Editing Plant physiology (section)

==Aims==
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The field of plant physiology includes the study of all the internal activities of plants—those chemical and physical processes associated with [[life]] as they occur in plants.  This includes study at many levels of scale of size and time. At the smallest scale are [[molecule|molecular]] interactions of [[photosynthesis]] and internal [[diffusion]] of water, minerals, and nutrients.  At the largest scale are the processes of plant [[Developmental biology|development]], [[season]]ality, [[dormancy]], and [[reproductive]] control.  Major subdisciplines of plant physiology include [[phytochemistry]] (the study of the [[biochemistry]] of plants) and [[phytopathology]] (the study of [[disease]] in plants). The scope of plant physiology as a discipline may be divided into several major areas of research.

[[Image:Plant physiology.png|thumb|240px|Five key areas of study within plant physiology.]]
First, the study of [[phytochemistry]] (plant chemistry) is included within the domain of plant physiology.  To function and survive, plants produce a wide array of chemical compounds not found in other organisms.  [[Photosynthesis]] requires a large array of [[pigment]]s, [[enzyme]]s, and other compounds to function.  Because they cannot move, plants must also defend themselves chemically from [[herbivore]]s, [[pathogen]]s and competition from other plants.  They do this by producing [[toxin]]s and foul-tasting or smelling chemicals.  Other compounds defend plants against disease, permit survival during drought, and prepare plants for dormancy, while other compounds are used to attract [[pollinator]]s or herbivores to spread ripe seeds.

Secondly, plant physiology includes the study of biological and chemical processes of individual plant [[cell (biology)|cells]]. Plant cells have a number of features that distinguish them from cells of [[animal]]s, and which lead to major differences in the way that plant life behaves and responds differently from animal life.  For example, plant cells have a [[cell wall]] which maintains the shape of plant cells.  Plant cells also contain [[chlorophyll]], a chemical compound that interacts with [[light]] in a way that enables plants to manufacture their own nutrients rather than consuming other living things as animals do.

Thirdly, plant physiology deals with interactions between cells, [[tissue (biology)|tissues]], and organs within a plant.  Different cells and tissues are physically and chemically specialized to perform different functions.  [[Root]]s and [[rhizoid]]s function to anchor the plant and acquire minerals in the soil.  [[Leaf|Leaves]] catch light in order to manufacture nutrients. For both of these organs to remain living, minerals that the roots acquire must be transported to the leaves, and the nutrients manufactured in the leaves must be transported to the roots.  Plants have developed a number of ways to achieve this transport, such as [[vascular tissue]], and the functioning of the various modes of transport is studied by plant physiologists.

Fourthly, plant physiologists study the ways that plants control or regulate internal functions.  Like animals, plants produce chemicals called [[plant hormone|hormones]] which are produced in one part of the plant to signal cells in another part of the plant to respond.  Many [[flowering plant]]s bloom at the appropriate time because of light-sensitive compounds that respond to the length of the night, a phenomenon known as [[photoperiodism]].  The [[ripening]] of [[fruit]] and loss of leaves in the winter are controlled in part by the production of the gas [[Ethylene as a plant hormone|ethylene]] by the plant.

Finally, plant physiology includes the study of plant response to environmental conditions and their variation, a field known as [[#Environmental physiology|environmental physiology]].  Stress from water loss, changes in air chemistry, or crowding by other plants can lead to changes in the way a plant functions.  These changes may be affected by genetic, chemical, and physical factors.