Gradients in photosynthetic capacity through the leaf affect the shape of the irradiance-response curve. These gradients in photosynthetic capacity were manipulated by restraining leaves in different orientations. The shape or curvature of the light-response curve can be defined by Θ, where Θ=0 is a rectangular hyperbola and Θ=1 is a Blackman curve. Horizontal leaves had the highest Θ values when their adaxial (top) surface was illuminated and lowest Θ value when their abaxial (bottom) surface was illuminated