2.7. Evaluation of plant survival rates
In the four 2014/2015 experiments, the topmost youngest, fully expanded leaf, was used to determine the survival rates of pearl millet and sorghum during the flood treatments, because in most cases, the selected leaf was the last to turn brownish. In each plot all individual plants were assessed during the flood treatment to determine the extent to which the leaf tissue colour had changed, i.e. from green to brown, relative to total leaf area. The leaf was assigned a percentage score such that 0% represents a healthy green leaf denoting a fully live plant, 50% indicates half brown-half green leaf thus a plant withstanding stress, and 80–100% denotes nearly whole brown leaf area without chlorophylls hence considered as dead. In fact, plants did not recover after this condition (80–100% score).