Improvements in plant productivity (biomass) and yield have centered on increasing the efficiency of
leaf CO2 fixation and utilization of products by non-photosynthetic sink organs. We had previously
demonstrated a correlation between photosynthetic capacity, plant growth, and the extent of leaf starch
synthesis utilizing starch-deficient mutants. This finding suggested that leaf starch is used as a transient
photosynthetic sink to recycle inorganic phosphate and, in turn, maximize photosynthesis. To test this
hypothesis, Arabidopsis thaliana and rice (Oryza sativa L.) lines were generated with enhanced capacity
to make leaf starch with minimal impact on carbon partitioning to sucrose. The Arabidopsis engineered
plants exhibited enhanced photosynthetic capacity; this translated into increased growth and biomass.
These enhanced phenotypes were displayed by similarly engineered rice lines. Manipulation of leaf starch
is a viable alternative strategy to increase photosynthesis and, in turn, the growth and yields of crop and
bioenergy plants.