Transcript 23 Plant Structure and Function teacher ppt

Chapter 23 Plant Structure and
Function
Plant Tissue
Vascular Plants have four basic types of tissue
1.
2.
3.
4.
Vascular tissue
Ground tissue
Epidermis
Meristematic Tissue
Plant Tissue
Vascular Tissue
 Xylem – transports
water and minerals
 Phloem – transports
sugars
Ground tissue –
surrounds the
vascular tissue some
store water or sugars,
others lend support to
the plant
Epidermis – layer of
flattened cells secrete
the waxy cuticle
Meristems – regions of
actively dividing cells
found in ares that are
growing
ROOTS
 Roots - anchor plant to the ground
and absorb water and minerals.
Make up 1/3 of weight of a plant.
 Absorption actually takes place in
the root hairs. Increases the
surface area of a root.
 Growth of a root takes place in a
root cap by cell division.
 Some roots have specialized
functions like food or water
storage.
STEMS
 Shoots - made up of the stem and leaves. In some cases,
it also includes the flowers and fruits.
 Stems support the leaves so they can capture sunlight.
 Stems also connect the roots to the leaves and contain
the vascular tissue needed for transport of water and
minerals.
 Stems can be modified for storage.
LEAVES
 Leaves are the main sites for photosynthesis.
 Leaves contain chloroplasts which contain the
chlorophyll needed for photosynthesis.
LEAVES
 Thin and Flat –
advantageous for
photosynthesis
 Cuticle - leaves contain a
waxy outer layer that
prevents it from losing
too much water.
 Stomata – tiny pores that
allow carbon dioxide to
enter and water and
oxygen to exit
LEAVES
 Inside a leaf are


layers of photosynthetic
cells
Bundles of vascular
tissue (veins in leaves)


Xylem
Phloem
How Plants Function
 Transpiration - Water Movement in Plants

occurs in Xylem
 Translocation - Food Movement in Plants

Occurs in phloem
 Growth and Plants Hormones
 Other (Sunlight, Temperature, and Gravity)
Water Movement in Plants
 Water travels from
roots  trunk/stem 
leaves
 Travels to all the parts of the
plant through the xylem.
 Direct result of
Transpiration in Plants
Transpiration
 The loss of water vapor from a plant through
its stomata
 More than 90% of water entering plant passes
through plant and evaporates through the
stomata
Stomata and Transpiration
 Stomata Specialized pores
located in plant
cuticle that enables
plant to exchange
gases with the
atmosphere
Stomata and Transpiration
 Two guard cells
surround the
stomatal pore and
control the opening
and closing of the
stomata.
The Role of Stomata
 Gas Exchange:
 The plant must open stomatal pore during photosynthesis
to allow CO2 inside the plant and O2 out.
 Evaporation:

Helps cool the plant but sometimes the
transpiration is so rapid that the loss of water
begins to exceed the intake and the stomata may
close to prevent wilting.
Transpirational Pull
 As transpiration takes place, it creates a “pull or
tension” drawing water from the xylem and ultimately
from the soil
 When plants transpire, the water potential in cells
adjacent to the stomata drop because they lose water
into the atmosphere. This cause a chain reaction
which pulls water from other cells eventually pulling
water from the xylem, root, and soil.
Translocation
 The transport of
nutrients (food) formed
during photosynthesis
within the phloem to
all parts of the plant.
Flow of Materials in Plants
Leaves
Carbohydrates (food) produced via photosynthesis
Transpiration in the leaves causes the plant to lose water.
Phloem
Translocation occurs in phloem to move carbs to roots and stem
Xylem
Water moves upward to the leaves
Roots and Stem
Absorb water in the xylem
Plant Growth
 Primary Growth – Growth that lengthens

Meristems – region where plants grow using cell
division, this growth occurs in the tips of roots and
shoots and enable the plant to grow in length
 Secondary Growth - Growth that thickens

Woody plants (trees and shrubs) thicken by producing
xylem and phloem. Rings of a tree are layers of xylem
and phloem
Plant Hormones
Auxin - produced in the tips of stems, causes
cell walls to become more flexible

If a stimulus causes auxin to concentrate more on
one side of a stem, the cells on that side will
elongate. Thus, the stem grows toward light.
Plant Hormones
 Gibberellin
 Stimulate cell division,
elongation, and the sprouting
of seeds.
 Ethylene
 Stimulates fruit ripening.
Also promotes the dropping
of leaves, flowers, and fruits.
Other Factors - Tropism
• Photoperiodism – the
response of plants to
periods of light and dark
• Geotropism – response of
plant to gravity
• Helps plant determine which
way to grow roots.
• Thigmotropism – response
of plants to touch
• Helps climbing plants find
support structures