The above theoretical maximum efficiency is attained at low light intensities. At full sunlight, plants may suffer the effect of absorbing excess light energy resulting in a decline in radiation conversion efficiency and a potential for photoinhibition17–19. Furthermore, there is a fixed energy cost for maintenance respiration using approximately 20% of gross assimilates plus the cost of growth respiration using approximately 30% of the remaining assimilates20. In view of the above, it appears that actual field efficiency may be approaching the upper limit14 when it reaches 5%. Such an efficiency is attainable and has been shown for field-grown maize during the period of rapid growth21 and during maximum growth phase of wheat grown under controlled environment conditions22. Plants under most field conditions, however, conserve less than 1% of the energy of sunlight falling on a field during the growing season. From such observations, it has been inferred that there is remarkable scope for improvement of photosynthetic productivity and consequently, agricultur