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1.2.3 Transport in plants
As plants become larger and more complex, transport systems become essential to supply nutrients to
and remove waste from individual cells

The supply of nutrients from the soil relies upon the flow of water through vascular system as does the
movement of the products of photosynthesis…

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In leaf
Vascular bundles form the midrib and veins
Dicotyledons
Has a branching network of veins that get smaller as they spread away from the
midrib
Within each vein the xylem can be seen on top of the phloem
Monocotyledons
Xylem
A plant transport tissue that carries water from the…

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contain very little cytoplasm and no nucleus
lined end to end to form tube
sugars are usually sucrose
sap
dissolved sucrose
tube called sieved tubes
tube contains sieve plates
cross walls at intervals perforated with pores
allows sap to flow through
Companion cells
small cells with a large nucleus and…

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Then passes through the plasodesmata from one cell to the next
Once inside the cytoplasm water can move through continuous cytoplasm from cell to
cell
Vacuolar pathway (C)
Similar to the symplast pathway but water is not confined to the cytoplasm
It moves through the vacuoles as well
Water uptake…

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Water movement up stem
3 processes that help water move up stem
Root pressure
Water is driven into the xylem by osmosis by the action of the endodermis moving
minerals into the xylem by active transport
This forces the water into and up the xylem
Root pressure can only account…

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Water keeps cells turgid
The flow of water can carry useful minerals
Evaporation of water can keep the plant cool
Measuring rate of transpiration
Podometer
Important that there are no air bubbles
Water uptake is about 99% of water loss through transpiration
Water loss in the leave is replaced by…

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Most plants can reduces water loss by adaptations of structure and behaviour
A waxy cuticle on the leaf will reduce water loss due to evaporation through the
epidermis
Stomata are often in the under suface of the leaf
Reduces evaporation due to direct heating from the sun
Stomata close at…

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Sugars are made during photosynthesis and converted to sucrose and loaded into
the phloem
This occurs during late spring summer and early autumn
Stores in other parts of the plants are sources during early spring when leaves are
growing
Here the leaves act as sinks
Other sources include roots where…

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If plant is supplied with radioactively labelled carbon dioxide it soon appears in the
phloem
Removing a ring of bark which contains the phloem results in sugars collecting above
ring
An aphid feeding on a plant can be used to show that the mouth parts are taking food
from the…

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