Soil Phytotoxic Accumulation Effects on Plant Growth

7 SOIL PHYTOTOXIC ACCUMULATION EFFECTS ON PLANT GROWTH 

Toxic substances produced in soil under anaerobic conditions at low redox potentials can influence plant growth. Potential phytotoxins in reduced soil include 

Oxygen diffusion from aerial parts of wetland plants to roots and the subsequent sulfide oxidation in the rhizosphere have been considered major mechanisms allowing a high level of sulfide tolerance in some species (Joshi and Flollis, 1976). Oxygen release from young seedlings 

FIGURE 7.25 Relationship between net photosynthetic rate (P ) and hydrogen sulfide concentration for Spartina alterniflora. (Redrawn from Pezeshki et ah, 1988.) 

Under anaerobic soil conditions, organic substrates are often not decomposed completely to carbon dioxide. Incompletely oxidized intermediates and end products toxic to plants often accumulate in waterlogged soils. These intermediates and end products include lactic acid, ethanol, acetaldehyde, and aliphatic acids such as formic, acetic, or butyric acid. Ethylene is also sometimes present in abnormally high concentrations in waterlogged or anaerobic soil. 

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