Glossary - general

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Pachycaul – thick-stemmed and sparsely branched; often used of bottle-shaped trunks – Opposite: leptocaul

Pachychalazal seed – the chalaza develops in all directions and builds by intercalary growth a new container for the endosperm and embryo; the wall of the container is usually highly vascularized

Palate – the projection on the lower corolla lip near the throat of many zygomorphic bilabiate flowers (i.a. in Lentibulariaceae)

Palea (pl. paleae) – (1) (Poaceae) one of the chaffy scales or thin colourless bracts amongst the flowers on the receptacle; (2) (Poaceae) the inner of the two bracts enclosing the floret

Paleaceous – chaffy, chaff-like in texture

Palinactinodromous venation – actinodromous, the primary veins with one or more subsidiary radiations above the primary one

Palisade – fence-like, with a horizontal row of vertical shapes

Palisade (of exo- or endotesta) – cells elongated, closely packed and erect, present especially in the mesophyll of leaves

Palmate – in lobed or compound leaves, when all lobes or leaflets originate from one central point, like the palm and fingers of the hand

Palmate venation – when the main veins or nerves of a leaf originate at one point and spread from there; with three or more primary veins arising from a common point (digitately reticulate venation)

Palmatifid – cut to a palmate form, the divisions reaching about the middle

Palmatilobate (of plane shapes) – lobed, the lobes radiating from a central point, like the fingers of a hand

Palmatipartite – lobed with the central lobe the largest, the lobes occupying more than half of the leaf

Palmatireticulate venation – reticulate venation with palmate main veins

Palmatisect – lobed, with the central lobe the largest, and the lobes almost extending to the base

Pandurate, panduriform – fiddle-shaped, i.e. oblong to elliptic but constricted at the mid-point

Panicle – a multiple compound botryoid with continuously decreasing flower numbers on the branches of the second order and continuously decreasing branching orders towards the apex of the inflorescence; an inflorescence in which the main axis has several lateral branches, each of which is several-flowered; more specifically, in which both the main axis and/or lateral branches are indeterminate (i.e. racemose or monopodial, not terminated by a flower)

Paniculate – with inflorescence a panicle

Pantoaperturate pollen grain – with apertures distributed over the surface and sometimes forming a regular pattern

Papilionaceous – shaped like a pea-flower, with a large posterior petal (vexillum), two lateral petals (alae), and two anterior often connate petals (carina)

Papillae – soft small protuberances

Papillate – with papillae, with soft small protuberances

Papillose – bearing many small nipple-like projections

Papillulose – with minute nipple-like projections

Pappus – a series of bristles, hairs or scales surrounding the corolla base and later the fruit apex (e.g. in Asteraceae)

Papulose – with pimples or small pustules

Papyraceous – papery; with the thickness or consistency of paper

Parabolic leaf – ovate-oblong or ovate, obtuse and contracting below the apex

Paracarpous – the carpels of a syncarpous gynoecium are congenitally fused only by their margins and the placentation is parietal

Paracladia – subsidiary branches following the pattern of main branches

Paracytic stomata – stoma on each side with one or more subsidiary cells parallel with the guard cells and the longitudinal axis of the pore; with two subsidiary cells surrounding and parallel to the guard cells

Parallel venation – all veins running in the same direction at fairly close intervals; with veins extending from base to apex, essentially parallel

Parallelocytic stomata – allelocytic stomata with an alternating complex of three or more C-shaped subsidiary cells of graded sizes parallel to guard cells

Parallelodromous venation – with two or more primary veins originating beside one another at the lamina base and running more or less parallel to the apex where they converge

Parastichy – a spiral linking primordia by some constant in their order of development

Paratact – (irregularly) helical aestivation where the innermost segment is immediately adjacent to the outermost segment

Paratracheal parenchyma – axial parenchyma associated with vessels or vascular tracheids

Parenchyma – soft tissue, consisting of cells with thin unlignified primary walls and with retained cytoplasm

Parietal cell – the cell or cells which are cut off from the archesporial cell(s) prior to meiosis and which form part of the megasporangium of the ovule and the endothecium of the anther

