PAR stands for Photsynthetically Active Radition. Which is between 400 - 700 nm Photosynthetic rate is maximum in blue and red light. Green light induces lowest rate of photosynthesis.

DCMI stands for dichloro dimethyl urea. It can inhibit electron flow during light reaction of photosynthesis. Non cyclic photophosphorylation can be inhibited by DCMI.

They are proteinaceous pigments, soluble inwater, and do not contain Mg and Phytol tail. They exist in two forms such as
1. Phycocyanin found in cyanobacteria
2. Phycoerythrin found in rhodophycean algae (Red algae).

Quantasomes are the morphological expression of physiological photosynthetic units, located on the inner membrane of thylakoid lamellae. One quantasome contains about 230 chlorophyll molecules. It constitutes a photosynthetic unit.

(i) No. there is no scientific proof for this statement. During day time photosynthesis takes place oxygen is evolved.
(ii) This reaction requires light hence the above statement is incorrect.

(i) Group A shows maximum photosynthesis. chlorophyll pigments of the spectrum is (400 - 450 nm), hence the photosynthesis is high.
(ii) Group B will show negligible amount of photosynthesis, because chlorophyll does not absorb any light in this region (500 - 550nm). It reflects green.

1) When photons are activated reaction centre of Pigment system II(P680), electrons are moved to the high energy level. Electrons from high energy state passes through series of electron carriers like Plastoquinone, Cytochrome complex, Plastocyanin and finally accepted by PSI (P700). During this movement of electrons from PS II to PS I ATP is generated.
2) PS I (P700) is activated by light, electrons are moved to high energy state and accepted by electron acceptor molecule Ferredoxin Reducing Substance (FRS). During the downhill movement through Ferredoxin, electrons are transferred to NADP⁺ and reduced into NADPH + H⁺ (H⁺ formed from splitting of water by light).
3) Electrons released from the Photosystem II are not cycled back. It is used for the reduction NADP⁺ in to NADPH ⁺ H⁺. During the electron transport it generates ATP and hence this type of photophosphorylation is called Non-Cyclic Photophosphorylation. The electron flow looks like the appearance of letter 'Z' and so known as Z scheme.
4) When there is availability of NADP⁺ for reduction and when there is splitting of water molecules both PS I and PS II are activated. Non-Cyclic electron transport PS I and PS II both are involved co-operatively to transport electrons from water to NADP⁺. In oxygenic species Non-cyclic electron transport takes place in three stages:
i) Electron transport from water to P 680: Splitting of water molecule produce electrons, protons and oxygen. Electrons lost by the PS II (P680) are replaced by electrons from splitting of water molecule.
ii) Electron transport from P 680 to P 700: Electron flow starts from P 680 through a series of electron carrier molecules like Plastoquinone (PQ), Cytochrome b6-f Complex, Plastocyanin (PC) and finally reaches P700 (PSI).
iii) Electron transport from P 700 to NADP+: PSI (P700) is excited now and the electrons pass to high energy level. When electron travels downhill through ferredoxin, NADP+ is reduced to NADPH+ H+.

(i) C₄ cycle/Di - carboxylic acid pathway/ Di - carboxylation pathway is an adaptive mechanism.
(ii) It takes place in two phases. First phase takes place in stroma of mesophyll cells, where the CO₂ acceptor molecule 3-Carbon compound, phosphoenol pyruvate (PEP) to form 4-carbon oxalo acetic acid (OAA). The first product is a 4-carbon and so it is named as C₄ cycle. Oxalo acetic acid is a dicarboxylic acid and hence this cycle is also known as dicarboxylic acid pathway.
(iii) Carbondioxide fixation takes place in two places one in mesophyll and another in bundle sheath cell.
(iv) C₄ plants requires 5 ATP and 2NADPH + H⁺ to fix one molecule of CO₂.

Stage: I Mesophyll Cells

(i) Oxaloacetic acid (OAA) is converted into malic acid or aspartic acid and is transported to the bundle sheath cells through plasmodesmata.
Stage: II Bundle Sheath Cells
(i) Malic acid undergoes decarboxylation and produces a 3 carbon compound Pyruvic acid and CO₂.
(ii) The released CO₂ combines with RUBP and follows the calvin cycle and finally sugar is released to the phloem.
(iii) Pyruvic acid is transported to the mesophyll cells.

1) Plants having C₄ cycle are mainly of tropical and sub-tropical regions and are able to survive in environment with low CO₂ concentration.
2) C₄ plants are partially adapted to drought conditions.
3) Oxygen has no inhibitory effect on C₄ cycle since PEP carboxylase is insensitive to O₂.

1) During photosynthesis oxygen is evolved from water.
2) Electrons for the reduction of CO₂ are obtained from water.
3) Reduced substance produced, later helps to reduce CO₂
2H₂0+ 2A\(\rightarrow\)AH₂+O₂

Carotenoids are yellow to orange pigments, mostly tetraterpens and these pigments absorb light strongly in the blue to violet region of visible spectrum. These pigments protect chlorophyll from photo-oxidative damage. Hence, they are called as shield pigments.

C₄ plants are more advantageous than C₃ plants because increasing the proportion of C₄ plants on earth could assist biosequestration of CO₂ and represent an important cilmate change avoidance strategy.