Glossary - general

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Tangential bands (of axial parenchyma) – situated tangentially (close to) the vascular tissue

Tannin granules – hard dark brown granular inclusions found in some cells

Tapering – gradually narrowing

Tapetal – relating to tapetum

Tapetum – innermost layer of cells of the microsporangium (pollen sac) wall that nourish the developing pollen grains

Tap root – the primary root, going straight down

Tardily – slowly, reluctantly

Tectate pollen grain – provided with tectum

Tectum (of pollen grains) – tegillum; the layer of sexine, which forms a roof over the columellae, granules or other infratectal elements

Teeth (of dentate, serrate and crenate leaf margins) – small regular protuberances

Tegmen (of seed) – the inner coat of the seed, in bitegmic species formed from the inner integument; part of the seed coat which develops from the inner integument

Tegula – (Orchidaceae) a stalk to which the pollinia are attached; tegula is derived from the epidermis of the rostellum

Tendril – terminal slender coiling structure derived from branch, leaf or inflorescence, used in climbing

Tension wood – reaction wood in hardwood angiosperms; formed above the affected part of the plant, pulling against the strain; tension wood is composed almost entirely of cellulose (rendering the wood prone to shrinkage)

Tenuinucellar ovule, tenuinucellate ovule – with a thin megasporangium (nucellus with only an epidermal cell layer outside the meiocyte) up to megagametophyte formation; the archesporial cell develops directly into a megaspore cell without formation of a megasporangium; no parietal cells are present between the megagametophyte and the epidermis of the ovule – Opposite: crassinucellar

Tenuous – thin, narrowed, weak, fine

Tepal – division of the perianth, i.e. a sepal or petal, used especially when the distinction between petal and sepal is unclear

Tepal nectary – perigonal nectary; nectary situated on a tepal

Tepaloid stamen – a stamen with a shape similar to a tepal

Terete – circular in cross-section, usually of a cylindrical structure without grooves or ridges

Terminal – at apex of part under discussion; (of inflorescence) terminating the axis, as opposed to axillary

Ternate – (1) arranged in a whorl or cluster of three; (2) ternate-trifoliolate

Ternate-pinnate – when three pinnate leaflets are borne at the summit of the main petiole

Ternate-trifoliolate – with three leaflets attached to one point

Ternatisect (of a two dimensional structure) – divided in three almost to the base

Terrestrial – on land, i.e., not in water

Tertiary – (1) (adjective) third-order, one order down from secondary; (2) (noun) (pl. tertiaries, used in Araliaceae) lateral branches of the main branches

Tesselated surface – with markings in squares or rectangles

Tesselated venation – with a distinct midvein and numerous longitudinal and transverse secondary veins, forming a patterns of squares and rectangles

Testa (of seed) – the outer coat of the seed, in bitegmic species formed from the outer integument; part of the seed coat which develops from the outer integument

Testal – adjective for testa

Tetra- – four-

Tetracolpate pollen grain – with four colpi

Tetracyclic flower – with four whorls (series) of floral parts (sepals, petals and stamens)

Tetracytic stomata – surrounded by four subsidiary cells, two of which are parallel to and two (often smaller) at right angles to the long axis of the guard cells; guard cells surrounded by four regularly arranged subsidiary cells

Tetrad (of pollen grains) – group of four pollen grains formed from a single microsporocyte (pollen mother cell) that are released from the anther as one unit

Tetradynamous – with four long and two short stamens, as in many Brassicoideae

Tetragonal – with four angles in cross-section

Tetragonal tetrad – the cells (e.g. pollen grains) in the tetrad are equidistant and in one plane

Tetrahedral tetrad – the cells (i.a. pollen grains) in the tetrad are equidistant and at the four points of a tetrahedron

Tetrahedriform – shaped like a tetrahedron, with four faces; pyramidal

Tetramerous flower – with the constituent parts in whorls of four

Tetrasporangiate anther – four-celled; with four microsporangia

Tetrasporic megagametophyte – developing from all four megaspore nuclei from the megaspore tetrad

Textured – the way a structure feels to the touch

T-hair – T-shaped unicellular or multicellular hair (as seen from the side)

Thalloid – in the form of a thallus, a vegetative body without differentiation into stem and leaf (in, i.a., Podostemaceae)

Thallus – vegetative tissue, not clearly divided into stem and leaf (as in Lemna)