Parietal placentation – the ovules are attached to the inner surface of the outer wall of a usually unilocular syncarpous ovary; the ovules are situated along the sutures in a paracarpous gynoecium or on the intrusive placentae which in their turn are attached to the sutures

Parietal tapetum – see Secretory tapetum

Paripinnate – evenly pinnate, terminated by a pair of opposite leaflets

Partial inflorescence – primary branches of an inflorescence (i.a. in Cyperaceae)

Partite – cleft, but not quite to the base

Patelliform – shallowly disc-shaped, like a knee-cap

Patelloid – circular with a rim

Patent – spreading, held at 90o from the subtending axis

Paxillate veins – the areoles of the venation are present in orientated fields and often appear as if laid down by a series of brush strokes

Pearl body – see Pearl gland

Pearl gland – pearl body; small multicellular spherical short-stalked and dehiscent gland with an apical stoma; pearl glands probably function as food bodies

Pectinate – like a comb, with very close narrow and parallel divisions

Pedate – resembling palmate, but the side divisions further divided successively, one from the other, thus not all arising from the same point

Pedate venation – with the lateral veins once or several times divided

Pedate-laciniate – minutely dissected at the margin with the narrow lobes almost free, but joined at the base

Pedatilobed – side lobes lobed, i.e. divided but not to the midrib; see also Pedate

Pedatipartite – with pedate division, the lobes almost free

Pedatisect – lateral lobes divided almost to the midrib

Pedicel – the stalk of an individual flower in an inflorescence

Pedicellate flower – with a pedicel (stalk)

Peduncle – (1) the lower unbranched common part or stalk of an inflorescence, as distinct from the rachis; the branches are called first order branch (or partial-peduncle), second order branches etc., and the main axis above the peduncle called peduncle or rachis; (2) the general name for a flower stalk bearing either a solitary flower or a cluster, or the common stalk of several pedicellate or sessile flowers

Pedunculate inflorescence – with a stalk

Peel (of an outer layer) – to detach in flexible strips or sheets

Peeling – coming away in strips

Peg (of cystoliths) – cellulose expansion of the cell wall, which is covered with crystals

Pellucid – translucent, not quite transparent but with some light passing through when held up to the light (e.g. of gland dots in leaves of Rutaceae)

Pellucid-punctate lamina – with whitish dots through which some light penetrates

Peloric flower – actinomorphic monstrosity of normally zygomorphic flower

Peltate – round and attached in or near the centre; of a leaf, with the petiole attached to the blade, away from the margin

Peltate leaf – with the petiole attached to (the middle of) the abaxial surface; the vasculature is strictly annular or the vascular bundles form a circle

Pendant – hanging

Pendulous ovule – hanging

Penicillate – (1) with a tuft of hairs at the end; (2) pencil-shaped, i.e. long and narrow

Penniform venation – with the veins in a pinnate pattern, i.e. branching off from the midrib at intervals at an angle

Penninerved – see Penniform venation

Penni-parallel venation – with veins extending from midrib to margins, essentially parallel

Pentacolpodiorate pollen grain – with five compound apertures each with two pores in furrows

Pentacyclic, 5-merous, pentamerous floral unit – with the parts in fives

Pentagonal, pentagonous – with five angles

Pentalacunary node – with five leaf gaps

Pentamerous flower – with its constituent parts in five and/or in multiples of five

Pentarch stele – with five xylem strands

Pentatomosulcate pollen grain – with a five-armed sulcus

Pepo (fruit type) – gourd fruit in Cucurbitaceae, berry-like but with a hard rind (exocarp) and parietal placentation

Peponiform – shaped like a pepo, resembling a pepo

Per- – very, intensifying prefix in Latin compounds, e.g. in per-similis, very alike

Percurrent – running through the entire length

Perennate – to last throughout the year or from one season to the next; self-renewing by lateral shoots from the base

Perennating – surviving the most difficult season (e.g. the dry or cold season), lasting the whole year through or from one season to the next

Perennial – living for several to many years; as opposed to annual or biennial; usually restricted to non-woody plants

Perfoliate – when the stem passes through the blade of a leaf or through a basally connate pair of leaves

