Photosynthesis Under Field Conditions. VI. Solar Radiation Balance and Photosynthetic Efficiency1

Synopsis A spectrophotometer with a sensitive range lying between 0.3 and 1.0 μ and its calibration and use are described. The spectrophotometer was used to measure the spectral characteristics of 0.3‐ to 10‐μ radiation penetrating a dense stand of corn 300 cm. high (26,000 plants/acre, 29‐inch rows, LA1 = 4.3) planted in north‐south oriented rows. Transmission was quite low for the visible range, but was 30 to 40% from 0.75 to 0.9 μ. Efficiency of photosynthesis was 0.42 times the yield obtained from laboratory‐grown Chlorella.