Answer: The colour of A before the starch test is GREEN while after the starch test is BLUE- BLACK. The equation for photosynthesis is
6CO2 + 6H2O → C6H12O6 + 6O2.
Explanation:
PHOTOSYNTHESIS is the process by which green plants use energy from sunlight to manufacture their own food. It is a building up process since simple inorganic compounds such as carbondioxide and water are built up into large organic compounds such as glucose and OXYGEN is given off as a by product.
Oxygen given out in photosynthesis occurs in the light stage during the process of photolysis of water. This occurs when the chlorophyll traps, absorbs and captures light energy and become energised. The energised chlorophyll supplies energy which is to split molecules of water into hydrogen ion ( H+) and hydroxyl ion ( OH-). The hydroxyl ion is reconverted to water and oxygen is given out as a by product.
To show that chlorophyll is NECESSARY for photosynthesis, a variegated leaf with green and yellow patches is used for an experiment.
The green portion is marked A and the yellow portion marked B. The leaf is tested for starch using the procedure below:
--> place leaf in boiling water for half a minute to kill it.
--> decolorize leaf by placing it in hot alcohol.
--> dip decolorize leaf in hot water to soften it.
--> place leaf on tile and add iodine solution to it.
RESULT: It would be found that only the green parts contain starch as blue+black colouration is observed while yellow area is unaffected by iodine.