Perforate pollen grain – tectum punctured by numerous holes less than 1 µm in diameter

Perforation plates (of vessel elements) – perforations; openings at the ends of the vessel element which connect the individual elements; the perforation plates may be simple (with a simple opening), scalariform (with several to numerous elongated openings on top of each other in a ladder-like arrangement), foraminate (with several round openings) or reticulate (with numerous openings forming a net-like pattern)

Pergamaceous, pergamentaceous endocarp – like parchment or thick paper

Perianth – collective term for the sepals and corolla, or for the tepals

Perianth tube – the lower united part of the perianth

Periblast – a disc- or umbrella-like expansion of the collar

Pericarp – (1) the wall of the ripened ovary; divisible into exocarp (epicarp), mesocarp and endocarp when a distinction between the three can be made; fruit wall; (2) the fleshy layer (united ectocarp and mesocarp) surrounding the stony endocarp in, e.g., Commiphora

Perichalazal seed – the chalaza is extended in the median plane; a perichalaza surrounds the megasporangium as a hoop or band

Pericladium – the sheathing leaf base expands and surrounds the supporting branch

Periclinal cell walls – parallel to the surface

Pericolpate pollen grain – see Pantocolpate

Pericycle – the outermost, often parenchymatous (in the root) or sclerenchymatous (in the stem) cell layer of the stele, situated immediately beneath the endodermis

Periderm – loosely synonymous with the bark of a tree; consisting of the cork or bark cambium, the phellogen – see Phellogen

Perigone – term used for perianth in monocots, as the origin is unclear (might be derived from bracteoles rather than tepals)

Perigonial hairs – (Typhaceae) hairs deriving from the perigonium

Perigonial nectary – see Tepal nectary

Perigonial tube – a tube formed by the perianth parts

Perigoniate – adjective of perigone

Perigonium – (Typhaceae) perianth

Perigynous – when the sepals, petals and stamens are carried up around the ovary on a hypanthium

Peripheral – on the edge

Periphery – outside edge

Periplasmodial tapetum – see Amoeboid-periplasmodial tapetum

Periporate pollen grain – see Pantoporate

Perisperm – food storage tissue of seeds in some clades; the perisperm is usually formed from the megasporangium (or some similar or adjacent tissue), i.e. the layer outside the endosperm; the perisperm usually contains starch as a reserve (rarely oil or proteins)

Perivascular sclerenchyma – pericyclic sclerenchyma; the sclerenchyma is situated along the outer periphery of the vascular cylinder (and not originating in the phloem)

Perpendicular – at right angles to the axis of its attachment

Perreticulate tectum (of pollen grains) – structural elements fused distally and forming an open reticulum

Persistent – remaining in place, not falling off – Opposite: caducous, deciduous

Pertectate pollen grain – eutectate; with a continuous tectum

Perula (pl. perulae) – scale on a leaf bud

Perulate bud – vegetative bud covered by scales

Petal – a single free unit of a completely divided corolla or second floral whorl

Petaliferous – bearing petals

Petaline – referring to the petals

Petaloid – formed/coloured like a petal; (of stamens) without filament/anther distinction, but like a petal with marginal microsporangia

Petasus – the degenerated antipodal cells of the megagametophyte, which persist as a chalazal cap-like structure

Petiolate – with a petiole (leaf stalk), not sessile

Petiole – leaf stalk; the basal and usually narrowly cylindrical part of the leaf which carries the vascular bundles and is intermediate in position between stem and blade

Petioloid – resembling a petiole, but with thin strip of lamina running alongside midrib

Petiolule – stalk of individual leaflet in a compound leaf

Phalanges – bundles of stamens

Phanerocotylar germination – when the cotyledons are exposed and photosynthetic; in phanerocotylar seedlings the cotyledons are exposed and photosynthetic

Phanerophyte – with perennating buds on shoots well above ground

Phanomer – the elongated photosynthetic part of the cotyledonary hyperphyll of a monocot seedling

Phellogen – cork or bark cambium, from which is produced the phellem from the outer surface and the phelloderm from the inner surface

Phloem – the main tissue with nutrient-transporting function in vascular plants

Phloem pool – a transport pool comprising phloem intermediary cells and phloem sap

