Understanding Plant Nutrition: Testing Leaves for Starch

Learn about testing leaves for starch in plants, the importance of starch as a storage molecule, and the procedure for conducting an iodine test to detect starch levels. Explore the steps involved, the rationale behind each step, and the significance of destarching plants before experimentation.

• Plant nutrition
• Starch testing
• Iodine test
• Destarching plants
• Experiment setup

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Uploaded on Sep 13, 2024 | 0 Views

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1. Plant Nutrition Testing leaves for starch

2. Recap Starch is used for storage Glucose will be converted to starch for storage Starch is a large molecule and is insoluble It is not reactive It can be stored as starch granules in chloroplast, in root and in fruits.

3. Iodine test Brown to blue-black Testing for starch

4. General procedure 1. Take a leaf from the plant and drop it into boiling water for 30 seconds 2. Remove the leaf and place it into a boiling tube with ethanol inside a water bath 3. Take the leaf out and wash it with water to rehydrate and soften 4. Spread the leaf on a white tile and cover it with iodine solution Can you explain the thoughts behind each step?

5. Planning for an experiment the variables Dependent variable Things that you would measure Independent variable Things that you would change Controlled variable Other things that would affect the dependent variables (Biotic/Abiotic) For validity Making sure the change is only coming from the independent variable

6. Planning for an experiment the set up Control Set-up A set up that is the same as the experimental set up but removing the independent variable For comparison of the effect of the independent variable Repeat For reliability Identifying patterns and anomalous

7. Do we start the experiment right away? What would extra starch from the beginning do to the experiment?

8. Destarching plants Leaves that we are testing should not have any starch in them at the beginning of the investigation Starch present before the investigation will affect the result (overestimation) Cannot be sure that the leaves are photosynthesizing during the experiment. Procedure Leave plants in a dark cupboard for at least 24 hours Starch will be used up through respiration

9. Variables that you can test for Light Chlorophyll Carbon Dioxide You can only test one at a time The others will be kept the same as they are the controlled variables

10. The variables - Light Use a piece of black paper or aluminium foil to cover up both sides of the leave

11. The variables - Chlorophyll Use variegated leaves for the investigation

12. The variables Carbon Dioxide Add Sodium Hydroxide to Absorb and Remove all Carbon Dioxide Add Sodium Bicarbonate to Increase Carbon Dioxide

13. Another method to investigate on photosynthesis Count the number of bubbles in a given time What are the limitations of counting bubbles?