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CHAPTER 35 ROOTS AND MINERAL NUTRITION ROOT STRUCTURE AND FUNCTION Taproot system o Consists of one main root that formed from the seedling’s enlarging radicle Radicle o Embryonic root Fibrous root system o Has several to many roots of similar size developing from the end of the stem Adventitious roots o Do not arise from pre-existing roots but from the stems Roots have root caps and root hairs Root cap o Protective, thimble-like layer many cells thick that covers the delicate root apical meristem Root hairs o Short-lived tubular extensions of epidermal cells located just behind the growing root tip The arrangement of vascular tissues distinguishes the roots of herbaceous eudicots and monocots In most herbaceous eudicot roots, the central core of vascular tissue lack piths Epidermis o Single layer of protective tissue that covers plant roots Cortex o Composed primarily of loosely packed parenchyma cells o Composes the bulk of a herbaceous eudicot root o Lack supporting collenchyma cells o May develop sclerenchyma as they age Symplast o Continuum of living cytoplasm, which is connected from one cell to the next by cytoplasmic bridges Plasmodesmata Apoplast o Consists of the interconnected porous cell walls of a plant, along which water and mineral ions move freely Endodermis o Inner layer of the cortex o Regulates the movement of water and minerals that enter the xylem in the
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root’s center o Has a Casparian strip Casparian strip o Contains a fatty material that is waterproof o Forces water and minerals from the apoplast into the cytoplasm of the endodermal cells Aquaporins o Integral membrane proteins that facilitate the rapid transport of water across the membrane Carrier-mediated active transport o Mineral ions are pumped against their concentration gradient
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This note was uploaded on 04/04/2008 for the course BIO 101 taught by Professor Martin during the Fall '08 term at Rutgers.

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