Question

Sclereids are present in (a) Fruit wall of nuts (b) Seed coat of legumes (c) Leaves of tea (d) All of these

Short answer

The correct answer is (d) All of these. Sclereids are present in all the mentioned plant parts: the fruit wall of nuts, the seed coat of legumes, and the leaves of tea.

Step-by-step solution

Understand the phenomenon of Sclereids

Sclereids, which are stiff, nonstretchable cells, are a part of sclerenchyma cells in plants. They add hardness and stiffness to plant parts by their thick cells walls which are composed of cellulose, hemicellulose, and lignin.

Analyze Each Option

Now, let's check each option - (a) the fruit wall of nuts, (b) the seed coat of legumes, (c) the leaves of tea. (a) Sclereids provide hardness to the shells of nuts; thus, they are present in the fruit wall of nuts. (b) They also provide the hardness to the seed coat of legumes and (c) sclereids provide the stiffness to the leaves of the tea plant.

Choose the Correct Answer

Having examined each option, it is evident that sclereids are present in every given plant part: the nut shells, the legume seed coats, and the tea plant leaves.

Key concepts

Sclerenchyma cells

Sclerenchyma cells are a type of plant cell known for their rigidity and strength. They serve an integral role in the structural support framework of plants. Unlike other cell types, sclerenchyma cells are characterized by their thick lignified cell walls which provide plants with the necessary support to stand upright and resist bending or breaking under pressure. There are two main types of sclerenchyma cells: fibres, which are elongated and typically found in stems and leaves, and sclereids, which are more varied in shape and distributed throughout the plant including in the seeds, stems, and leaves.

Understanding sclerenchyma cells is key to comprehending plant structure and defense mechanisms, such as why some plant parts like nuts and legumes have hard protective layers. Sclereids, in particular, are responsible for the 'gritty' texture of pears and add strength to nutshells, making them tough to crack. Throughout a plant's life, these cells become specialized to strengthen and support the plant tissue in which they are found. Once fully developed, sclerenchyma cells are typically dead, containing no protoplasm and leaving a strong cell wall that maintains the shape and structure of the plant.

Plant tissue hardness

The hardness of plant tissues is a critical trait that serves to protect plants from various environmental stresses and predators. It is often the result of specialized cells known as sclereids. These cells, by contributing to plant tissue hardness, play a prominent role in the plant's defensive architecture. For example, the tough seed coat of legumes and the rigid fruit wall of nuts are manifestations of plant tissue hardness. This trait is not just for protective purposes but also influences how plants interact with their surrounding environment.

When it comes to leaves, such as those of the tea plant, the presence of sclereids helps in maintaining their shape, reducing damage from strong winds or heavy rain. Furthermore, plant tissue hardness is vital during the plant's reproductive phase as the robust seed coats provided by sclerified cells contribute to seed dispersal and prevent premature germination. This hardness factor is a crucial aspect in a plant's life cycle and is an evolutionary adaptation to ensure survival and reproductive success.

Cell walls in plants

Composition and Function

The cell wall in plants is a complex structure that plays multiple crucial roles, including maintaining cell shape, providing protection, and regulating growth. It is primarily composed of cellulose fibers which are embedded in a matrix of hemicellulose, pectin, and in many cases, lignin. Cellulose lends tensile strength to the wall, whereas lignin is responsible for the rigidity and waterproof qualities. In sclerenchyma cells, lignin deposition is significant, contributing to the stiffness of the cell walls and, consequently, the overall hardness of certain plant tissues.

Significance of Lignification

Lignification, or the process of depositing lignin within the cell walls, is a hallmark of sclerenchyma cells, including sclereids. This process is vital for plants not only mechanically but also biologically, as lignified walls become more resistant to decay and pathogen invasion. The enhanced strength and impermeability of lignified cell walls safeguard the plant against environmental challenges and contribute significantly to the plant's longevity and structural integrity. For students studying botany, understanding the composition and function of cell walls, particularly in sclerenchyma cells, provides a clearer insight into how plants grow, develop, and survive in their habitats.