Plant Tissues.pdf

 it gives rise to the ground tissues of the plant Promeristem gives rise to the meristems above Function: -involved in the perception of gravity and is known to determine the direction of root growth -produce mucilage that acts as a lubricant to aid root penetration into the s...

 it gives rise to the ground tissues of the plant Promeristem gives rise to the meristems above Function: -involved in the perception of gravity and is known to determine the direction of root growth -produce mucilage that acts as a lubricant to aid root penetration into the soil -forms a protective sheath around root tips Function: - for photosynthesis and storage of organic products -for repair and regeneration of damaged tissue (capable of cell division) Parenchyma cells containing starch in Ranunculus root c.s. Special types of parenchyma cells a. chlorenchyma - photosynthetic parenchyma - with abundant chloroplast - thin cell walls allow for light and carbon dioxide to pass through the chloroplast b. glandular cells (glandular trichomes) - Parenchyma cells that secrete nectar, fragrances, mucilage, resins and oils - cells contain few chloroplast but with abundant dictyosomes and endoplasmic reticulum c. transfer cells - Parenchyma cells that function for short distance transport of materials between cells - with highly convoluted cell walls - invagination of the cell wall increases the surface area of the cell membrane 20 x increasing the capacity for transport - occur in areas with high solute transport Ex. secretory glands of carnivorous plants, nectar secreting tissue of the plant d. aerenchyma - parenchymatous tissue consisting of large amounts of intercellular spaces - the space improves the gas exchange capacity of the tissue ex. spongy mesophyll of leaves for photosynthesis - also provide maximum support with minimal metabolic requirements  Lamellar collenchyma collenchyma Annular collenchyma parenchyma Lacunar collenchyma brachysclereids (stone cell) - isodiametric in shape -present in pulp of fruits, cortex, pith, pericarp of coconut shell brachysclereids (stone cells) in pear fruit  macrosclereids - rod like sclereids - present in bark and seed coat of leguminous plants macrosclereids in the bean seed coat and leaf tissue. osteosclerieds - bonelike sclereids - in seed coat and fruit wall Osteosclereids in the bean seed coat  astrosclereids - star shaped sclereids astrosclereids - in leaves of dicots and gymnosperms Sclerenchyma fibers c.s. Fibers Vascular tissue Fibers 1. Xylary fibers - fibers associated with xylem xylary fibers vessel element (xylem) 2. Extraxylary fibers - fibers associated with the cortex, pericyle and phloem (ex. phloem fiber cap) Epidermis Cortex Cortical fibers (Phloem fiber cap) A. Epidermis (Dermal Tissue) B. Vascular tissues  G E S S Stoma S E E G Types of trichomes Anatomy of a glandular trichome Colleter – secrete sticky substances; mostly on bud scales ex. Rosa Glandular trichome Muntigia calabure stem Scale trichomes Two types of conducting cells (tracheary elements): i. tracheids -long thin cells with tapered ends -water moves from cell to cell by simple pits (thinner regions where only primary walls are present) -secondary walls are hardened with lignin  Types of pit: 1. simple pits 2.bordered pits – with extra wall material that reinforces the pit membrane Bordered pits Tracheids with bordered pits  wider, shorter, thinner walled and less tapered than tracheids - aligned end to end forming long micropipes - the end walls are perforated (perforation plates) enabling water to flow freely - side walls provided with pits for lateral transport of water  Classification of the Xylem tissue 1.primary xylem - xylem tissue produced by the procambium in the primary body 2 kinds: i.protoxylem – the first formed elements of the primary xylem ii. metaxylem – primary xylem which has undergone differentiation after the protoxylem 2.secondary xylem – produced by the vascular cambium Protoxylem (P) and metaxylem (M) P P M M P P  Associated tissue of the xylem a. Xylem parenchyma -thin walled living parenchymatous cells -for storage of substances and lateral transport of water and minerals b. Xylem fibers - sclerenchyma fibers that form the wood in older plants Associated tissue of the xylem (Xylem fiber) Xylem (ray) parenchyma Xylem fibers Vessel element Vessel element Vessel element Tracheid Tracheid  Tracheids Xylem fibers Vessel element Xylem parenchyma Two components: a. Xylem tissue b. Phloem tissue -conduct nutrient organic compounds (sugars) and some mineral ions from site of synthesis (leaves) to other parts of the plant body  Cell components of the phloem tissue: i.sieve tube members/elements -cells are alive at functional maturity -protoplast have no organelles ex. nucleus, ribosomes and vacuoles -end walls have pores called sieve plates where fluids flow from cell to cell -functions to transport sugars throughout the plant body  Cell components of the phloem tissue: ii. companion cells -connected to sieve tubes by plasmodesmata -living cells whose organelles may also function for the adjacent sieve tube member -functions to help load and unload sugars into the sieve tube members  Associated Tissue of the Phloem: i. Phloem Parenchyma Phloem - thin walled living fiber parenchyma cells near sieve tube members ii.Phloem Fibers Sieve tube member -supporting tissue compose of sclerenchyma fibers - forms the phloem fiber cap  Phloem fibers (phloem fiber cap) Phloem parenchyma Companion cells Sieve tube members