Bio Nutrients in Flowering Plants (leaf structures) (chapter 12)

network of veins

-carry water and mineral salts to the cells in the leaf blade

-carry manufactured food from the cells of the leaf to other parts of the plant

Lamina

1. large s.a. to v. ratio

-maximize absorption of sunlight

2. thin

provide short diffusion distance for CO2 to rapidly diffuse into the inner cells of the leaf

petiole (leaf stalk)

1. positions leaf

-maximize exposure to sunlight

Cuticle

1. waxy

-reduces water loss through evaporation from the leaf

-prevents the invasion of viruses and bacteria

2. transparent

-allows sunlight to reach the inner cells of the leaf

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Epidermis (upper and lower)

❓ single layer of closely packed cells covered on the outside by the cuticle

-no chloroplast

-⭐ protects the inner cells of the leaf

palisade mesophyll

1.long, cylindrical

2. nearest and 90° to the upper epidermis + closely packed together

-⭐allows more cells to be packed beneath the epidermis to capture maximum light energy for photosynthesis

3. largest no. of chlorophyll

-nearest to the surface, so most chloroplast

-⭐trap as much light energy as possible

spongy mesophyll

1.irregularly shaped, contains less chloroplast

2.⭐loosely packed, with large intercellular air spaces

-allows higher rate of diffusion of gases (CO2) into the leaf for a higher rate of photosynthesis

3. all mesophyll cells are covered with a thin film of moisture

-allows CO2 to dissolve and diffuse into the cell while O2 diffuses out simultaneously

3. contains vascular bundle

-xylem transports water to mesophyll cells

-phloem transports sucrose away from mesophyll cells

why are there large intercellular air spaces among the spongy mesophyll cells?

➡ allows for rapid diffusion of gases into and out of the cell

• Increased surface area in contact with air, more gases exchange

• Shorter diffusion distance

• Maintains a steep co centration gradient for constant exchange of gases