Light energy conversion in field crops in comparison with the photosynthetic efficiency under laboratory conditions
Mededel Landbouwhogesch Wageningen 58(4): 1-12
For leaves of sugar beet, the relation between the incident light intensity and the rate of photosynthesis has been determined. The maximum quantum yield was found to be 0.10. In these experiments, the efficiency of solar energy conversion in sugar beet leaves varies between 17.6% at low light intensities and 2.2% at full sunlight. The efficiency of these crops reaches 7-9% in the middle of the season. Between 80 and 90% of the total organic matter was produced in only 44.5% of the growing season. During these 2.5 months beets are at least as efficient in solar energy conversion as mass-cultured algae. Comparison of the estimated photosynthetic rates in sugar beet leaves under field conditions with the actually measured optimum rates at comparable intensities under laboratory conditions, revealed that the photosynthesis rate in the field crop was at least 60% of the optimum rate during a great part of the season.