Sclereid

Komórka kamienna w bananie

Dionysia kossinskyi sclereids

Sclereids are a type of plant cell known for their thick, lignified walls, which contribute to the hardness and stiffness of plant tissues. They are a specialized form of sclerenchyma cells, which serve the primary function of providing mechanical support and protection to various parts of the plant. Unlike their counterpart, the fibres, sclereids are more variable in shape and often shorter. They are found in many different parts of plants, including the seed, fruit, stem, and leaves.

Types of Sclereids

Sclereids can be classified into several types based on their shape and location within the plant:

• Brachysclereids, or stone cells, are roughly isodiametric and can be found in the pear flesh, giving it a gritty texture.
• Astrosclereids are star-shaped and are commonly found in the leaves of certain plants, contributing to their stiffness.
• Osteosclereids resemble bone in shape and are often located in the layers around the vascular bundles.
• Fibrosclereids are elongated and can be found in the xylem or the hard shells of nuts.
• Trichosclereids, or hair-like sclereids, extend into the intercellular spaces of the plant tissue.

Function

The primary function of sclereids is to provide mechanical support and protection. Their hard, lignified walls help to reinforce the plant's structure, making it resistant to external pressures and damage. In addition, sclereids can also play a role in deterring herbivory by making the plant tissues harder to consume or by damaging the digestive systems of herbivores.

Distribution

Sclereids are distributed throughout various parts of the plant. Their presence in the seed coats helps protect the embryo during development and dispersal. In fruits, such as pears, sclereids contribute to the texture. In leaves and stems, they help maintain the plant's rigidity, allowing it to stand upright and resist bending or breaking under its own weight or external forces.

Development

Sclereids develop from parenchyma cells that undergo a secondary thickening process, where additional layers of cell wall material, primarily lignin, are deposited. This process is regulated by the plant's genetic makeup and environmental factors, which can influence the density, distribution, and morphology of sclereids.

Ecological and Economic Importance

Sclereids play a significant role in the ecology of plants by providing structural support and protection against herbivores and environmental stresses. Their presence in fruits and seeds affects the dispersal and germination strategies of plants, influencing ecological interactions and biodiversity. Economically, sclereids impact the texture and quality of certain fruits and vegetables, which can affect consumer preferences and market value.