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Glossary: P is for ... polygamous pioneer population.
by Ariadne Unst
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- palmate (adj.)
- Radiating from a single point like the spreading
fingers of an outstretched hand.
- Pangea (n.)
- The single continent formed 400 MYA from collision of the ancient continents
of Gondwanaland, Laurentia, and others.
- panicle (n.)
- A loose compound flower (inflorescence) produced by branching. The branches are
and the flowers have a
- parasite (n.)
- An organisms that lives on another (its host), from which it
obtains food and shelter. As the parasite depends upon the host, it usually
does not kill the host but harms it by causing the host to use some of its
resources to feed the parasite.
- parenchyma (n.)
- Soft cell tissue of plants. Found in stem pith and in pulp of some fruits.
- parsimony, principle of (n.)
- If two answers exist to a problem or a question, and if, for one answer to
be true, well-established laws of logic and science must be modified, ignored,
or suspended, while for the other answer to be true no such sleight-of-hand is
needed, then the simpler of the two answers (the second) is much more likely
to be correct. (parsimonious, adj.)
- pathogen (n.)
- An organism or substance that causes
Includes parasitic microorganisms (bacteria, viruses), fungi, and larger
parasitic plants and animals.
- peat (n.)
- Undecomposed or only slightly decomposed organic matter accumulated under
conditions of excess moisture. Semi-carbonized remains of plants (such as
moss, sedge, trees), some animal residues, and often some mineral soil. Plant
residues show little, if any, morphological change.
- pedicel (n.)
- The stalk supporting a single flower that is part of an
- pedocals (n.)
- Soils rich in calcium. Formed where water is scarce, so there is less
leaching of salts from the soils.
- peduncle (n.)
- The stalk of a flower cluster or of a solitary flower.
- perennial (n.)
- A plant that lives more than two years.
- perfect flower (n.)
- A flower having both stamens and carpels; may or may not have a
- perianth (n.)
- A collective term for the floral envelopes, usually the combined
corolla of a flower.
- pericarp (n.)
- The wall of a ripened ovary (fruit). It is homogeneous in some genera. In
others it is composed of three distinct layers,
- permafrost (n.)
- Permanently frozen ground; generally refers to a layer at some depth below
the soil surface. Persists over at least two consecutive winters and the
intervening summer. A layer above it, which thaws in summer, is the active
- pest (n.)
- Any species that is considered obnoxious (usually with regard to its
interference with human commercial and/or convenience interests).
- petal (n.)
- Part of the
one of a circle of modified
surrounding the reproductive organs and usually brightly colored.
- petiole (n.)
- The stem of a leaf; the leafstalk.
- phenotype (n.)
- The plant as observed. The product of the interaction of the genes of an
organism (the genotype) with the environment.
- phloem (n.)
- The layer of cells that forms a pipeline to carry sugars and other food
materials from the leaves (where they are produced) to the branches, roots,
and the rest of the tree. The cells produced on the outside of the cambium
become part of the phloem. Some of the phloem cells age and die each year, and
they become part of the outer bark.
- photosynthesis (n.)
- Chemical process in the cells of green plants, which form carbohydrates
and atmospheric oxygen from carbon dioxide and water, through sunlight acting
The chemical elements that are reorganized are carbon, oxygen, and hydrogen.
- phylogeny (n.)
- The history of the evolution
of a species or group. The evolutionary development and history of a species
or higher taxonomic grouping of organisms. Sometimes called a family
- phylum (n.)
- A division of plants and animals. It ranks below a kingdom
and above a class.
Its members are believed to have a common evolutionary ancestor. Also called
- pinnae (n.)
- Divisions (leaflets) of a compound leaf.
- pinnate (adj.)
- Like a feather; having the arrangement and shape of
a feather, with segments arranged feather-like on either side of a common axis.
- pioneer (n.)
- A species adapted to be a good invader of a newly exposed soil surface,
where it persists until supplanted by successor species.
Usually a pioneer plant has small, windblown seeds or other properties
that facilitate their distribution.
- pistil (n.)
- Ovule-bearing organ of an angiosperm
composed of ovary, style, and stigma.
- Pleistocene (n.)
- [Greek pleistos = most and kainos = new, recent.]
The time period from 1 MYA (million years ago) to
10,000 years ago.
During this time, glaciation advanced and retreated several times,
and man evolved physically and
- polyandrous (adj.)
- Plants bearing many stamens.
- polyanthous (adj.)
- Plants bearing many flowers.
- polycephalous (adj.)
- Plants bearing many flower heads
- polygamous (adj.)
- Plants bearing both perfect and imperfect
(unisexual and bisexual) flowers.
- polymorph (n.)
- One of several forms of an organism.
- population (n.)
- A group of interbreeding individuals of the same species; they are
separated but not isolated from other interbreeding groups of the same species.
- protein (n.)
- Any of the highly complex nitrogenous organic compounds. They are
synthesized by plants and are a chief component of living matter.
- proximal (adj.)
- Relatively near the central axis or the point of attachment.
- A subdivision of
that consists of ferns and their allies.
- pterocarpous (adj.)
- Having winged fruits.
- pterospermous (adj.)
- Having winged seeds.
- pubescence (n.)
- A growth of hair or fine down on plants.
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