WJEC GCSE Biology 3 Transport in Plants

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  • Created on: 22-05-12 17:05
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Megan Nolan
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Transport in Plants
The movement of water molecules across a partially permeable membrane from a region of high
water concentration to a region of low water concentration. Larger molecules such as starch and
sucrose cannot move across these membranes as they are too big.
Onion epidermis (skin)
Has a completely permeable cell wall and a semi permeable cell membrane
Salt solution (etc.) can move through cell wall in between cell wall and membrane
Cell wall remains the same size and shape
Membrane becomes loose and detached from cell wall plasmolysed
If in distilled water, the water concentration will always be higher outside because of
starch (etc.) inside.
Turgid Full of water swollen and hard
Plasmolysed Membrane has come away from cell wall
Flaccid Floppy/ not firm
Cell A (distilled water)
This cell is turgid because the water concentration is higher outside, so the water moves into the
cell through the semi permeable membrane.
Cell B (Salt Solution)
This cell is plasmolysed because the salt solution moves in through the fully permeable cell wall.
There is a higher water concentration inside due to salt outside. Net water movement is out by

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Megan Nolan
Experiments are often shown with visking tubing as it represents a semi permeable
Petri dish lids reduce evaporation of water
There is no mass change in boiled potatoes as the membranes are ruptured and fully
permeable so every molecule can move through in both directions.
Xylem and Phloem:
Gases enter and exit the plant through the leaves.
Water is absorbed from the soil through the roots.
The upper and lower parts of the plant are connected by the stem.…read more

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Megan Nolan
Adaptations of leaves:
For diffusion
Thin and flat decrease distance travelled by gases
Air spaces to increase the speed of diffusion
Stomata (pores on underside of leaf) let gases in and out
Guard cells: when there is a low CO2 level, there is a higher water gain, and guard cell
become turgid and open. High CO2 levels cause water loss and guard cells become flaccid
and close.…read more

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Minerals and mineral deficiencies in plants;
Artificial fertilisers i.e.…read more


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