B3.1 Gas Exchange

stomata

small openings on the leaf surface that allow for gas exchange

guard cells

specialised cells that surround stomata and regulate their opening and closing to control gas exchange and minimise water loss

waxy cuticle

layer that reduces water loss while still allowing gas exchange through the stomata

stomatal density

number of stomata per unit area on the leaf surface

transpiration

loss of water vapor from stem and leaves of plants

potometer

device used for measuring the rate of water uptake of a plant shoot

palisade mesophyll

layer of vertically elongated, tightly packed cells located just below the upper epidermis

spongy mesophyll

lower, porous layer of tissue within a leaf, located below the palisade mesophyll

upper epidermis

topmost single layer of cells covering plant leaves that act as a protective barrier

lower epidermis

single layered, protective outer skin on the underside of plant leaves

air space

intercellular gaps that form through cell separation or death to facilitate gas exchange

pith

soft spongy tissue that functions in nutrient storage and transport within plants