Our study on Arabidopsis, a model species, and rice, an important
crop, extends our earlier conclusion of a close relationship
between starch levels, CO2 assimilation, and plant growth between
WT and leaf starch mutants in Arabidopsis [12]. Our Arabidopsis and
rice data indicates that increases in leaf starch not only serves as
a larger transient reserve to support heterotrophic growth in the
dark but also increases the photosynthetic capacity of the plant
by alleviating potential feedback due to Pi deficiency. Together
they confer enhanced plant growth and seed yields, although the
latter is achieved through different effects on reproductive development
in rice. The rice lines UpReg1-16 and UpReg2-3 had the
largest increase in the number of reproductive organs (panicles)
per plant, whereas UpReg2-19 had more grains per panicle. Hence,
the enhanced supply of carbon and energy supplied by starch in rice
increases the number of reproductive organs or number of seeds
developed per organ.