PhytoplanktonSmall, often single-celled plants that live suspended in bodies of water.
phytoremediationThe use of plants actively to remove contaminants or pollutants from either soils (e.g. polluted fields) or water resources (e.g. polluted lakes).
phytostatApparatus designed for the semi-continuous chemostatic culture of plant cells.
phytosterolA plant-based compound that can compete with dietary cholesterol to be absorbed by the intestines, resulting in lower blood cholesterol levels.
PIBALPilot balloon. A small helium-filled meteorological balloon that is tracked as it rises through the atmosphere to determine how wind speed and direction…
PictographA design drawn in pigment upon an unprepared or ground rock surface.
PiezometerA nonpumping well, generally of small diameter, for measuring the elevation of a water table.
Piezometric Level (or Surface)Confined groundwater is usually under pressure because of the weight of the overburden and the hydrostatic head.
Piezometric surfaceThe surface at which water will stand in a series of piezometers.
PigAn air manifold having a number of pipes which distribute compressed air coming through a single large line.
pigmentA substance that gives color to tissue. Pigments are responsible for the color of skin, eyes, and hair.
PileRelatively slender structural element which is driven, or otherwise introduced, into the soil, usually for the purpose of providing vertical or lateral…
Pilot Balloon(Abbrev. PIBAL)- A small helium-filled meteorological balloon that is tracked as it rises through the atmosphere to determine how wind speed and direction…
Pilot Report(Abbrev. PIREP)- A report of inflight weather by an aircraft pilot or crew member.
Pilot scaleThe size of a system between the small laboratory model size (bench scale) and a full-size system.
PingoA large frost mound of more than one-year duration.
pinocytosisThe engulfing of a minute droplet of liquid by a living cell.
PioneeringThe first working over of rough or overgrown areas.
pipeA circular conduit constructed of any one of a number of materials that conveys water by gravity or under pressure.
Pipe trenchA temporary excavation in which pipe is placed and eventually covered with soil material.
pipetteWidely used device for accurate dispensing of small volumes of liquids.
PipingThe erosion of embankment or foundation material (soil) due to leakage. The action of water passing through or under an embankment dam and carrying with…
PIREPPilot Report. A report of inflight weather by an aircraft pilot or crew member.
pistilCentral organ of the flower, typically consisting of ovary, style and stigma. Usually referred to as the female part of a perfect flower.
PitAn area consisting of a number of gaming tables.
Pit run gravelNatural gravelly material taken from excavation. Gravelly material which is not processed.
Pitch ControlA method of controlling a wind turbine's speed by varying the orientation, or pitch, of the blades, and thereby altering its aerodynamics and efficiency.
PitchingFishing technique in which worms or jigs are dropped into cover at close range with an underhand pendulum motion using a long bait-casting rod, and…
PithouseA semi-subterranean dwelling with an excavated floor and earthen superstructure supported by posts and beams.
Pitot TubeA device for measuring the velocity of flowing water using the velocity head of the stream as an index of velocity.
Pivotal supplierA power supplier whose capacity must be used to meet peak demand and whose capacity exceeds the market’s supply margin.
Place-Based ManagementA conservation or management regime that includes a legally-defined area with greater conservation regulation or statutory law applying inside its…
PlacedTo put in a particular place or in a particular state.
PlacentaThe organ that nourishes the developing fetus in the uterus.
PlacerAn alluvial deposit of sand and gravel containing valuable minerals. (nps geo)
Placer miningThat form of mining in which the surficial detritus is washed for gold or other valuable minerals.
PlageIn solar-terrestrial terms, an extended emission feature of an active region that exists from the emergence of the first magnetic flux until the widely…
Plage CorridorIn solar-terrestrial terms, a space in chromospheric plage lacking plage intensity, coinciding with polarity inversion line.
PlagenilIn solar-terrestrial terms, spotless disc free of calcium plage.
PlainsAn extensive area that ranges from level to gently sloping or undulating.
PlanA benefit your employer, union or other group sponsor provides to you to pay for your health care services.
Plan Position IndicatorAn acronym for Plan Position Indicator. A PPI displays radar data horizontally using a map projection.
Planck TimeThe period of time immediately after the creation of the universe (10-43 s) during which quantum gravity is the principal phenomenon governing the…
Planetary Boundary LayerThe layer within the atmosphere between 1 km and the earth's surface where friction affects wind speed and wind direction.
