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+ Complex Tissues + Complex Tissues ! Complex tissues are made up of two or more cell types. ! Xylem - Chief conducting tissue for water and minerals absorbed by the roots. ! Vessels - Made of vessel elements. ! Long tubes open at each end. ! Tracheids - Tapered at the ends with pits that allow water passage between cells. ! Rays - Lateral conduction. + Complex Tissues - Xylem ! Tracheids ! Long, thin cells with pointed ends that conduct water vertically ! Line up in columns like pipes by overlapping their tapered ends ! die when reach maturity ! Water conducted through tubes made up of tracheid cell walls ! Wherever two ends join, small holes in the cell wall called pits line up to allow water to flow from one tracheid to another. + Complex Tissues - Xylem ! Pits always occur in pairs so that a pair of pits lines up on either side of the middle lamella, or center layer, of the cell wall. + Complex Tissues - Xylem !Vessel elements !barrel-shaped cells with open ends that conduct water vertically. !line up end to end forming columns, called vessels, that conduct water. !Some have completely open ends, while others have narrow strips of cell wall material that partially covers the ends !Die at maturity, like tracheids. + Complex Tissues - Xylem ! Ray cells………. ! Long lived parenchyma cells that extend laterally like the spokes of a wheel from the center of a woody stem out towards the exterior of the stem ! alive at maturity ! Transport materials horizontally from center outward + Complex Tissues - Xylem ! Xylem fibers – ! long, thin sclerenchyma cells ! Xylem parenchyma cells- that run parallel to the ! Living cells vessel element ! Distributed among tracheids and vessels ! Help strengthen and support xylem ! Store water and nutrients + Complex Tissues - Phloem ! Phloem brings sugar [glucose from photosynthesis] from the leaves to all parts of the plant body. ! Phloem is a living tissue at maturity. ! Two most common cell types……. ! Sieve Tube Elements - Large, cylindrical ! Sieve Plates – Porous/perforated region ! Companion Cells - Narrow, tapered ! Phloem also contains rays, fibers, and parenchyma cells. + Complex Tissues - Phloem ! Sieve tube element- ! Long, straw-like cells that link end to end to form sieve tubes ! Have lots of holes in the cell wall, forming a perforated plate called a sieve plate that allows the sugar solution to pass from one cell to the next in the sieve tube ! Alive at maturity ! Have no nucleus of their own, rely on their adjacent companion cell + Complex Tissues - Phloem Companion cells….. • Living, nucleated cells that occur adjacent to sieve tube element •Regulate the sieve tube elements and help them maintain themselves. Phloem ray cells….. • extend laterally through stems allowing horizontal transport of materials • phloem and xylem rays form from the same cell – similar in structure and function + Complex Tissue- Phloem ! Phloem fibers….. ! Long, thin sclerenchyma cells that run parallel to sieve-tube elements ! Help strengthen and support the phloem ! Phloem parenchyma cells….. ! Living parenchyma cells located between sieve tubes ! Stores water and food + Dermal Tissues !Dermal tissues cover plant surfaces or create barriers that protect the plant. !There are three tissue in the dermal tissue system: ! Epidermis ! Endodermis ! Periderm + Dermal Tissue- Epidermis ! A single layer of cells that separates the inside of the plant from its environment. ! Made mostly of parenchyma-like cells that are alive at maturity. + Dermal System- Epidermis ! Three primary functions of epidermis: ! Prevent water loss ! Epidermal cells secrete a waxy material called cutin, which forms a waxy layer called the cuticle on the outside of the plant. ! The cuticle provides water-proofing to the plant tissues so that their water does not evaporate into the air. ! Epidermal cells packed tightly together with very little space between the cells to prevent water evaporation. + Dermal System- Epidermis ! Protect plant from fungi and other attackers: ! The waxy cuticle and closely spaced cells prevent fungi, bacteria, and insects from being able to access the plant tissues. ! The wax makes the cells harder to penetrate, and the tightly packed cells prevent attackers from slipping into the interior of the plant through gaps between cells. + Dermal System- Epidermis ! Allow plant to exchange materials with the environment: ! Plants do gas exchange with the atmosphere. ! Plants need to take carbon dioxide from the air in order to do photosynthesis and they release oxygen gas as waste. ! The cuticle stops water loss but also prevents gas exchange. ! Plants use openings in the epidermis called stomata for gas exchange. ! Guard cells open and close stomata as needed. + Dermal System- Epidermis ! Plants absorb water and minerals from the soil. ! Roots absorb water and minerals from the soil through their surface cells. ! Plants like orchids that grow up in the trees produce aerial roots called velamen. The peidermis of velamen is several cells thick and modified so that it’s very absorptive, allowing the plant to capture water and minerals from the air. + Dermal System- Epidermis + Dermal System- Endodermis ! The endodermis is a layer of cells between the cortex and vascular tissue in the roots, as well as some stems and leaves. ! Important to the overall water balance of plants because it helps regulate the uptake of water from the soil and helps prevent the loss of water from plants. + Dermal System- Periderm ! The periderm is the outermost tissue in woody plants, forming the outer bark. ! It is composed of mostly cork cells and parenchyma cells. ! The cork cells of the periderm help protect the stem. ! Layers of cork cells are produced by the cork cambium. + Dermal System- Periderm ! The cork cells produce a waxy substance called suberin, which helps protect the stem from water loss and attack from fungi and other pests. ! Cork cells die at maturity. ! The parenchyma cells of the periderm allow gas exchange with the environment. ! The cork cambium also produces clusters of parenchyma cells, forming pockets of tissue called lenticels. + Dermal System- Periderm ! The parenchyma cells aren’t waxed, so they can still exchange gasses like carbon dioxide and oxygen with the environment. + Complex Tissues ! Secretory Cells and Tissue ! Secretory cells may function individually or as part of a secretory tissue. ! Flower nectar ! Citrus oils ! Glandular hair mucilage ! 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