Lec 7 - BIS2B Fall 2009 Lecture 7 Plant Resources The Nitrogen Cycle Roots obtain nutrients actively from the soil water solution Carbonic acid >

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BIS2B Fall 2009 Lecture 7. Plant Resources & The Nitrogen Cycle
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Roots obtain nutrients actively from the soil water solution. Carbonic acid > nutrient cations, which are taken up by the plant. Cation exchange with clay particle provides nutrients to plant: Ca, K, Mg, Notice absence of nitrogen, which is usually the nutrient limiting plant growth in nature!
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p. 786 - 787 Sadava. 1. Clay particles effectively hold and exchange cations, retained in the A (soil) horizon. 2. Most roots and most nutrient uptake occurs in the A horizon. 3. No comparable ABIOTIC mechanism for holding and exchanging anions, such as NO 3 - , nitrate. 5. Much N is in BIOTIC form, organic material, detritus, dead plant and animal material. 6. Detritus decomposes slowly. Soil animals, termites, earthworms, et cet. accelerate decomposition. 7. Decomposition releases ammonium ions, NH4+, which are taken up by roots more readily than nitrate ions. 8. In Agriculture, N fertilization accelerates plant growth. It is an outside supply of nitrate & ammonium.
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Out of thin air…and back into it! “In denitrification and nitrogen fixation, we see the visceral biological forces at work and intimate union of life with the fluxes and pools of global metabolism.” Tyler Volk, 1998. GAIA’s BODY: Toward a physiology of Earth. As quoted in Wolfe, D. W. 2001. “Tales from the Underground: A Natural History of Subterranean Life.”
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The Global Nitrogen Cycle 1. N FIXATION, biotic or Haber Bosch. X. Plant uptake of NH4 & transform it into protein. 2. NITRIFICATION, bacteria
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This note was uploaded on 04/21/2010 for the course BIS 2C BIS 2C taught by Professor Rizzo during the Winter '09 term at UC Davis.

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Lec 7 - BIS2B Fall 2009 Lecture 7 Plant Resources The Nitrogen Cycle Roots obtain nutrients actively from the soil water solution Carbonic acid >

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