Planetary boundary layer turbulence structureIn the Earth's atmosphere, the planetary boundary layer is the air layer near the ground that is affected by diurnal heat, moisture, or momentum transfer…
PlanktonCollectively, all organisms (plants and animals) suspended in the water which are not independent of water movements.
Plankton (planktonic)The aggregate of small plant and animal organisms that float or drift in fresh or salt water.
planktonic foraminiferaMarine zooplankton that passively float or weakly swim, and have calcium carbonate skeletons that are present in large numbers on the surface of the ocean.
Planned Unit Development (PUD)A real estate project in which individuals hold title to a residential lot and home while the common facilities are owned and maintained by a homeowners'…
PlanningThe process of setting development goals and policy, gathering and evaluating information, and developing alternatives for future actions based on the…
Planning basisGuidance concerning: (1) size of planning area (distance); (2) time dependence of releases; and (3) flood characteristics of releases.
Planning standard(s)Standards which emergency plans of the dam operating organization and local authorities should conform to.
PlantStation where mechanical, chemical, and/or nuclear energy is converted into electric energy.
Plant associationA grouping of plant species, or a plant community, that recurs across the landscape.
plant breeders' rights(Abbreviation: PBR). Legal protection of a new plant variety granted to the breeder or his successor in title.
plant cell immobilizationEntrapment of plant cells in gel matrices so that they are protected from physical damage.
Plant factorThe capacity factor of an entire generating facility including all available generating units. (See also capacity factor)
plant genetic resources(Abbreviation: PGR). The reproductive or vegetative propagating material of: 1.
plant growth regulatorAn organic compound, either natural or synthetic, and other than a nutrient, that modifies or controls one or more specific physiological processes within…
Plant-incorporated protectantsFormerly referred to as plant-pesticides, plant-incorporated protectants (PIPs) are substances that act like pesticides produced and used by a plant to…
Plant-use electricityThe electric energy used in the operation of a plant. This energy total is subtracted from the gross energy production of the plant; for reporting…
plantibodyAn antibody expressed transgenically in an engineered plant.
plantletA small rooted shoot regenerated from cell culture following embryogenesis or organogenesis.
plaqueA film of mucus that traps bacteria on the surface of the teeth. Plaque can be removed with daily brushing and flossing of teeth.
Plasma(PLAZ-muh) The clear, yellowish, fluid part of the blood that carries the blood cells. The proteins that form blood clots are in plasma.
plasma cellsAntibody-producing white blood cells derived from B lymphocyte s.
plasma membrane(PLAZ-muh MEM-brayn) The outer membrane of a cell.
plasmalemmaThe lipid bilayer and associated proteins and other molecules that surrounding the protoplast, within the cell wall.
PlasmidAn circular self-replicating non-chromosomal DNA molecule found in many bacteria, capable of transfer between bacterial cells of the same species, and…
Plasmid (p)A circular DNA molecule, capable of autonomous replication, which typically carries one or more genes encoding antibiotic resistance proteins.
plasmodesma(pl.: plasmodesmata) Fine protoplasmic thread that connects adjacent plant cells by passing through the plant cell wall.
plasmolysisShrinkage of protoplasm caused by removal of water from a cell through osmosis when surrounded by a hypertonic solution.
Plastic limitThe water content corresponding to an arbitrary limit between the plastic and the semisolid state of consistency of a soil; water content at which a soil…
PlasticityA phenomenon used to describe a cell that is capable of becoming a specialized cell type of different tissue.
Plasticity indexNumerical difference between the liquid limit and the plastic limit.
plastidA general term for a number of plant s which carry non-nuclear DNA. Includes the pigment -carrying bodies: 1. chloroplasts in leaves, 2.
plastoquinoneOne of a group of compounds involved in the transport of electrons as part of the process of photosynthesis.
plate1. Verb: to distribute a thin film of micro-organisms or plant cells onto a solid medium. 2. Noun: refers to the two segments of a Petri dish or similar.
PlateletsSmall, irregularly-shaped bodies in the blood that contain granules. These cells are important components of the blood coagulation (clotting) system.
platformA generic radar term, often used to encompass the pedestal and antenna assembly; sometimes including the radar control, display and analysis hardware and…