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Aerenchyma in stem cross section of a typical wetland plant. Aerenchyma or aeriferous parenchyma [1] or lacunae, is a modification of the parenchyma to form a spongy tissue that creates spaces or air channels in the leaves, stems and roots of some plants, which allows exchange of gases between the shoot and the root. [2]
Sclerenchyma is the tissue which makes the plant hard and stiff. Sclerenchyma is the supporting tissue in plants. Two types of sclerenchyma cells exist: fibers cellular and sclereids. Their cell walls consist of cellulose, hemicellulose, and lignin. Sclerenchyma cells are the principal supporting cells in plant tissues that have ceased elongation.
The surface of these roots is covered with porous lenticels, which lead to air-filled spongy tissue called aerenchyma. This tissue facilitates the diffusion of gases throughout the plant, as oxygen diffusion coefficient in air is four orders of magnitude greater than in water. [2] Pneumatophores of mangrove plant
Limnobium laevigatum is a floating aquatic plant, which can be mistaken for water hyacinth (Eichornia crassipes) due to their superficial similarity.Juvenile plants grow in rosettes of floating leaves that lie prostrate upon the water surface, a distinguishing character of the juvenile plant is the presence of spongy aerenchyma tissue upon the abaxial surface (underside) of the leaf.
Sclereids are a reduced form of sclerenchyma cells with highly thickened, lignified cellular walls that form small bundles of durable layers of tissue in most plants. [1] The presence of numerous sclereids form the cores of apples and produce the gritty texture of guavas .
The first lignified secondary walls evolved 430 million years ago, creating the structure necessary for vascular plants. The genes used to form the constituents of secondary cells walls have also been found in Physcomitrella patens. This suggests that a duplication of these genes was the driver of secondary cells wall formation. [2]
The basic function of the xylem is to transport water upward from the roots to parts of the plants such as stems and leaves, but it also transports nutrients. [ 1 ] [ 2 ] The word xylem is derived from the Ancient Greek word, ξύλον ( xylon ), meaning " wood "; the best-known xylem tissue is wood, though it is found throughout a plant. [ 3 ]
A lenticel is a porous tissue consisting of cells with large intercellular spaces in the periderm of the secondarily thickened organs and the bark of woody stems and roots of gymnosperms and dicotyledonous flowering plants. [2] It functions as a pore, providing a pathway for the direct exchange of gases between the internal tissues and ...