Download Grapevine Anatomy and Physiology

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.
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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
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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
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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.
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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.
Calyptra: (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.
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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.
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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 ß1→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-Dglucosamine units arranged in ß1→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.
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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.
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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.
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Crop 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.
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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.
Dormancy: (Latin ‘dormire’ = to sleep) Temporary suspension of visible growth of plants, buds or
seeds. Growth cannot resume without special environmental cues.
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Ecosystem: (Greek ‘oikos’ = house) A major interacting system that involves both living organisms
and their physical environment.
Enzyme: (Greek ‘en’ = into; ‘zyme’ = yeast, sourdough) A →protein (or →RNA) capable of
speeding up (catalyzing) specific biochemical reactions by lowering the required activation energy,
but is unaltered itself in the process; a biological catalyst, the “workhorse” of a biochemical
reaction.
Ethylene: H2C=CH2; The only gaseous plant hormone. Ethylene induces organ abscission and
dormancy, and root hair formation. Ethylene acts by increasing the tissue’s sensitivity to
→gibberellin.
Evolution: Change in the genetic makeup of a population of organisms over time due to
→mutations and subsequent unequal reproduction (natural selection) of individual organisms.
→Species often evolve by giving a →gene a new job, rather than by “inventing” new genes.
Fatty acid: Organic molecule made up of a polar (hydrophilic, i.e. water-attracting) head with two
oxygen atoms and a hydrophobic (i.e. water-repellent) chain (‘tail’) of carbon atoms to which
hydrogen atoms are bound. The hydrocarbon tail can be saturated (i.e. all carbon atoms are joined in
single bonds) or unsaturated (i.e. some carbon atoms are joined in double bonds). Important
constituent of cell →membranes, fats, oils, and waxes.
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Feedback: Regulation of the rate of a biochemical pathway by its own products; can be positive (a
product speeds up the pathway) or negative (a product slows down the pathway by inhibiting an
earlier step).
Fertilization: Fusion of the sperm cells (male) from the pollen tube with the egg cells (female) of
the ovule, resulting in the →zygote and leading to →fruit set. Also, the application of mineral plant
nutrients to the soil or the leaves.
Field capacity: The percentage of water a particular soil can hold against the action of gravity, i.e.
the water remaining in the soil immediately after all free water has drained away and before the soil
begins to dry down, which occurs at a soil matrix potential around -10 kPa.
Fluorescence: Light emission by an excited (unstable, higher energy) molecule (such as
→chlorophyll upon light absorption) upon its reversion to the ground (normal, stable, lower energy)
state. The emitted light is always of a longer wavelength (lower energy) than the absorbed light.
Fruit: A mature ovary (berry) or cluster of mature ovaries.
Fruit set: A stage of berry development 1 to 3 weeks after blossoming when most of the flowers
have fallen and those remaining have set and developed into berries. Also called berry set stage or
shatter stage; fruit set is preferred.
Gamete: Female or male reproductive (sex) →cell (e.g. egg and sperm), produced by →meiosis.
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Gene: The fundamental hereditary unit, composed of multiple pairs of →DNA bases and usually
located within a segment of a →chromosome. The “recipe” for a →protein; also, a developmental
“switch” switching on or off in specific tissues at specific times; also a “device” to extract
information from the environment. Genes can be switched on/off (i.e. “expressed”/”repressed”) by
acetylation/deacetylation (i.e. addition/removal of a COCH3 group) of the supporting histone
protein, or by demethylation/methylation (i.e. removal/addition of a CH3 group) of the DNA itself.
Genome: The complete set of →DNA of a particular organism. Grapevines, like all plants, have
three distinct genomes: one in the →nucleus (where genome refers to the entire ~500 million basepair DNA sequence of one set of →chromosomes), one in the →mitochondria, and one in the
plastids (e.g. →chloroplasts). The range of genetic variation in a population of individual organisms
(i.e. in a →species) forms its gene pool.
Genotype: The genetic makeup (set of →genes) of an individual organism.
Gibberellins: Also termed gibberellic acids. Group of over 100 structurally similar plant hormones,
a few of which are biologically active and mainly induce cell elongation and cell differentiation in
meristematic tissues. Gibberellins are cyclic diterpenoids and are produced in meristematic shoot
and root tips and leaf vascular tissues.
Girdling: The removal of a complete ring of outer and inner bark (outward of the →cambium) from
a shoot, cane or trunk. Also called cincturing or ringing. Girdling temporarily interrupts the transport
of assimilates in the →phloem.
