Transcript roots, stems, and leaves

Roots, Stems, and Leaves
• The three main plant organs are roots, stems, and
leaves.
• These organs are made up of three main kinds of tissues:
– dermal tissue
– vascular tissue
– ground tissue.
Plant Tissues
• Dermal tissue –
– the “skin” of a
plant.
– protects the plant
and prevents water
loss.
Plant Tissues cont.
• Vascular tissue
– moves water and
nutrients throughout
the plant.
• Xylem tissue
– moves water.
– made up of
tracheids and
vessel elements.
• Phloem tissue
– moves sugars.
– consists of sieve
tube elements and
companion cells.
Plant Tissues cont.
• Ground tissue– all the cells that lie between dermal and vascular tissues.
– made up mostly of parenchyma cells.
• Parenchyma cells have thin cell walls and function in
photosynthesis and storage.
– Collenchyma and sclerenchyma
• These cells have thick cell walls that help support the plant.
Plant Tissues cont.
• Meristematic tissue– responsible for plant
growth.
– Produces new cells by
mitosis.
– Develop specialized
structures and functions
when mature in a process
called differentiation
– found at the tips of stems
and roots.
Roots
• 2 types of roots– Taproot : One big primary root + small secondary roots
– Fibrous root: Primary and secondary roots = same size
• Functions:
– anchor a plant in the ground.
– absorb water and dissolve nutrients from the soil.
• Root pressure forces water upward through the xylem toward
the stem.
Stems
• Functions:
– They produce leaves, branches, and flowers.
– They hold leaves up to the sunlight.
– They also carry water and nutrients between roots and leaves.
• Arrangement of tissues
– Monocots: vascular bundles are scattered
– Dicots : vascular bundles are arranged in a ring.
• These vascular bundles contain xylem and phloem tissue.
• Growth:
– Primary : grows longer
– Secondary: grows wider
Leaves
• main organs of
photosynthesis.
– make food (sugars)
– made up of a
specialized ground
tissue called mesophyll
cells.
• Mesophyll : many
chloroplasts responsible
for photosynthesis
• veins : Xylem and
phloem tissues
• Stomata: small
openings
– prevent water loss.
Transport in Plants
• Capillary action:
– Cohesion- forces between
water and water molecules
– Adhesion – forces between
water and other molecules
• Transpiration pull
– water moves from areas
where there is plenty of
water to areas where there
is little water.
• Pressure-flow
hypothesis
– explains how phloem
transport happens
• sugars move from areas
of high concentration to
areas of low
concentration.
Which part is responsible for photosynthesis?
D
C
B
A
If a plant becomes too dry, are the stomata in
the leaves more likely to be open or closed?
• Which tissue is found in the center of a
plant stem?
– A. dermal tissue
– B. vascular tissue
– C. ground tissue
• Which of the three kinds of ground
tissue serve mainly for storage?
– A.parenchyma
– B. collenchyma
– C. sclerenchyma
• Cells that can differentiate into many plant
tissues are found in
A. the vascular cylinder.
B. dermal tissue.
C.meristematic tissue.
• Photosynthetic tissues in a leaf include the
– A.phloem.
– B.vein.
– C.palisade mesophyll.
• A process in which water is lost through
the leaves of a plant is called
– A.transpiration.
– B.photosynthesis.
– C.glycolysis.