internal leaf anatomy

waxy cuticle

S: transparent

F: allows light to reach mesothelioma cells for photosynthesis to occur

S: waterproof

F: reduces water loss via evaporation from leaf surfaces

upper/lower epidermis

• both layers consist of closely packed epidermal cells and produce the waxy cuticle

• upper epidermis does not have any chloroplast

• lower epidermis has chloroplasts only in the guard cells

stoma

• tiny openings formed by 2 guard cells, which allow for gaseous exchange to occur

• stoma size is controlled by guard cells

  • light present: guard cells open stoma

  • light absent: guard cells close stoma

palisade mesophyll layer

S: just under upper epidermis

F: receive as much sunlight as possible for photosynthesis

S: contains many chloroplasts

F: to increase rate of photosynthesis across the cells

S: long, cylindrical and vertically arranged

F: allows many palisade mesophyll cells to be closely packed together, increasing rate of photosynthesis carried out by this layer

spongy mesophyll layer

• fewer chloroplasts than palisade mesophyll cells

• consist of irregularly shaped cells that have large intercellular air spaces between cells, allowing for rapid diffusion of gases in and out of the mesophyll cells

intercellular air spaces

• mesophyll cells are coated with a thin film of moisture which allows carbon dioxide to dissolve in it before diffusing into mesophyll cells

• increases surface area to volume ratio for carbon dioxide and oxygen to quickly diffuse in and out of the mesophyll cells

vascular bundle

• phloem

  • carries manufactured food substances made by leaves too the rest of the plant

• xylem

  • brings water and mineral salts absorbed from the soil by the roots to the leaves for photosynthesis