally result in differences among →phenotypes in a population.

Alternate phyllotaxy: Leaf arrangement in grapevines in which there is one leaf at a node and leaves on two consecutive nodes are on opposite sides.

Amino acid: (Greek ‘Ammon’, the Egyptian Sun god, near whose temple ammonium salts were first prepared from camel dung) Organic acid made up of a chain of carbon atoms to which hydrogen, oxygen, nitrogen and, sometimes, sulfur atoms are attached; comes in 20 different forms. The units or ‘building-blocks’ from which →protein molecules are built. An important food source for yeast during fermentation.

Anther: (Greek ‘anthos’ = flower) The part of the stamen that develops and contains pollen and is usually borne on a stalk (filament).

Anthocyanin: (Greek ‘anthos’ = flower; ‘kyanos’ = blue) A water-soluble blue or red pigment, belonging to the phenolic class of flavonoids, found in the cell vacuoles of the skin (and sometimes pulp) of dark grapes. Anthocyanins are responsible for the red-purple color of dark grapes, leaves in the fall, and wine.

Apical dominance: (Latin ‘apex’ = tip; ‘dominari’ = to rule) The phenomenon in annual shoots whereby the growing shoot apex inhibits outgrowth of lateral shoots.

Apoplast: (Greek ‘apo’ = away, distant; ‘plastos’ = formed) The totality of spaces within a plant that are outside its cell →membranes, including cell walls, intercellular spaces and →xylem conduits.

Arginine: An amino acid; the main nitrogen storage substance of grapevines.

Assimilate stream: The flow of photosynthetic assimilates, or food materials, in the phloem; moves from →source to →sink down a pressure gradient.

Assimilation: (Latin ‘assimilare’ = to align, to integrate) The conversion of inorganic chemicals occurring outside the plant body into organic compounds inside the plant.

ATP: Adenosine-triphosphate; the almost universal energy currency of biological organisms; functions as a donor of phosphate groups. It consists of the purine base adenine linked to the sugar ribose (adenine + ribose = adenosine) and three phosphate molecules and is produced during →respiration. ATP also is a constituent of →RNA and, following removal of oxygen, of →DNA.

Auxin: (Greek ‘auxanomai’ = to grow) Plant →hormone that mainly stimulates the pattern of cell division and differentiation (‘growth hormone’), and controls organ formation and →apical dominance. Very generally, auxin is transported to tissues to induce them to grow. The major auxin is indole-3-acetic acid (IAA), a carboxylic acid produced both from the →amino acid tryptophan and from one of its precursors.

Bark: Tough external covering of a woody stem or root external to the →vascular cambium; comprised mostly of old →phloem tissue.

Basal bud: →Bud at the base of a shoot or cane, not classified as a bud at a count node. Such buds do not normally break in the same season as buds at count nodes but may remain latent on old wood for many years; if stimulated by severe pruning, they may produce shoots that may or may not be fruitful, depending on cultivar.

Blade: The broad, expanded portion of a leaf; the lamina.

Bloom: Flowering as indicated by shedding of the →calyptras covering the reproductive organs of grapevine flowers. Bloom also refers to the waxy coating on grape berries that gives a frosted appearance to dark colored grape varieties.

Bleeding: Sap flow. The exudation of sap from pruning wounds before →budbreak; serves to dissolve and push out air bubbles in the →xylem and to rehydrate the buds.

Brassinosteroids: Group of plant →hormones that may induce cell expansion (‘growth hormone’). Brassinosteroids are produced locally, mostly in the epidermis. The major active brassinosteroid of grapevines is castasterone, produced from a cholesterol-like compound.

Bud: Rounded organ (winter bud or eye) at the node of a cane or shoot formed in the axil of the leaf containing an undeveloped (embryonic) shoot protected by overlapping scales. These buds appear single but typically comprise at least three ‘true buds’ at each node; a more developed primary bud between two less prominent secondary buds.

Budbreak, budburst: The stage of bud development when green tissue becomes visible. The emergence of a new shoot from a bud during spring.

Bud fruitfulness: A ‘fruitful bud’ has one or more inflorescence primordia which give rise to clusters. One measure of fruitfulness is the number of clusters per shoot. Fruitfulness is an inherited characteristic which is also influenced by environmental factors at the time of inflorescence primordium initiation.

