Types of Plastids

Plastids evolved as a result of an endosymbiotic relationship between photosynthetic prokaryotes and algae’s eukaryotic progenitors. Extreme modifications in plastid functions, including the creation of regulatory networks, occurred during the subsequent co-evolution of the enveloped plastid and eukaryote cells.Despite the fact that plastids are prevalent subcellular organelles in plants, previous study has favoured photosynthetic plastids such as chloroplasts or carotenoid-rich plastids such as chromoplasts.Furthermore, most current research on plastid regulatory mechanisms has focused on light switching and hormone therapies.

Types of Plastids

Undifferentiated plastids are called “proplastids” and are mainly found in meristematic and reproductive tissues, and they are identified as being small and having clear ultrastructures. They can be differentiated into “leucoplasts” in white, “chloroplasts” in green, and “chromoplasts” in either yellow, orange or red. Intermediate forms of chloroplasts are called “etioplasts” and senescent forms of chloroplasts are called “gerontoplasts”. Leucoplasts are categorised by their lack of colour, but can be further separated according to their biochemical characteristics based on their contents, such as starch enriched “amyloplasts”, protein enriched “proteinoplasts”, and lipid enriched “elaioplasts”

Proplastids

Proplastids are plastids that are undifferentiated and have a simple structure. So that organelle transmission can happen from generation to generation. When compared to other forms of plastid, they are colourless and small, with no distinguishing morphological features.

They’re primarily present in plant meristematic and egg cells, and occasionally during pollen generation in Pelargonium and barley species.

In the legume family, nodule proplastids in root tissues have also been shown to play an important part in nitrogen fixation biochemistry.

Chloroplasts

All photosynthetic organisms have chloroplasts, which are one of the most well-studied forms of plastids.

Photosynthetic protein complexes help them convert light energy into chemical energy. Multiple stacks of disk-like single lipid layers, known as thylakoids, form grana in chloroplasts, which build enormous lipid surface layers that attach photosynthetic protein complexes. The borders of the disk-like thylakoids also create plastoglobules, which contribute to expanding the lipid bilayer’s interior area.

Plastoglobules are found to be sites of carotenoid breakdown for apocarotenoid synthesis and accumulation of non-endogenous carotenoid.

Etioplasts

Etioplasts are a sort of intermediate plastid seen primarily in dark-grown seedlings. They are easily detected in seedlings that develop under the soil in natural conditions. They are a temporary stage of chloroplast development that is also seen as a condition of austerity because they prevent the formation of photosynthetic molecules and structures that are superfluous in the dark. Single well-arranged paracrystalline prolamellar bodies and tubular pro thylakoids are generated within etioplasts, and they are interspersed with numerous small plastoglobules containing significant levels of carotenoids, primarily lutein and violaxanthin, which aid in the transition to chloroplasts.

Amyloplasts

Starch granules that hold high density starch distinguish Amyloplasts. Various lipids, such as free fatty acids, lysophospholipids, lysophosphatidylcholine, and lysophosphatidylethanolamine, are also contained in the starch granules during the creation of amyloplast membranes.

Elaioplast

Elaioplasts have ultrastructures that are packed with hydrophobic materials like lipids and terpenoids. They are specialised for lipid biosynthesis and storage, although they also serve a variety of roles in different tissues. Elaioplasts are exported into secretory pockets in citrus fruits and can have a significant impact on aroma and taste.

Proteinoplasts

Proteinoplasts (also known as protoplasts, aleuroplasts, and aleuronaplasts) are plastid structures that include protein bodies, usually in the cytosolic region.Proteinoplasts are found in many different types of cells at various stages of plastid development, and they are assumed to have a function in protein storage according to their location and contents. Furthermore, the tobacco root proteinoplasts displayed high oxidase activity, which could indicate a specialised function.

Chromoplasts

Because they acquire enormous amounts of carotenoids, chromoplasts exhibit vibrant hues, which are determined by certain types of carotenoids. The concentrated carotenoids that form globular, round, coiled shaped carotenoid crystals at the mature stage of chromoplast formation are created and stored in hydrophobic structures called plastoglobules during chromoplast growth.

Gerontoplasts

Gerontoplasts are chloroplast-derived plastids that have been modified to allow for plastid recycling. They are most commonly found during senescence or under stressful situations. Because chloroplasts contain up to 80% of the leaf nitrogen pool, chloroplast breakdown and nutrient recycling are critical for plant viability.

Autophagy, Senescence Associated Vacuoles (SAV), and Chloroplast Vesiculation have all been implicated in the breakdown of chloroplast proteins (CV)

Type of plastids help in photosynthesis

Chloroplasts are a special type of plastid that aids in photosynthesis.

The chloroplast is a type of plastid that aids in photosynthesis. One of the most well-known plastids discovered in plant leaves is this one. The photosynthesis process is carried out by chloroplasts, which are mostly made up of thylakoids.

Photosynthesis is carried out in thylakoids. As a result, we can say that they serve as a storage and manufacturing facility for pigments in the plant.

Conclusion

Types of Plastids Undifferentiated plastids are called “proplastids’ ‘ and are mainly found in meristematic and reproductive tissues, and they are identified as being small and having clear ultrastructures. Intermediate forms of chloroplasts are called “etioplasts’ ‘ and senescent forms of chloroplasts are called “gerontoplasts”. They are a temporary stage of chloroplast development that is also seen as a condition of austerity because they prevent the formation of photosynthetic molecules and structures that are superfluous in the dark. Single well-arranged paracrystalline prolamellar bodies and tubular pro thylakoids are generated within etioplasts, and they are interspersed with numerous small plastoglobules containing significant levels of carotenoids, primarily lutein and violaxanthin, which aid in the transition to chloroplasts. Various lipids, such as free fatty acids, lysophospholipids, lysophosphatidylcholine,  and lysophosphatidylethanolamine, are also contained in the starch granules during the creation of amyloplast membranes. They are specialised for lipid biosynthesis and storage, although they also serve a variety of roles in different tissues.