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Glutamine: An →amino acid; the primary form in which assimilated nitrogen is transported in the
→xylem and →phloem of grapevines.
Glycoside: (Greek ‘glykys’ =sweet) Compound consisting of a sugar bound to another molecule
belonging to a variety of chemical classes.
Gradient: Difference in concentration or other physical entity per unit distance or across a
→membrane.
Grafting: The (usually deliberate) fusion of parts from two or more different plants. A union of
different individuals in which a portion, called the →scion, of one individual is inserted into a stem
or root, called the stock or →rootstock, of the other individual.
Gravitropism: (Latin ‘gravis’ = heavy; Greek ‘tropos’ = direction) Orientation of plants or plant
organs in relation to gravity.
Guttation: (Latin ‘gutta’ = drop) The exudation of liquid water from leaves, caused by root pressure
resulting from osmosis.
Haploid: Containing only one copy of a →chromosome set in the cell; →gametes are haploid.
Heterozygous: Having two →alleles (i.e. two distinct copies of a →gene, often one dominant and
one recessive) at the same chromosome position (locus) but on different →chromosomes within a
chromosome pair of a →diploid →cell. The dominant alleles determine the →phenotype, because
their instructions are preferred over those of the recessive alleles.
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Homozygous: Having the same →allele (i.e. two identical copies of a →gene) on both
→chromosomes of →diploid cells.
Hormone: (Greek ‘hormaein’ = to stimulate) Organic substance produced in minute amounts in one
plant part (tissue or organ), from which it is transported to another part of the same plant on which it
has a specific effect. Hormones function as highly specific chemical signals between cells.
Humus: Decomposing organic matter in the soil.
Hybrid: The result of a cross between differing plants or taxonomic units. Most modern grape
cultivars are intraspecific hybrids (obtained by crossing vines of the same →species), but some are
interspecific hybrids (obtained by crossing vines belonging to different species).
Inflorescence: The flowering cluster of a grapevine.
Internode: The section of a shoot or cane between two adjacent nodes.
Latent bud: A bud that has remained undeveloped for a year or longer; usually the source of a
→water shoot.
Lateral: A brach or side shoot arising from a prompt bud in the axil of a true leaf on a main shoot.
Lateral growth is promoted by topping the main shoot; lateral shoots may vary in length from a few
mm to > 1 m. Also, a branch of the main axis of a cluster.
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Leaf: A flat, thin expanded organ growing from the shoot, consisting of a broad →blade, a →petiole
and two inconspicuous stipules (leaf-like structures) at the base of the petiole.
Leaf scar: The scar left on the shoot after a leaf falls.
Lenticel: Porous region of the →periderm with loosely packed cells; permits gas exchange.
Lipid: Small, water-insoluble (i.e. hydrophobic) molecule made up of →fatty acids, sterols, or
isoprenoids; important component of cell →membranes.
Macronutrient: (Greek ‘macros’ = large; Latin ‘nutrire’ = to nourish) Inorganic chemical element
that is required in large amounts for plant growth, such as nitrogen, potassium, phosphorus, calcium,
magnesium and sulfur.
Matrix: The aqueous content of a →cell or cell organelle with its dissolved solutes.
Maturity: Stage of fruit development when it has reached satisfactory quality for which it is
intended.
Meiosis: (Greek ‘meioun’ = to make small) Special type of →cell division that occurs in anthers and
ovaries and reduces a diploid cell to four haploid cells to become →gametes. Random halfing of
pairs of →chromosomes and random exchange (mixing) of maternal and paternal →genes before
meiotic cell division produces genetic variation and repairs →DNA damage in sexually reproducing
organisms.
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Membrane: (Latin ‘membrana’ = skin) Thin, tough, hydrophobic (bi-)layer consisting of →lipids
and →proteins, that surrounds →cells and cell organelles, separating their contents from the
surroundings. Membranes are barriers to the free passage of ions and other molecules.
Meristem: (Greek ‘meristes’ = divider) Tissue in which cell division predominates. The
undifferentiated, perpetually young plant tissue from which new cells arise. Also see
→cambium.
Apical meristem: The meristem at the tip of a root or shoot.
Intercalary meristem: (Latin ‘intercalare’ = to insert) Meristem that produces new primary
tissues between more differentiated tissues, as in an internode of a shoot, or in the interveinal
part of a leaf.
Micronutrient: (Greek ‘mikros’ = small; Latin ‘nutrire’ = to nourish) Inorganic chemical element
that is required only in very small, or trace, amounts for plant growth, such as iron, copper,
manganese, zinc, molybdenum, nickel and boron.
