13.2. Differentiation, Dedifferentiation and Redifferentiation

The cells derived from root apical and shoot-apical meristems and cambium differentiate and mature to perform specific functions. This act leading to maturation is termed as differentiation. During differentiation, cells undergo few to major structural changes both in their cell walls and protoplasm. For example, to form a tracheary element, the cells would lose their protoplasm. They also develop a very strong, elastic, lignocellulosic secondary cell walls, to carry water to long distances even under extreme tension.

Differentiation is the process where cells become specialized for specific functions. This occurs in cells that are part of the plant's growth areas, specifically root and shoot apical meristems. For instance, when some cells become tracheary elements, which are essential for transporting water, they give up their internal components (protoplasm) to develop stronger and thicker cell walls. These adaptations enable them to withstand internal pressure as they move water throughout the plant.

Think of differentiation like a person choosing a career. Just as a student might go from general studies to specializing in a specific field like engineering or medicine, plant cells evolve from general, undifferentiated cells to specialized ones that perform crucial tasks. Tracheary elements, similar to skilled engineers, have the specific structures necessary to perform their roles effectively.

Plants show another interesting phenomenon. The living differentiated cells, that by now have lost the capacity to divide can regain the capacity of division under certain conditions. This phenomenon is termed as dedifferentiation. For example, formation of meristems – interfascicular cambium and cork cambium from fully differentiated parenchyma cells.

Dedifferentiation refers to the ability of mature, specialized cells to revert back to a less specialized form and regain the capacity to divide. This usually happens when an organism needs to replace damaged parts or grow new tissues. For instance, certain types of differentiated cells in older plant tissues can transform back into meristematic cells, which can then grow and form new structures like cambium, contributing to the plant's ability to grow thicker stems or roots.

Imagine someone who has spent years working in a specialized job suddenly deciding to go back to school to learn something new. Just like this person regains the ability to learn and adapt, dedifferentiated plant cells can start dividing and develop into new tissue types, essentially giving the plant a chance to heal or adapt after injury.

While doing so, such meristems/tissues are able to divide and produce cells that once again lose the capacity to divide but mature to perform specific functions, i.e., get redifferentiated.

Redifferentiation occurs when the cells that have gone through dedifferentiation undergo another transformation to become specialized cells again. After assuming a meristematic state, these cells can divide for a while before settling back into specialized roles, performing functions akin to what is seen in differentiated cells. This process ensures that the plant can maintain its essential functions while also being able to adapt and grow.

Consider a person who has switched from a technical job to pursuing a new career in management, and after some time, returns to the technical field to become an expert once again. This ability to adapt and specialize anew is similar to redifferentiation, where plant cells cycle back to specialized functions after temporarily being in a more generalized state.

Recall, in Section 13.1.1, we have mentioned that the growth in plants is open, i.e., it can be indeterminate or determinate. Now, we may say that even differentiation in plants is open, because cells/tissues arising out of the same meristem have different structures at maturity.

The concept of 'open differentiation' means that cells emerging from the same source can differentiate into various types based on their position and environment. This variability allows plants to adapt their structures to specific roles within the plant, leading to diversity in cell function even when they originate from the same location. This adaptability helps maximize the function of each part of the plant.

Think about how siblings from the same family can grow up to be very different people with unique personalities based on their experiences and roles within their family. Similarly, plant cells can develop into various types, such as root-cap cells or epidermal cells, even when they are derived from the same meristematic tissue.

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