Biology / Unit 3 Bio 0581 short lesson, about 20 seconds
Leaf Structures: Mesophyll, Stomata, and Guard Cells
Captions available
The idea
Photosynthesis occurs mainly in the mesophyll, a leaf's chlorophyll-rich middle layer; gases exchange through pores called stomata, each controlled by a pair of guard cells.
In practice
Guard cells swell or shrink with osmotic changes to open or close a stoma, balancing gas exchange against water loss.
Where people slip
Stomata sit mainly on a leaf's underside to reduce water loss from the sun-facing upper surface.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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