page_title: Glossary of botanical terms
section_title: P
hierarchical_section_title: Glossary of botanical terms / P
caption_attribution_description: English: Knobs on bark of a Knobthorn tree at Zinyathi lodge, Steenbokpan, Limpopo
context_page_description: This glossary of botanical terms is a list of definitions of terms and concepts relevant to botany and plants in general. Terms of plant morphology are included here as well as at the more specific Glossary of plant morphology and Glossary of leaf morphology.
context_section_description: pachycaul
  with a disproportionately thick trunk
  pachycladous
  with disproportionately thick stems
  palea
  
  1. the upper of two bracts enclosing a grass flower, major contributors to chaff in harvested grain.
  2.  Chaffy scales on the receptacles of many Asteraceae.
  3.  Chaffy scales on the stipe of many ferns.
  paleate
  Bearing paleae or chaffy scales, as in description of the receptacle of a capitulum of a plant in the Asteraceae.
  paleaceous
  Chaff-like in texture.
  palmate
  1.  leaf with veins radiating out from a central point (usually at the top of a petiole), resembling spread out fingers pointing away from the palm.
  2.  A compound palmate leaf has leaflets that radiate from a central point (usually at the top of a petiole).
  palmatifid
  Deeply divided into several lobes arising from more or less the same level.
  palmatisect
  Intermediate between palmate and palmatifid, i.e. the segments are not fully separated at the base; often more or less digitate.
  panicle
   A compound raceme; an indeterminate inflorescence in which the flowers are borne on branches of the main axis or on further branches of these.
  papilionate
  Butterfly-like; having a corolla like that of a pea.
  papilla
   
  A small, elongated protuberance on the surface of an organ, usually an extension of one epidermal cell.
  pappus
  In daisy florets, a tuft or ring of hairs or scales borne above the ovary and outside the corolla (representing the reduced calyx); a tuft of hairs on a fruit.
  paraperigonium
  An anomalous secondary outgrowth of the perianthal meristem with ramifying vasculature. See also perigonium, perianth, and corona.
  parasite
  An organism living on or in a different organism, from which it derives nourishment. Some plant species are parasitic. Compare saprophyte and epiphyte.
  parenchyma
  A versatile ground tissue composed of living primary cells which performs a wide variety of structural and biochemical functions in plants.
  parietal
  Attached to the marginal walls of a structure, e.g. ovules attached to placentas on the wall of the ovary. See placentation.
  paripinnate
  Having an even number of leaflets (or pinnae), i.e. terminated by a pair of pinnae as opposed to a single pinna. Compare imparipinnate.
  parthenocarpy
  The development or production of fruit without fertilization. Compare stenospermocarpy.
  patent
  Spreading; standing at 45–50° to the axis. See also erecto-patent.
  patulous
  See patent.
  pauciflor
  Having few flowers per inflorescence. Compare pluriflor and uniflor.
  pectinate
  Pinnately divided with narrow segments closely set like the teeth of a comb.
  pedate
  Having a terminal lobe or leaflet, and on either side of it an axis curving outwards and backwards, bearing lobes or leaflets on the outer side of the curve.
  pedicel
  The stalk of a flower; may also be applied to the stalk of a capitulum in the Asteraceae.
  peduncle
  The stalk of an inflorescence.
  peltate
  Shield-like, with the stalk attached to the lower surface and not to the margin.
  pellucid
  Transmitting light; for example, said of tiny gland dots in the leaves of e.g. Myrtaceae and Rutaceae that are visible when held in front of a light.
  pendulous
  Hanging, for example an ovule attached to a placenta on the top of the ovary. Compare suspended.
  penicillate
  Tufted like an artist's brush; with long hairs towards one end.
  penninervation
  With pinnately arranged veins.
  pentamerous
  In five parts, particularly with respect to flowers, five parts in each whorl. See also trimerous and tetramerous.
  pepo
  A type of berry formed from an inferior ovary and containing many seeds, usually large with a tough outer skin (e.g. a pumpkin or cucumber).
  perennating
  Of an organ that survives vegetatively from season to season. A period of reduced activity between seasons is usual.
  perennial
  A plant whose life span extends over several years.
  perfect
  (of a flower) Bisexual; containing both male and female reproductive parts in the same inflorescence. Contrast imperfect.
  perfoliate
  With its base wrapped around the stem (so that the stem appears to pass through it), e.g. of leaves and bracts.
  perforate
  With many holes. Used to desc
caption: Like the so-called "thorns" on a rose stem, the sharp projections on the trunk of the "knobthorn", Senegalia nigrescens are prickles, botanically speaking
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