Aerobic rhizosphere processes

Molecular oxygen regulates both aerobic and anaerobic microbial metabolisms (Bodelier, 2003). Because of intense competition for O2, aerobic rhizosphere bacteria may be adapted to low O2 concentrations and periods of anoxia. Competition for O2 among microbial species, and between biotic and abiotic processes, has received relatively little attention (Laanbroek, 1990) but is likely to influence rhizosphere oxidation rates. Aerobic processes that occur in the wetland rhizosphere are those found in other aerobic-anaerobic interface environments and... 

Nitrification-denitrification reactions are the major pathway for N loss from wetland ecosystems to the atmosphere. The process involves a series of sequential microbial processes that include mineralization of organic nitrogen to ammonium, oxidation of ammonium to nitrate, and denitrification of nitrate to nitrous oxide or dinitrogen gas. Nitrification-denitrification in wetlands occurs primarily in two zones the aerobic-anaerobic interface at the surface of the flooded soil or sediment, and the oxidized rhizosphere of wetland plants (Figure 16.6). 

Iron deficiency is a serious nutritional disorder in many crops on neutral and alkaline aerobic soils because of the low availability of iron. However, some gramineous plants such as barley and wheat have developed a specific strategy to acquire sparingly soluble iron in soil they produce MAs which, as already mentioned, are involved in the iron acquisition process as phytosiderophores. The process of iron acquisition by plants has been divided into four steps, namely Fe-deficiency-induced biosynthesis of MAs inside the roots, secretion of MAs to the rhizosphere, solubilization of sparingly soluble inorganic Fe(III) in soils by chelation with MAs, and specific uptake of MA-Fe(III) complexes by the roots [32],... 

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