Plant Tissues Lab Report IB International Baccaleaureate Biology

Objective: improving skills in using the microscope, preparing temporary mounts, observing characteristics of plant cells, testing for starch, osmosis and turgidity within plant cells.

Materials Required:

1. Red Pepper
2. Green pepper
3. Tomato
4. Potato
5. Banana
6. Radish
7. Moss leaves
8. Iodine solution
9. 20% sucrose solution
10. Droppers
11. 7 Glass slides
12. 7 cover slips
13. Razor
14. Light Microscope

Method:

1. Observe tissues from plant material under high power (x 400)
2. Draw individual cells showing starch grains, chloroplasts, chromoplasts, anthyocyanins (vacuolar pigments)
3. Measure the size of 3 cells of your choice
4. Add sucrose solution to radish to compare plasmolysis and turgidity in plant tissues

Table 1: Plant Tissues Observed at 400 x

Plant Tissue

Mountant Medium

Green Pepper

Water

Red Pepper

Water

Moss Leaves

Water

Banana

Iodine Solution

Potato

Iodine Solution

Radish

Water

Radish

20% sucrose solution

Observations:

It is quite evident that the Red Pepper and the Green Pepper have cells very similar to each other. The eccentric shape of the cells, the numerous chromoplasts that dot the cytoplasm and even how they encircle the nucleus make the two tissues alike on a cellular level. The biggest difference between the two cells was the colors. The red pepper is red in color and this is due to the chromoplasts in the cytoplasm. The green pepper is light green because, although chromoplasts are present, the chloroplasts have a dominating green color.

When observing the Radish cells in both water and sucrose media, they were notable similarities and differences. Both had a deep red color which could be assumed to be the cytoplasm and both preserved their hexagon shape regardless of the medium. The main difference between the two was noticing that the radish cells in sucrose had red and clear patches while the radish in water turned out to have a uniform, velvet color. This is due to the fact that when radish cells are put in sucrose, their inner-environment, in terms of sugar, is hypertonic compared the outer-environment, and therefore water is poured out to reach equilibrium. This then causes the cell membrane to shrivel up as seen in the diagram and that is why the amount of "red" decreases. When the radish is then put into H2O, we notice that the cells take on a very rigid hexagonal shape. They also acquire a uniform, velvet color. This is due to the fact that the inner-environment of the cell is hypotonic compared to the water medium and so, water is poured into the cell to reach equilibrium, and hence the cell membrane (which is red) expands and gives all the cells the full "red" color.

The banana, and the potato have many starch grains and they are visible because they are stained with the iodine. Iodine and starch grains react to create either purple or black color (starch grains initially do not have a pigment). Both pant cells had a circular shape rather than the expected geometric shape. Both cells possessed many starch grains. The reason for which a large number of starch grains is present in the cells becomes very vague in speculation. Both banana and potato do not contain distinct seeds as do the other plants. Taking this into consideration, the banana and the potato might need the excess starch to help in the growth of their offspring. Both plants are asexual reproducers; some potatoes sprout roots from their body which indicates that the growth of their offspring is present within them, which means that they will need to provide their offspring with enough sugar; bananas have flowers and are seedless otherwise and thus are also asexual reproducers. This fact may account for the large number of starch grains in the cells.

The moss leaf cells were numerous and concentrated. They were small and the chloroplasts occupied the majority of the space within the cells. The chloroplasts are what account for the moss' green color.