biology 1406 lab report
1.) Explain why a leaf appears dark in color after treating with iodine? 2.) Why is starch production an indication that photosynthesis is occuring? These two questions are for a lab report that I must turn in next week. I only tested the leaf that had remained in the light. So, can you please answer both questions as if you had only tested the leaf that had remained in the light and ignore the leave that had been remained in the dark for two days please. I also need for you to write a paragraph of the prediction/hypothesis at the very beginning. And one paragraph at the very end stating if your prediction/hypothesis was correct. Each question should be answered in one full page single spaced. These are the steps for the lab just in case you need a better understanding of the questions. 1.) Locate the two geranium plants in lab. One plant has remained in the light and the other has been kept in the dark for two days or more.
2.) Write a prediction for the presence of starch in both the light-grown and dark-grown leaves in Table 9.1
3.) Remove a single leaf from each plant. Remove stem from one leaf in order to distinguished the light-grown leaf from the dark-grown. Label one petri dish(l) for light and one for(d) for dark. Continue to keep the leaves separate throughout the experiment.
4.) Put 150ml of dH2O into beaker, place on hot plate, and bring to a boil. Use 3-4 boiling chips if needed. Instructor will set up hot plate with ethanol. Caution: Ethanol will boil more quickly due to low boiling point!
5.) Place leaves in the boiling water for 2-3 minutes until softened. This kills the plant tissue and breaks down the membranes.
6.) Using forceps remove leaves from water and place them in boiling ethanol for 2-3 minutes until bleached white. This will remove the photosynthetic pigments from each leaf.
7.) Once bleached white use the long forceps provided to remove each leaf from the ethanol and return to appropriate petri dish.
8.) Dip each leave in hot water to soften.
9.) Test for Starch. Place leaves in petri dish filled with Lugol’s iodine solution. Allow the leaves to soak in the Lugo’s solution for 2-3 minutes. If starch is present, the leaf will be stained a blue-black color.
10.) Gently rinse the leaves with hot water. Using forceps spread the leaves flat in each petri dish and return to table.
11.) Observe the staining of each leaf. Draw what you observe in Figure 9.4 and record results in Table 9.1
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