AgroForestryTree Database
Glossary - I
imbibition
The process of seeds absorbing water from their surroundings or the stage at which they do it, for example, after a dry seed has been planted in moist soil.
imbricate (of sepals/petals) See also valvate
Overlapping as in a tiled roof.
imparipinnate (of leaves) See also pinnate, paripinnate
A pinnate leaf with an unpaired terminal leaflet occurring centrally.
impervious soil
1. Soil through which water, air or roots cannot penetrate. No soil is ever completely impervious.
2. A soil resistant to penetration by water and, usually, by air and roots.
inarching See also grafting, rootstock, scion
Similar to grafting in that both rootstock and scion plants are on their own roots at the time of grafting. It differs in that the top of the new root stock plant usually does not extend above the point of the graft union.
induplicate
With the margins bent inwards, and the external face of these edges, applied to each other, without twisting.
inoculate
Bringing the pathogen into contact with a susceptible plant.
in situ See also ex situ
'On the site'. When applied to tree plantations, refers to seed planted in the same area as it was collected.
in vitro
Cultivating of plant materials in a septic or germ-free nutrient media under laboratory
inbreeding
1. The breeding of closely related individuals; if carried through enough generations the families can become homozygous, that is, have the same genotypes within their chromosomes.
2. The mating of individuals that are closely related genetically. Mating in a population consisting of a few individuals.
3. The mating of individuals more closely related than individuals mating at random.
incised (of leaves)
Sharply and deeply cut.
incompatibility
In breeding systems, strictly the inability of gametes to unite and form a zygote. Frequently restricted to the inability of pollen to fertilize through pollen tube growth, being arrested in the style. Inability of embryos to develop.
indefinite (of flower parts)
Of a number large enough to make a precise count difficult.
indehiscent See also dehiscent
Fruits not opening to release seeds.
indeterminate (of a stem)
1. When it continues to grow from the apex. Of an inflorescence, when the terminal flowers open last and therefore the growth or elongation of the main axis is not arrested by the opening of the first flowers (for example, as in a panicle).
2. Having the axis or axes of plants not ending in a flower or bud; resulting in elongation.
indeterminate flowering
A plant in which flowering is more or less continuous until climatic conditions become unfavourable.
indeterminate growth See also determinate growth
A pattern of development in which the apical meristem remains vegetative, that is, does not produce flowers, so that new leaves and stems continue to be produced while flowers are also forming.
indigenous See also exotic
Native to a specified area, not introduced. An indigenous tree is one that grows naturally within a specific environment or within certain predetermined boundaries.
indumentum
A covering, usually of hairs.
inferior (of ovaries)
An ovary with the sepals, petals and stamens attached to its apex.
infested
Containing great numbers of insects, mites, nematodes and so on, as applied to an area or field. Also applied to a plant surface or soil contaminated with bacteria, fungi, and so on.
infiltration
1. The downward entry of water into soil or other material.
2. The flow of a liquid into a substance through pores or other openings; connoting flow into a soil as opposed to percolation, which strictly means flow through a porous substance.
inflorescence
1. A group of flowers, usually set apart from the foliage leaves. The inflorescence is classified according to its mode of branching, which may be racemose (indefinite and not terminating in a flower) or cymose (definite, terminating in a flower).
2. The system in which flowers are arranged about a plant axis. The term includes the branch stems, flower stalks and bracts as well as the actual flowers.
infructescence
The inflorescence converted into fruits.
inoculation
Of rhizobia or mycorrhizae. The deliberate introduction of material containing microorganisms into soils, nursery composts or living plants.
inoculum
A preparation containing live microorganisms (rhizobia, mycorrhizal fungi) that can be used to add to the soil, or directly to the seeds, so as to inoculate suitable plant species with these favourable organisms. Commercial preparations can be as a liquid suspension, or a gel, or they may be peat based.
inserted
Growing out of another organ. See also mixed cropping, multiple cropping
1. The cultivation of 2 or more crops simultaneously on the same field, with or without a row arrangement (row intercropping or 'mixed intercropping').
2. The growing of 2 or more crops on the same field with the planting of the 2nd crop after the 1st one has already completed development. Also called relay cropping.
intermediate seed storage behaviour
A category of seed storage behaviour intermediate between those defined as orthodox and recalcitrant.
intermittent growth
Non-continuous growth without the predictable regularity of rhythmic growth; hence intermittent branching.
internode See also node
A region of the stem between 2 successive nodes.
involucel See also bracteole
A whorl of bracteoles.
involucre See also bract
A whorl of bracts beneath an inflorescence.
irregular (of flowers)
Not regular; not divisible into halves by an indefinite number of lingitudinal planes; zygomorphic.
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