response of sorghum and sunflower to short-term waterlogging. IV. Water and nutrient uptake effects

The effect of waterlogging on water use and nutrient uptake in sunflower and sorghum was investigated in relation to stage of development of the crops and the timing and duration of waterlogging. Waterlogging at the vegetative and floral initiation stages of plant growth induced a reduction in water use of sunflower, with corresponding declines in leaf expansion and leaf water potential; in sorghum, the transpiration rates were much lower than for sunflower and relatively unaffected by waterlogging. Waterlogging at anthesis, however, caused an immediate reduction in water use in sunflower with a similar but delayed effect in sorghum. The differences in response of these two species are discussed in relation to the relative importance of water stress and nutrient uptake. Plant analysis at maturity indicated that waterlogging at any growth stage reduced both total and seed phosphorus in sunflower; similar effects were recorded with sorghum, with the exception of anthesis waterlogging which did not reduce nutrient uptake. Waterlogging effects on plant potassium levels were variable.