Phyllanthoid branching – (Phyllanthaceae) a special type of growth, in which the vertical stems bear deciduous, floriferous (flower-bearing), plagiotropic horizontal to oblique branches; the leaves on the vertical main stem are reduced to scales, cataphylls, whereas the leaves on the other stems and branches have a normal development

Phyllaries – (Asteraceae) the bracts surrounding the capitulum; constituent bracts of involucre

Phylloclade – portion of stem or branch (several nodes and internodes) flattened and expanded to serve the functions of a leaf

Phyllode, phyllodium – a laterally flattened photosynthetic blade derived from the petiole

Phyllodic leaf base – petiole taking on the functions of a leaf: flattened and leaf-like

Phyllotaxy – arrangement of leaves on the axis

Phytomelan – inert C-rich black carbonaceous substance without nitrogen, probably derived from catechol; phytomelan forms a crust-like covering of some seeds (in, e.g., Asparagales)

Pigmented – coloured

Pilate tectum (of pollen grains) – with pila

Pileiform – shaped like a cap

Pileus – cap-shaped; in Pandanaceae fruits, a more or less free stigmatic remnant

Pilose – hairy with rather long, patent, simple hairs; close to villous/villose

Pilot roots – (Hydnoraceae) rhizome-like fleshy succulent roots, which are the main vegetative component of the parasite and may play an important role in water relations in the dry environment of the plants; osmosis from the pilot roots may cause the surrounding soil to become somewhat more moist, thereby stimulating growth of nearby host roots toward the Hydnora pilot roots; haustorial roots differentiate on the ridges of the pentagonal pilot roots and make contact with the host roots

Pilum (of pollen grains) – a sexine element, usually standing directly on the nexine and consisting of a rod-like part (columella) and an expanded apical part (caput)

Pin-eyed (of dimorphic flowers) – the long-styled flower with exserted style – Opposite: thrum-eyed

Pinna (pl. pinnae) – leaflet of a pinnate leaf, or first division of a pinnate leaf where this division is itself divided into leaflet

Pinnate, pennate – divided into a central axis and several lateral ribs of leaflets (like a feather)

Pinnately reticulate venation – with secondary veins arising from midrib or midvein

Pinnate venation – the secondary veins departing from the midvein along its length

Pinnatifid – pinnately lobed, the lobes shallow

Pinnatilobate – pinnately divided

Pinnatipartite – pinnately divided to about halfway

Pinnatisect – pinnately divided almost to the midrib

Pinnule – the leaflet of a bipinnate leaf, a second order pinna, the first order segment of a pinna

Piperad embryogenesis – the zygote undergoes a vertical or longitudinally orientated oblique division; the second division is also in the longitudinal plane, although at right angles to the plane of the earlier division resulting in four cells; transverse division may subsequently take place in these cells

Pistil – (1) in apocarpous flowers, used for the unit of separate carpel, style and stigma; (2) in syncarpous flowers, used for the whole gynoecium; (3) the female organ of a flower, consisting when complete of ovary, style and stigma

Pistillate – female; or flower with only female organs

Pistillodium, pistillode – a rudimentary, sterile gynoecium

Pith – see Medulla

Pithy – with spongy tissue

Pitted – with small depressions

Placenta – the part of the ovary to which the ovules or sedds are attached; sometimes raised or thickened

Placental intrusion – condyle; inward projection of the endocarp around which the seed is folded

Placenticidal capsule – see Septicidal capsule

Placentoid theca – an ingrowth of parenchymatous tissue into the microsporangia

Plagiotropic ovule – with the nucellar sagittal plane horizontal and the micropyle present toward the side of the carpel

Plagiotropic shoot – lateral branch, more or less horizontal or at an angle from the vertical; distinct from orthotropic, vertical

Plane – flat, level, even

Plano-convex – flat on one side, convex on the other

Plasmalemma – cell membrane

Plasmodial pseudo embryo sac – (Podostemaceae) a quadricellular megagametophyte develops from four nuclei, the micropylar quartet, in the apical portion of the megasporangium, whereas the basal megasporangial region gives rise to a ‘nucellar plasmodium’, also called a ‘pseudo-embryo sac’; antipodal cells are absent and double fertilization probably does not take place (the polar cell degenerates and no endosperm is formed); the nucellar plasmodium replaces the endosperm as a nutritive structure

