Sclereids

Sclereids are specialized cells formed in a variety of shapes.

They have lignified secondary cell walls and are non-living at maturity.

Their primary function is for mechanical support and protection.

Several of the different sclereid types include:

• Brachysclereids
• Macrosclereids
• Osteosclereids
• Astrosclereids
• Trichosclereids

Brachysclereids resemble parenchyma cells in shape, but are made almost entirely of secondary cell wall.

These non-living cells are also called stone cells because they form the "grit" in pear fruit.

The inner portion of a sclereid cell is called the Lumen. The lumen is an empty space in the center of a non-living cell bounded by secondary cell walls.

Macrosclereids are elongated sclereids usually found in the outer layer in the seed coat of legume seeds.

These cells are responsible for restricting water uptake by hard-seeded legumes.

They are also called Malphigian cells after the pioneering Italian 17th century plant anatomist.

The light line is a continuous line just beneath the outer surface of the macrosclereids in some legume seed coats.

It is actually, an optical refraction of light due to the properties of the macrosclereid.

It was once thought to be responsible for making these cells impermeable to water, but this is probably not the case.

Osterosclereids (also called bone or hour-glass cells) are columnar cells similar to macrosclereids except they are enlarged at the ends making them bone-shaped.

Trichosclereids are uncommon cells. They can be found in the leaves of olive and the aerial roots of the Swiss cheese plant (Monstera sp.).

These long trichosclereids are from macerated roots of the Swiss cheese plant.