Planning Introduction Stomata are pores on the bottom of leaves of vascular plants. The function of stomata is to allow gaseous exchange (transpiration) between the plant and the external environment (see diagrams below). This process is carried out by the plant, which controls the opening and closing of stomata via the guard cells. The more stomata a leaf contains the greater the rate of gas exchange and the less water it will be able to accumulate. Stomata pores are formed between pairs of specialized guard cells.
The wall adjacent to the stomata is thicker than the other walls. When a guard cell wells or shrinks due to the gain or loss of water, the thickened wall is the only one to maintain its form. Consequently when the guard cells shrink, they shift towards each other, closing the stomata. Water enters the guard cells by osmosis. The amount and direction of movement of water is influenced by several factors, one of which is light. Light has an indirect effect.
The guard cells of stomata through which most water loss comes about by transpiration are sensitive to light intensity. They open during periods of light and close as the light intensity falls. These changes allow remonstration either to take place or not. Another factor which affects whether stomata stay open or closed is the water balance of the plant. If a plant carries on to lose more water to the air than it can gain from the soil, the stomata eventually close. This decreases water loss by transpiration and allows the plant time to restore its water balance.
Aim I will carry out a method that is valid and reliable to allow me to investigate I t there is a statistically significant difference in stomata density ( the number of stomata in a specified area of a leaf) between two temperate plant leaves (the Holly and the Privet) ND two tropical plant leaves (the Mexican Snowball and the Aloe Vera). Hypothesis There is a statistically significant difference in stomata density between the temperate plant leaves and the tropical plant leaves and this difference is not due to chance.
Null Hypothesis There is no significant difference in the stomata density between the temperate plant leaves and the tropical plant leaves and if there is any difference in the number of stomata then it is due to chance. Procedure to carry out investigation: the Nail varnish- soleplate method. Apparatus 1. Clear nail varnish 2. Clear soleplate 3. Arm plate or dryer 4. Counter 5. Three leaves from each plant specie 6. Microscope with magnification XX 7. Three microscope slides 8. ABA coat 9. Permanent marker or label Method 1. Ensure you have all the apparatus listed above before carrying out this method. 2. Cut your first leaf from your first plant make sure its young, healthy, dry and clean, note down which area you cut from on the plant so for the repeat you do not cut from the same area of the plant. 3. Place your leaf on the tile and smear a very thin layer of clear nail varnish on the tip of the leaf on the underside of the leaf were the tomato are.
Make sure the leaf is dry because if you apply nail varnish to a wet leaf it may not dry very well and cause it to be cloudy. Also make sure the layer of nail varnish is thin and clear so it will be easier to see the stomata on the varnish without any crystals in the varnish. 4. Dry the leaf, perhaps on a hot plate or a warm dryer but don’t leave it any longer than necessary as it might damage the stomata on the surface. Place the underside of the leaf upwards on the hot plate. 5.
Place the leaf on the tile and cut some soleplate, enough to cover the tip or were the varnish is. Press down the soleplate onto the leaf until there are no gaps between them. Make sure you do not get any fingerprints or dirt/dust on the soleplate as these may affect you when you come to count the number of stomata on the leaf. 6. Peal the soleplate off the leaf and press it down onto a clean microscope slide making sure there are no gaps between them. Label the slide with the initials of the name of the plant lead, and area tot the lead .
This should be the tip tort the first slide. 7. Place the slide under a microscope at magnification XX which magnifies to an area of 9. 6(m. This magnification was the most suitable out of the other two magnifications fox and XIII because it covers a greater area of the leaf and also allowed me to count stomata on every plant leaf which I had found difficult to do with the other two magnifications, when I conducted a preliminary to check which magnification was the best to count stomata from each of the different plant leaves. . Under the microscope adjust the view to get the best observation of the stomata using the fine focus adjuster, then move the slide and look for an area that has a high magnitude of stomata. Make sure there are no damaged parts, no nail varnish blobs and no vein shapes. 9. Count the number of stomata in that area using a counter without moving the slide. Record the count in a results table (see below) repeat this procedure for the middle and bottom of the same leaf. 10.
Start this method again for two more leaves of the same plant species. 11. Repeat the entire method again for the 3 other different species of plant leaves. Results table вЂў There should be four of these tables for each species of plant leaf. I Name of plant I Number of stomata on the tip of the I Number of stomata on he middle of Number of stomata on the bottom of I Leaf I leaf I the leaf I I Leaf one I I Leaf two I I Leaf three Why I chose the nail varnish-soleplate method?
Before I had conducted and decided on the nail varnish-soleplate method I had performed a simpler method, which involved firstly slicing out a thin section at the base of the leaf of the four different species of plant leaf and placing each on a microscope slide and then beneath a microscope for observation. But this method presented more difficulties then the nail varnish-soleplate method, such as: as nard to distinguish between the stomata and the plant cells in the lead, so it made counting stomata more complex.
This difficulty is absent in the nail varnish- soleplate method because I used nail varnish instead of cutting the thin section. It was very tricky to slice a very thin section of the leaf were the stomata are. Firstly because I could damage the stomata and secondly it was very fiddly because I had to use a scalpel to slice accurately a very thin layer and I could have easily got scratched, especially when it came to slicing the Aloe Vera plant leaf which contained a very slippery sap.
There is no slicing in the nail varnish-soleplate method so the mentioned difficulties are not present. Finally I decided that this was not the correct method to use because of the flaws (listed above) which will prevent me from obtaining valid and reliable results. But also because the nail varnish-soleplate method proved easier, less damaging and it allowed me to count stomata quickly and efficiently which in turn allows me obtain reliable and valid results. How I will obtain valid results from my nail varnish- soleplate method.
