The researchers studied how different cowpea plants respond to water stress by measuring their chlorophyll levels and stability. They found that under drought conditions, the chlorophyll content decreased, but the ratio of chlorophyll-a to chlorophyll-b increased slightly. Certain cowpea genotypes showed higher chlorophyll stability than others. The study also revealed a positive correlation between chlorophyll stability and shoot biomass, suggesting that chlorophyll levels could be used as a reliable indicator for selecting plants that can thrive in water-limited environments.