Fig. 6. Relative UV-B transmittance (T) detected by biodosimeter packets on surfaces of vertical simulated grass blades placed at various heights (H) in a tall fescue canopy of 18 cm height. T was determined relative to UV-B irradiance measured horizontally above the canopy by a YES broad-band radiometer. Each value is a mean of six measurements made in each of 2 d. Error bars denote standard deviation.