Photosynthesis and Plant Responses Section 2

Information sourced from notes and textbook. iGCSE biology Plants as organisms, photosynthesis and plant responses section 2

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  • Created by: emma
  • Created on: 24-11-12 16:21

Targets for Section 2

  • Learn about carnivorous plants
  • Explain what a limiting factor is
  • List the factors that affect the rate of photosynthesis
  • Interpret data on the effects of light temperature and CO2 on greenhouse crop yeilds 
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Carnivorous Plants

Some plants survive in environments where the soil is very nutrient-poor.

How do carnivorous plants obtain the minerals that they need?

They digest insects using enzymes and use the products to create new materials for the plant.

Insects are attracted to the sweet liquid inside the adapted leaves of 'pitcher plants'. Once inside they cannot get out and are re digested by enzymes produced by the plant.

Venus fly traps have sensitive hairs that act as triggers, closing the leaves quckily when an insect lands. Enzymes digest the insect and the soluble nutrients are absorbed into the plant.

Peat bogs are formed from many layers of dead plants - because the plants don't decay they don't release their nutrients into the soil. Carnivorous plants have become adapted to this nutrient poor habitat.

Sundew plants trap insects with droplets of sticky fluid on ther leaves.

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Limiting Factors 1

Photosynthesis can only occur at a maximum rate if there is sufficient:

- Light

- CO2

- Temperature

A limiting factor is something that limits the rate of photosynthesis.

If a graph has the axis labelled 'Light intensity' and 'rate of photosynthesis' then where the graph slopes upwards the limiting factor is light, where the graph levels off however the limiting factor is either CO2 or temperature.

And it's same with CO2 and temperature, if either of them is on the axis then where the graph slopes it's one of them, and when it levels off it's the other two.

The highest rate of photosynthesis will be achieved when all the variables are just as the right level. These conditions are called the optimum conditions.

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Limiting Factors 2

Examples of when limiting factors are important are as follows:

- Why do you think that farmers prefer to grow tomatoes in greenhiyses rather than outside?

  The environment can be controlled. Light, CO2 and temperature can be maintained at an optimum.

- A cold temperature can be a limiting factor on photosynthesis but if it gets too hot the rate of photosynthesis will rapidly decrease. Why?

 The enzymes controlling the photosynthesis denature.

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