Biology
Hypothesis: I predict that the leaves taken from the outer area of a shrub have a higher stomatal index (/density) than those taken from the centre of a shrub this are due to light levels.
Explanation: Plants have stomata to obtain carbon dioxide from the atmosphere and remove oxygen produced in photosynthesis. During photosynthesis the chloroplasts in the leaf cells synthesize as a result of exposure to light, while oxygen is produced as a by-product. As the outer leafs are exposed to higher light levels the stomatal density has to be high and because the inner leaves are exposed to lower light levels they will so have a lower stomatal density than the outer leafs. This is known as an adaptation, (leaves in the centre of a shrub are exposed to small amounts of light meaning they have little of stoma because if they had many then they would lose lots of water (by transpiration). Leafs must grow the correct amount of stoma (for gas exchange/water loss) to the light levels in an area (even if they are shaded) this gives them a balance.
Method:
1. Obtain two leaves from a shrub, (One from the centre and one from the outer area)
2. Paint a thick patch of clear nail polish on each of the leaves surfaces (lower/upper epidermis) being studied. (Make a patch at least one square centimetre.
3. Allow the nail polish to dry completely on both sides of the leaves.
4. Tape one piece of clear cellophane tape to each of the dried nail polish patches.
5. Gently peel the nail polish patches from the leaves by pulling on a corner of the tape and peeling the fingernail polish off the two leaves sides. These are the leaf impressions you will examine.
6. Tape your peeled impressions one at a time to a very clean microscope slide. Use scissors to trim away any excess tape.
7. Scan the slide until you find a good area where you can see the stomata. Each stoma is bordered by two sausage-shaped cells (guard cells) that are usually smaller than surrounding epidermal cells. Count
Explanation: Plants have stomata to obtain carbon dioxide from the atmosphere and remove oxygen produced in photosynthesis. During photosynthesis the chloroplasts in the leaf cells synthesize as a result of exposure to light, while oxygen is produced as a by-product. As the outer leafs are exposed to higher light levels the stomatal density has to be high and because the inner leaves are exposed to lower light levels they will so have a lower stomatal density than the outer leafs. This is known as an adaptation, (leaves in the centre of a shrub are exposed to small amounts of light meaning they have little of stoma because if they had many then they would lose lots of water (by transpiration). Leafs must grow the correct amount of stoma (for gas exchange/water loss) to the light levels in an area (even if they are shaded) this gives them a balance.
Method:
1. Obtain two leaves from a shrub, (One from the centre and one from the outer area)
2. Paint a thick patch of clear nail polish on each of the leaves surfaces (lower/upper epidermis) being studied. (Make a patch at least one square centimetre.
3. Allow the nail polish to dry completely on both sides of the leaves.
4. Tape one piece of clear cellophane tape to each of the dried nail polish patches.
5. Gently peel the nail polish patches from the leaves by pulling on a corner of the tape and peeling the fingernail polish off the two leaves sides. These are the leaf impressions you will examine.
6. Tape your peeled impressions one at a time to a very clean microscope slide. Use scissors to trim away any excess tape.
7. Scan the slide until you find a good area where you can see the stomata. Each stoma is bordered by two sausage-shaped cells (guard cells) that are usually smaller than surrounding epidermal cells. Count