Bio%20201%20S12%20Lect%2012%20%28True%29%20v2

Of 1 g kg dry weight micronutrients

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Unformatted text preview: by green) •  yellowing can also result from Fe deficiency because Fe is needed for chlorophyll synthesis •  N can easily move around the plant body; Fe cannot; in iron deficiency, growing leaves tend to show symptoms before older leaves that are finished growing defining required nutrients: hydroponic experiments •  Defining nutrients required for plant growth: hydroponics - research began in the mid 1800s on macronutrients •  Most recent work (much more precise control needed to demonstrate micronutrient requirements) - 1983 defined Nickel as an essen<al micronutrient •  see expt in Fig. 36.3 hPp://www.instructables.com/id/ Expandable_Hydroponics_System_from_Junk_Flood_an/ Soil •  provides: –  mineral nutrients –  water –  oxygen for roots soil horizons •  A: crucial for growing crops; leeching by water movement removes nutrients to B horizon, where they are oMen not available to plant roots; also contains decaying organic maPer •  can be lost by erosion [1930s Dust Bowl in Midwest, Great Plains] •  sand: air space plen<ful but doesn't hold much water •  clay: doesn't have much air space but binds minerals well •  loam: contains adequate amounts of sand, silt (fine par<cles), and clay - best for growing plants •  B: contains leeched minerals but liPle or no decaying organic maPer; some plant roots can reach B •  C: bedrock; plant roots typically do not reach C •  oMen essen<al for mineral availability to plant roots –  many crucial ions posi<vely charged (K+. Mg2+. Ca2+, NH4+); clay is nega<vely charged •  H+ from this aqueous reac<on in soil CO2 + H20 <- > H2CO3 <- > H+ + HCO3- •  •  •  •  binds to clay strongly and displace weaker binding mineral ca<ons (posi<vely charged ions) This is called ion exchange –  The displaced mineral ions are thus more available for plant uptake However, crucial nega<ve ions (anions): Nitrate (NO3- ) and Sulfate (SO42- ) cannot be maintained in the A soil horizon in the same way; leach very easily => most A horizon N is in the form of decaying organic maPer (slowly breaks down and releases NH4+, plants uptake this) clay fer<lizers in agriculture •  agricultural plant growth rapidly depletes nutrients •  most common elemen...
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This note was uploaded on 10/02/2013 for the course BIO 201 taught by Professor True during the Spring '08 term at SUNY Stony Brook.

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