Extracts from this document...

Introduction

Aim The aim of my particular experiment was to investigate into the possible existence of distribution of stomata within different leaf types. My investigation also requires me to research into the rate of transpiration into the different leaf types and if this has an effect of the distribution of stomata on the leaves surface. Prediction I predict that the environment of which I found my particular leaf type had an effect on the stomata distribution in my particular leaf type. From the background knowledge I predict that those plants grown in a dryer environment and thus must adapt to such climate and within this situation they will have less stomata on there leaves thus giving less transpiration from the leaves. The leaves that I obtained from a dryer environment may have up to less than 150 stomata per 2mm of leave surface where those in a moist living area have more than 500 stomata per 2 mm. My prediction also includes that most of the stomata will be 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. With such a prediction I would need to carry out the background research on each particular leaf type chosen to research. Background Knowledge Dermal tissue is a kind of complex tissue consisting both of flattened cells covering the upper and lower surfaces of the leaf and of specialized cells called guard cells. Guard cells regulate gas exchange between the environment and the interior of the leaf by controlling the size of the stomata, openings through which gas exchange takes place. ...read more.

Middle

Slides- These were required as a base to place my replica upon n order to see the replica under the microscope. Cover Slips- These were required in order to keep the replica on the slide in order to easily see the replica on the microscope so that the replica nail polish didn't curl up or com off the slide. Fine Forceps- These were required to peel of the nail vanish once dry from the leaf surface and placing it onto the slide without it curling up or having my finger prints over the replica and thus being unable to see the replica. Microscope- This was required in order for me to visualise a good picture of the replica to give me a big enough magnification of the stomata on each leaf surface. Materials: Holly Leaf, Privet Leaf, Variegated Holly Leaf, Ivy Leaf Fair Test The variables: In order 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 of the stomata depending on the location the leaf type came from this will therefore be the only variable to be changed. There fore the key variables involved include the leaf type the epidermis layer which I will also be changing and the different environments which my leaf types came from. By having three different variables I am able to compare and contrast the distribution of stomata in each leaf to give e more reliable and accurate results. I will use the same size slides and cover slips, I will also use an equal amount of nail vanish on each leaf surface by using one large sweep of the brush onto the surface. Three different people will count the number of stomata on each replication, to get an unbiased number and then an average will be taken. Only the stomata in the field of view will be counted, to ensure everyone is counting the same surface area and it is equally fair for each replication. ...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. A successful alternative is to use a clear water based varnish. A half litre tin is cheap, and can be divided up into smaller amounts for ease of use. Paint the opaque varnish thinly on to the leaf to produce a clear film. Leave it to dry as usual. This particular water based varnish takes longer to dry, so if the leaves are coated during one lesson, the impressions can be peeled off and examined the next. The varnish is non toxic, so can be used on living plants without removing the leaves this means that plants do not have to be denuded for this experiment. In addition to revealing the stomata, the cell walls also show up for a clearer image. Other suggestions include producing impressions on acetate film, by placing a leaf in propanone and then pressing it onto the acetate. Although this does not work for some plant leaves, especially those that have an uneven surface and the leaf still has to be removed from a plant. Another method is to rub a board pen over the surface. The solvent-based ink permeates the leaf, showing up the stomata. However, this seems to work only with certain types of pen probably related to the strong solvent in the pen. Although this raises more severe health and safety issues. 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.

This student written piece of work is one of many that can be found in our GCSE Green Plants as Organisms section.