To obtain valid results I will carry out a fair and efficient method which will include a number of intros to make it a fair test, these controls are: вЂў Making sure my magnification is the same for every plant leaf because if it is different then the area it magnifies will vary for each leaf; this therefore will be unfair and in turn will give me inconsistent and invalid results. вЂў Making sure the apparatus I use are the same for every plant leaf thus to make it a fair test I cannot use apparatus that are not from my method.
For example making sure that I don’t use a different colored nail varnish, because I had earlier found out that colored nail varnish has crystals that conceal he stomata and you can’t really see stomata that well in colored nail varnish as you do in clear nail varnish. вЂў Making sure all the equipment such as the soleplate, nail varnish microscope slide and the leaves as well are all clean with no dust, damaged and fingerprints or dirt marks, which could increase experimental errors. Ђў Making sure that the coat of nail varnish is very thin and fully covering the area of the leaf under investigation. вЂў Making sure there are no gaps between the section of leaf and the soleplate and between the soleplate and the slide because the APS may hinder me when I come to count stomata and affect my final result. This is particularly true with the tropical plant leaves as they may have fewer stomata in their leaves.
How I will obtain reliable results from my nail varnish-soleplate method. I will obtain reliable results by keeping the experiment as fair and valid as possible; I will repeat my data to obtain an average hence reducing the error in my results. I will also count stomata from three different areas of the leaf which will give me greater accuracy and reasonable results. How I will treat my data after I obtain it. Firstly I will produce a well labeled set of results tables.
Then I will use my data to calculate a standard deviation (shows the spread of data about the mean) value for each of the different species of plant leaf, using this equation: вЂў Standard deviation = ( (x -x) n-l Definition tot equation = Sum of x = mean number of stomata x = number of stomata n = number of samples (which in this case is 9 samples) Next I will produce a standard deviation bar chart showing the number of stomata for each of the different plant leaves it will also show the spread of data about each mean (standard deviation) for the different plant leaves.
On my X- axis I will have the name of the species of plant leaf and on my Y- axis the mean number of stomata. After this I will use the chi- squared test which is a statistical test used to decide either to approve your null hypothesis or to reject it, through this equation: вЂў Chi squared test = ((0 – E) E Definition of equation ( = sum of O = observed data E = expected data Finally I will write up a concise and clear conclusion on everything I have done with my data since I obtained it and whether I have accepted or rejected my null hypothesis and why.
Analyzing Aim: In this section: вЂў I will use my results (below) to carry out standard deviation calculations (using the equation for standard deviation) for each of the four plant leaves. I will then obtain a standard deviation value for each plant leaf. вЂў I will use the standard deviation values to draw a bar chart showing the spread of my data about the mean for each of the plant leaves and also identify if there are any trends or patterns from the data and also derive valid conclusions using biological knowledge as well. Ђў After completing my standard deviation calculations, I will carry out a chi- squared test using the chi-squared test tutorial) trot which I will attain a chi-squared value. From this value I will be able to identify if my observed values are significant and also decide whether I will accept or reject my null hypothesis. Results: Below are my observed results counted from 3 leaves from each plant.
The second part of my hypothesis states that the difference in the stomata density teen the temperate plant leaves and the tropical plant leaves is not due to chance; this part of my hypothesis requires me to provide scientific biological evidence to verify it, so I have researched into the responses and adaptations of leaf stomata in different environmental conditions. In the course of my research I have come to know that: 1. The primary role of stomata is to open and close so that the rates of water loss and carbon dioxide uptake can be in accordance with one another. Stomata apply a barrier against the diffusion of carbon dioxide and water pour through the leaf, when the stomata are closed; the hindrance to gas exchange is much stronger which makes the stomata more efficient in their role. 2.
A degree of environmental conditions can affect stomata opening; these can be bright light, wet soil, low wind speeds, and if the leaf temperature is below the optimum temperature. Reverse conditions will satisfy the closing of stomata. 3. Plants may also influence the rate of gas exchange by varying the number of stomata in new leaves when they are formed especially in spring and summer time, for example if more stomata are armed the more carbon dioxide is taken up and the more water vapor is released. Therefore the quantity of stomata in the leaf can significantly strengthen or weaken the plants control over the water loss rate and the carbon dioxide uptake rate. 4.
Photosynthetic plant organelles can only function over a limited range of temperatures, so when they are heated these organelles, which are essential for phosphorescently and carbon fixation will denature. To prevent the organelles trot denaturing, the plant will open its stomata and allow water to evaporate thus causing the temperature of the leaf to fall steadily. . If water is scarce I. E. A drought, intense evaporation may cause disorder to the photosynthetic organelles in the plant, therefore plants in drought conditions may have fewer stomata to transpire less and store more water in their leaves then plants in temperate conditions. 6. The magnitude of stomata pores has a huge effect on the rate of gas exchange. The rate of gas exchange for the whole leaf is established by the responses of the stomata to the environmental condition. . Finally I have also found out that the amount of stomata on a leaf can be a good indicator of its original environment, and its espouse to different environmental condition. The Chi – Squared Test I will use the chi-squared test to find out if there is a statistically significant difference between my observed values and my expected values. Significance of observed values is a measure of whether a difference has occurred by chance. To help me decide the significance of my result I will use Fisher’s table of chi-squared critical values. For my result to be significant there must be less than a 5% probability that the result is due to chance.