Plastids are cytoplasmic organelles that contain DNA and multiply independently of nuclear genes during mitosis and are dispersed more or less evenly to daughter cells. Correns (1909) discovered for the first time that plastids might be passed to offspring through the egg cytoplasm while examining leaf colouration in Mirabilis jalapa (four O’clock plant). The cytoplasm of the zygote in a variegated strain of Mirabilis contains both green and colourless plastids. These plastids are unequally distributed during cell division in the zygote to generate the embryo. On germination, such an embryo develops a variegated plant with three types of branches: green foliage, colourless foliage, and variegated (green and white) foliage. It was discovered that seeds produced by green branches created only green plants, while seeds produced by colourless branches produced colourless seedlings that did not survive due to a lack of chlorophyll. Seeds from the variegated branch, on the other hand, might create three types of progeny: green, colourless, or variegated plants.
This is because a variegated plant’s egg cell contains both green and white plastids. Some cells will obtain only green plastids, some only white plastids, while still others will receive both green and white plastids during cell division. Similarly, the offspring of such a branch may be green, white, or multicoloured. Through the cytoplasm of the egg, all kids receive maternal foliage traits
Plastids
Plastids are organelles with a double membrane that are present in the cells of plants and algae. Plastids are used in the production and storage of food. These frequently include pigments involved in photosynthesis as well as a variety of pigments that can alter the colour of the cell.
Types Of Plastid
There are several varieties of plastids, each with a distinct purpose. Among these, a few are classed primarily according to the presence or lack of biological pigments and their developmental phases.
- Chloroplasts
- Chromoplasts
- Gerontoplasts
- Leucoplasts
- Chloroplasts
Chloroplasts are biconvex, semi-porous, double membraned organelles found inside the mesophyll of plants. They are the locations where food is synthesised through the process of photosynthesis.
- Chromoplasts
The term “chromoplasts” refers to a place within the plant where all pigments are stored and generated. Typically, they are found on blooming plants, aged leaves, and fruits. Chloroplasts transform chromoplasts. Chromoplasts contain carotenoid pigments that contribute to the variety of colours found in leaves and fruits. The primary purpose of its vibrant colour is to attract pollinators.
- Gerontoplasts
These are essentially aged chloroplasts. Geronoplasts are the chloroplasts of leaves that assist in their conversion to other organelles when the leaf is not actively photosynthesising, which occurs in the fall months.
- Leucoplasts
These are non-pigmented, colourless organelles. Leucoplasts are often present in the majority of the plant’s non-photosynthetic sections, such as the roots. They serve as storage facilities for carbohydrates, lipids, and proteins, depending on the plants’ requirements. They are mostly employed for amino acid and fatty acid conversion.
Three kinds of leucoplasts exist:
- Amyloplasts — Amyloplasts are the most numerous of the three and are responsible for storing and synthesising starch.
- Proteinoplasts – Proteinoplasts aid in the storage of proteins required by a plant and are commonly found in seeds.
- Elaioplasts – Elaioplasts aid in the storage of fats and oils required by the plant.
Plastid Inheritance
Numerous plants are descended from plastids from a single parent. Angiosperms acquire their plastids from the female gamete, but a large number of gymnosperms receive their plastids from male pollen. Algae inherit their plastids from a single parent. Plastids-DNA inheritance appears to be entirely uniparental. The inheritance of plastid appears to be more irregular during hybridisation.
Conclusion
We conclude that Plastids perform vital metabolic and signalling tasks in chloroplasts, such as photosynthetic processes. The function of plastids, however, is not confined to the generation of metabolites. The absence of plastids in the generative cell of pollen following uneven mitosis is frequently cited as a cause for maternal inheritance of plastid-associated characteristics in plants.