Question

a plant is kept in sunlight for 8 hours but it doesn't show positive test with iodine. it means that

Answer 1

there is absence of chlorophyll in the leaves.

Answer 2

if some of the leaves aren't green then the possibility of them carrying out photosynthesis may be equal to zero or one other reason is that the other factors needed for photosynthesis to take place wasn't available...Moreover you should make sure that the test is carried out properly.