Bunch: Australian term for grape →cluster.

Callus: (Latin ‘callos’ = hard skin) Mass of undifferentiated →somatic cells. Parenchyma tissue which grows over a wound or graft and protects it against drying or other injury, or cells which develop from plant pieces in tissue culture.

Calypt ra: (Greek ‘kalyptra’ = cover, veil) The fused petals (cap) of the grape flower that fall off at bloom. The root cap.

Cambium: (Latin ‘cambiare’ = to exchange) Meristematic (dividing) tissue that produces parallel rows of cells.

Vascular cambium: (Latin ‘vasculum’ = small vessel) A thin, cylindrical sheath of undifferentiated meristem between the bark and wood. When active, it produces secondary xylem (to the inside) and phloem (to the outside) resulting in growth of the diameter of stems (shoots, trunks) and roots.

Cork cambium: (= phellogen) Meristem which is in part responsible for the development of the bark. Produces cork cells, the outer walls of which are impregnated with fatty substances impervious to water and gases.

Cane: Mature, woody one-year-old →shoot from the previous growing season, which generally has more than six count nodes. A shoot becomes a cane after →periderm formation.

Canopy: The above-ground portion of a grapevine, comprising the →trunk, →cordon, shoots, leaves, and fruit.

Capacity: The total growth of a grapevine, including the production of crop, leaves, shoots and roots in one growing season. Capacity can be estimated from a vine’s total weight of fruit and shoots.

Carbohydrate: (Latin ‘carbo’ = ember; ‘hydro’ = water) Organic compound made up of sugar units. Consists of a chain of carbon atoms to which hydrogen and oxygen atoms are attached in a 2:1 ratio; examples are sugars, →starch and →cellulose.

Carotenoid: Yellow, orange, or red photosynthetic →pigment in plant cell →chloroplasts. Carotenoids become visible in leaves and grape berries when →chlorophyll breaks down and are responsible for the yellowish-orange fall colors of leaves.

Cell: Structural and functional unit of all living organisms, enclosed in a plasma membrane and containing the →cytoplasm, →nucleus, and other organelles (such as →chloroplasts, →mitochondria, and →vacuoles). Plant (and animal) cells are typically 10-30 μm in diameter, but many bacteria are only 1-2 μm long.

Cellulose: A linear water-insoluble →carbohydrate (a homopolysaccharide), composed of 10,000 to 15,000 glucose units arranged in ?1→4-glucan chemical bonds, forming straight fibrous chains held together by hydrogen bonds; the main cell wall substance of plants and some fungi.

Chilling: Low but above-freezing temperature. Chilling stress refers to the damage or injury caused to plant tissues by low temperatures (usually < 15°C).

Chimera: A plant consisting of more than one genetically distinct populations of →cells, usually due to a →mutation in one of the two cell layers of the shoot apical →meristem.

Chitin: A linear →carbohydrate (a homopolysaccharide), composed of thousands of N-acetyl-d-glucosamine units arranged in ?1→4-glucan chemical bonds, forming extended rigid fibers similar to those of →cellulose; the main cell wall substance of fungi and of all the hard parts of arthropods, but not found anywhere in plants.

Chloroplast: →Chlorophyll-containing photosynthetic →cell organelle. Chloroplasts descended from symbiotic microorganisms that invaded (or were ‘swallowed’ by) larger cells and still have their own →genes.

Chlorophyll: (Greek ‘chloros’ = green, yellow; ‘phyllon’ = leaf) Green photosynthetic pigment in plant cell →chloroplasts; the receptor of light energy in →photosynthesis.

Chlorosis: Loss of →chlorophyll and yellowing of some or all the cells of a tissue or organ.

Chromosome: A segment made up of chromatin, which consists of the histone →proteins acting as spools around which a single large →DNA molecule winds that contains many →genes in the →cell →nucleus of all higher organisms (other than bacteria and archaea).

Clone: (Greek ‘klon’ = twig) A group of vines of a uniform, genetically identical type, derived by →vegetative propagation from a single original mother vine.

Cluster: Fruiting (reproductive) structure of the grapevine with grape berries.