Plasmodial tapetum – see Amoeboid-periplasmodial tapetum

Platanoid leaf tooth – with the medial secondary vein narrowing to the foraminate glandular apex, higher order laterals forming brochidodromous loops which converge at the apex yet do not join it

Pleated – with pleats, i.e. parallel folds; folded like a fan, along many ribs

Pleiomerous – with more whorls than the normal number

Pleonanthic stem – (Arecaceae) where flowering is not followed by death – Opposite: hapaxanthic

Pleurogram – seed areole (i.a. in Fabaceae)

Pleurotropous ovule – the micropyle points to the side (faces laterally); the raphe is either above (dorsal) or below (ventral)

Plicae (sing. plica) (of perianth) – folds

Plicate – with parallel folds, pleated longitudinally

Plicate carpel – a folded carpel; the usual type of carpel; the carpel primordium is initially U-shaped, and if no meristematic cross-zone (the area between the arms of the U) develops, the carpels are plicate – Opposite: ascidiate carpel

Plicate ptyxis – with parallel folds, pleated longitudinally, like a fan

Plumose – softly feathered; as bristles which have fine hairs or cell ends on each side, wider than the axis itself (when side hairs are much smaller)

Plumose stigma – feather-like

Plumule – plumula; the shoot bud of an embryo or a seedling, inserted above the cotyledon(s)

Plumulose – (Euphorbiaceae) a little plumose

Plurilobate – with many lobes

Plurilocular – with several locules

Pluriovulate placenta, carpel or ovary – with many ovules

Pluriseriate – having several rows

Pneumatophore – erect (breathing) root protruding above the soil, present especially in mangroves

Pod – a general term for a dry dehiscent fruit, including 1) a legume, formed of a single carpel; 2) a siliqua, two-celled and divided by a thin partition

Podium – small stalk or similar support

Poikilohydric – with the ability to sustain an equilibrium between the water contents in the cells and the environment

Polar area – see Apocolpium

Polar nuclei – the two nuclei in the centre of the central cell of the normal type megagametophyte, which fuse with each other and with one of the male gametes; this fusion results in the formation of the usually triploid primary endosperm nucleus

Pollen brush – (Faboideae) a dense aggregation of erect trichomes emanating entirely from the style, and functioning in secondary pollen display by transporting pollen grains from the dehisced anthers and exposing them to pollinators

Pollenkitt – a sticky oily material produced by the complete degeneration of the tapetum; the Pollenkitt covers the pollen grains and may hold these together during their dispersal also adhering the grain to the stigma; the Pollenkitt is rich in lipids and other pigmented substances

Pollen mass – pollen grains cohering into a single body (pollinium)

Pollen pump mechanism – secondary pollen presentation; the growing expanding style pushes the pollen through the anther tube, the pollen grains then becoming successively liberated through the apical pore of the tube

Pollen sac – the chamber of the stamen in which pollen grains are formed

Pollen tube – the germination tube emerging from a germinating pollen grain

Pollinarium (of flowers) – (Asclepiadoideae, Orchidaceae) the complete set of pollinia (in asclepiads) the corpusculum and translator arms, or (in Orchidaceae) viscidium or viscidium and stipe; when there are two viscidia, each half of the set might be termed a pollinarium

Pollinium (pl. pollinia) – pollen grains cohering into a single group and distributed as such (i.a. in Asclepiadoideae and Orchidaceae)

Polyad (of pollen) – group of more than four pollen grains

Polyandry – with numerous stamens in the androecium

Polyarch stele – with numerous xylem strands

Polycytic stomata – guard cells incompletely enclosed by a single subsidiary cell and surrounded by a number of additional adjacent epidermal cells

Polyderm – a layer which is produced by a lateral meristem formed within the pericycle; lamellae of paired concentric layers, consisting of endodermal and parencymatous cells, are cut off externally by the pericyclic meristem

