Abscission: normal separation of flowers, fruit and leaves from plants.
Abscisic acid: plant hormone that regulates seed maturation; with water stress it closes stomata, promotes root growth and inhibits shoot growth; promotion of leaf senescence.
Acclimation: natural process of becoming inured to a climate.
Achene is a small single-seeded dry fruit.
Adventitious: a plant organ that arises from an unexpected position, eg. sprouts that arise directly from roots, as in raspberry, or small plants that can arise from certain leaves.
Aggregate fruit: a fruit formed by the coherence or connation of pistils that were distinct in the flower, eg blackberries.
Air layering, (marcottage): multiplying a plant by inducing rooting on a root or shoot.
Alkaloids: a large family of nitrogen-containing metabolites in many vascular plants which defends against predators and includes toxins, medicinals, stimulants and sedatives.
Allele: copy of each gene on a chromosome; differences may lead to different traits.
Allelopathy: release by plants of substances into the soil that have negative effects on neighbours, thus decreasing competition for water and nutrients.
Alternate bearing: tendency of many fruiting species to produce large crops one year, but only meagre crops in the next year or years.
Androecious: plants that bear staminate (male) flowers only.
Androgynous: bisexual, with male and female flowers in the same inflorescence.
Andromonoecious: male and bisexual flowers on the same plant, but without female flowers.
Anoxic: absence of oxygen.
Anther: pollen-bearing part of a stamen at the top of a filament.
Anthesis: the period when the flower opens, often used to refer to the bursting of the pollen sacs and pollen release.
Anthocyanins: pigmented water-soluble flavonoids responsible for most of the red, pink, purple and blue colours in plants.
Apical dominance: in most higher plants the growing apical buds inhibit the growth of lateral buds.
Apomixis: reproduction without fertilisation or formation of gametes. An apomict usually is genetically identical with its source plant.
Arbuscules: branched structures of mycorrhizal fungi that form within penetrated cells; the sites of nutrient transfer between the fungus and the host plant.
Aril: a fleshy appendage of the seed, either on a seedcoat or arising from the base of the seed.
Asexual reproduction: Vegetative reproduction; reproduction without fertilization such as with tubers, bulbs or rooted stems, or from sexual parts such as unfertilised eggs or other cells in the ovule.
Autogamy: fertilization of a flower with its own pollen.
Autosomes: any chromosome that is not a sex chromosome.
Auxin: a compound with biological activities similar to but not necessarily identical to indole actetic acid. Induces cell elongation in stems, cell division in callus, lateral root formation at cut surfaces of stems, parthenocarpic fruit growth and ethylene formation.
Axil: the angle formed between any two adjoining organs, such as stem and leaf.
Backcross: a hybrid resulting from crossing an existing hybrid with one of its parents, thereby increasing the genes of that parent.
Bark:the collective term for all the tissues outside the cambium of a woody stem or root.
Berry: fleshy or pulpy indehiscent fruit with one or more seeds embedded in the fleshy tissue of the pericarp.
Biennial bearing: cropping every other year.
Biotic: referring to what is living.
Bisexual: having both male and female present and functional in the same flower or inflorescence, hermaphrodite.
Bletted: some very astringent fruits are best if bletted. Fruits are left to ripen till they are very soft, when full sweetness and flavour develops.
Bloom: fragile powdery surface layer, eg the waxy bloom of plums and grapes.
Brackish: somewhat salty.
Bract: a modified, reduced leaf or leaflike part just below and protecting an inflorescence or stalk, often small.
Breba: first or spring crop of edible figs.
Brix: the angle of light transfer through a fruit pulp solution is positively correlated with increasing concentration of dissolved substances, mainly sugars. This change in angle can be measured by a refractometer and quoted as degree Brix. Levels below 8 are low in sugar and greater than 18 is very sweet.
Bud: an immature or embryonic shoot, flower or inflorescence, frequently enclosed in scales.
Bud ring: several closely spaced buds without subtending leaves.
Bud sport: mutant arising from a bud.
Budding: Grafting by inserting a bud into a slit or hole made in the bark of a stock plant.
C3 plants: plants in which the first stable product of photosynthetic carbon dioxide fixation is a 3-carbon compound.
C4 plants: plants in which the first stable product of carbon dioxide fixation is a four-carbon compound.
Calcareous: soils containing calcium carbonate.
Callus: a small hard protrusion of undifferentiated (parenchyma) tissue formed at a wounded surface.
Calyx: collective term for the outer separate or united sepals of a flower; the outer series of flower parts.
CAM plants: plants that fix carbon dioxide during the night into a 4-carbon compound.