Conducting an experiment to find out what effect the surface area has on the rate of transpiration.

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Introduction:

¶In my investigation I plan on conducting an experiment to find out what effect the surface area has on the rate of transpiration.

¶Plants are autotrophic i.e. they make there own food (energy) through the process of photosynthesis.

 6CO2 + 6 H2O → C6H12O6  + 6O2

¶For the above process plants require carbon dioxide and water as well as sunlight. They get the carbon dioxide from the air and water is absorbed from the soil through the process of osmosis.

¶Plants add considerable volume of moisture to the atmosphere. After absorbing water trough their roots, the water travels up the stem to the leaves where over 90% of the absorbed water is lost through the process named transpiration. The sun provides the energy required turning the water in the leaves to vapour, and then vaporised water diffuses out of the plant in to the atmosphere through stomata in the leaves.

The diffusion of water out of plant reduces the pressure at the top of the plant, but a high pressure is created at the bottom of the plant so the water moves up the stem into region where it is needed. The loss of water vapour from the plants is called Transpiration. It is a passive process.

Diagram book Page 35

Water from the plant may be lost from three sites;

∙ Leaves:

∙ Flowers:

∙ Stems (herbaceous, lenticels on woody stems):

¶Most of the water loss occurs through the stomata in the leaves. There is also some water loss through the cuticle of leaves, it is only less than 10%, but this depends on the thickness of the waxy layer and on different plants.

Plan:

In my investigation I will be looking at the effect of the leaves surface area on the rate of transpiration. From the scientific knowledge, preliminary work and background research I have made the following prediction.

Hypothesis:

¶ The rate of water up take is directly proportional to the surface area of the leaves on the plant. As the surface area is reduced the time taken for the water to travel the stem over the same distance will increase.

The reason I will be monitoring the rate of water up take is that the apparatus available to me is a potometer; this device measures the water uptake in a plant. Rate of water up take is approximately the same as the transpiration as 99% of the water is lost through evaporation and only 1% is used in plant’s metabolic reactions.

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Justification of Hypothesis:

¶Leaves have stomata, water evaporates though the stomata, when there are more leaves the density of stomata will increase i.e. the larger the surface area of the leaves, more stomata will be present so more water will evaporates. More water loss mean higher the rate of transpiration so water uptake will be more this will be seen on the potometer.

There are many other factors other than Leaves surface area that affect the rate of transpiration, these are listed below and explained how they will be controlled.

1) Light: The light does not have a ...

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