No abstract

Abstract-Soil reduction caused by flooding has profound effects on species adaptation and mineral nutrition of higher plants. Anaerobic conditions inhibit normal root respiration of higher plants. Alternate metabolic pathways may be utilized in combination with the development of anatomical characteristics that result in the internal movement of oxygen to the roots. Soil organisms use other oxidants when the oxygen supply is interrupted, which results in profound changes in oxidative states of many metals and nonmetals, and changes in soil reaction and conductivity. The products of reduction are primarily nitrogen gas, manganous manganese, ferrous iron, sulfide sulfur, methane, and organic acids. These reduction products alter the availability of soil nutrients and can drastically alter the soil acidity. Plant-soil interactions on flooded soils can sometimes be altered, as has been demonstrated by the use of phosphorus fertilizer on southern pine and zinc on rice.

Loblolly pine seedlings were grown under flooded and drained conditions in a greenhouse pot study. Flooded roots developed aerenchyma tissue within the stele between the xylem poles, extending from the phloem outward to the pericycle. Large intercellular spaces were present in the pericyclic parenchyma within the phellogen of flooded woody roots. Flooded stems exhibited lenticel hypertrophy. Large intercellular spaces in the cortex were continuous with intercellular spaces in the pericyclic parenchyma of the root. Flooding of roots generally resulted in accumulation of Fe on the epidermal surface and in as well as between cortical cell walls inward to the endodermis. Fe accumulated in and between the precursor phloem cells and became more evident in the region of maturation. In roots with secondary thickening, little Fe was visible in the phloem but was present in helical secondary walls of tracheids. Fe also accumulated on and in bordered pits of root tracheids. Results suggest that flooded loblolly pine seedlings possess a limited internal aeration system and that diffusion of oxygen into the root system may be responsible for the presence of oxidized Fe within the stele.

No abstract

Soil reduction caused by flooding has profound effects on species adaptation and mineral nutrition of higher plants. Anaerobic conditions inhibit normal root respiration of higher plants. Alternate metabolic pathways may be utilized in combination with the development of anatomical characteristics that result in the internal movement of oxygen to the roots. Soil organisms use other oxidants when the oxygen supply is interrupted, which results in profound changes in oxidative states of many metals and nonmetals, and changes in soil reaction and conductivity. The products of reduction are primarily nitrogen gas, manganous manganese, ferrous iron, sulfide sulfur, methane, and organic acids. These reduction products alter the availability of soil nutrients and can drastically alter the soil acidity. Plant-soil interactions on flooded soils can sometimes be altered, as has been demonstrated by the use of phosphorus fertilizer on southern pine and zinc on rice.