WHAT ARE CHROMOPLASTS? - ANATOMY AND PHYSIOLOGY - 2025

The cromoplastos are cellular organelles that handle plant carotenoid pigments accumulate through which will be red, orange and yellow to some fruits, roots and old leaves.

These chromoplasts are part of the family of plastids or plastids, which are elements of plant cells that perform fundamental functions for plant organisms.

In addition to chromoplasts, there are also leukoplasts (they do not have pigments and their only function is to store), chloroplasts (their main function is photosynthesis) and proplastidia (they also do not have colors and fulfill functions associated with fixing nitrogen).

Chromoplasts can be derived from any of the plastids mentioned above, although they are most commonly derived from chloroplasts.

This is because the characteristic green pigments of chloroplasts are lost, and yellow, red and orange pigments produced by chromoplasts are given way.

Chromoplast functions

The main function of chromoplasts is to generate color, and some studies have concluded that this color assignment is important in promoting pollination, since it can attract animals responsible for pollinating or distributing seeds.

This type of plaster is very complex; it is even believed that all its functions are not yet known.

Chromoplasts have been found to be quite active in the metabolic field of plant organisms, due to the fact that they carry out activities related to the synthesis of different elements of these organisms.

Similarly, recent studies have found that chromoplast is capable of producing energy, a task previously attributed to other cellular organs. This process of respiration has been called chromorespiration.

The different types of chromoplasts that exist will be detailed below, and we will discuss chromo-respiration and the implications of this recent discovery.

Types of chromoplasts

There is a classification of chromoplasts based on the form that pigments take. It is important to note that it is very common for there to be different types of chromoplasts within the same organism.

The main types of chromoplasts are: globular, crystalline, tubular or fibrillar, and membranous.

On the other hand, it is also important to note that there are fruits and plants whose chromoplast composition can be confusing, to the point of not being able to identify with certainty what type of chromoplast it contains.

An example of this is the tomato, whose chromoplasts have both crystalline and membranous characteristics.

The characteristics of the main types of chromoplasts will be detailed below:

Globular

Globular chromoplasts are formed as a consequence of the accumulation of pigments and the disappearance of starches.

These are chromoplasts rich in lipid elements. Inside the chromoplasts are the so-called plastoglobules, which are small drops of lipid that contain and transport carotenes.

When they arise, these globular chromoplasts generate globules that do not have a membrane that covers them. Globular chromoplasts are usually found, for example, in kiwi fruit or lechoza.

Crystalline

Crystalline chromoplasts are characterized by having long, narrow, needle-shaped membranes in which pigments accumulate.

A kind of carotene crystals are then generated that are located within sections surrounded by membranes. These chromoplasts are commonly found in carrots and tomatoes.

Tubular or fibrillar

The most peculiar characteristic of tubular or fibrillar chromoplasts is that they contain structures in the form of tubes and vesicles where pigments accumulate. These can be found, for example, in roses.

Membranous

In the case of membranous chromoplasts, the pigments are stored in membranes wrapped in a coil, in a helical manner. This type of chromoplast is found, for example, in daffodils.

Chromorespiration

Chromoplasts have recently been found to fulfill an important function, previously reserved only for cell organelles, chloroplasts and mitochondria.

Scientific studies, published in 2014, found that chromoplasts are capable of producing chemical energy.

This means that they have the ability to synthesize adenosine triphosphate (ATP) molecules to regulate their metabolism. So chromoplasts have the ability to generate energy on their own.

This process of energy generation and synthesis of ATP is known as chromo-respiration.

These findings were produced by researchers Joaquín Azcón Bieto, Marta Renato, Albert Boronat and Irini Pateraki, from the University of Barcelona, ​​Spain; and they were published in the American journal Plant Physiology.

Chromoplasts, despite not having the ability to carry out oxygenic photosynthesis (the one in which oxygen is released), are very complex elements, with active action in the metabolic area, which even have functions unknown until now.

Chromoplasts and cyanobacteria

In the framework of the discovery of chromo-respiration, there was another interesting finding. In the structure of chromoplasts, an element was found that is usually part of an organism from which plastids are derived: cyanobacteria.

Cyanobacteria are bacteria physically similar to algae that are capable of photosynthesis; They are the only cells that do not have a cell nucleus and can carry out this process.

These bacteria can withstand extreme temperatures and inhabit both salty and fresh waters. These organisms are attributed the first generation of oxygen on the planet, which is why they have great importance in evolutionary terms.

So, despite the fact that chromoplasts are considered inactive plasts in terms of the photosynthesis process, the research carried out by scientists from the University of Barcelona found an element of the respiration of cyanobacteria in the respiratory process of chromoplasts.

In other words, this finding could indicate that chromoplasts may have functions similar to those of cyanobacteria, organisms so decisive in the perception of the planet as it is now known.

The study of chromoplasts is in full swing. They are so complex and interesting organelles that it has not yet been possible to fully determine the extent of their functions, and what implications they have for life on the planet.

References

1. Jiménez, L. and Merchant, H. "Cellular and molecular biology" (2003) in Google Books. Retrieved on August 21, 2017 from Google Books: books.google.co.ve.
2. "Structure and function of plastos" at the Institute of Higher Education in Mexico City. Retrieved on August 21, 2017 from the Institute of Higher Education in Mexico City: academicos.iems.edu.mx.
3. "They discover that plant chromoplasts produce chemical energy, like mitochondria and chloroplasts" (November 7, 2014) in Trends21. Retrieved on August 21, 2017 from Trends21: trends21.net.
4. Stange, C. "Carotenoids in Nature: Biosynthesis, Regulation and Function" (2016) in Google Books. Retrieved on August 21, 2017 from Google Books: books.google.co.ve.
5. "Chromoplasts" in Encyclopedia. Retrieved on August 21, 2017 from Encyclopedia: encyclopedia.com.