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Unit 5 Plants
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Economic value: wood products/lumber Connect the vascular tissue in the leaves to the vascular tissue in the roots, allowing water and dissolved substances to be transported throughout the body
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Raise and support the leaves (maximizing photosynthesis) and reproductive organs (maximizing the likelihood of being pollinated and producing fruits and seeds)
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Herbaceous Plants: plants that have stems that do not contain wood Relatively pliable stems Stems carry out photosynthesis Thin epidermis
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Vascular tissue in herbaceous plant stems are arranged in vascular bundles Vascular bundles contain xylem and phloem Xylem is always closer to the centre of the stem Phloem is always closer to the outside of the stem In monocots: ▪ Vascular bundles found through out the ground tissue In dicots: ▪ Vascular bundles form a ring
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Woody plants: Stems that contain wood Woody stems are relatively hard Have bark Usually do not carry out photosynthesis
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Wood stems grow thicker every year due to the presence of the vascular cambium Vascular Cambium: the meristematic cell layer in the vascular tissue that divides to form new xylem and phloem tissue Xylem is on the inside of the vascular cambium Phloem is on the outside
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Wood is many layers of xylem tissue cells Sapwood is the younger xylem through which water and minerals are transported to the leaves Eventually, the older xylem fills up with resin and oils and they no longer conduct water forming the heartwood which is very rigid and helps support the tree
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https://www.youtube.com/watch?v=jrXSHLy AQeQ https://www.youtube.com/watch?v=jrXSHLy AQeQ
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Bark consists of all tissues found outside the vascular cambium Phloem ▪ transports sugars made in the leaves throughout the plant. Cork cambium ▪ meristematic tissue that produces cork Cork ▪ the tough, outer layer of the tree that prevents water loss from the stem
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Growth only happens in the spring and summer In spring, vascular cambium grows rapidly, producing large xylem cells that have relatively thin walls that form a layer of lighter-coloured wood In summer, fewer xylem cells are produced and they have thicker cells walls that form a layer of darker-coloured wood The spring and summer wood together forms one growth ring
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Function of Roots: Anchors the plant Keeps it upright Absorbs waters and nutrients (0ther than carbohydrates) Store water and carbohydrates
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Taproot: a root system composed of a large, thick root; can have smaller lateral roots Fibrous: a root system made up of many small, branching roots
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Tip of root contains the root cap and a meristem Root Cap: mass of cells that form a protective covering for the meristem at the root tip; allows the root to penetrate the soil with minimal damage
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Root hairs project out of the epidermis and increase the surface area allowing for greater water and nutrient absorption Root cortex is a region of parenchyma cells beneath the epidermis where carbohydrates can be stored and water can be transported fro the epidermis to the xylem Endodermis: is the innermost layer of cells in the root cortex
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The endodermis cell walls are wrapped with a wax-like substance forming a continuous barrier called the Casparian strip. The Casparian strip prevents substances from passing through the spaces between the endodermal cells
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Vascular tissue is arranged differently in monocot roots and eudicot roots
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