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Cell types 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. Back to main biology menu Back Next Back to cell types menu Back to main selection menu Cell types Sclereids Several of the different sclereid types include: Brachysclereids Macrosclereids Osteosclereids Astrosclereids Trichosclereids Brachysclereids in purple coneflower seed. Back to main biology menu Back Next Back to cell types menu Back to main selection menu Cell types Sclereids 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. Back to main biology menu Back Next Lumen Back to cell types menu Pits Back to main selection menu Cell types Sclereids Macrosclereids are elongated sclereids usually found in the outer layer in the seed coat of legume seeds. Macrosclereids 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. Back to main biology menu Back Next Seed coat in eastern redbud (Cercis). Back to cell types menu Back to main selection menu Cell types Sclereids If the seed coat is macerated with appropriate chemicals, you can see the isolated shape of a macrosclereid. Macrosclereids Seed coat in eastern redbud (Cercis). Back to main biology menu Back Next Back to cell types menu Back to main selection menu Cell types Sclereids 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. Back to main biology menu Back Next Macrosclereids Light line Seed coat in eastern redbud (Cercis). Back to cell types menu Back to main selection menu Cell types Sclereids Electron micrograph of the seed coat in honeylocust (Gleditsia). Macrosclereids Back to main biology menu Back Next Back to cell types menu Back to main selection menu Cell types Sclereids 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. Macerated pea seed coats show groups of osteosclereids. In side view, you see the typical "bone shape" Back to main biology menu Back Next Back to cell types menu Back to main selection menu Cell types Sclereids Astrosclereids are branched, pointed, irregular (often star - shaped) sclereids. Astrosclereids are not a common type of sclereid. They can be found in specialized tissues like the floating leaves of water lily. Back to main biology menu Back Next Back to cell types menu Back to main selection menu Cell types Sclereids 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. Back to main biology menu Back Back to cell types menu Back to main selection menu
