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Phenotypic plasticity When organisms with the same genotype display different
phenotypes in response to different environmental conditions.
Phenotyping The process of determining or measuring an organism’s phenotype,
often involving automated sensors or imaging systems (proximal remote sensing) and computing power (e.g., high-throughput phenotyping).
Phloem The vascular tissue that conducts sugars and metabolites between organs
in the plant. The tissue is composed of several types of specialized cells for conducting, support, or regulation and other control functions.
Photochemical reflectance index (PRI) A narrowband normalized difference
index, typically using a band at or near 531 nm (that responds to changes in
the relative amounts of xanthophyll cycle pigments), referenced to a band at
or near 570 nm that does not respond to these changes. Under some conditions
over short time periods (e.g., diurnally varying illumination), PRI can provide
an indicator of xanthophyll cycle activity and changing photosynthetic light-use
efficiency. Under longer (seasonal) periods or across individual plants within a
landscape, it is often correlated with the relative concentrations of chlorophylls
and carotenoids or the amount of green canopy material (e.g., leaf area index),
both of which can be indicative of relative photosynthetic activity.
Photogrammetry The discipline of making maps, Earth surface measurements,
or 3-D models from photographs.
Photon An elementary particle describing a quantum of electromagnetic radiation
(e.g., light) that is described by both particle and wave properties.
Photosynthetic capacity The maximum photosynthetic rate for a specific species under a set of environmental conditions, often defined as full sunlight,
optimal temperature, and ambient carbon dioxide concentration. Is often standardized to a specific temperature such as 25 °C for comparison among taxa.
For describing enzyme kinetic processes, is often broken down into the carboxylation (RuBisCO)-limited rate Vc max and maximum electron transport rate J .
Correlates strongly with leaf nitrogen, phosphorus, and specific leaf area (SLA).
Phycocyanins Accessory blue photosynthetic pigments found in cyanobacteria,
including those comprising potentially harmful algal blooms.
Phylogenetic diversity The evolutionary distances between species or individuals,
represented in terms of millions of years since divergence from a common ancestor or molecular distances based on accumulated mutations since divergence.
Phylogenetic clustering The tendency of close relatives to occur together in an
area (or within a community) more often than expected by chance.
Phylogenetic conservatism The tendency of close relatives to be more similar to
each other in traits or niches than expected by chance as a consequence of shared
ancestry.
Phylogenetic diversity (PD) The amount of evolutionary history represented by a
set of taxa: typically the total length of branches on a phylogenetic tree connecting them, though the number of speciation events is also sometimes used. See
also Faith’s phylogenetic diversity index.
Phylogenetic endemism The amount of evolutionary history (represented by the
amount of branch length, measured in a genealogy containing all species present
in an area) that is uniquely represented in that specific geographical location.
Glossary
Phenotypic plasticity When organisms with the same genotype display different
phenotypes in response to different environmental conditions.
Phenotyping The process of determining or measuring an organism’s phenotype,
often involving automated sensors or imaging systems (proximal remote sensing) and computing power (e.g., high-throughput phenotyping).
Phloem The vascular tissue that conducts sugars and metabolites between organs
in the plant. The tissue is composed of several types of specialized cells for conducting, support, or regulation and other control functions.
Photochemical reflectance index (PRI) A narrowband normalized difference
index, typically using a band at or near 531 nm (that responds to changes in
the relative amounts of xanthophyll cycle pigments), referenced to a band at
or near 570 nm that does not respond to these changes. Under some conditions
over short time periods (e.g., diurnally varying illumination), PRI can provide
an indicator of xanthophyll cycle activity and changing photosynthetic light-use
efficiency. Under longer (seasonal) periods or across individual plants within a
landscape, it is often correlated with the relative concentrations of chlorophylls
and carotenoids or the amount of green canopy material (e.g., leaf area index),
both of which can be indicative of relative photosynthetic activity.
Photogrammetry The discipline of making maps, Earth surface measurements,
or 3-D models from photographs.
Photon An elementary particle describing a quantum of electromagnetic radiation
(e.g., light) that is described by both particle and wave properties.
Photosynthetic capacity The maximum photosynthetic rate for a specific species under a set of environmental conditions, often defined as full sunlight,
optimal temperature, and ambient carbon dioxide concentration. Is often standardized to a specific temperature such as 25 °C for comparison among taxa.
For describing enzyme kinetic processes, is often broken down into the carboxylation (RuBisCO)-limited rate Vc max and maximum electron transport rate J .
Correlates strongly with leaf nitrogen, phosphorus, and specific leaf area (SLA).
Phycocyanins Accessory blue photosynthetic pigments found in cyanobacteria,
including those comprising potentially harmful algal blooms.
Phylogenetic diversity The evolutionary distances between species or individuals,
represented in terms of millions of years since divergence from a common ancestor or molecular distances based on accumulated mutations since divergence.
Phylogenetic clustering The tendency of close relatives to occur together in an
area (or within a community) more often than expected by chance.
Phylogenetic conservatism The tendency of close relatives to be more similar to
each other in traits or niches than expected by chance as a consequence of shared
ancestry.
Phylogenetic diversity (PD) The amount of evolutionary history represented by a
set of taxa: typically the total length of branches on a phylogenetic tree connecting them, though the number of speciation events is also sometimes used. See
also Faith’s phylogenetic diversity index.
Phylogenetic endemism The amount of evolutionary history (represented by the
amount of branch length, measured in a genealogy containing all species present
in an area) that is uniquely represented in that specific geographical location.
Glossary