DENDROLOGY

Detailed explanation-1: -Chlorophyll a, chlorophyll b, carotene and xanthophyll are different pigments found in a chloroplast. Among these, only chlorophyll a can participate directly in photosynthesis. All other pigments absorb light and transfer it to chlorophyll a. Hence, they are called accessory pigments.

Detailed explanation-2: -Solution: P680 is a specialised form of chlorophyll a present in the reaction center of PSII. Reaction center chlorophyll a molecules are directly involved in photosynthesis by directly ejecting electrons. Hence they are not accessory pigments.

Detailed explanation-3: -There are three pigments that are most effective in driving photosynthesis: the primary pigment is chlorophyll a, and the main accessory pigments are chlorophyll b and carotenoids. Neither chlorophyll a nor b has the ability to absorb green light, which is why the leaves of plants appear green.

Detailed explanation-4: -Chlorophylla is not an accessory pigment.