Polyembryony – several or numerous embryos develop in each ovule – see also Adventitious embryony, Cleavage polyembryony and Simple polyembryony

Polyforate pollen grain – polyporate; with several pore-like apertures

Polygamodioecious – with functionally hermaphrodite as well as either male or female flowers

Polygamomonoecious – with functionally hermaphrodite as well as male and female flowers

Polygamous – with male, female and hermaphrodite flowers on the same or different plants

Polygonate – two dimensional shape with many corners

Polyhedral (of a three dimensional structure) – with many faces or sides

Polymorphic organ – with several forms, variable

Polymorphic stem – with more than two distinct morphological forms, either on a single plant or on different plants within the same species

Polypantoporate pollen grain – with numerous pore-like apertures distributed over the surface

Polypetalous flower – with the petals free from each other – Opposite: gamopetalous

Polyporate pollen grain – with several or numerous pore-like apertures

Polyrugate pollen grain – with several or numerous elongated to furrow-like globally distributed apertures

Polysepalous – (1) with many free sepals; (2) the opposite of gamosepalous

Polystele – with more than one vascular cylinder

Polystichous – when leves are borne in many series

Polysymmetrical – see Radially symmetrical

Polytelic inflorescence – with branches not terminating in a flower

Ponticulus – (Anacardiaceae) a type of placental obturator at base of funiculus

Porate pollen grain – with one or more simple apertures which are circular in surface view and have a length:width ratio of <2:1

Porcellanous – smooth, shiny, semi-transparent, white and thin, i.e. like porcelain

Pore – small hole; usually used of anthers, when these open by an apical hole, or of the outer wall structure of pollen grains

Poricidal anther dehiscence – porose; the anther opens by pores

Poricidal capsule – pore capsule; a capsule which dehisces (opens) by pores

Porogamy – the pollen tube penetrates and grows down the ovule through the micropyle before reaching the megagametophyte; the normal way

Pororate pollen grain – with one or more compound apertures in which both the inner and outer parts are circular in surface view

Porrect – pointing upwards at a slight angle from the vertical

Post-anthetic – after anthesis (flowering) is over

Posterior, posticous – at or towards the back, next to or towards the main axis – Opposite: anterior

Postgenital occlusion (of carpels) – the carpel margins are initially open and fusion takes place after the differentiation of the carpel; postgenital occlusion may take place directly through fusion of the tissue or indirectly by secretion of the cells of adjacent margins

Pouched – with bag-like hollow

Praemorse, premorse (of the apex of a plant shape) – ending abruptly, as if bitten off, i.e. with a ragged end

P-protein – a stringy protein in mature sieve elements that blocks sieve plate pores when the sieve tube is damaged; P-proteins are formed in the nucleus or elsewhere, and may be aggregated (non-dispersed) or non-aggregated (dispersed)

Precocious – appearing or developing early, often used of flowers which appear before the leaves

Prehensile – clasping, grasping

Prickle – a sharp outgrowth from the epidermis, detachable without tearing the organ

Primary – (1) (adjective) first, in order of development or sequence; (2) (noun; pl. primaries) first order branch

Primary leaf – the first leaf of an embryo or a seedling, which is present above the cotyledonary node

Primary phloem – phloem derived from an apical meristem

Primary meristem – arising in the tissue of the embryo and continuing its existence in the organ where it originated; apical meristem is a primary meristem present at the root and stem tips

Prismatic – shaped like a prism, a long solid with flat faces separated by angles; prism is an abundant crystal form (usually of calciumoxalate), either consisting of single cubical or tetrahedral crystals

Probract – (Cucurbitaceae) small, often glandular, foliar structures present at the base of the peduncle

Process – any small projecting part

Procumbent – leaning over or reclining, often to the extent of lying along the surface of the ground or over other vegetation but not rooting at the nodes

Produced – brought forward

Proembryo – a multicellular or globular stage between the zygote and the embryo

Profuse – with a great many, rich

Prolate – of a globose shape, drawn out towards the poles

Proleptic branch – a branch formed by development from an axillary bud primordium including a period of rest; the prophylls are usually basal

