Glossary - general
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Idioblast – isolated specialized cells containing non-living substances, such as reserve nutrients, excretory materials, pigments, minerals, oil, latex, gum, resin, tannin, crystals (of calcium oxalate, carbonate or silica)
Imbricate aestivation – when the adjacent sepals/petals partly overlap like tiles
Imbricate-quincuncial aestivation – a type of imbricate aestivation, where two sepals/petals are completely external, two completely internal, and one with one margin overlapping and the other overlapped
Immersed – sunk completely into
Imparipinnate leaf – unevenly or odd-pinnate, i.e. pinnate with a single terminal leaflet
Imperfect flowers – with one set of the sexual parts normally present, the other set (e.g. stamens) absent
Imperforate tracheary element – common term of tracheids, fibre tracheids and libriform fibres
Imperforate tectum (of pollen grains) – absence of holes in the tectum
Impervious – impassable to fluid
Inaperturate pollen grain – omniaperturate pollen grain; pollen grain without any opening or aperture; the pollen tube germinates through any part of the pollen wall (usually the side adjacent to the stigmatic receptive surface)
Inappendiculate – without appendage
Incipient – beginning
Incised – cut rather deeply; this term is intermediate between toothed and lobed
Included – not protruding from the surrounding structure or organ – Opposite: exserted
Included phloem – phloem islands surrounded by xylem in the secondary vascular tissue; cambium present between phloem and xylem
Incompletely tenuinucellar ovule – the ovule has a megasporangium in which the meiocyte is covered at the apex only by the epidermis but, in addition, by subepidermal tissue at its flanks and/or by more tissue at the megasporangium base
Incrassate – thick, stout
Incrassated – made stout
Incrustation – coating of mineral (non-organic) matter
Incubously – inserted obliquely, so that the distal part covers the base of the next one up (e.g. of leaves on a stem)
Incumbent anther – bent adaxially-inwards 90o
Incumbent embryo – with the cotyledons situated face to face and folded sideways so that the radicula lies against the face of one of the cotyledons; ‘in embryos derived from curved ovules the cotyledons are incumbent when they are at right angles to the plane formed by the long axis of the seed plus chalaza’
Incurved – bending inwards
Indefinite shoot growth – continuous
Indehiscent fruit – not splitting open
Indented – marked with a dent, a sharp impression
Indeterminate – (1) (of shoot) capable of more or less indefinite extension; (2) (of inflorescence) with the lower or outer flowers opening before the upper or inner ones, and with the floral axis continuing to grow indefinitely
Indument(um) – any covering consisting of hairs or scales
Induplicate – (Arecaceae) V-shaped in cross-section
Induplicate aestivation – the margins of adjacent sepals/petals incurved (folded inwards) but not overlapping
Induplicate ptyxis – opening along adaxial folds
Indurated – hardened
Induration – hardened part
Indurescent – becoming hardened
Indusium (of flower) – a cup covering the stigma (i.a. in Goodeniaceae)
Inferior ovary – where the calyx is above the ovary; rarely of other flower parts, if inserted below the ovary (not recommended); the flower apex becomes concave during or after formation of the perianth so that the lower part of the gynoecium appears to be sunken into the floral base at anthesis
Inflated – blown up
Inflexed – bent or curved inwards
Inflorescence – the part of the plant that bears the flowers, including all its bracts, branches and flowers, but excluding unmodified leaves
Infra- – below, beneath
Infralocular – positioned below or beneath the ovary locules
Infratectum – part of the ectexine present between the tectum and the foot layer, and including columellae and/or granules
Infructescence – the part of the plant that bears the fruits, including all its bracts, branches and fruits, but excluding unmodified leaves
Infundibuliform – funnel-shaped, i.e. abruptly widening from a narrow cylindrical part to a wider distal part
Innovation – (1) new shoot, which eventually becomes separate from the parent as its lower part dies; (2) (Poaceae) a new shoot which carries on further growth of the plant without becoming detached
Inrolled leaf or petal – with the margins rolled inwards (involute)
Insectivorous – plants deriving (part of) their nutrition from insects they have captured; antiquated term now replaced by ‘carnivorous’, indicating that these plants do not only capture insects, but other animals as well
Inserted – placed in
Intectate pollen grain – without a tectum yet with sculpturing
Integument – the covering of an organ; the outer envelope of an ovule
Integumental tapetum – endothelium; one or several layers of radially elongated and metabolically very active cells in the inner epidermis of the inner (or single) integument; the integumental tapetum is separated from the adjacent megasporangium and megagametophyte by cuticular layers
Inter- – between
Intercalated – inserted, placed between
Intercarinal – between keels or ridges
Intercolpate (of pollen grains) – present between colpi
Intercolpium – see Mesocolpium