Theca (pl. thecae) – the locule(s), usually two, of an anther

Theoid leaf tooth – with the medial vein ending in an expanded and opaquely congested apex, not associated with lateral veins

Thorn – short pointed woody structure derived from a reduced branch

Throat (of tubular flowers) – (1) part where the corolla tube widens into the mouth; (2) the apical part of the corolla tube immediately below th mouth (in, e.g., Rubiaceae)

Thrum-eyed (of dimorphic flowers) – the short-styled flower with only the stamens visible in the corolla throat – Opposite: pin-eyed

Thyrse – (1) open inflorescence with a racemose primary branching and not terminated by a flower; a mixed inflorescence with the main axis a raceme and secondary (lateral) axes in the form of cymes; (2) a compact panicle of more or less cylindrical form

Thyrsoid inflorescence, thyrsiform inflorescence – closed inflorescence with a racemose primary branching and cymose secondary (lateral) axes and terminated by a flower;

Tile cells – radial files of dead, empty, erect cells in vascular rays, much narrower radially than the procumbent cells of the ray and interspersed among them; in the Durio type of tile cells the radial files of dead, empty, erect cells in vascular rays are about the same height as the procumbent cells of the ray; in the Pterospermum type of tile cells the radial files of dead, empty, erect cells in vascular rays are two to several times higher than the procumbent cells of the ray

Tilosome – (Orchidaceae) cell of innermost layer of velamen with complex, often lignified, wall processes bordering on passage cells of exodermis

Tomentellous – shortly tomentose

Tomentose – densely covered in short soft hairs, these somewhat curly and matted

Tomentulose – delicately tomentose, somewhat tomentose

Tomentum – a felt-like covering of downy hairs

Tooth – small pointed projection, usually triangular

Toroid (three-dimensional shape) – in the shape of a torus, a ring-shaped cylinder

Torulose – cylindrical with contractions or swellings at intervals

Torus – (1) a ring-shaped cylinder; (2) the receptacle of a flower; the term is usually employed when part of the receptacle is swollen into a distinct cushion, as in many Ochnaceae

Torus (of bordered pits) – a thickening of the primary wall material in the central part of the pit membrane inside the margo

Trabeculate – having the appearance of minute girders

Tracheary element – general term for any water-conducting cell in the xylem (e.g. tracheids and vessel members)

Tracheid – a capillary tube formed from a series of dead cells in the xylem, or a single such cell, water-conducting and fairly broad, in which at least the primary cell wall of the end walls remains intact

Tracheoidal tegmen – tegmen containing tracheary elements

Trailer – prostrate plant that does not root; also (less correctly) plant with long branches hanging down from trees

Trailing habit – prostrate on the ground, but without rooting

Transfer cells – metabolically very active companion cells with few plasmodesmata and numerous labyrinthine intrusions of the their walls; intermediary cells have numerous plasmodesmata which branch in the outer part of the cell walls adjacent to the bundle sheath cells

Transitional lateral wall pitting – a scalariform-like pattern in which some long pits extend the full width of a vessel face, whereas other pits are much shorter two or three pits replacing a long one

Translator – (Asclepiadoideae) the narrow connecting structure between pollinia, which is derived from stigmatic secretions connecting the corpusculum with the pollinia

Transseptal vascular bundles – the vascular bundles to the ovules in a completely syncarpous gynoecium, which do not run up the ovary in the axial tissue, but are found in the ovary wall, curving over at the apex and finally supplying the ovules

Transverse – (1) at right angles to another organ; (2) (of anthers) used for anther opening when the slits are at right angles to the longitudinal axis of the anther; also called explanate

Transversely – lying crosswise, at right angles

Trapeziform (of a plane shape) – with four sides, two of which are parallel

Tree – perennial woody plant with secondary thickening, with a clear main trunk; the distinction between tree and shrub is fluid, but generally accepted to be dependent on the single trunk, and on height, a tree being at least two or three metres tall

Triad – (1) (Poaceae) used for groups of three spikelets; (2) (Arecaceae) group of three florets, the central female, the flanking ones male; (3) (Amaranthaceae) a cluster of three flowwers, a fertile one flanked by two sterile ones

Triarch stele – with three xylem strands

Tricarinate – with three keels

Trichoblast – a specialized cell in the rhizoderm that develops into a root hair

Trichome – hair, bristle or scale

Trichome hydathode – specialized multicellular hairs, which secrete water from the plant