Proliferating antipodal cells – antipodal cells continuing to divide and multiply

Proliferation – production of off-shoots (lateral shoots for propagation)

Proliferous – with adventitious buds on the leaves or on the flowers (rarely roots), such buds being capable of rooting and forming separate plants

Prominent – jutting out beyond another organ

Prominulous – slightly prominent

Prophyll – the first leaf or two leaves formed along an axillary shoot; the bracteole(s) of an inflorescence or a flower

Prop root – root growing out of the lower stem or branch and into the soil; stilt root

Prosenchyma – a type of parenchyma consisting of elongated cells with tapering ends, occurring in supporting and conducting tissue; tissue of starch-containing parenchyma cells with walls lined with lignin

Prostelic – when an axis consists of a single concentric vascular bundle

Prostrate – lying flat

Protandrous flower – pollen is shed before the stigma is receptive, i.e. first functionally male and afterwards functionally female

Protein crystalloid (of sieve tube plastids) – one or more crystalloids of protein which are present in many sieve element nuclei and consist of densely packed parallel thin rodlets; after the nuclei disintegrate in the maturing sieve element the crystalloids are released into the cell lumen, where they persist intact

Proteoid roots – specialized superficial short lateral roots arising in dense groups and having limited growth

Proteranthous – producing an inflorescence after the leaves have fallen

Protocorm – (Orchidaceae) small corm structure formed during the early in germination and development and possessing a mycorrhiza

Protogynous flower – the stigma receptive before the anthrs open, i.e. first functionally female and afterwards functionally male

Protostele – with a solid central vascular column

Protoxylem – the early primary xylem tissue, which is produced by the procambium; the tracheary elements of the protoxylem have spiral or annular thickenings in their cell walls; the subsequently formed primary xylem is called metaxylem, the tracheary elements of which have continuously thickened cell walls with pits

Protracted – drawn out

Protuberant – bulging out

Proximal – nearest to the point of attachment, basal – Opposite: distal

Proximal cell (of trichoblast) – a protodermal cell divides asymmetrically and gives rise to a proximal trichoblast and a distal more vacuolate epidermal cell, an atrichoblast

Pruinose – covered with a waxy, frost-like powder or bloom, as in a plum

Pseudanthium (pl. pseudanthia) – an inflorescence consisting of several reduced flowers, the whole resembling a single flower (e.g. Euphorbia, Cornus and Asteraceae)

Pseudaril – resembling an aril but attached to an endocarp (which encloses the seed), not to the seed (e.g. in Commiphora)

Pseudo- – (1) seemingly (e.g. pseudo-axillary); (2) a prefix denoting a resemblance to another state or organ

Pseudo-aperture (of pollen grains) – a thinning of the exine which, although superficially resembling an aperture, is not associated with a thickening of the intine and is presumed not to function as an exitus (the site of exit of the pollen tube from the sporoderm)

Pseudo-axillary – seemingly (but not really) axillary

Pseudobulb (of storage organ) – resembling a bulb, but not homologous; a swollen internode or couple of internodes (i.a. in Orchidaceae)

Pseudo-capsule – dry dehiscent fruit which, on opening, discloses not seeds but one-seeded nutlets (e.g. in Commiphora)

Pseudocarp – a false fruit, consisting of ovary as well as other parts of the plant

Pseudo-cortex – a structure formed by basally expanded and sheathing petiole bases fused with the preceding internode; at the end of the growing season the sheath, petiole, and lamina are detached together, which is initiated by the formation of a periderm at the junction of the pseudocortex and the real cortex (e.g. in Greyia); the sheath-like structure is part of the stem and abscises together with the dilated leaf bases which partially encircle the nodes

Pseudo-crassinucellar ovule – megasporangium without a hypodermal cell layer outside the meiocyte; by periclinal divisions in the epidermis the meiocyte attains a deeper position – see Nucellar cap

Pseudo-fruit – false fruit; consisting of both ovary tissues and other parts of the flower and sometimes of the inflorescence

Pseudo-loculus – a locule-like cavity delimited by structures other than carpellary margins

