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Plant Systems
Part II
Plant Tissues
• A tissue is a group of cells working together to perform a
similar function.
– The cells in tissues are specialized to perform specific
functions.
– All these cells develop from unspecialized cells during
cellular differentiation
Recall: what were unspecialized cells called in animals?
Stem Cells!
• In plants, these cells are not called stem cells – they are called
meristematic cells
• A region of a plant that is rich in meristematic cells is called the
meristem region
Tissue Systems
• Plants have 3 major tissue
systems:
1. Dermal
•
Covers outer surface of plant
2. Vascular
•
•
Found in every root, shoot and
leaf
System is continuous (all plant
parts joined by vascular tissues)
3. Ground
•
All other tissues
Dermal Tissue System
Epidermal Tissue
Thin layer of cells
covering all non-woody
surfaces of a plant
Periderm Tissue
Tissues on the surface
of the plant that
produce bark on stems
and roots
Dermal Tissue System
Dermal Tissue System
Cells of the Dermal tissue system:
– Epidermal root cells have extensions (root hairs) to absorb
water and minerals
– Epidermal leaf cells produce a layer of wax to waterproof
surface
– Some have developed for defense purposes
Vascular Tissue System
• This is the transportation system that moves
water, minerals and other chemicals around
the plant
• All vascular tissues are connected
Vascular Tissue System
Xylem
Transports water and
dissolved minerals
from the roots to the
leaves and stems
Phloem
Transports dissolved
food materials and
hormones throughout
the plant
Vascular Tissue System
Vascular Tissue System
Xylem
– Transports water and dissolved
minerals upwards from the roots
– Cells are hollow tubes with rigid walls
• No cytoplasm, nucleus or organelles
(allows for easier transportation of water)
– MATURE xylem cells are not
considered living tissue
Vascular Tissue System
Phloem
– Transports sugars produced by
photosynthesis (and hormones)
– Phloem can move sugars downwards
from the leaves and stems or upwards
from the roots
– Phloem cells are alive when functioning
Ground Tissue System
• The ‘filler’ between dermal and vascular tissues
• Functions:
– In green parts of plant, they manufacture nutrients
via photosynthesis
– In stems, they provide storage and support
– In roots, they store carbohydrates
Photosynthesis – Tissues Working
Together
• Because sugar (glucose) is so important
to all components of a plant, it must
have a system in place to transport the
sugars
• Oxygen is also required by plant cells
(for cellular respiration)
– Leaves produce more O2 than is needed,
and any excess is released as waste
Recall: Plants and Food
- Since plants cannot move like animals do to obtain food,
they must make their own food through a process called
photosynthesis.
light energy + carbon dioxide + water  glucose + oxygen
glucose
Photosynthesis – Absorbing Light
light energy + carbon dioxide + water  glucose + oxygen
• Leaves that are wide and thin are
ideal for light absorption. Why?
– Greater SA
Remember: Photosynthesis occurs in chloroplasts
Photosynthesis – Absorbing Light
• Chloroplasts are contained
in the mesophyll layers
– Palisade mesophyll is
located where there is
maximum light
– Spongy mesophyll is
located throughout leaf with
air pockets in between
• Mesophyll layers as a
whole are part of ground
tissue system
Photosynthesis – Obtaining CO2
• CO2 will naturally diffuse
into a leaf. To avoid too
much diffusion, the leaf is
coated with a layer of
epidermal tissue called the
cuticle
• Gases enter and exit
through openings in the
leaf called stomata
• Stomata are controlled by
guard cells.
Photosynthesis – Obtaining Water
• Leaves will close their
stomata when water levels
are low
• Leaves obtain water
through vascular tissues
(xylem and phloem)
– Arranged as bundles called
vascular bundles and run
from root to leaf
– Root hairs (epidermal) grow
into soil from roots and
obtain water via diffusion
– Water is transferred via
xylem, from the roots to the
leaves
1. What is a tissue?
2. Name the three tissue types in plants and briefly
describe their function.
3. What is the difference between dermal and
periderm tissues?
4. Describe the difference between the xylem and
phloem.
5. What is the difference between the spongy and
palisade mesophyll?
6. How does the shape of a leaf help photosynthesis
take place?
7. What is a stomata? How do the guard cells open
and close?