1. Monocots vs.
Dicots

2. Plant Classification
• Plant bodies can be divided into two parts ROOTS
and SHOOTS
– Roots - below the ground
– Shoots – above the ground (ie. Stems, flowers and
leaves)
• Plants can be divided into two groups, based on
the structure of their roots and shoots:
a) Monocots
b) Dicots

3. Monocots
Grass
Onions
Orchids

4. Monocots vs. Dicots
• Type of angiosperms
• There are several differences between
monocots and dicots

5. Difference 1:
• Number of seed leaves (or cotyledon)
Monocots vs Dicots
One seed leaf Two seed

6. Difference 2:
• Vascular Bundles (transport vessels in plants)
Monocot vs. Dicot
Scattered throughout Arranged in ring
stem in stem

7. Difference 3:
• Flower Parts
Monocot vs. Dicot
Multiples of 3 Multiples of 4 or 5

8. Difference 4:
• Mature Leaves
Monocot vs. Dicot
Narrow leaves Broad leaves
Parallel veins Branching veins

9. Cross section of a
monocot leaf
Cross section of a
dicot leaf

10. Difference 5:
• Roots
Monocot vs. Dicot
Fibrous roots Taproot

11. Cross section
of a monocot
root
Cross
section of
a dicot root

13. Distributing Materials
Plants

14. Learning Goals
• Be aware that many plants have a
vascular system used to transport water
and nutrients.
• Be able to describe the purpose and
structure of xylem and phloem.
• Describe transpiration and translocation.

15. Distributing Materials
• Plant cells need water, oxygen, certain nutrients
and glucose just like animal cells.
Photosynthetic cells also need carbon dioxide
and sunlight.
• Small plants such as mosses and liverworts will
obtain all of these requirements by diffusion.
These plants are non-vascular.

16. Vascular Plants
• For large plants many cells are located
large distances from the source of the
nutrients they require and diffusion would
be inadequate.
• For example a plant obtains water and
many nutrients from the soil. The leaves
of trees are a long way away from the
roots. Root cells require glucose but are
very far from the leaves that produce it.
• Larger plants therefore have evolved a
transport system that moves such
materials around the plant.

17. Xylem and Phloem
• Plants have two transport systems:
– Xylem transports water and nutrients up the
plant from the soil
– Phloem transports sugars throughout the
plant
• Xylem and Phloem consist of tubular pathways
through which fluids flow through that are
continuous with the roots, stems and leaves.
• Xylem and Phloem together make up the
vascular system of plants.

18. Xylem and Phloem
• You can see the vascular system of many
plants: the “veins” in blades of grasses and
leaves and the stringy part of celery.
• The arrangement of xylem and phloem is
different in the various parts of a plant.

19. Vascular Tissue in the Root
• Within the root the vascular tissue is located in
the centre of the root and is known as the stele
• The stele is enclosed by the endodermis

20. Vascular Tissue in the Stem
• In the stem vascular tissue takes the form of bundles
in dicot plants.
• The xylem is located towards the inside of the stem
• The phloem is located towards the outside of the
stem

22. Vascular Tissue in the Leaves
• Vascular tissue in the leaves also takes the form
of bundles but these bundles run across the leaf
as “veins”
• Xylem forms the upper part of the bundle
• Phloem forms the lower part of the bundle

25. Xylem
• Xylem includes:
– Fibres: have thick walls which act as supporting tissue
– Parenchyma cells: living cells with thin walls that store
materials and also provide support. They are found
between the xylem vessels.
– Xylem vessels: cells arranged on top of each other that
form a column. The sides of these cells are thickened with
lignen. These cells die and loose their nucleus and
cytoplasm as well as their end walls becoming one long
tube.
– Tracheids: long dead cells that have tapered ends. The
end walls of these cells are not fully disintegrated so the
ends of these cells form “pits”. Water passes from one
“pit” to the next.

27. Xylem
• The tracheids of xylem can appear to have
spirals due to the lignin. This lignin can
form in different ways to form different
patterns.

28. Phloem
• Phloem consists of:
– Sieve tubes: consist of many cells arranged above
each other to form a tube. These cells are alive and
their end walls are perforated forming a “sieve
plate”
– Companion cells: living cells that sit alongside the
sieve tube cells. Involved in moving sugars into and
out of the sieve tube cells. These cells are linked to
the sieve cells by plasmodesmata (strands of the
cytoplasm).
– Phloem also has parenchymal cells and support
fibres.

32. Transpiration
• Transpiration (loss of water from the leaves)
drives the upward movement of xylem “sap”
• As water is cohesive (sticks together) therefore
the removal of water from the surface of the
leaves draws water from the xylem vessels to
replace this water. This in turn draws water from
xylem vessels in the stem and eventually the
roots causing net upward movement of water.

34. Translocation
• Translocation is the movement of organic
compounds produced by the plant such as
carbohydrates and amino acids.
• Translocation occurs through the phloem.
• Translocation occurs downwards as roots are often
“sinks” for storing carbohydrates.
• Translocation can also occur upwards as new shoots
and growth will need a supply of carbs.
• Translocation is an active process requiring energy.

35. Translocation
• Movement of fluids through phloem occurs due to
pressure gradients.
• Pressure will build up in a area in which a
material is being actively pumped into the sieve
tubes. It will be decreased in the area at which
this material is being used.
• This difference in pressure will cause the net
movement of material to the place that it is
required.