Pseudo-monad (of pollen grains) – cryptotetrad; (Cyperaceae) a pseudomonad is formed, when three of the four pollen nuclei of the original tetrad degenerate, whereas a single nucleus completes the mitosis and forms the functioning pollen grain

Pseudo-monocyclic tepal whorl – having a false appearance of a monocyclic arrangement of the perianth parts

Pseudo-monomerous gynoecium – a syncarpous gynoecium seemingly consisting of a single carpel, yet in reality of two or more connate carpels all but one degenerate

Pseudo-monosporic megagametophyte – only one of the four megaspore nuclei contributes to the formation of the female gametophyte (a modified and reduced variation of the Drusa type, as in Limnanthaceae, or of the Allium type, as in Podostemaceae)

Pseudopetiole – petiole with adnate stipules alt. pulvinus (leaf base) directed away from the main axis of the stem (the stipules are adnate at this part of the stem and are seemingly adnate to the petiole)

Pseudopollen – (Orchidaceae) a powdery mass resembling pollen and present on the labellum of the flower in some orchid species; pseudopollen is formed by special (often moniliform) hairs

Pseudosamara – samaroid fruit; resembling a samara without being one

Pseudo-siphonostele – a type of eustele resembling a siphonostele

Pseudo-staminate – with pseudo-staminodia

Pseudo-staminodium – (Amaranthaceae) appendage between the filaments; pseudo-staminodia are not modified stamens

Pseudostem – ‘false’ stem consisting of leaf sheaths or leaf bases, the apical meristem remaining at ground level (i.a. in Zingiberales)

Pseudo-stipule – metastipule; stipule-like structure derived from leaf

Pseudo-syncarpous – apocarpous, with carpels strongly coherent (connivent) without being fused

Pseudo-uniseriate flower – with seemingly a single whorl of tepals, stamens etc.

Pseudo-verticillate – with spirally arranged leaves concentrated at the end of the branches, appearing like whorls

Psilate tectum (of pollen grains) – with a smooth surface, without sculpturing – Opposite: ornamented

Ptyxis – vernation; the way in which a leaf is folded in bud; the arrangement of bud scales or young leaves in a bud

Puberulent – minutely pubescent, the hairs hardly visible to the naked eye

Puberulous – shortly pubescent

Pubescent – covered with fine, short, soft hairs

Pulp – juicy or fleshy tissue of a fruit

Pulverulence – minute powdering

Pulverulent – as if sprinkled with powder

Pulvinate petiole – with a pulvinus, a swelling on the petiole (either proximal or distal, or both)

Pulviniform disc – (Simaroubaceae) cushion-shaped disc

Pulvinulus – swollen part of the leaflet stalk (petiolule)

Pulvinus (pl. pulvini) – swelling on the petiole (either proximal or distal, or both)

Puncta (sing. punctum) – small round dots or glands, or depressions

Punctate – dotted, marked with dots or translucent glands

Punctate tectum (of pollen grains) – scrobiculate tectum; with puncta (rounded or elongate tectal perforations, less than 1 µm in length or diameter)

Punctiform – shaped like a point or dot

Punctitegillate tectum (of pollen grains) – see Punctate tectum

Punctulate – marked with minute dots, depressions or glands

Pungent – ending in a rigid sharp point

Purpurescent – tinged with purple; turning purple

Pusticulate – with minute blisters

Pustulate – with slight elevations like pimples or blisters

Pustule – pimple, blister

Pustuliform – shaped like a blister

Putamen (pl. putamina) – the hard endocarp of a stone fruit, a hard layer around the seed; endocarp

Pyramidal – shaped like a pyramid, usually of inflorescences which are narrow proximally and widen out gradually, the distal part being more or less flat-topped

Pyrene (of fruit) – the stone, i.e. the seed plus a hard layer of the endocarp (often sculptured) surrounding the seed

Pyriform – pear-shaped, as the fruit of Pyrus communis

Pyrophyte – perennial plant growing in regularly burned areas, usually showing morphological and/or physiological adaptations; usually appearing after the annual fires and before the first rains

Pyrophytic – growing in regularly burned areas

Pyxidium (of capsular fruit) – pyxis; with circumscissile dehiscence

Pyxis – see Pyxidium