Glossary - general
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Ob- – against, as a botanical prefix usually indicating “the other way round from the usual” (e.g. ovate is egg-shaped, whereas obovate is egg-shaped with the attachment point at the base and the widest part near the top)
Obclavate – clum-shaped, with the thicker end near the attachment point
Obconical – conical with the narrow part near the base and the wide part near the apex
Obcordate – heart-shaped, with the narrow end near the base and the wider, notched end near the apex
Obdiplostemonous androecium – with the stamens in two whorls, twice as many as the petals, the outer alternate with the outer perianth whorl, the inner alternate with the inner perianth whorl
Obdiplostemony – see Obdiplostemonous androecium
Obhaplostemonous androecium – with the stamens in one whorl, as many as the petals or the sepals and opposite the inner perianth whorl if present
Obhaplostemony – see Obhaplostemonous androecium
Oblanceolate – narrowly obovate and tapering to a point at both ends
Oblate (of a globose shape) – flattened at the poles
Obligate life form or habitat requirement – restricted to this life form or habitat and not occurring as or in any other – Opposite: facultative
Oblique – (1) (of leaf) when the two sides of the leaf are unequal near the base; (2) (of ovary) when the ovary is at an angle to the axis or plane of symmetry of the flower
Oblong (of a plane shape) – longer than broad, with the margins parallel for most of their length
Obovate – egg-shaped (two-dimensional) with the broadest part near the apex
Obovoid – egg-shaped (three-dimensional) with the broadest part towards the apex
Obpyriform (of a three dimenisonal shape) – like an inverted pear, i.e. with the broadest part proximal
Obreniform – kidney-shaped, with the point of attachment at the rounded side, not in the sinus
Obsolete – rudimentary
Obtriangular (of a two-dimensional shape) – like an inverted triangle, i.e. with the narrowest part proximal
Obtrullate – obverse of trullate, shaped like a bricklayer’s trowel
Obturator – (1) small body with pollen mass; (2) process of ovary wall descending on the micropyle (funicular obturator, integumentary obturator, placental obturator) – see also Ponticulus
Obtuse – of an apex or base, not pointed, blunt
Ocreola, ochreola – the reduced ocrea (ochrea) of an inflorescence
Ocrea, ochrea – 1) of a leaf sheath, an extension beyond the petiole insertion (e.g. in Arecaceae); 2) a tubular stipule sheathing the stem (e.g. in Polygonaceae)
Ocreate, ochreate – with an ocrea (ochrea)
Odorous – smelling; producing a smell
Offsetting – producing a lateral shoot for propagation purposes
Oil cell – a type of idioblast containing and secreting oils (lipids, ethereal oils, etc., secreted by plastids); oil cells frequently have a suberized cell layer between the cellulose layers
Oleaginous – oily
Oleo-resin – natural mix of a resin and an essential oil, forming a balsam or turpentine
Oligarch vascular bundles – containing few fibro-vascular bundles; vascular bundle with few rays
Omniaperturate pollen grain – the exine is very thin or absent and the intine thick, so that no specific apertural region can be distinguished and thus the whole surface can be considered apertural in nature
Onagrad embryogenesis – a vertical wall in the apical cell and a transverse wall in the basal cell give rise to a T-shaped tetrad; the apical cell contributes to the major portion of the embryo; the hypophyseal region (producing the initials of the root cortex and root cap and completing the embryo) is derived from the basal cell
Opaque – not translucent or transparent; impenetrable to light
Open aestivation – apert aestivation; the margins of adjacent (usually reduced) sepals/petals do not touch each other
Operculate – with a lid
Opercule, operculum – a lid or cover
Operculum (of fruit) – a lid-like covering of a pyxidium, which detaches when the fruit is ripe
Operculum (of leaf) – (Cephalotaceae, Nepenthaceae, Sarraceniaceae) the leaflet preventing a pitcher from a surplus of rainwater
Operculum (of pollen grains) – a thickened, distinctly delimited structure of the ectexine or sexine, which covers a part of an ectoaperture
Operculum (of seed) – a lid-like hard structure on the seed coat, which becomes detached during the germination
Opposite – (1) (of leaves and branches) when two are borne on the same node but on diametrically opposed sides of the stem; (2) (of other organs) when placed e.g. in front of the petals instead of alternating with them
Opposite lateral wall pitting – intervascular pits forming lateral series on vessel walls, not spirally but horizontally distributed, either on vessel-vessel interfaces or on vessel-ray interfaces
Oppositipetalous – see Antepetalous
Oppositisepalous – see Antesepalous
Opposititepalous – see Antetepalous
Orbiculate – disc-shaped
Orbicular – (1) (two-dimensional) with a circular outline; (2) (three-dimensional) globose
Orientation – relative position, place
Orifice – opening, mouth
Ornamented pollen grain – with sculpturing on the surface (e.g. spines, tuberculae, reticulations, granules) – Opposite: psilate, smooth
Orthoamphitropous ovule – a type of amphitropous ovule, in which the trace proceeds straight to the megasporangium via the basal body
Orthocampylotropous ovule – a type of campylotropous ovule, in which the trace proceeds straight to the base of the megasporangium
Orthostichy – a vertical line joining an organ to the next organ immediately above it on the stem
Orthotropic shoot – vertical branch or stem; distinct from plagiotropic
Orthotropous ovule or seed – with a straight axis, the base of the funicle proximal, the micropyle distal
Os (of pollen grains) – endoaperture
Osmophore – a type of gland, in which the floral fragrance originates (produced and released); various floral parts may be differentiated as osmophores; osmophores consist of glandular tissue usually several cell layers in depth, the outer epidermal layer possessing stomata
Osseous – bony
Osteosclereid – elongated sclereid with swollen ends
Ostiolar – of the mouth, e.g. ostiolar bracts, those at the ostiole of a fig
Ostiole – mouth, as in the aperture at the apex of a fig
Oval – broadly elliptic; ‘elliptic’ is a better term
Ovary – the ovule-bearing part of the gynoecium; the (usually enlarged) part of the pistil which contains the ovules and eventually becomes the fruit
Ovate – egg-shaped (two-dimensional), about twice as long as broad, with the wider part below the middle
Ovoid – egg-shaped (three-dimensional), with the broad part below the middle/nearest the base
Ovule – the immature seed in the ovary before fertilization; comprises the funicle, chalaza, inner (tegmen) and outer (testa) integuments, nucellus (megasporangium) and embryo sac (megagametophyte)