(a) List three events that occur during the process of photosynthesis. State in brief the role of stomata in this process.

(b) Describe an experiment to show that sunlight is essential for photosynthesis.

(a) Three Events of Photosynthesis: Information is transmitted from one plant cell to another through plasmodesmata and hormones.

Role of Stomata in Photosynthesis. Inward diffusion of carbon dioxide and outward diffusion of oxygen.

(b) Sunlight is Essential for Photosynthesis: It is the source of energy for photosynthesis. Light is visible part of the electromagnetic radiations. It has a wavelength of 390-760 nm. Photosynthetically active radiations or PAR are 400-700 nm. Natural source of light is sun but artificial light can also provide energy to plants for their photosynthesis. Plants absorb light mostly in violet-blue and red parts of visible light. Violet-blue light carries more energy as compared to red light. Plants growing under shade of others receive mostly green and some violet light. They have lower rates of photosynthesis.

Light has two functions, photolysis of water and excitation of chlorophyll to emit electrons. Photolysis of water produces oxygen, protons, and electrons. Electrons and protons (Hydrogen ions) help in producing ATP and NADPH2, popularly called assimilatory power.