Mitochondrion, pl. mitochondria: →Cell organelle responsible for →respiration; the ‘power plant’
providing energy for metabolic processes. Mitochondria descended from symbiotic microorganisms
that invaded (or were ‘swallowed’ by) larger cells and still have their own →genes.
Mitosis: (Greek ‘mitos’ = string, loop) The process of →DNA duplication, →chromosome
replication (by lengthwise splitting) and →cell division during growth. Each of two identical
daughter cells receives one set of chromosomes from the mother cell.
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Mutation: (Latin ‘mutatio’ = change) A spontaneous or engineered change in the →genotype which
may alter the →phenotype. Mutations generally result from copying errors during →mitosis (in
which case they can be multiplied only by vegetative propagation) or →meiosis (in which case they
can be passed on to the next generation) and provide the raw material for →evolution and plant
breeding.
NAD, NADP: Nicotinamide adenine dinucleotide, nicotinamide adenine dinucleotide phosphate;
→coenzymes that serve as carriers of hydrogen atoms and electrons.
Necrosis: (Greek ‘nekrois’ = death) Uncontrolled, sudden death of some or all the cells of a tissue or
organ due to loss of →membrane integrity and water flooding the cells.
Node: (Latin ‘nodus’ = knot) The enlarged portion of a shoot or cane at which leaves, clusters,
tendrils, and/or buds are located at regular intervals.
Nucleus: The dense central organelle of the cell, which contains the →chromosomes and is enclosed
by a nuclear →membrane.
Osmosis: (Greek ‘osmos’ = impulse, thrust) The diffusion of water across a selectively permeable
→membrane. In the absence of other forces, osmotic water movement is in the direction of higher
solute concentration (lower water concentration or →water potential).
Overcropping: The production of more crop than the vine can bring to maturity by normal harvest
time.
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Own-rooted: A vine grown from a cutting that develops its own root system as opposed to a vine
grafted or budded onto a →rootstock.
Pathogen: A disease-causing agent or organism.
Pedicel: The stalk of an individual flower or berry in a grape cluster.
Peduncle: The stalk attaching a →cluster to the →shoot; the branched axis of a cluster apart from
the →pedicels of individual flowers.
Perennial: (Latin ‘per’ = through; ‘annuus’ = year) A plant, such as the grapevine, in which the
vegetative structures live through multiple growing seasons.
Periderm: The →cork cambium and the water-proof tissues it produces; outer bark.
Permanent wilting point: The percentage of water remaining in the soil when it has dried down so
much that a plant growing in that soil fails to recover from wilting even if placed in a humid
chamber. Occurs at a soil matrix potential around -1.5 MPa.
Pest: Species, strain or biotype of any plant, animal or pathogen harmful to plants or plant products.
Petiole: The stalk attaching the →leaf blade to the shoot.
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pH: A symbol denoting the relative concentration of hydronium ions (H3O+) or protons (H+, in
mol/L) in a solution; pH = -log[H+] → [H+] = 10-pH. pH values run from 0 to 14, and the lower the
value the more acidic is a solution, i.e. the more protons it contains; pH 7 is neutral (e.g. pure water
and →cytoplasm), less than 7 is acidic (e.g. grape juice) and more than 7 is alkaline (e.g. lime soil).
Phenols, phenolics: A broad range of ultraviolet-light absorbing organic compounds, all of which
have a hydroxyl (OH) group attached to an aromatic ring (a ring of six carbon atoms containing
three double bonds); includes cinnamic acids, flavonoids, stilbenes, tannins and lignins. Phenolics
are important determinants of wine quality, mainly through →tannins and →anthocyanins, and
contribute to disease resistance of grapevines.
Phenotype: The whole of all the characteristics of an individual organism; the physical expression,
resulting from interaction with the environment, of the →genotype during its development.
Phloem: (Greek ‘phloos’ = bark) The food-conducting and storing tissue of plants, which is
composed of living cells. In grape old phloem comprises most of the bark.
Photosynthesis: (Greek ‘photos’ = light; ‘syn’ = together; ‘tithenai’ = to place) The conversion of
light energy to chemical energy, and the process by which a plant converts carbon dioxide and water
into carbohydrates. Solar radiation is the energy source for this process.
Phytochrome: (Greek ‘phyton’ = plant; ‘chroma’ = color) A pigment →protein located in the
→cytoplasm of plants that acts as a light sensor. Photoreceptor for red and far-red light; involved in
a number of timing processes, such as leaf formation, flowering, dormancy and seed germination, as
well as shade-avoidance responses.
