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Find out where the stomata are located, on the upper or lower epidermis of a leaf.

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Introduction

stomata investigation Aim: The aim of this science investigation is to find out where the stomata are located, on the upper or lower epidermis of a leaf. Prediction: My prediction is that most of the stomata are found on the lower epidermis of a leaf. I have based this prediction on the function of stomata; to let gases in and out of the leaf i.e. to allow exchange of CO2 and O2 between the inside of the leaf and the surrounding atmosphere and to allow the escape of water vapour from the leaf. To reduce water loss the leaf has a waxy cuticle on the upper epidermis, which is waterproof, so the leaf uses the lower epidermis for gas exchange. Science about Stomata: Stomata are pores perforating the epidermis of the leaves and stem. They are usually most numerous in the lower epidermis of the leaf where there may be as many as 400 per mm, there are generally fewer in the upper epidermis and fewer in the stem. Their functions are: (1) To allow exchange of carbon dioxide and oxygen between the inside of a leaf and the surrounding atmosphere. (2) To permit the escape of water vapor from the leaf. Stomata are important in several physiological processes, not just photosynthesis, but they also represent a hazard in that they may permit excessive evaporation from the leaf. ...read more.

Middle

The fixation of carbon dioxide in the dark reactions of photosynthesis creates a concentration gradient that carbon dioxide continues to diffuse into the leaf. Plan: The aim of this investigation is to try and count the number of stomata, therefore a method has to be devised to try and view the number of stomata. Viewing a leaf under a microscope does not allow the number of stomata to be counted, as the microscope is not powerful enough. Therefore an alternative would be to get an imprint of the leaf. This can be achieved by painting the upper and lower leaf with nail varnish, and when dry to remove the nail varnish and stick it on to some sticky tape and then viewing under a microscope and recording the number of stomata on each side of the leaf. Fair Test: To make this investigation a fair test, the test will be carried out on different types of leaves to see if this will affect the number and location of the stomata. Also three different people will count the number of stomata, so to get an unbiased number and then an average will be taken. The stomata in the field of view will only be counted, to ensure everyone is counting the same surface area. The same magnification will be used when viewing under the microscope. ...read more.

Conclusion

The time varies in which the colour change takes place depending on the temperature and humidity. Generally the pink colour develops more rapidly on the lower epidermis of the leaf than upper surface, the reason already being discussed in the investigation. Conclusion: My prediction that the greatest number of stomata will be found on the lower epidermis was proved correct, as was seen by all the leaves inspected. Other than the Crassula all the other leaves proved without doubt that the greatest number of stomata are found on the lower epidermis. The grape ivy, spider plant, begonia and the geranium were all thin leaves without a visible waxy cuticle so the stomata are located on the lower epidermis to prevent excessive water loss as they have no waxy cuticle to protect them. Also they are relatively thin leaves so the exchange of CO2 and O2 can occur relatively quickly and easily through the stomata of the lower epidermis. Further Work: If this investigation was to be carried out again I would use a greater variation of leaves, different shapes, sizes, thickness and leaves from different habitats to see what affect this would have. Also when peeling off the nail varnish the area would be calculated so that everyone was counting in the same area also make sure that everyone repeated the test. Attempts should be made to carry out similar investigations ...read more.

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