Plastids – Class 11 | Chapter – 8 | Short Notes Series PDF

Plastids: The plastid (Greek: plastós: formed, molded – plural plastids) is a major double-membrane organelle found in the cells of plants, algae, and some other eukaryotic organisms. Plastids were discovered and named by Ernst Haeckel, but A. F. W. Schimper was the first to grant them a clear definition. Plastids are the site of manufacture and storage of important chemical compounds used by the cell. Thus, they are primarily responsible for activities related to making and storing food. They often contain pigments used in photosynthesis, and the types of pigments in a plastid determine the cell’s color. They have a common evolutionary origin and possess a double-stranded DNA molecule that is circular, like that of prokaryotic cells.

Most Common plastids

• Chloroplasts
• Chromoplasts
• Gerontoplasts and
• Leucoplasts

Chloroplasts

Chloroplasts are biconvex shaped, semi-porous, double membraned, cell organelle found within the mesophyll of the plant cell. They are the sites for synthesizing food by the process of photosynthesis.

Chromoplasts

Chromoplasts is the name given to an area for all the pigments to be kept and synthesized in the plant. These can be usually found in flowering plants, ageing leaves and fruits. Chloroplasts convert into chromoplasts. Chromoplasts have carotenoid pigments that allow different colours that you see in leaves and fruits. The main reason for its different colour is for attracting pollinators.

Gerontoplasts

These are basically chloroplasts that go with the ageing process. Geronoplasts refer to the chloroplasts of the leaves that help to convert into different other organelles when the leaf is no longer using photosynthesis usually in an autumn month.

Leucoplasts

These are the non-pigmented organelles which are colourless. Leucoplasts are usually found in most of the non-photosynthetic parts of the plant like roots. They act as a storage sheds for starches, lipids, and proteins depending on the need of the plants. They are mostly used for converting amino acids and fatty acids.

Leucoplasts are of three types:

• Amyloplasts – Amyloplasts are greatest among all three and they store and synthesize starch.
• Proteinoplasts – Proteinoplasts help in storing the proteins that a plant needs and can be typically found in seeds.
• Elaioplasts -Elaioplast helps in storing fats and oils that are needed by the plant.

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By Team Learning Mantras