AgroForestryTree Database
Glossary O
obovate (of leaves)
Having the outline of an egg, with the broadest part above the middle and attached at the narrow end.
ochrea
A cup-shaped structure formed by the joining of stipules or leaf bases around a stem.
open forest
A 'forest' where the canopy is not closed and a large proportion of the area does not carry trees.
open pollination
Uncontrolled pollination brought about by wind or insects.
open-rooted seedlings
See bare-rooted planting.
open storage
Storage conditions where seeds are exposed directly or indirectly to ambient relative humidity land sometimes also temperature.
opposite (of leaves)
Occurring in pairs on opposite sides of the stem; (of stamens) inserted in front of the petals.
orbicular
More or less circular.
organic matter See also soil organic matter
1. A general term for plant and animal material in or on the soil and in all stages of decomposition. Readily decomposed organic matter is often distinguished from the more stable forms that have already passed through the stage of rapid decomposition.
2. Carbon containing materials of either plant or animal origin; exists in all stages of decomposition in soil.
organic soil See also mineral soil
Soil containing a high percentage of organic matter (>20%).
origin
For an indigenous stand of trees, the place in which the trees are growing. For a non-indigenous stand, the place from which the seed or plants were originally introduced.
ornamental See also multipurpose tree
Any tree or plant cultivated for its beauty. This does not mean that it has no other uses. For example, Chlorophora excelsa is often planted as an avenue tree along roadsides (in Uganda); its stately appearance in no way diminishes its usefulness for timber. Ornamentals with other uses in agroforestry are Cassia spp. and Senna spp.
orthodox seed See also recalcitrant seed
Seed that can be dried and stored at subzero temperatures without damage and with beneficial effects on longevity.
orthodox seed storage behaviour
Mature whole seeds not only survive considerable desiccation (to at least 5% mc] but their longevity in air-day storage is increased in a predictable way by reduction in seed storage moisture content and temperature.
orthotropic See also dimorphic branching, plagiotropic
Of branching, stems that only grow vertically.
outbreeding
1. Mating unrelated parents.
2. A system of producing progeny sexually that involves the frequent exchange of genetic material between individuals of a population. Outbreeding plants may be self-infertile or have mechanisms to ensure outcrossing.
outcrossing See also outbreeding
A cross, usually natural, to a plant of a different genotype.
ovary
The hollow basal region of a carpel, containing one or more ovules and surmounted by the style(s) and stigma(s). It is made up of one or more carpels which may fuse together in different ways to form one or more chambers (locules). The ovary is generally above the perianth parts (superior) or below them (inferior).
ovate (of leaves)
Having the outline of an egg with the narrow end above the middle.
oven-dry soil
Soil that has been dried at 105 deg. C until it reaches constant weight.
over-bark See also dbh, under bark
Measurement of the diameter or circumference of a trunk or branch made with the bark.
overstorey See also stratification, understorey
The portion of trees in a forest stand forming the upper crown cover.
ovoid (of leaves)
Egg-shaped.
ovule
The structure in the chamber (locule) of an ovary containing the egg cell within the embryo sac which is surrounded by the nucellus. It is enclosed by two integuments. The ovule develops into the seed after fertilization.
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