Interfascicular cambium – present between the vascular bundles; together with the fascicular cambium developing into an annular cambium during the growth of the stem; the annular cambium produces a cylinder of secondary phloem towards the cortex and secondary xylem inwards
Interfascicular wood rays – present between the vascular bundles
Interlocular – in between the locules of the ovary
Internal phloem – primary phloem present adaxially or internally to the xylem
Internode – the part of the stem between two nodes
Interpetiolar – present between the petioles of opposite leaves; characteristic of stipules in, e.g., Rubiaceae
Interpetiolar stipules – present between the petioles of opposite leaves
Interphyll – (Zingiberales); scale-like and sometimes membranous blade-less leaf (leaf-sheath) usually present on the second node of a unit branch of the shoots in, e.g., Marantaceae
Interspersed – scattered amongst
Interstaminal – present between the stamens
Interstice – (1) part, interval; usually referring to small air spaces; (2) (Araceae) a flowerless part on the spadix
Intertracheary pits (of vessel elements) – bordered or unbordered lateral pits present on the radial vessel walls, forming vessel-to-vessel contacts and often occurring in serial arrangement; intertracheary pits may be opposite, scalariform or alternating
Interxylary phloem – formed by a single internal cambium; the strands of interxylary phloem are intercalated into secondary xylem that has a distribution of vessels not related to the phloem
Intine (of pollen grains) – the innermost of the major layers of the pollen grain wall underlying the exine and bordering the surface of the cytoplasm
Intra- – on the inside of, within
Intracauline – arising from the cortical part of the stem (e.g. adventitious roots in Bromeliaceae)
Intragynoecial compitum – a tract of transmission tissue in the gynoecium which is common to all the carpels of the one flower and that allows pollen grains landing on any one stigma or part of a stigma to fertilize ovules in any carpel
Intrajugal vittae – (Apiaceae) intrajugal secretory canals, intrajugal oil ducts present in the primary ribs above the vascular bundles in the pericarp
Intraluminal columellae (of pollen grains) – columellae present within lumina in a semitectate exine
Intramarginal – within or near the margin
Intramarginal veins – veins present within or close to the leaf margin
Intrapetiolar – present between the petiole and the stem
Intrapetiolar stipules – stipules inserted between the petiole and the stem, i.a. in some Melianthaceae and Erythroxylaceae
Intrastaminal – inserted between stamens and ovary, or within the stamens
Intravaginal squamules (intravaginal scales) – (Alismatales) squamulae intravaginales, squamulae intraaxillares; two to numerous scale-, gland- or colleter-like non-vascularized trichomes present on the adaxial side of the leaf base (leaf axil); intravaginal squamules consist of usually two (sometimes more) layers and numerous cells, and secrete a protective mucilage
Intraxylary phloem – phloem present within the xylem/wood vessel bundle; formed at the margin between pith and primary xylem
Intricate branching – dense, tangled
Introrse anther – opening inwards, towards the centre of the flower
Intrusive – pushing or projecting into another organ
Intrusively parietal placentation – the placenta projects (sometimes deeply) into the ovary locule
Invaginated – enclosed in a sheath
Invagination – enclosing in a sheath
Invasive tapetum – the microsporocytes are in the centre of the anther locule and surrounded by layers of tapetal cells; the tapetal cells may invade the anther locule yet do not fuse; plasmodesmata do not develop at the microsporocyte stage (cf. amoeboid-periplasmodial tapetum); instead the cell walls break down successively in the tapetal cell layers and discharge protoplasm into the anther locule; the tapetum is not enclosed by a perispore membrane; the free microspores are surrounded by the tapetal protoplasm, which degenerates
Inverted vascular bundle – with the xylem outside and the phloem inside
Invested in – clothed in
Involucel – a secondary involucre around the parts of an inflorescence
Involucrate – with an involucre (a cluster of bracts)
Involucral bract – see Involucre
Involucre – a series of bracts, usually inserted close together and appressed, below or around a compact head of flowers (e.g. in Asteraceae)
Involute ptyxis – leaf margins rolled inwards and upwards towards the adaxial surface; frequently occurring in water plants having floating peltate or cordate lamina – Opposite: revolute
Iridaceous – shaped like an Iris leaf, i.e. sword-shaped (ensiform), narrow and acute
Iridescent – many-coloured, with rainbow sheen
Iridiform leaf – resembling an Iris, with a flat leaf the two folded halves of which are fused so that the vascular bundles point both ways
Irregular flower – the parts of the calyx or corolla are dissimilar in size or shape (i.e. asymmetrical or zygomorphic flowers)
Isobifacial leaf – with similar upper and lower surfaces
Isobilateral leaf – a flat leaf without any upper or lower surface
Isodiametric (i.a. of venation) – with an equal diameter in all directions
Isomerous – with the numbers of successive floral organs equal, such as sepals, petals and stamens
Isomorphic leaves – with all leaves on the plant of the same type – Opposite: anisomorphic leaves
Isostylous – see Homostylous
Isthmus – narrowed part connecting two wider parts