Plastids: Types, Functions, and Evolution

A plastome, i.e genome of plastid is a double stranded circular DNA.

Leucoplasts are required for monoterpene synthesis. Monoterpenes are terpenes, a class of organic compounds, produced by a variety of plants, particularly conifers. Leucoplasts contain droplets of lipid-like material at their margins leading to the belief that these organelles are involved in monoterpene synthesis. Leucoplasts contain enzymes of the monoterpene pathway, thus they might be involved in monoterpene synthesis.

Option 4 is correct; besides storing starch, plastids can also synthesise terpenes and fatty acids which can be used for producing energy and as raw material for the synthesis of other molecules.

Etioplasts are the chloroplasts that have not been exposed to light. They are usually found in flowering plants (Angiosperms) grown in the dark or if a plant is kept out of light for several days.

Pyrenoids are present in the chloroplasts of all species of algae. Their main function is to act as centres of carbon dioxide (CO₂) fixation, by generating and maintaining a CO₂ rich environment around the photosynthetic enzyme Rubisco.

Glaucocystophyta class of algae contain primary plastids muroplasts, which are similar to chloroplasts except that they have a cell wall that is similar to that of prokaryotes.

Dinoflagellates exhibit the process of kleptoplasty; they take up algae as food and keep the plastid of the digested alga to profit from the photosynthesis; after a while, the plastids are also digested.

Gymnosperms inherit plastids from male gamete.

Plastids, responsible for photosynthesis, possess numerous internal membrane layers called thylakoids. These are the sites of light absorption and ATP synthesis, and contain many proteins, including those involved in the electron transport chain. Photosynthetic pigments such as chlorophylls a, b and c, and some others like xanthophylls, carotenoids and phycobilins are also embedded within this membrane, thus plastids are responsible for photosynthesis containing numerous internal membranes.

Chromoplasts serve as attractants and identifiers. They are responsible for distinctive colours of flowers and fruits and thus, serve as attractants for pollination and identifiers for several plants.

Amyloplasts are the largest leucoplasts. They function in storage of starch.

Elaioplasts are the leucoplasts which store fats.

This is the correct match. Phycobilisomes are found in plastids of cyanobacteria, Alfaalfa show bi-parental inheritance of plastids. In Rafflesia plastid, genome loss was evidenced in 2014 and Haptophyta algae have complex plastids derived by secondary endosymbiosis of a red alga.