The researchers studied how the amount of water in wheat leaves affects the accuracy of measuring leaf area and nitrogen levels. They found that a new spectral index could predict leaf area well in plants lacking water, but not in well-watered plants. Even when leaves were mostly water, the index still worked if the plant didn't have enough water. This means that water in leaves can hide important information in certain light wavelengths. These findings suggest that using certain light wavelengths can help monitor plant health during droughts.