Scientific research towards improving the biomass productivity of crops has become inevitable because of the inherent constraints towards improving the biomass partitioning. This factor alone so far has been of great significance for rapid spurt in economic yield. Photosynthetic efficiency is expected to be directly related to biomass production. Hitherto, this trait has not been affected by selection and genetic improvement. A substantial number of photosynthetic mutants have been isolated and characterised but it remains an open question yet as to what component or step(s) in photosynthesis are rate limiting under specified conditions. In the absence of this knowledge, screening of genotypes for maximum photosynthesis rate (Pmax) has been resorted to, but it may not be directly correlated with yield. Adequate genetic variability has been reported for this trait along with fair degree of genetic advance. Further, where the factors responsible for diluting the assodation of biomass productivity with photosynthetic efficiency were taken care of perfect relations have been established. The incorporation of photosynthetic indices in breeding protocols is therefore, strongly advocated and depending on the nature of gene action appropriate breeding programme formulated. Further stability and adaptability studies are unavoidable as photosynthetic indices are labile to the environmental conditions. Integration of the tools of classical genetics and molecular biology in manipulating the photosynthetic efficiency for improving biomass productivity will become an absolute necessity in the years to come.
Photosynthesis, photosynthetic efficiency, photosynthetic apparatus, biomass, crop productivity
