The glucose made by photosynthesis is turned into starch. If iodine solution is added to a leaf, the parts that contain starch go a blue-black colour. In the diagrams below shade in the parts that you think will turn blue-black when iodine solution is added. Ok, so I am revising [studying, for Americans] for a science test, and my science teacher has given me some work to do, but I am struggling on a question. The question is above. These diagrams are added below.  Thanks!

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The concept to remember is that photosynthesis takes place in the chloroplasts which are found in green leaves primarily in the mesophyll, the middle layer of the leaf. Photosynthesis results in glucose and this can be converted to a larger carbohydrate known as starch to be stored for later use.

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The concept to remember is that photosynthesis takes place in the chloroplasts which are found in green leaves primarily in the mesophyll, the middle layer of the leaf. Photosynthesis results in glucose and this can be converted to a larger carbohydrate known as starch to be stored for later use.

In the first diagram, the leaf is all green and grown in the light so virtually anywhere you put Lugol's solution (the iodine test) on the leaf, it will turn blue-black to indicate the presence of starch.

In the picture where the leaf is all green but grown in the dark for 48 hours there should be no starch present. The leaf should have used up the stored starch for energy to stay alive while it was kept in the dark environment. There could be some remaining, though.

The last picture on the right side of the top row shows a variegated leaf with a white border grown in the light. Starch will be present in the green areas only. The white area contains cells which lack chloroplasts therefore, no photosynthesis will occur and no starch will be present in those cells.

On the left side of the bottom row, the leaf is all green but has aluminum foil covering a part of it in a strip. Since it was grown in the light, starch will be present in the green areas that are not covered by the foil.

The next picture shows a dead leaf. Since it was grown in the light, there may still be some starch left in the leaf and should show a positive result.

Finally, the last picture shows a variegated leaf, grown in the light with an aluminum strip making a cross section covering both green and white areas. Starch will only be found in the green areas that are uncovered by the foil and not in the white areas since they lack chloroplasts. Any cells under the foil will not receive sunlight so there will not be any production of starch.

Since I am unable to shade the diagrams you provided, I hope my detailed answer will enable you to do so based on the individual responses I provided for each picture. Good luck.

 

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