Plant Tissues and Organs 2024 PDF

PLANT TISSUES AND ORGANS PAPER 1 - 23 MARKS TISSUE: ► Group of similar cells adapted for a particular function ORGANS: ► Group of different tissues performing a specific function CELL DIFFERENTIATION: ► Cells develop specific structures for specific functions MERISTEMATIC TISSUE...

PLANT TISSUES AND ORGANS PAPER 1 - 23 MARKS TISSUE: ► Group of similar cells adapted for a particular function ORGANS: ► Group of different tissues performing a specific function CELL DIFFERENTIATION: ► Cells develop specific structures for specific functions MERISTEMATIC TISSUE NAME LOCATION FUNCTION Apical Meristem Present at the growing tip of Increase in length of stem and root stem and root Lateral Meristem Found on the lateral sides of Increase in width of (also called roots and stem stem and root cambium) PERMANENT TISSUE ►Dermal tissue ►Vascular tissue ►Ground tissue DERMAL TISSUE TISSUE STRUCTURE FUNCTION Epidermis Outer layer around roots, Protects the underlying stems and leaves tissues from injury Single layer of brick-shaped Regulates gaseous and cells water loss Cells are transparent with no Allows sunlight through for intercellular air spaces photosynthesis Covered with a waxy cuticle Reduces water loss (Stem and leaf) Specialised epidermal cells root hairs (roots) To increase surface area for guard cells (stem and water absorption leaves) Transpiration  A Root hair (to draw) Surface view of epidermal cells Stomata (to draw) GROUND TISSUE TISSUE STRUCTURE FUNCTION PARENCHYMA Thin cell walls Stores food and water Large intercellular spaces Allows for gaseous exchange Large vacuoles and water movement SCLERENCHYMA Thick cells walls of lignin Structure and support Cells are dead and hollow Two types i.e. sclereids and fibres COLLENCHYMA Cells wall thickened in the corners Structure and support CHLORENCHYMA Specialised parenchyma with chloroplasts Photosynthesis To identify  VASCULAR TISSUE TISSUE STRUCTURE FUNCTION XYLEM Consists of xylem vessels and tracheids Transport water and Cells are elongated mineral salts from the Contains no living material roots to the rest of the plant Cell walls thickened by lignin Strengthening and support tissue Perforation plates Easy transport of water Walls of vessels and tracheids with pits For lateral transport PHLOEM Living, elongated cells without thickened Transport organic walls substances from the leaves to the rest of the plant Consists of sieve tubes and companion Companion cells to cells support sieve tubes End walls of sieve tubes with sieve plates Easy transport to form continuous tubes ROOT ANATOMY Functions of root systems: ►Anchorage ►Support ►Storage ►Absorption of water and mineral salts ►Transport ►Reproduction  External structure of the root REGION FUNCTION Root cap Protects the meristem Helps root tip to slide through soil easily Meristematic region Active cell division Region of elongation Where root grows longer Mature region Many root hairs to increase the surface area for water absorption With lateral roots and fully differentiated tissues  Internal structure of the root Epidermis: ► Outer layer of the root ► contains finger-like outgrowths, the root hairs. Cortex: ► Consists of parenchyma cells with large intercellular air spaces. ► Inner-most layer consists of a single layer of cells called the endodermis. ► The radial and transverse walls of the endodermis contain thickened strips known as the Casparian strips Internal structure of the root continued… Central cylinder: ► Under the endodermis there are thin-walled cells called the pericycle - Function of the pericycle is to form lateral/side roots ► On the inside of the pericycle is the vascular tissue that consists of xylem and phloem. STEM ANATOMY Functions of stems ► Transport ► Support and positioning: ► Hold leaves for photosynthesis ► Hold flowers for pollination and seed dispersal ► Tendrils, hooks and twining stems to support climbing plants ► Storage ► Reproduction- asexually ► Tubers, bulbs, rhizomes, stolons ► Anchorage ► Stolons and rhizomes ► Protection ► Thorns (spines) ► Photosynthesis ► Green ‘leaf like’ stems Internal structure of the stem Epidermis: ► forms the outer layer of the stem. Cortex: ► consists of collenchyma, parenchyma and endodermis. Central cylinder: ► Xylem and phloem occur in vascular bundles in the stem. ► The xylem is on the inside and the phloem on the outside. ► A layer of meristematic tissue, the cambium, occurs between the xylem and phloem. ► Cambium makes secondary thickening possible. ► The central region of the stem is the pith and consists of parenchyma cells LEAF ANATOMY Functions of the leaf ► Photosynthesis ► Transpiration ► Gaseous exchange Internal structure of the leaf  LEAF STRUCTURE FUNCTION SECTION Epidermi Covers upper and lower surfaces of the leaf Protects the underlying tissues. s Transparent Allows light through for photosynthesis. Waxy cuticle covers the epidermis. Cuticle reduces excessive moisture loss. Contain stomata Stomata are responsible for gaseous exchange and transpiration Mesophyl Palisade cells: Responsible for photosynthesis Elongated cells under the upper epidermis. (chlorenchyma) For deep penetration of light Contain large amount of chloroplasts. Maximum photosynthesis No intercellular air spaces between the cells Cell walls are thin Easy diffusion Spongy cells: Parenchyma cells with large intercellular air Responsible for photosynthesis and spaces gaseous exchange Contain many chloroplasts Vascular Xylem and phloem Xylem transports water and dissolved bundles mineral salts to the mesophyll cells Phloem transports produced organic nutrients to other parts of the plant. https://www.youtube.com/watch?v=J7vgZI1COoE