Difference in number of Stomata in different leaves

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Biology Coursework

An investigation will be carried out to see how the numbers of stomata differ in different plant species. Stomata are tiny openings found on the underside of the plant leaf. [1] The pore is formed by a pair of cells called ‘Guard Cells’. Guard cells control the opening of the stomata. These pores on the underside of the plant leaf allow carbon dioxide to enter. Carbon dioxide is used in photosynthesis. At the same time when the stomata are open Oxygen and water vapour escape from inside of the plant.

Water vapour leaving the plant is called Transpiration. This occurs mostly in leaves of the plant but can be from the flower and the stem.

Hypothesis

The leaves of different plants and the sections of leaves will have different number of stomata. The amount of stomata on the plant leaf is dependant on the environment. The plants that are in temperate environment will have many more stomata than the plants that are in Tropical environments.

Null Hypothesis

There is no difference in the number of stomata in any plant leaf or any section of the plant. Any difference is purely due to chance

I will investigate how to find out the different number of stomata in a plant leaf.

Experiment

Apparatus

Nail Varnish

Microscope

Microscopic slide

Lab coat

Tape

Plant leaf

Step by Step

  1. Get apparatus
  2. Take a leaf from a plant and mark 3 sections, top, middle and bottom (to later investigate under the microscope)
  3. Add nail varnish to the  bottom of the leaf
  4. Wait for the nail varnish to dry, you can place it on a warm object to dry it quicker but it should no be placed on a hot object as it can affect the leaf.
  5. Once the nail varnish is dry put tape on in and then remove the tape, making sure the nail varnish sticks to the tape.
  6. Stick the tape on the microscopic slide
  7. Count the number of stomata in your marked areas
  8. Add the results to a table (see Table1)
  9. Repeat the steps to get 3 results for each section and then repeat with other leaves.
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I carried out a preliminary experiment where I counted the number of stomata by placing the plant leaf under the microscope. The experiment shown is more accurate than my preliminary experiment as some plants leaves were too thick to be viewed properly under the microscope so they had to be cut thinner to make it easier to see under the microscope. It isn’t accurate as whilst cutting; the stomata got damaged making the count unreliable.

The method is repeated 3 times to make the results more accurate and the reliable and ...

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Incorrect use of capitals in some places. Spelling, grammar and punctuation adequate.

The level of analysis is good as two different types of experiments are used and two different methods of analysis. However, the reason for using the chi squared test or standard deviation is not stated, so I am not sure why these tests were used. The amount of plants used from each climate is a good sample, but if the test was repeated there should have been a much wider range used. Improvements suggested were good, and reflected on the experiment well.

Overall a good example piece of coursework. Introduction is adequate, but could explain transpiration and the process what occurs a bit better. Sets up the scientific background for the experiment well. The hypothesis is good apart from the fact that the candidate could explore why plants in tropical and temperate environments may differ in the number of stomata. Conclusion and the rejection of the null hypothesis are good. Response to the question in general is to a high level, although the science behind the experiment could be mores solid. Meaning and communication of the experiment is clear.