The theoretical maximum limit of photosynthetic efficiency
(Pe) is estimated to be 4.6 and 6.0% for C3 and C4 plants, respectively.[7]
However, these limits are hardly achieved. The
conversion efficiency in the growth phase comes within 70%
of these limits, thus 3.2 and 4.2% are assigned to the Pe of C3
and C4 plants, respectively.[8] There is a 20% ratio of root deposit
to photosynthesized carbohydrates (Rp),[6] 30% rhizodeposit
availability for microorganisms (Ra),[9] and 9% microbial
fuel cell energy recovery (Er).[10] Our estimations of the CE for
C3 and C4 plants are 0.017 and 0.022%, respectively