a closer look at leaves ap biology spring 2011. leaf structure and function variation in leaf types:...
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A Closer Look at Leaves
AP BiologySpring 2011
Leaf Structure and FunctionVariation in leaf types:
Eudicot leaves:Simple: undivided, many lobed Compound: blades divided as leafletsThin, flat blade, which is attached to the stem
by means of a stalk, or petiole
Leaf Structure and FunctionMonocot leaves:
Flat blades, the base of which forms a sheath around the stem
Leaf Structure and FunctionEvergreens: pants that maintain their leaves
throughout the yearDeciduous plants: lose their leaves as
winter approaches
Leaf Structure and FunctionLeaves are adapted to local environmental
conditions Most plants orient their leaves perpendicular
to the suns rays to collect energy for photosynthesis
Plants growing in hot and dry regions orient their leaves parallel with the suns rays to conserve water and reduce heat absorption
Leaf Fine Structure Epidermis: covers all leaf surfaces May be smooth or covered with hairs, scales,
or other specializations Has small openings or stomata which allow
for gas exchangeWaxy cuticle covers epidermis to minimize
water loss
Leaf Fine Structure Mesophyll: photosynthetic parenchyma
Photosynthetic parenchyma cells (in mesophyll layer) are located between the extensive surface areas of the upper and lower epidermis
Leaf Fine Structure Mesophyll:
CO2 enters through stomata and diffuses through air spaces into the photosynthetic tissue
O2 byproduct is released from the plant
Leaf Fine Structure Mesophyll:
Dicots have two layers of mesophyllThe columnar and spongy parenchyma Monocots are not divided into two layers
Single layer
VeinsVeins: the leafs vascular bundles Form a network for water, solutes, and
photosynthetic productsEudicots: large veins branch into smaller one
embedded in the mesophyll Monocots: veins are similar in length and run
parallel with the leafs long axis