Nutrient_Uptake_and_Roots - Ioana Dobre Nutrient Uptake and...

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Ioana Dobre Nutrient Uptake and Roots 2 basic types of roots - Tap root – typical of dicots with deep primary root and many laterals - Fibrous root – monocots with adventitious roots from stem (finely divided, derived not from root tissue but from stem material) Specialty roots such as the stilt root in mangrove - Found in “walking palms” - Stem produces adventitious roots that come out of the stem, go down into the soil and anchor the plant - Seen in mangroves and other tropical plants, where the plants are trying to adapt to very soft soil layer and frequent flooding Root anatomy - Root cap with root hairs which facilitate water and mineral absorption - 3 different zones Zone of cell division (meristem i.e rapidly dividing tissue ) Zone of elongation (c ells once formed, elongate under the influence of plant hormones) Zone of differentiation Tissues at the root tip - Root cap mainly consists of dead lignified cells that protect the growing root as it penetrates the soil - Cell division zone with apical meristem near cap gives rise to 3 differentiated meristems which divide to form differentiated tissues: 1) Protoderm – forms epidermis 2) Ground meristem – forms parenchyma 3) Procambium – forms vascular bundles ( Vascular bundles consist of xylem and phloem, and they’re found at the center of the root) ) - Meristem makes hormone IAA – most important plant hormone! It moves from the tip into the zone of elongation ) The vascular bundle contains phloem and xylem which are surrounded by a tissue called endodermis (very important) - Endodermis surrounds the stele (xylem + phloem) - The inner ring of the endodermis is called the pericycle - The cortex (Endodermis, parenchyma + epidermis) is surrounded by the epidermis
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Ioana Dobre - The parenchyma (less differentiated tissues) – serves as starch storage **Take a look at the in-class diagrams of the root How does IAA work? - It works on the cells that have been produced by mitosis and stimulates them to grow - Pumps H+ ions into the cell wall and K+ ions move from the outside into the cell - K+ entry increases the salt concentration inside the cell and thus it draws water through osmosis - This increases the osmotic pressure and cases the cells to swell up - The H+ make the cell wall malleable so that later on when the IAA level drops and H+ ions disappear the cell wall can become rigid again Differentiation zone Cortex (outer part):
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Nutrient_Uptake_and_Roots - Ioana Dobre Nutrient Uptake and...

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