Ground Tissues Lesson 5 PDF

GROUND TISSUES GROUND TISSUES  Ground Tissue System TISSUE CELL TYPES LOCATION FUNCTION Parenchyma Parenchyma Throughout the Primary sites of plant the metabolic...

GROUND TISSUES GROUND TISSUES  Ground Tissue System TISSUE CELL TYPES LOCATION FUNCTION Parenchyma Parenchyma Throughout the Primary sites of plant the metabolic functions (photosynthesis, storage, secretion) Collenchyma Collenchyma Under the Flexible support stem epidermis in primary plant body. Sclerenchyma Fiber, Sclereid Throughout the Rigid support and plant protection.  Parenchyma tissue ▪Simple tissue ▪Composition: parenchyma cells ▪ with thin primary cell walls; ▪ always alive, usually isodiametric and only seldom elongated. Parenchyma cells and relatively large intercellular spaces in a cross-section through the stem of Geum urbanum. The preparation has been stained with coriphosphin. The middle lamina displays a red fluorescence. Parenchyma tissue ▪large vacuoles for storage ▪Occurrence: Found throughout the plant body ▪ Most common type of cell and tissues. ▪With an ability to differentiate into other kinds of cells Parenchyma…. ▪Functions: Primary sites of the metabolic functions. ▪Photosynthesis ▪Storage – starch grains, oil droplets, water and salts (sometimes visible as crystals) ▪Secretion – Resins, tannins, hormones, enzymes, and sugary nectar Types of Parenchyma I. Aerenchyma: ▪Intercellular spaces filled with air - helping in aeration and buoyancy ▪Large in size and many in number. ▪Cells occupy a smaller area - provide the required strength to the aquatic plants ▪Air spaces are also seen in roots of grasses, petioles of canna, aroids etc.  Types of Parenchyma II. Chlorenchyma: ▪Cells of photosynthetic parenchyma contain numerous chloroplasts. ▪Commonly seen in leaves, sometimes in young shoots. ▪ ▪Cells of Chlorenchyma are of two types – 1) Palisade cells that is elongated and compactly arranged. 2) Spongy cells that are spaciously arranged and irregularly shaped.  Types of Parenchyma III. Prosenchyma ▪ Cells are elongated, have thick walls and serve as a supporting tissue. Example: Endosperm cells of seeds. IV. Armed Parenchyma ▪Cells are stellate in shape with inward projections of cell wall as arms. collenchyma tissue ▪Simple flexible tissue ▪Composition: Collenchyma cells; living ▪ elongated; cell walls of unevenly thickened and are especially thick in the corners. ▪Occurrence: long strands near stem surfaces just beneath stem epidermis and along leaf veins. (Hypodermal) ▪Function: Support ▪Three forms of collenchyma are recognized based on the types of thickenings – ▪1. Thickening is on the tangential wall – lamellar collenchyma. ▪2. Deposition of pectin is in the corners where several cells meet-angular collenchyma. ▪3. Thickenings are around the intercellular spaces – lacunar collenchyma.  sclerenchyma tissue ▪Composition: Sclerenchyma cells ▪ Cells with primary and secondary cell walls. ▪ Secondary cell walls becomes strong and due to extreme hardening (Lignified) ▪ At functional maturity, s.c. are often dead. ▪ At maturity, usually the cells are devoid of protoplast. ▪Occurrence: throughout the plant body, common in stems and certain leaves. ▪Function: Mechanical Support Classification of Sclerenchyma cells ▪Sclereids ✓ short cells that are variable in shape ✓Occurrence: shells in nuts and the stones of fruits (cherries and peaches) ✓Sclereids are commonly found in fruit wall, seed coat, epidermal scales, and occasionally found in cortex, pith, mesophyll and petiole of submerged aquatics. ▪Fibers ✓ Long, tapered cells that often occur in groups or clumps. ✓ Abundant in wood, inner bark and leaf veins of flowering plants ✓ Longest fiber is seen in Boehmeria nivea (55 cms).  There are many types of sclereids 1. Asterosclereids are star shaped 2. Macrosclereids are similar to palisade cells 3. Osteosclereids are bone like that are enlarged at their ends 4. Brachysclereids parenchyma are isodiametric like 5. Trichosclereids are hard needlelike branched cells