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Bicarbonate directly induces iron chlorosis in susceptible soybean cultivars
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Four soybean [Glycine max (L.) Merr.] cultivars differing in susceptibility to iron (Fe) chlorosis in wet calcareous soils were grown in nutrient solutions to characterize the effects of phosphate (P) and bicarbonate (HCO3-) in inducing chlorosis. NaHCO3 (0 or 10 mM), P(10 or 400 uM as NaH2PO4 and NH4+(0 or 300 uM) as (NH4)2SO4 were factorial treatments in a nutrient solution. Low Fe availability was maintained by supplying 5 uM Fe + 10 uM EDDHA and excess CaCO3 (pH 7.5). With no HCO3- added, T203 (extremely chlorosis susceptible) was green at 10 uM P, but severely chlorotic at 400 uM P; Wayne (chlorosis susceptible) was green at both P levels. Addition of HCO3- caused chlorosis in T203 and Wayne at 10 or 400 uM P. Chlorosis resistant AP9 and Hawkeye remained green with added P or HCO3-. Chlorosis ratings (1 = green to 5 = severely chlorotic) in the 0 HCO3- + 10 uM P, 0 HCO3- + 400 uM P and 10 HCO3- + 400 uM P treatments, respectively, were: 1.0, 1.0 and 1.5 for AP9; 1.0, 1.0 and 1.4 for Hawkeye; 1.0, 1.2 and 3.9 for Wayne; and 1.0, 4.2 and 4.6 for T203. Low Fe concentrations in young leaves corresponded with high chlorosis ratings. In the absence of HCO3-, Wayne was not chlorotic at either concentration of solution P, although this cultivar is known to be highly susceptible to chlorosis in the field. Bicarbonate-induced chlorosis in Wayne was not a result of increased solubility or plant uptake of P. Thus, HCO3- was a direct factor in causing soybean chlorosis and likely is also a cause in soils. [AS/SS]
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 Record created 1985-06-03, last modified 2019-03-04

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