(a) Experiment to show that green plants require sunlight for photosynthesis;
(i) Take two potted plants and get them well watered
(ii) De-starch the leaves by keeping plants in a dark cupboard 'at least for 24 hours/overnight
(iii) Then test leaf samples of both plants for starch
(iv) The result is negative/yellowish-brown colour which shows absence of starch
(v) Leave one potted plant in the dark cupboard as a control and put the other plant in sunlight for 4-6 hours
(vi) Re-test leaves from both plants for starch. You will discover that
(vii) leaves from plant exposed to sunlight show presence of starch, while those from the control plant/kept in dark cupboard shows absence of starch
(viii) This indicates that sunlight is necessary for photosynthesis.
(b) Other conditions necessary for photosynthesis include the following:
(i) Presence of water
(ii) carbon dioxide
(iii) chlorophyll/chloroplast
(vi) suitable temperature
(c) Site or part of dicotyledonous leaf where photosynthesis occurs is the palisade layer; because it contains more chloroplasts/chlorophyll; than the spongy layer/other parts. Palisade cells are located just beneath the upper epidermis; where the chlorophyll could absorb more sunlight
(d) Fate of food manufactured by green plants:
(i) Manufactured food/glucose; is trans-located to various parts of the plant through the phloem
(ii) This can be combined with other elements such as nitrogen and sulphur to form proteins; for growth. It can also be converted to starch and stored. It is needed/used in respiration/metabolic activities. It is broken down into carbon dioxide and water to produce energy. Other products like lipids and cellulose can also be manufactured from glucose.