Chromoplasts

Chromoplasts are easily found in fruits, roots, flowers, and leaves; chromoplasts are the reason for the distinctive colours in fruits, flowers, roots, and ageing leaves. The most classic example is while ripening of the conversion of the chloroplast into chromoplasts. 

Chromoplasts explanation

Basically, chromoplasts are a type of plastids; now, what are plastids? Plastids are a subunit of plant cells found in algae and some other eukaryotic organisms. There are mainly three types of plastids -chromoplasts, chloroplasts, and leucoplasts. In terrestrial plants or land plants, chlorophyll is present in the plastids, which helps in photosynthesis; the chlorophyll plastids are called chloroplasts. Plastids can store food pigments like starch and can also synthesise fatty acids, which plants in the formation of further energy use. Chromoplast is coloured plastids used for pigment synthesis and storage. 

Chromoplasts are generally found in mature tissues and are obtained from the mature plastids. Chromoplasts and chloroplasts have identical DNA; the only very subtle difference they have in their DNA was found after a liquid chromatography analysis of tomato chromoplasts, which led to the revelation of the increased amount of cytosine methylation.  

The properties of chromoplasts 

The most important function of chromoplasts is to synthesise and store pigments, including orange, yellow, and many more red pigments. As per the colour variation, it depends upon the pigment they have. The major purpose of the chromoplasts and their colour pigmentation is to attract pollinators or coloured fruit eaters, which will help the plant in the dispersion of the seed. Moreover, chromoplasts are also found in the roots of plants like carrots, turnips, and sweet potatoes.  

In autumn, when the leaves change colours, it is because the leaves lose the green pigment, also known as chlorophyll. Often, the term chromoplasts are used to describe any form of plastid with pigment; this is done to differentiate the Chromoplast from different types of leucoplasts. Leucoplasts are also plastids but don’t have any pigments. 

Classification and structure of chromoplasts

Chromoplasts can be classified and differentiated into four major types.

• The chromoplasts are composed of proteic stroma with granules. 
• The chromoplasts are composed of crystals of proteins and non-crystalline solid pigment granules. 
• The chromoplasts are composed of protein and crystals of pigments. 
• The chromoplasts only consist of crystals. 

These four types of chromoplasts are discovered under a light microscope; an electron microscope reveals more levels, allowing more classification of chromoplasts’ structure such as globules, membranes, fibrils, crystals, and tubules.  

The electron microscope further brings five more categories, including globular chromoplasts: this contains plastoglobuli, which have to bear carotenoid pigments. Crystalline chromoplasts: as crystals, pure carotene is implanted. Tubular chromoplasts: In lipoprotein tubules. Carotenoids are present. Fibrillary chromoplasts and membranous chromoplasts:  in almost 20 concentric membranes, they are present. 

It is also discovered that different types of chromoplasts can coincide together in the same organ. To understand the different categories, here are some examples that include carrots with crystalline chromoplasts and mangoes with globular chromoplasts. 

What does a chromoplast do? 

The essential role of chromoplasts in a plant is attracting and bringing pollinators for pollination. As the chloroplasts have colour pigments, they attract animals and birds, which ultimately helps in the dispersal of seeds. The carotenoids present in chromoplasts have antioxidants. In carrots, carotene is the precursor of vitamin A.  Fucoxanthin is known to work against obesity and has shown an anti-diabetic effect. 

Difference between chromoplast, chloroplast, and leucoplast? 

Chloroplasts are plastids that are pigmented in different colours like green, mostly in yellow and red. While chloroplasts are generally in green colour, where leucoplasts are colourless. Chloroplasts consist of chlorophyll and other carotenoids, and chromoplasts consist of carotenoids and xanthophylls; they don’t have chlorophyll. Leucoplasts don’t have any such pigments. 

Chromoplasts give a distinct colour to the plants and their different parts. Chloroplasts perform the function of photosynthesis and produce food for plants. Leucoplasts store starch, proteins, and fat and have several nucleoids and granular stroma. Chloroplasts have ribosomes, thylakoids, and a lamellar system. Chromoplasts do not have any lamellar system.  

Conclusion

To conclude the topic of the biology of chromoplasts, it can be said that chromoplasts are part of the plant cell. More specifically is a type of plastid. There are three main types of plastids: chromoplasts, chloroplasts, and leucoplasts. Chloroplasts have a green pigment called chlorophyll present in them; thus, it plays the function of photosynthesis. Leucoplasts store the food in starch and fat form for the plant. Chromoplasts have colourful pigments, mostly red, yellow, and green. They are found in different parts of plants like fruits, roots, flowers, and leaves; chromoplasts are the reason for the distinctive colours in fruits, flowers, roots, and ageing leaves. The foremost function of the chromoplasts is to attract the pollinators like insects, birds, small fruit-eating animals for the dispersal of seed and pollination.