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Phytotoxic: Causing injury or death of plants or portions of plants.
Pigment: A substance that absorbs light, often selectively (i.e. only particular bands of
wavelengths); →anthocyanin, →chlorophyll, →phytochrome.
Pollination: (Latin ‘pollen’ = fine dust) The transfer of pollen from the male part of a flower
(anther) to the female part of a flower (stigma).
Primordium: (Latin ‘primus’ = first; ‘ordiri’ = to begin to weave) A cell or organ in its earliest
stage of differentiation.
Prompt bud: Axillary bud that develops into a →lateral shoot in the same season that the bud is
produced.
Protein: (Greek ‘proteios’ = primary) A complex organic compound, a.k.a. polypeptide, composed
of a string of just a few to several thousand →amino acids. Proteins are folded into a plethora of
three-dimensional shapes that define their functin. Also →enzyme.
Pruning: The cutting away of a portion of the annual vegetative growth of a grapevine to maintain
the desired number and spacing of →buds or →nodes per vine.
Summer pruning: Trimming or topping of growing shoots during the growing season to
regulate shoot length, reduce →cluster shading and maintain canopy shape.
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Winter pruning: Also called ‘dormant pruning’. Carried out during the dormant period to
regulate the node number and maintain vine form.
Q10: The proportional change in respiration rate per 10°C increase in temperature; e.g. for Q10 = 2,
respiration will double for each 10°C rise in temperature.
Rachis: (Greek ‘rachis’ = backbone) The central axis of a →cluster stem.
Raisin: A dried grape.
Receptacle: The part of the axis of the flower stalk that bears the floral organs.
Respiration: An intracellular process in which molecules, particularly pyruvate in the Krebs cycle,
are oxidized (i.e. have electrons removed) to produce energy (→ATP). The complete breakdown of
sugar or other organic compounds, such as malate, to carbon dioxide (CO2) and water.
RNA: Ribonucleic acid; the chain molecule that translates the genetic code (→DNA) into →amino
acids and hence →proteins. RNA is a working copy and transport form of genetic information (i.e.
the link between DNA and protein). It consists of long chains of nucleotide building blocks
comprised of a purine or pyrimidine base, ribose sugar and phosphate and is produced from →ATP
and other nucleotide triphosphates.
Root: The below-ground axis of the grapevine, which serves to anchor the plant and to absorb and
conduct water and nutrients; it bears only lateral roots. The true root develops from the hypocotyl of
the embryo; the grapevine root is a taproot, an axis with lateral roots initiated near the tip.
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Rootstock: Specialized stock material to which fruiting varieties of grapes are grafted as →scions to
produce a commercially acceptable vine. Grape rootstock varieties are used for their tolerance or
resistance to root parasites, such as phylloxera and nematodes, for their vigor, or tolerance to
adverse soil conditions.
Sap: The fluid contents of the →xylem or the sieve elements of the →phloem. The fluid contents of
the →vacuole are called cell sap.
Scion: The →shoot or →cane portion that is grafted or budded onto a →rootstock.
Senescence: (Latin ‘senescere’ = to grow old) Ageing. The ordered degradation of cell constituents
that ends in death of the cell.
Sexual reproduction: Propagation of plants by means of seeds following fertilization.
Shoot: The current growing season’s green stem growth. It becomes a →cane when over half of its
length becomes woody with a tan or brown color.
Sink: An assimilate-importing plant organ. All plant organs unable to meet their own nutritional
demands may act as sinks, i.e. expanding leaves, growing fruit or storage organs when they are
being replenished.
Sinus: The gap in the margin between two individual lobes of a →leaf blade. The petiolar sinus is
the gap at the attachment of the →petiole.
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Somatic cell: (Greek ‘soma’ = body) A body →cell. All cells of a plant are somatic except the cells
(spores) produced by →meiosis that develop into →gametes (but even these are derived from
somatic cells, unlike in animals where somatic and germ line cells are kept separate). Somatic cells
(e.g. from shoot tips or leaf disks) can be forced through tissue culture to form somatic embryos that
can develop into whole plants which are →clones of their mother plant.
Source: An assimilate-exporting plant organ. Photosynthesizing leaves are the primary sources, but
storage organs, such as the trunk or roots, may also serve as important sources, especially during
budbreak.
Species: Population or groups of populations of sexually reproducing organisms that interbreed with
each other but are reproductively isolated from other populations.
Spur: A short fruiting unit of one-year growth; the basal section of a →cane which is cut back to
one to three →buds. These are used in spur →pruning to provide fruiting shoots for the current year
and in cane pruning to provide replacement canes for the following year.
