Transcript 21.4 Leaves TEKS 4B, 5B, 10B, 10C

21.4 Leaves
TEKS 4B, 5B, 10B, 10C
The student is expected to:
4B investigate and explain cellular processes,
including homeostasis, energy conversions,
transport of molecules, and
synthesis of new molecules;
5B examine specialized cells, including roots,
stems, and leaves of plants...;
10B describe the interactions that occur
among systems that perform the functions
of transport, reproduction, and response in
plants;
10C analyze the levels of organization in
biological systems and relate the levels to
each other and to the whole system
21.4 Leaves
TEKS 4B, 5B, 10B, 10C
KEY CONCEPT
Leaves absorb light and carry out photosynthesis.
21.4 Leaves
TEKS 4B, 5B, 10B, 10C
Most leaves share some similar structures.
• The blade is usually broad and
flat.
– collects sunlight for
photosynthesis
– connects to the stem by a
petiole
blade
petiole
21.4 Leaves
TEKS 4B, 5B, 10B, 10C
• Mesophyll is between the leaf’s dermal tissue layers.
cuticle
upper
epidermis
palisade
mesophyll
spongy
mesophyll
lower
epidermis
21.4 Leaves
TEKS 4B, 5B, 10B, 10C
• Guard cells surround each stoma.
– Stomata open and close when guard cells change
shape.
– When stomata are open, water evaporates and gas
exchanges.
– Stomata close at night and when plant loses too much
water.
guard cells
stoma
21.4 Leaves
TEKS 4B, 5B, 10B, 10C
• Leaves may be simple, compound, or double compound.
Simple leaf
Compound leaf
Double compound leaf
21.4 Leaves
TEKS 4B, 5B, 10B, 10C
• Leaf veins may be parallel or pinnate.
Parallel veins
Pinnate veins
21.4 Leaves
TEKS 4B, 5B, 10B, 10C
• Leaf margins may be toothed, entire, or lobed.
Toothed margin
Entire margin
Lobed margin
21.4 Leaves
TEKS 4B, 5B, 10B, 10C
Most leaves are specialized systems for photosynthesis.
• There are two types of mesophyll cells.
– both types contain chloroplasts
– palisade mesophyll absorbs sunlight
– spongy mesophyll connects to stomata
cuticle
upper
epidermis
palisade
mesophyll
xylem
spongy
mesophyll
phloem
lower
epidermis
stomata
21.4 Leaves
• Leaves have many adaptations.
– for extreme temperatures,
ex: pine needles
TEKS 4B, 5B, 10B, 10C
21.4 Leaves
• Leaves have many adaptations.
– for extreme temperatures,
ex: pine needles
– for water loss,
ex: cactus spines
TEKS 4B, 5B, 10B, 10C
21.4 Leaves
• Leaves have many adaptations.
– for extreme temperatures,
ex: pine needles
– for water loss,
ex: cactus spines
– for aquatic environments,
ex: water lily
TEKS 4B, 5B, 10B, 10C
21.4 Leaves
• Leaves have many adaptations.
– for extreme temperatures,
ex: pine needles
– for water loss,
ex: cactus spines
– for aquatic environments,
ex: water lily
– for getting food,
ex: Venus’ flytrap
TEKS 4B, 5B, 10B, 10C