B4 Plants

B4 plants,leaf: structure,adaptations.Osmosis,Photosenthisis

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  • Created by: Momin
  • Created on: 29-04-12 15:17

B4 Plant Leaf

Leaf adaptations;

  • - Broad and have a large surface area
  • - Thin less distance to travel for gasses etc
  • - Chlorophyll - to absorb the sunlight
  • - Stomata -Allows Carbon Dioxide/Oxygen to diffuse in and out. 

Leaf structure;

  • Waxy Cuticle - Are Protective and Transparent,
  • Upper epidermis - Thin and transparent so that more sunlight can be absorbed,
  • Palisade Mesophyll - Are at the top to absorb light,
  • Spongy Mesophyll - Air spaces between each each so the Carbon Dioxide can diffuse in and out,
  • Vein - is in the corner (Xylem transports water - Phloem transports food substances)
  • Lower Epidermis - Guard cells have chloroplasts,gaseous exchange is controlled.
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Water in cells

Water in cells;

Too Much Water in Plants - Plants adapt to different water levels, too much means that the contents of the cells push against the cell (this is turgor pressure),it helps support the cell,the cell is turgid.

Too little water in Plants - Plant cells become  flaccid, as they lose their turgor pressure, Can also become plasmolysed.

Too much water in Animal cells - Animal cells don't have cell walls and therefore when they absorb too much water they burst (Which is called Lysis).

Too Little Water in Animals - The cell shrivels up (Which is called a crenation)

Animal cells keep the water in their cells constant to avoid the extremes but plant cells are more tolerant because of their cell wall.

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Gaseous exchange of plants day'n'night

Gaseous exchange of plants day'n'night;

In the day Plants take in Carbon Dioxide, this means that Oxygen is produced (As a result of photosyntheses in the plant) inside the plant,there is a higher concentration of Oxygen ,than outside it.Therefore by diffusion the oxygen leaves the plant.At the same time Carbon Dioxide is being used up,and more is diffused in,as the concentration outside is larger than inside.

At night there is no sunlight,so photosyntheses cannot occur so respiration happens instead. Oxygen is used up by the plant and Carbon Dioxide is produced (through respiration).The concentration of Carbon Dioxide inside the plant is higher than outside so the carbon Dioxide diffuses out. At the same time Oxygen is being used so more diffuses in as the concentration outside is higher than inside.

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Osmosis, Root Hair cells,Transpiration,What affect


Is the movement of water, across a partially permeable membrane, from a high concentration to low.

  • 1) Higher Concentration of water in the soil,than inside the root cell.
  • 2) Root hair cells have a large surface area because of the microscopic hair cells.

Transpiration is the loss of water from cells 

  • Water is lost through Evaporation & Diffusion.
  • Water is drawn up through the Xylem & Root hair cells.
  • Transpiration allows the plant to have a constant stream of water keeping it cool.
  • Transpiration allows the plant to have a constant supply of Water and minerals.
  • Transpiration allows the plant to keep its shape (because of turgor pressure)
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Transpiration in plants is affected by?

1) Light Intensity - Stomata closes in the dark therefore water cannot escape.

2) Temperature - Water Particles move faster, so evaporation and diffusion happen faster.

3) Air Movement - If the air is still the concentration of water inside and outside the plant is high so no diffusion occurs. So when its windy the particles the concentration becomes low outside and the water diffuses outside quickly as its high inside but low outside.

4) Air Humidity - If the air is humid it means the concentration of water in the air,is equal to the concentration inside the plant so no diffusion occurs

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