1) Emerson conducted experiment with chlorella using monochromatic light to measure quantum yield. (photosynthetic yield).
2) He found that the monochromatic light oflonger wavelength (far red light) when supplemented with shorter wavelength of light (red light) enhanced photosynthetic yield.
3) This enhancement of photosynthetic yield is referred to as Emerson's Enhancement Effect

Yellow (C₄₀H₅₆O₂) pigments are like carotenes but contain oxygen. Lutein is responsible for yellow colour change of leaves during autumn season. Ex: Lutein, Violaxanthin and Fucoxanthin.

Chlorophyll molecules have a tadpole like structure. It consists of Mg-Porphyrin head (Hydrophilic Head) and (Lipophilic tail) Phytol tail. The Porphyrin head consists of four pyrrol rings linked together by C-H bridges. Each pyrrole ring comprises of four carbons and one nitrogen atom. Porphyrin ring has several side groups which alter the properties of the pigment.

1) In light reaction of photosynthesis, Photolysis of water is due to strong oxidant which is yet unknown and designated as Z or Yz. Widely accepted theory proposed by Kok et al., (1970) explaining photo oxidation of water is Water Oxidising Clock (Or) S' State Mechanism.
2) It consists of a series of 5 states called as S_o,S₁, S₂,S₃ and S₄. Each state acquires positive charge by a photon (hv) and after the S₄ state it acquires 4 positive charges, four electrons and evolution of oxygen. Two molecules of Water go back to the S_o. At the end of photolysis 4 H⁺, 4 e- and 0₂ are evolved from water.

Chlorophyll is synthesized from intermediates of respiration and photosynthesis. Succinc acid an intermediate of Kreb's cycle is activated by the addition of Coenzyme A and it reacts with a simple amino acid glycine and the reaction goes on to produce chlorophyll a. Biosynthesis of Chlorophyll a requires Mg, Fe, Cu, Zn, Mn, K and Nitrogen.