AgroForestryTree Database
Glossary A
abortive
Imperfectly developed, indimentary, non-functional.
abscission
Natural separation of leaves, flowers and fruits from plants. Generally associated with deterioration of a specialized layer of thin-walled cells.
accession
To record in order of acquisition; in the case of seed sources, a numbered seed lot.
achene
Dry, indehiscent fruit containing only one seed.
acid soil
A soil having a pH less than 7.0 degrees of soil acidity are recognized. Soil is regarded as 'very acid' when the reaction is less than pH 5.0.
actinomorphic ( of flower)
Radially symmetrical
acuminate
Tapering to a point
adnate See also connate
Joined or attached to; applied to different organs fused during development.
adpressed
Pressed closely together but not joined. (for example, conifer leaves may be pressed close to the stem of the plant).
adventitious
Growing from an unusual position (for example, roots from a leaf or stem).
afforestation See also reforestation
1. Conversion of bare land into forest land by planting of forest trees.
2. The planting of a forest crop on land that has not previously, or not recently, carried a forest crop.
agroforestry
A system for mixed arable farming and forestry that has been practised in many parts of the tropics. Tree crops are interspersed with food-crop patches on a continuous basis, sometimes as hedge (often called alley cropping)
agronomic variety See also variety, cultivar
A distinctive seedling popular or clone with enough favourable characteristics to warrant cultivation. Agronomic varieties are given non-Latin names according to priority rules which vary among different crops.
agronomy
That part of agriculture devoted to the production of crops and the management of the soil on which they are grown. The scientific utilization of agricultural land.
agropastoral system
A land-use system in which crops and livestock (but not trees) are the only components.
agrosilvicultural system
An agroforestry system for the concurrent production of agricultural crops (including woody perennial crops) and forest crops. The forest crops serve either a productive or a service role. Woody perennial and agricultural crops are chosen first for their productive capacity.
agrosilvipastoral system
Any agroforestry system that includes trees or shrubs and herbaceous food crops and pastures and animals.
air-layering, marcotting
A technique of propagating using an undetached stem to which the rooting medium is applied by securing it in an appropriate container, for example, a polythene bag.
air-dry soil See also oven-dry soil
Soil that has been spread out to dry, usually in thin layers in the shade, until it reaches a constant weight. Final water content may vary somewhat with environmental conditions. Applies also to plant materials that often can be sun dried.
alkali soil
1. A soil having a high degree of alkalinity (pH of 8.5 or higher) or having a high exchangeable sodium content (15% or more of the exchange capacity) or both. When saline soils are leached, and if calcium levels are low, exchangeable calcium is replaced by sodium and the soils become highly alkaline and deflocculate.
2. A soil that has such a high a degree of alkalinity or percentage of exchangeable sodium, or both, that the growth of most crop plants is reduced. This is true if the pH is 8.5 or higher, or if the percentage of exchangeable sodium is 15% or more. Such soils are highly dispersed so that air and water movements are very slow. In popular usage, saline soils have been called 'white alkali' soils. True alkali soils, because of dispersion of the organic matter, have been called 'black alkali' soils.
alkalinity See also salinity
Amount of cations balanced by weak acids expressed as milli-equivalents of neutralized hydrogen ions in 1 litre of water.
all-aged
Applied to a stand in which, theoretically, trees of all ages are found, including those of felling age.
allelopathy
1. An interaction between different plants or between plants and micro-organisms in which substances (allelochemicals) produced by one organism affect the growth of another (usually adversely).
2. The suppression of germination or growth or the limiting of the occurrence of plants, as a result of the release of chemical inhibitors by some plants.
3. The influence of plants (other than microorganisms) upon each other arising from the products of their metabolism.
alley cropping
An agroforestry intercropping system in which species of shrubs or trees are planted at spacings relatively close within row and wide between row, that is, in the 'alleys', to leave room for herbaceous cropping between.
alluvial soil
Soil developed from transported and relatively recently deposited material (alluvium) characterized by little or no modification of the original material by soil-forming processes.
alluvium
1. Clay, silt, sand, gravel pebble or other detrital materials deposited by water.
2. A sediment deposited by streams and varying widely in particle size. The stones and boulders, when present, are usually rounded or subrounded. Some of the most fertile soils are derived from alluvium of medium or fine texture.
amenity
The application of horticulture practices for leisure-oriented or aesthetic purposes.
ammonification
The biochemical process in which ammonical nitrogen is released from organic compounds containing nitrogen.
androecium See also gynaecium
A collection of stamens that form the male reproductive organs of a flowering plant. These may be borne together with the female reproductive organs within the same flower of an individual plant
anemophilous
Wind pollinated.
annual plant See also seasonal plant
A plant that completes its life cycle within 1 year.
anthesis
The opening of a flower bud; the exposure of stamens and stigmas to pollinating agents; the span of life of a flower.
anthocyanin
The pigment usually responsible for pink, red, purple, violet and blue colours in flowering plants.
anthracnose
Irregular dead areas on leaf margin, between and across and/or along veins, often moving onto the shoots and small twigs; sometimes whole leaves are engulfed.
apetalous
Without petals.
apex (adj. apical)
The tip of an organ; the growing point.
apical control
The control of tree crown development in which interactions between shoots determine branch elongation.
apical dominance
The control over lateral bud or shoot development exerted by plant growth regulators from a shoot apex in the current year of growth.
apical meristem
The growing point of the plant. The tissue at the tip of the stem or root in which cells undergo division.
apiculture
Bee keeping.
apocarpous
With carpels free from each other.
apomixis
Reproduction in which sexual organs or related structures develop as seeds but fertilization does not occur, so that the resulting seed is vegetatively produced.
aquaculture
Fish farming. In a broad sense, producing any product under water, for example, algae (seaweed), crustaceans (shrimp).
arable farming
See arable land.
arable land
Refers to land under crops, land under temporary meadows for mowing or pasture, land under market and kitchen gardens (including cultivation under glass) and land temporarily fallow or lying idle. Hence 'arable farming'.
arboriculture
A general term for the cultivation of trees.
aril
A fleshy or sometimes hairy outgrowth from the hilum or funicle of a seed.
asepalous
Without sepals.
asexual, asexual regeneration
Propagation of plants from vegetative parts, such as stems, leaves or roots; or from modified stems such as bulbs, tubers, rhizomes and stolons. This is accomplished without union of gametes.
attenuate
In plant morphology: growing narrower toward the base, or sometimes toward the tip.
auricle (adj. auriculate)
Small ear-like projections at the base of a leaf or leaf blade or bract.
autogamy
Self-fertilization in plants.
auxin
A phytohormone involved in many physiological processes including root and stem elongation, fruit set, cambium activity and sex determination. Indoleacetic acid (IAA) is the major naturally occurring auxin.
axillary
Growing in the axil, which is the angle between the upper side of the leaf and the stem.
axillary bud See also axillary
A bud borne laterally on the stem in the axil of a leaf.
axis
The main or central stem of a herbaceous plant or of an inflorescence.
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