Bio 101 Day 17

Bio 101 Day 17 - Roots and M ineral Nut r i tion Roots...

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Roots and Mineral Nutrition Roots -Anchor: plant securely in soil -Absorb: water and dissolved minerals for transport through plant (xylem) -Store: starch and glucose (phloem) -Opportunistic Relationships: -Mycorrhizae (fungi) facilitate root uptake of essential minerals—extend root absorption -Rhizobia (bacteria) fix N 2 in roots for leguminous plants in low N 2 Taproot System -Main root formed from the radical (embryonic root) in the seedling -Lateral roots can become large and produce other roots -Reach far into soil to obtain deeply located water -Eudicots (maple, oak, fruit trees, strawberries); dandelion, some gymnosperms Fibrous Root System -Found in plants growing in shallow soil: -onions, crab grass, some trees (tap root is replaced by wide spreading fibrous roots after a few years) -Adventitious roots of same size developing from end of stem -Branching lateral roots Plant Tissue System -All tissue systems are continuous throughout the plant:
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-vascular system in the leaf is continuous with… -the vascular system in the stem, which is continuous with… -the vascular system in the root Primary Root Tissue System -Dermal: epidermis, no cuticle which would prevent root hairs and reduce absorption -cellulose in cell walls absorbs water -Ground Tissue: -Parenchyma (amyloplasts) -No supporting collenchymas; develop sclerenchyma as mature -Intercellular spaces for water uptake and aeration -Vascular Tissue: xylem and phloem Epidermal Root Hairs Radish (raphanus)—Each hair is an extension of a single cell of the root epidermis just behind growing tip—increases surface area of root in contact with soil. Continually replaced. Water is absorbed through cell walls (cellulose) from epidermal layer through cortex (parenchyma) Cortex (Ground Tissue) -Loosely packed parenchymal cells, amyloplasts store starch as energy reserves -Intercellular spaces—a pathway for water uptake and aeration of root -Oxygen for aerobic respiration diffuses from air spaces in soil to intercellular spaces of cortex and now travels to other cells of the root STELE OF EUDICOT ROOT
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Cortex Cells filled with amyloplasts—(parenchyma) Epidermis Cell Pericycle Cell—gives rise to lateral roots and meristems Phloem Cell—conducts sugars in sieve tubes
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Bio 101 Day 17 - Roots and M ineral Nut r i tion Roots...

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