Question: What do you call a pore, found in the epidermis of leaves, stems, and other organs, that facilitates gas exchange, is part of the soil-plant-atmosphere continuum (SPAC),  the name of the pathway for water moving from soil through plants to the atmosphere
Context: The epidermis (from the Greek "ἐπιδερμίς", meaning "over-skin") is a single layer of cells that covers the leaves, flowers, roots and stems of plants.  It forms a boundary between the plant and the external environment.  The epidermis serves several functions: it protects against water loss, regulates gas exchange, secretes metabolic compounds, and (especially in roots) absorbs water and mineral nutrients.  The epidermis of most leaves shows dorsoventral anatomy: the upper (adaxial) and lower (abaxial) surfaces have somewhat different construction and may serve different functions.  Woody stems and some other stem structures produce a secondary covering called the periderm that replaces the epidermis as the protective covering. A lenticel is a porous tissue consisting of cells with large intercellular spaces in the periderm of the secondarily thickened organs and the bark of woody stems and roots of dicotyledonous flowering plants.  It functions as a pore, providing a pathway for the direct exchange of gases between the internal tissues and atmosphere through the bark, which is otherwise impermeable to gases.  The name lenticel, pronounced with an s] , derives from its lenticular (lens-like) shape.  The shape of lenticels is one of the characteristics used for tree identification. Homoiohydry is the capacity of plants to regulate, or achieve homeostasis of, cell and tissue water content.  Homoiohydry evolved in land plants to a lesser or greater degree during their transition to land more than 500 million years ago, and is most highly developed in the vascular plants.  It is the consequence of a suite of morphological innovations and strategies that enable plant shoots exploring aerial environments to conserve water by internalising the gas exchange surfaces, enclosing them in a waterproof membrane and providing a variable aperture control mechanism, the stomatal guard cells, which regulate the rates of water transpiration and CO exchange.  In vascular plants, water is acquired from the soil by roots and transported via the xylem to aerial portions of the plant.  Water evaporation from the aerial surfaces of the plant is controlled by a waterproof covering of cuticle.  Gas exchange with the atmosphere is controlled by stomata, which can open and close to control water loss, and diffusion of carbon dioxide to the chloroplasts takes place in intercellular spaces between chlorenchyma cells in the stem or in the mesophyll tissue of the leaf. A stoma is a pore, found in the epidermis of leaves, stems, and other organs, that facilitates gas exchange. Guard cells are specialized cells in the epidermis of leaves, stems and other organs that are used to control gas exchange.  They are produced in pairs with a gap between them that forms a stomatal pore.  The stomatal pores are largest when water is freely available and the guard cells turgid, and closed when water availability is critically low and the guard cells become flaccid.  Photosynthesis depends on the diffusion of carbon dioxide (CO) from the air through the stomata into the mesophyll tissues.  Oxygen (O), produced as a byproduct of photosynthesis, exits the plant via the stomata.  When the stomata are open, water is lost by evaporation and must be replaced via the transpiration stream, with water taken up by the roots.  Plants must balance the amount of CO absorbed from the air with the water loss through the stomatal pores, and this is achieved by both active and passive control of guard cell turgor and stomatal pore size. An integrated fluorometer is a system that measures the light reaction and the dark reaction of photosynthesis.  Software allows combined operation of gas exchange measurement and chlorophyll fluorescence measurement of a leaf.  These parameters are used to non-destructively measure the photosynthetic efficiency of plants.  The use of an integrated chlorophyll fluorometer provides the opportunity to measure additional measuring parameters that allow for a more exact measurement of photosynthesis than with gas exchange alone.  Advanced gas exchange instrumentation, by itself, is capable of measuring A/Ci curves, commonly used for plant characterization.  “A” is the term for photosynthetic rate (rate of CO exchange in the leaf chamber), and Ci is Sub-stomatal CO concentration or intracellular CO level within the leaf.  When measured over a range of CO levels above and below ambient conditions, A/Ci curves become possible.  With the addition of an integrated chlorophyll fluorometer, it becomes possible to measure more accurate A/C curves, or photosynthetic rate at the site of carboxylation in chloroplasts.  The integrated fluorometer allows measurement of mesophyll conductance, or the opposite of the resistance to CO transfer from intracellular air spaces to the site of carboxylation in chloroplasts.  Various integrated chlorophyll fluorometer measuring protocols, such as the Laisk Protocol, the Kok protocol and the Yin Protocol are used to measure or estimate g or mesophyll conductance.  For example: the Laisk protocol allows the measurement of Γ* or compensation point, and R or respiration in the dark.  Both values are required to calculate g or mesophyll conductance and C or CO at the site of carboxylation.  Parameters typically measured by the gas exchange portion of the system include: “A” or photosynthetic rate, “gs” or stomatal conductance, “Ci” or sub stomatal CO concentration, and “E” or transpiration. The soil-plant-atmosphere continuum (SPAC) is the pathway for water moving from soil through plants to the atmosphere.  Continuum in the description highlights the continuous nature of water connection through the pathway.  The low water potential of the atmosphere, and relatively higher (i.e. less negative) water potential inside leaves, leads to a diffusion gradient across the stomatal pores of leaves, drawing water out of the leaves as vapour.  As water vapour transpires out of the leaf, further water molecules evaporate off the surface of mesophyll cells to replace the lost molecules since water in the air inside leaves is maintained at saturation vapour pressure.  Water lost at the surface of cells is replaced by water from the xylem, which due to the cohesion-tension properties of water in the xylem of plants pulls additional water molecules through the xylem from the roots toward the leaf. An alveolus (plural: alveoli, from Latin "alveolus", "little cavity") is a hollow cavity found in the lung parenchyma, and is the basic unit of respiration.  Lung alveoli are the ends of the respiratory tree, branching from either alveolar sacs or alveolar ducts, which like alveoli are both sites of gas exchange with the blood as well.  Alveoli are particular to mammalian lungs.  Different structures are involved in gas exchange in other vertebrates.  The alveolar membrane is the gas exchange surface.  Carbon dioxide rich blood is pumped from the rest of the body into the capillaries that surround the alveoli where, through diffusion, carbon dioxide is released and oxygen absorbed. In botany, a stoma (plural "stomata"), also called a stomate (plural "stomates") (from Greek στόμα, "mouth"), is a pore, found in the epidermis of leaves, stems, and other organs, that facilitates gas exchange.  The pore is bordered by a pair of specialized parenchyma cells known as guard cells that are responsible for regulating the size of the stomatal opening. Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. Water is necessary for plants but only a small amount of water taken up by the roots is used for growth and metabolism.  The remaining 97–99.5% is lost by transpiration and guttation.  Leaf surfaces are dotted with pores called stomata, and in most plants they are more numerous on the undersides of the foliage.  The stomata are bordered by guard cells and their stomatal accessory cells (together known as stomatal complex) that open and close the pore.  Transpiration occurs through the stomatal apertures, and can be thought of as a necessary "cost" associated with the opening of the stomata to allow the diffusion of carbon dioxide gas from the air for photosynthesis.  Transpiration also cools plants, changes osmotic pressure of cells, and enables mass flow of mineral nutrients and water from roots to shoots. Two major factors influence the rate of water flow from the soil to the roots: the hydraulic conductivity of the soil and the magnitude of the pressure gradient through the soil.  Both of these factors influence the rate of bulk flow of water moving from the roots to the stomatal pores in the leaves via the xylem.
Answer: stoma