Photosynthesis Improvement as a Way to Increase Crop Yield

Abstract

Attempts to breed crop varieties with higher rates of photosynthesis have met with no success although considerable genetic variation in photosynthesis rates exist in several crop species and a positive correlation between leaf photosynthesis and prodpctivity is reponed in a number of experiments. An efficient partitioning of assimilated carbon seems to be more critical in detennining plant productivity. Selection for low darlt respiration or enhanced light interception have successfully increased net carbon gain by the plant Selection by survival under low CO₂ atmosphere in tobacco haploids and on Lolium multiflorum L. Italian ryegrass cultivar RvP population showed a significant increase in plant productivity even when the leaf photosynthesis rate was not high. For Italian ryegrass RvP population, the surviving plants under low CO₂ had bad significant increase in initial dry weight but the difference disappeared in the second regrowth. No single character of ryegrass or tabacco genotypes could account for their survival under low CO₂, Even though photosynthesis and plant production are closely related, large environmental and ontogenic-induced variations in leaf photosynthesis rate make it difficult to achieve a good estimate of its contribution to the entire plant carbon economy.