Trichosclereids – type of branched sclereid, with hair-like branches extending into intercellular spaces

Trichotomosulcate pollen grain – with a three-armed sulcus

Trichotomous – three-forked, branched into three

Tricolpate pollen grain – with three colpi

Tricolporate pollen grain – with three compound apertures with pores in furrows

Tricolporoidate pollen grain – with three colpi having indistinct ora

Tricuspidate – with three short sharp points

Tricytic stomata – the guard cells are surrounded by three subsidiary cells which resemble the normal epidermal cells

Trifid – split in three

Trifoliate – with three leaves

Trifoliolate – with three leaflets

Trigonous – obtusely three-angled

Triheterostylous species – with flowers of three types, having styles of three different lengths and often anthers on three different levels

Trilacunar node – with three leaf gaps left in the central vascular cylinder when corresponding numbers of leaf traces depart

Trilobate – with three lobes

Trimerous – in threes (e.g. of a flower with three sepals and three petals, etc.)

Trinucleate pollen grain – pollen grain containing three nuclei (cells), although the number of nuclei may vary among pollen grains of the same individual; trinucleate condition is often associated with gametophytic incompatibility systems

Trioecious – with male, female and hermaphrodite flowers on three separate plants

Tripartite – divided into three parts; consisting of three parts

Triplicate – in three

Triplostemonous androecium – with the number of stamens three times the number of tepals in the nearest perianth whorl

Triporate pollen grain – with three pores

Tripororate pollen grain – with three compound pores

Triquetrous – with three sharp angles

Triradiate – with three arms

Tristichous – arranged one above the other in three vertical rows

Trisulcate pollen grain – with three sulci

Tritegmic ovule – with three integuments (e.g. in Annonaceae)

Trizonocolpate pollen grain – having three colpi (groove-like apertures) aligned longitudinally, equidistant around the equator

Trochlea – (Passifloraceae) ring on the androgynophore

Trullate, trulliform – shaped like a brick-layers’ trowel

Truncate – ending abruptly in a more or less straight line, as if cut off

Trunk – the main axis of a tree, from the roots to where the crown branches; the base, plus the bole, plus the axis of the crown

Tuber – (1) a thickened branch of an underground stem, serving as storage organ, distinguished by bearing axillary buds (stem tuber); (2) a swollen root or branch of a root acting as a reserve store of nourishment or water (root tuber)

Tubercle – (1) a little tuber; used for any small growth (hypothetically) associated with symbiotic organisms; (2) a little protuberance

Tubercular – covered with knobbly or warty protuberances

Tuberculate – covered with wart-like protuberances or knobs

Tuberculate tectum (of pollen grains) – with knobbly projections

Tuberous root or stem – fleshy, swollen

Tubiform – shaped like a tube or cylinder

Tubular – cylindrical and hollow

Tubuliferopunctate tectum (of pollen grains) – with tubuli (small channels through the nexine)

Tuft domatia – resembling tufts of hairs, as in some Rubiaceae

Tufted – growing in right groups, e.g. of leafy stems, the bases of the individual plants touching; caespitose, clumped, tussocky

Tumid – inflated, swollen

Tunic – (1) coat of a bulb, consisting of dead leaf bases; (2) any loose membranous skin not formed by epidermis

Tunica (of root apex) – one or more outer layers which divide only anticlinally

Tunica-corpus construction – the apical meristematic region is differentiated into one or several outer peripheral layers, the tunica, with usually anticlinal cell divisions, and an inner cell mass, the corpus, with mostly periclinal cell divisions

Tunicated bulb – a bulb covered with complete enveloping coats, as in an onion

Turbinate – top-shaped, obconical and narrowed towards the apex (point)

Turgescent – becoming turgid on inflated

Turgid – swollen

Turion – (1) detachable vegetative buds; (2) a scaly sucker or shoot from the ground, as in Asparagus; (3) resting bud; bud resting during adverse season

Tussock – compact clump of grasses or grass-like plants

Tussock grass – grass growing in compact clumps

Twig – a small branch or shoot; more precisely, the current year’s shoot

Twiner (of a climber) – supporting itself by the stems (less often petiole or inflorescence) coiling around a structure or another plant

Twining plant or organ – coiling around a structure or another plant

Tyloses (of vascular tissue) – outgrowth from adjacent parenchymatous cells through a pit cavity in a vessel wall, more or less blocking the lumen