In a collaboration between RIPE researchers and cowpea breeders from Ahmadu Bello University, and the International Institute of Tropical Agriculture, the width of cowpea leaves was found to correlate with above-ground biomass across diverse germplasm and environmental conditions. This easy-to-measure trait can be readily used for selection in breeding programmes for cowpea biomass in Nigerian fields.

Crops grow dense canopies that consist of several layers of leaves--the upper layers with younger sun leaves and the lower layers with older shaded leaves that may have difficulty intercepting sunlight trickling down from the top layers.