6.2.2 (i). Simple Permanent Tissue

A few layers of cells beneath the epidermis are generally simple permanent tissue. What happens to the cells formed by meristematic tissue? They take up a specific role and lose the ability to divide. As a result, they form a permanent tissue. This process of taking up a permanent shape, size, and a function is called differentiation. Differentiation leads to the development of various types of permanent tissues.

Simple permanent tissue is a type of plant tissue that is formed when cells, originally derived from meristematic tissue, take on specific roles and stop dividing. This change in function and structure is known as differentiation, which results in permanent tissues that carry out different functions in the plant. The term 'permanent' indicates that these cells have found their specific places and jobs within the plant structure and will not grow or divide further.

Think of a student who begins in a school learning various subjects. Over time, they become specialized in one subject, like math. Once they focus on math, they might not need to learn other subjects in-depth anymore. Similarly, meristematic cells, once they find their function, specialize and become permanent cells that serve specific purposes in the plant.

Parenchyma is the most common simple permanent tissue. It consists of relatively unspecialised cells with thin cell walls. They are living cells. They are usually loosely arranged, thus large spaces between cells (intercellular spaces) are found in this tissue. This tissue generally stores food.

Parenchyma is one of the most abundant types of simple permanent tissue in plants. These cells are not heavily specialized, meaning they can perform various functions, the primary one being the storage of food. Their thin walls and loosely packed arrangement allow for air spaces between the cells, facilitating gas exchange and storage. This flexible nature allows parenchyma to adapt to different roles in various parts of the plant, such as storage in roots or photosynthesis in leaves when they contain chlorophyll.

Consider a sponge that can hold water in its holes. The parenchyma tissue acts like the sponge in that it has a lot of space to store and retain water and nutrients, which is crucial for the plant's survival.

In some situations, it contains chlorophyll and performs photosynthesis, and then it is called chlorenchyma. In aquatic plants, large air cavities are present in parenchyma to help them float. Such a parenchyma type is called aerenchyma.

Parenchyma can further differentiate into specialized forms such as chlorenchyma and aerenchyma. Chlorenchyma contains chlorophyll, enabling it to perform photosynthesis, while aerenchyma, found in aquatic plants, is characterized by its large air cavities. These cavities help the plants float in water, providing buoyancy and enabling them to access sunlight more effectively for photosynthesis.

Think about how a boat floats on water. Aerenchyma tissue, with its air-filled spaces, helps aquatic plants remain buoyant, much like air-filled compartments make a boat stable and afloat.

The flexibility in plants is due to another permanent tissue, collenchyma. It allows bending of various parts of a plant like tendrils and stems of climbers without breaking. It also provides mechanical support.

Collenchyma is a type of simple permanent tissue that provides flexibility to plants. Its cells have thickened corners and are elongated, which helps in supporting young, growing parts of the plant. This structural flexibility is crucial for plant parts that need to bend without breaking, such as the stems of climbing plants, which must navigate their growth among other structures and obstacles.

Imagine a young tree that bends in the wind but does not snap; the collenchyma provides the necessary strength and flexibility, similar to how a gymnast bends and stretches their body while maintaining control during performances.

Yet another type of permanent tissue is sclerenchyma. It is the tissue which makes the plant hard and stiff. We have seen the husk of a coconut. It is made of sclerenchymatous tissue. The cells of this tissue are dead. They are long and narrow as the walls are thickened due to lignin.

Sclerenchyma provides strength and rigidity to plants, making them tough and durable. Unlike parenchyma and collenchyma, the cells in sclerenchyma are dead at maturity and have thick, lignified walls. This tissue is found in areas where structural support is a priority, such as the hard shells of nuts or the fibers in the stems of certain plants.

Consider the tough outer shell of a coconut. This hard shell protects the seed within, just as sclerenchyma tissue provides protective strength to parts of the plant, ensuring its survival in tough environments.

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