The response of sorghum and sunflower to short-term waterlogging

Abstract

Sunflower and sorghum were waterlogged for nine days at the vegetative, budsvisible/initiation or anthesis stage of development under glasshouse conditions to document the changes which occurred in the soil environment. These changes were also monitored in the absence of plants. At all three stages, there was a rapid reduction in oxygen concentration followed by denitrification. The loss of nitrate was much greater in the presence of sunflower and sorghum. Other components of the redox system, manganese and iron, exhibited a slow increase in concentration as the duration of waterlogging was extended. However, increases were more marked at the later growth stages. Ethylene could be detected at all stages of water-logging although the highest levels were recorded during the first twenty-four hours at the vegetative stage under sunflower and sorghum. Toxins such as nitrite, volatile fatty acids and carbon dioxide appeared unimportant in this experiment. Similarly, observations on a range of cations suggested that nutrient availability was not a factor in causing waterlogging damage. The above changes in the soil environment are discussed in relation to observed effects on plant growth.