Seasonal estimates of transpiration from a millet crop using a porometer

Abstract

In West Africa, three populations of millet were grown to assess how growth was related to population and water supply. Stomatal resistance was measured with a porometer 3 times a day on 14 days, boundary-layer resistance was estimated on the same days using blotting-paper replicas for leaves, and wet- and dry-bulb thermocouples were used to determine concentration differences of water vapour. Changes in the mean rate of transpiration estimated from these quantities were strongly correlated with changes of green leaf area during the season. Seasonal changes of stomatal resistance were much less significant in determining the seasonal trend of transpiration rates. Estimates of water loss by transpiration agreed well with measurements of soil-water extraction obtained with a neutron moisture meter.