The document discusses transport processes in plants. It describes the functions of xylem and phloem tissues, which transport water and nutrients throughout the plant. Water and minerals are absorbed by root hairs through osmosis and active transport. Water moves up through the xylem vessels via transpiration pull. Transpiration is the evaporation of water from leaves, driven by factors like temperature, humidity and light intensity. The document also examines adaptations that reduce water loss through transpiration.

1. Transport in plants

2. LO:
• State the functions of xylem and phloem
• Identify the position of xylem and phloem as
seen in sections of roots, stems and leaves,
limited to non-woody dicotyledonous plants

3. • Identify root hair cells, as seen under the light
microscope, and state their functions
• State the pathway taken by water through
root, stem and leaf as root hair cell, root
cortex cells, xylem and mesophyll cells
• Investigate, using a suitable stain, the pathway
of water through the above ground parts of a
plant

4. • Explain that the large surface area of root
hairs increases the rate of the absorption of
water by osmosis and ions by active transport

5. Uptake of water and minerals
• Water– supports the plant
- reagent in many biochemical reactions
- transport medium
- by osmosis from the soil solution into the root cells
• Minerals – effect the water potential of plant tissues
– absorbed in the form of ions
– ion uptake depends on respiration (more oxygen = faster
absorbtion
– by diffusion or active transport

6. • https://www.youtube.com/watch?v=g7HbmU
nqGlM&t=85

7. Movement of water
Step 1: water loss from the leaves during
transpiration
Step 2: water crosses the membrane and
cytoplasm of cells of the endodermis
Step 3: water crosses the living cells of the
cortex either by osmosis or by suction
through the permeable cell walls
Step 4: water enters root hair cells by osmosis
(water moves down the a water potential
gradient)

8. Transport systems in plants
• Carried out by transport tissues:
– Xylem
grouped into vascular bundles
– Phloem

9. Xylem and phloem tissue

10. Root structure
- Root hairs are extended cells of
the epidermis
- Epidermis protects against
infection by fungi
- Cortex (pith) can act as a winter
store for starch
- Xylem and phloem form a strong
central rod

12. • https://www.twig-world.com/film/root-hairs-
4999/

13. Stem structure
• Vascular bundles in a ring with
soft cortex in the centre
• Cortex – turgid cells, suports
non-woody parts
• Epidermis protects against
viruses and bacteria

16. LO:
• State that water is transported from the roots to leaves
through the xylem vessels
• Define the term transpiration
• Explain how water vapour loss is related to the large
surface area of cell surfaces, interconnecting air spaces and
stomata
• Explain the mechanism by which water moves upwards in
the xylem in terms of a transpiration pull that draws up a
column of water molecules, held together by cohesion
• Explain how and why wilting occurs
• Explain the effects of variation of temperature and
humidity on transpiration rate

17. Transpiration
Loss of water vapour from plant leaves by
evaporation of water at the surfaces of the
mesophyll cells followed by diffusion of water
vapour through the stomata

18. = water movement through the plant – begins with the diffusion
of water vapour out of the leaf and evaporation from the leaf
surface (spongy mesophyll)
- 98% of the water taken up by a plant is lost to the
athmosphere by transpiration
• Evaporation
– From leaves
– Greatest loss of water through the stomata
- Is affected by:
- leaf structure may reduce transpiration(thick waxy cuticle, rolled
leaves, needle shaped leaves)
- conditions in the atmosphere (wind, high temperature, low humidity,
high light intensity)

19. • Wind moves humid air away from the leaf
surface and increases transpiration
• High temperature increase the water-holding
capacity of the air and increase transpiration
• Low humidity increases the water potential
gradient between leaf and atmosphere and
increases transpiration
• High light intensity causes stomata to open to
allow photosynthesis which allows
transpiration to occur

22. Translocation
- movement of sucrose and amino
acids in phloem;
- from regions of production to regions
of storage OR to regions of utilisation in
respiration or growth

23. The leaf and water loss
- Water is lost by evaporation and diffusion
from the leaf surface
- Stomata need to open so that the leaf can
take in carbon dioxide

24. • https://www.twig-world.com/film/plants-in-
extreme-environments-1184/

25. Adaptation of plants to reduce water loss
• Cacti
– Green stem carries out
photosynthesis
– Leaves reduced to spines to reduce
surface area for water loss
– Stomata are sunk in grooves to
avoid drying winds
– Swollen stem stores water

26. • Aquatic plants
– Leaves with little lignin in
the xylem, since the leaf
is supported by the
water
– A very thin cuticule
– Stomata on the upper
surface

27. • Wilting
– Leaves collapse ane stomata close to reduce heat absorbtion and
evaporation
• Leaf fall
– In very severe conditions plants allow the leaves to fall of so that
no water loss can occur

28. • https://www.youtube.com/watch?v=xGCnuXx
bZGk