Question

please answer this question no. 10 I'll follow you please

Answer 1

Testing a leaf for starch is the simplest photosynthesis lab. A positive test for starch in a leaf provides evidence that photosynthesis has occurred. The test for starch is a leaf is an is an extension of the Iodine Test for Starch.

Glucose is the product of photosynthesis, and is rapidly converted to granules of starch - a polymer of glucose - for storage. Starch granules have been visualized in the stroma of the chloroplast as well as the cytoplasm.

The test for starch in a leaf is also a part of the other photosynthesis experiments. So, take time to understand the test for starch in a leaf.

MATIRIAL REQURIED

• bunsen burner, tripod stand, wire

gauze(OR 90oC electric water bath

OR hot plate)

• 250 cm3 beaker

• boiling tube

• anti- bumping granules

• forceps

• test tube holder

• white tile

• leaf to be tested (hibiscus leaves are excellent)

• 90% ethanol

• iodine/potassium iodide solution

PROSEDURE

▪Remove a green leaf from a plant that has been exposed to sunlight for a few hours

▪Half-fill a 250cm3 beaker with water. ▪Heat the water until it boils. Keep the water at boiling point.

▪Use the forceps to place the leaf in the boiling water. Boil for 2 minutes.

▪Turn off the Bunsen Burner. (If you are using a heat source without a naked flame - electric water bath or hot plate - this step is unnecessary.)

Place the boiled leaf in a boiling tube containing 90% ethanol.

▪Place the boiling tube in hot water and boil for 10 minutes or until the leaf decolourizes. ( It may be necessary to replace the ethanol)

▪Gently remove the leaf and wash with a fine trickle of cold tap water.

▪Spread the leaf evenly on a white tile.

▪Add a few drops of iodine/potassium iodide solution to the leaf and note any observations

RESULT

▪The leaf was flaccid (soft) after being boiled in water

▪The ethanol changed from colorless to green

▪The leaf was brittle after being boiled in ethanol

▪The leaf become flaccid once more after being rinsed in cold water

▪After iodine solution was added...

OBSERVATION

▪No color change (Iodine Solution remains brown)

▪Iodine/Potassium Iodide solution changed

INTERPRETATIONS

▪Starch is not present

▪Starch is present

《IT MAY HELP YOU》