Coenzyme: Organic cofactor (often containing a vitamin) required for certain →enzymes to be active.

Cold hardiness: The ability of a grapevine to survive the extreme cold and drying effects of winter weather.

Competition: Interaction between organs of the same organism (e.g. shoot tips and inflorescences), members of the same population (e.g. grapevines in a vineyard), or of two or more populations (e.g. grapevines and weeds) to obtain a resource that both require and that is available in limited supply.

Cordon: The permanent arm arising from the trunk to form a part of the vine framework and which supports the fruiting one-year-old wood. Cordons are usually horizontal, but may be inclined or vertical.

Correlative inhibition: The phenomenon whereby distal (apical) buds on a cane, i.e. at the apex, break prior to and inhibit the growth of the proximal (basal) buds. Such inhibition is most obvious in early spring when, in cane-pruned vines, the most distal buds of the cane break and grow vigorously, while those towards the base of the cane grow weakly or not at all.

Cork: A secondary tissue produced by a cork →cambium in woody stems and roots; made up of nonliving cells with suberized cell walls, which resist the passage of gases and water vapor.

Cropping:

Crop: The amount of fruit borne on a vine.

Crop level: The amount of fruit (or number of clusters retained) per shoot or per meter of canopy length. Also used as synonym for →crop size.

Crop load: The crop size in relation to vine size (measured as pruning weight or leaf surface).

Crop recovery: The crop produced from new growth following frost injury.

C rop size: The yield per vine or per unit of land area (ha). Also used as synonym for →crop level.

Cultivar: A →variety of plant found only under cultivation. A group of plants that has been selected for a particular attribute or combination of attributes, that is clearly distinct, uniform, and stable in these characteristics, and that retains those characteristics when propagated.

Cuticle: (Latin ‘cutis’ = skin) Waxy or fatty layer on the outer wall of epidermal cells, formed of cutin and wax; largely impervious to water vapor and carbon dioxide; prevents uncontrolled water loss.

Cutting: A portion of cane usually 30-40 cm long, used for propagation.

Cytokinins: (Greek ‘kytos’ = hollow; ‘kinein’ = to move) Group of plant hormones that stimulate cell division and formation of →meristems in shoots but reduce it in roots. Zeatin is the main active cytokinin. Cytokinins are produced from →ATP (and ADP) and isoprenoids in the root tips, shoot meristems, and immature seeds and transported throughout the plant in both the xylem and phloem.

Cytoplasm: The internal, highly heterogenous volume of a →cell, composed of the →cytosol and various insoluble, suspended particles and organelles arranged in a porous, elastic network similar to a sponge filled with liquid.

Cytosol: Aqueous →cell solution with complex composition (e.g. →enzymes, →RNA, →amino acids, metabolites, ions) and gel-like consistency.

Differentiation: Developmental process by which a relatively unspecialized cell undergoes a progressive change to a more specialized cell. The increasing specialization of cells and tissues for particular structures or functions during development.

Diffusion: Net movement of molecules in the direction of lower concentration.

Diploid: Containing two copies of the same set of →chromosomes in each cell, normally arising from →fertilization.

DNA: Deoxyribonucleic acid; the helical chain molecule (polymer) that composes the →genes. DNA is the storage form of genetic information located in the →chromosomes. It consists of long chains of nucleotide building blocks comprised of a purine or pyrimidine base, deoxyribose sugar and phosphate. One pair of bases located on opposite strands of DNA constitutes a letter of the genetic code. Groups of three consecutive bases (triplets) specify (i.e. are the “recipe” for) the different →amino acids in addition to ‘start’ and ‘stop’ signals (i.e. ‘punctuation marks’ that determine beginning and end of a protein). The sequence of triplets determines the various →proteins.

Domestication: Selection of wild plants (or animals) for adaptation to cultivation and use by humans. The process usually involves selection of traits regarded as beneficial. Such traits may be present in wild plants or arise via spontaneous or induced →mutations.

Dorman cy: (Latin ‘dormire’ = to sleep) Temporary suspension of visible growth of plants, buds or seeds. Growth cannot resume without special environmental cues.

Ecosystem: (Greek ‘oikos’ = house) A major interacting system that involves both living organisms and their physical environment.