Transcript Plant Structures Leaves, Roots and Stem

Plant Structures
Leaves, Roots and Stems
Objectives
1. Describe the structure and function of leaves
2. Describe the structure and function of roots
3. Describe the function of stems
Classifying Plants
• Plants belong to Kingdom _____________
• Within this kingdom plants can be divided into
two major groups ___________ and ____
__________.
• Vascular plants can be further divided into two
major groups: Plants with seeds and plants
without seeds.
• Spermatophytes (seeded plants) can be divided
into two major groups: Naked seeds (pine cones)
and enclosed seeds (apple seeds)
Angiosperms
• Plants that produce
enclosed seeds.
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More divisions...
• Within the Angiosperms, there are two plant
classes, the Monocots and the Dicots.
Let’s look at some of the basic plant structures
more closely...
Leaves...
All leaves are responsible for:
• Absorbing the sun's rays
• The majority of photosynthetic production (which can
take place in any green part of a plant)
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Parts of the leaf
Blade:
Petiole:
Midrib and veins:
Photosynthesis
1. Leaves are the major site for photosynthesis
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Chlorophyll is found in organelles
called chloroplasts.
Photosynthesis is the process in
which carbon dioxide (CO2) and water
(H2O) are used to
produce carbohydrates and oxygen
(O2) in the presence of light and
chlorophyll.
Stomata
• Photosynthesis requires a constant supply of
carbon dioxide.
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Guard Cells
Stomata also regulates water loss.
• When stomata are open water is lost
(transpiration) and plant can exchange oxygen
for carbon dioxide.
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• Guard cells
Epidermal Cells
• Tightly packed in a single layer covered by a
waxy coating called the cuticle.
• Cuticle:
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Mesophyll
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1.
Located in the mid region of the leaf.
Primary site of photosynthesis in the leaf.
There are two types:
Palisade mesophyll (note how the cells are
shaped):
2. pongy mesophyll (note the irregularly shaped and
spaced cells):
Roots
Roots are responsible for:
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In a typical root we can distinguish the following
parts:
1. Primary root –
2. Secondary roots –
3. Root cap – a protective cap covering the
growing region of the root tip.
4. Root hairs –
Vascular System in Roots
• Located at the centre of each root.
• Vascular cylinder called a stele contains xylem
and phloem.
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Stems
Stems are responsible for:
•supporting leaves and flowers physically
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•using xylem and phloem to transport water and
nutrients to and from leaves, roots, and reproductive
parts like flowers, fruit and seeds.
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Stem Structure
• Herbaceous plants: Stems don’t contain wood
– Vascular bundles (arrangements of vascular tissue)
consists of xylem and phloem
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• Woody plants: Stems contain wood
– Vascular cambium:
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Major Tissues in Stems
Woody Stems (note: pith and cortex contain
parenchyma tissue)
More Stem Structures
• Bark: Protective outer layer.
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• Cork cambium: Layer between layers of bark
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