chapter 35 Roots and Mineral Nutrition

chapter 35 Roots and Mineral Nutrition - Roots and Mineral...

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Roots and Mineral Nutrition Root structure and function · Taproot- system consist of one main root that formed from the seedling’s enlarging radicle or embryonic root · Fibrous root system has several to many roots of similar size developing from the end of the stem with later roots branching off these roots. Originate first from the base of the embryonic root and later from stem tissue · Adventitious roots- roots originating from the stem, not the pre-existing roots · Root cap- protective, thimble like layer many cells thick that covers delicate root apical meristem · Lubrication helps root get through the soil · Cap sloughed off as cells travel, regenerates when fully gone · Root hairs- short-lived tubular extension of epidermal cells located just behind the growing root tip · Continually form in the area of cell maturation closest to the root tip to replace those that are dying off at the more mature end of the root hair zone Herbaceous Eudicot roots · Epidermis covers roots, single layer of protective tissue. Has root hairs but not a cuticle · Most of water that enters the cell moves along cell walls and does not enter the actual cell · Cortex made mostly of loosely packed parenchyma cells, composes the bulk of the root · Usually lack supporting collenchyma cells, because soil supports the root, though as they age they may develop some sclerenchyma · Storage- parenchyma usually have amyloplasts which store starch · Large intercellular spaces provide a pathway for water uptake and allow for aeration of the root · Symplast- continuum of living cytoplasm, connected from one cell to the next by bridges called plasmodesmata , moves some dissolved mineral ions through cortex · Apoplast- interconnected porous cell walls of a plant, along which water and mineral ions move freely · Endodermis- inner layer of the cortex, regulates the movement of water and minerals that enter the xylem in the root’s center · Structurally different- cells are snug and a special band like region, called a Casparian strip on its radial (side) and transverse (upper and lower) walls, contain suberin , a fatty waterproof material
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chapter 35 Roots and Mineral Nutrition - Roots and Mineral...

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