Starch: A complex insoluble carbohydrate, composed of a thousand or more glucose units arranged
in α1→4- and α1→6-glucan chemical bonds; the main food storage substance of grapevines.
Stoma, pl. stomata: (Greek ‘stoma’ = mouth) A minute opening bordered by guard cells in the
epidermis of leaves, stems and grapes through which gases pass. The stoma regulates the exchange
of carbon dioxide used in photosynthesis and water used in transpiration between the plant and the
atmosphere.
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Sucker: A →water shoot that emerges from the base of the established trunk of the vine, at or below
ground level.
Sucrose: A disaccharide (glucose plus fructose); the primary form in which sugar produced by
photosynthesis is transported in the →phloem of grapevines.
Symbiosis: (Greek ‘syn’ = together, at the same time) The mutually beneficial living together of two
or more species in a long-term relationship.
Symplast: (Greek ‘plastos’ = formed) The totality of protoplasts; i.e. everything inside a plant that
is bound inside a membrane. The continuum of cytoplasm interconnected by plasmodesmata and
excluding the →vacuoles.
Tannin: A macromolecule, belonging to the →phenolic class of flavonoids, found in the cell
vacuoles of the skin and seeds of grape berries. Tannins are responsible for the astringency and
bitterness of grapes and wine.
Tendril: (Latin ‘tendere’ = to extend) A part of the stem modified into a slender twining organ on a
shoot opposite a leaf that can coil around an object for support.
Terpene: An organic hydrocarbon or one of its derivatives, assembled from multiple isoprenoid
units; responsible for certain odors or flavors of grape berries (and of flowers, fruits, and leaves of
other plants).
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Tissue: A group of similar cells organized into a structural and functional unit.
Transpiration: (Latin ‘trans’ = over, beyond; ‘spirare’ = to breathe) The loss of water vapor by
plant parts; most transpiration occurs through →stomata. Transpiration is required for cooling of
plant tissues.
Trellis: A permanent structure that supports the vine framework, consisting of stakes, posts and,
usually, at least one wire.
Trunk: The main thickened stem a vine between the →roots and the →head or →cordon of the
vine.
Turgor: Outward pressure of cell sap due to water absorption by →osmosis across a →membrane,
balanced by the rigid cell wall; turgor pressure is necessary for cell expansion during growth.
Vacuole: Organelle of plant →cells for storage, degradation, and recycling of a wide variety of
compounds and waste products, surrounded by a membrane called tonoplast. Different types of
specialized vacuoles can be present within the same cell; may represent up to 90% of the volume of
a mature cell. Osmotic water absorption creates outward pressure (→turgor).
Variety: A group of closely related plants of common origin and similar characteristics within a
species. The so-called grape varieties are botanically →cultivars.
Vascular bundle: (Latin ‘vasculum’ = small vessel) A strand of tissue containing primary →xylem
and →phloem; used for conducting water, nutrients and assimilates.
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Vegetative propagation: Asexual propagation; the propagation of grapevines (and other organisms)
without fertilization but by means of cuttings, layering, meristem or shoot-tip culture, and
micropropagation.
Vein: A strand of vascular tissues in a flat organ such as a leaf.
Veraison: (French ‘vérer’ = to change) Onset of ripening of a grape berry as indicated by a change
in color, which is preceded by softening and the beginning of sugar accumulation.
Vigor: The rate of shoot growth measured by the change in shoot length over time.
Virus: Self-replicating complex of nucleic acids (either →DNA or →RNA) and →proteins that
infects living organisms and requires an intact host →cell for replication.
Water shoot: Rapidly growing shoot arising from a latent bud on a →trunk or →cordon. A noncount shoot that arises on wood older than one year and originates from a →base bud.
Water potential: A measure of water concentration. The free energy of an aqueous solution per unit
molar volume of liquid water; typically the sum of the component potentials arising from the effects
of →turgor pressure and dissolved molecules (→osmosis).
Weed: Generally an herbaceous plant not valued for use or beauty, growing wild, and regarded as
using ground or hindering the growth of grapevines.
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Wood: Secondary →xylem. The tissue produced on the inside of the vascular →cambium.
Xylem: (Greek ‘xylon’ = wood) The dead, woody portion of conducting tissues whose function is
the transport of water and minerals, and support of the roots, trunk, and shoots.
Zygote: Fertilized egg resulting from the fusion of a male and a female →gamete (→fertilization)
that forms a zygotic embryo which develops into a seed.
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