Restricting the above ground sink corrects the root/shootratio and substantially boosts the yield potential per paniclein field-grown rice (Oryza sativa L.)

Rice has shallow, weak roots, but it is unknown how much increase in yield

potential could be achieved if the root/shoot ratio is corrected. Removing all

tillers except the main one, in a japonica (Sakha 101) and an indica (IR64) rice

cultivar, instantly increased the root/shoot ratio from 0.21 to 1.16 in Sakha 101

and from 0.16 to 1.46 in IR64. Over 30 days after detillering, the root/shoot

ratios of the detillered plants decreased to 0.49 in Sakha 101 and 0.46 in

IR64 but remained significantly higher than in the controls. The detillered

plants showed two- or fourfold increase in the main tiller fresh weight, as

a consequence of more positive midday leaf relative water content (RWC),

and consistently higher rates of stomatal conductance and photosynthesis, but

not transpiration, compared with the controls. The enhanced photosynthesis

in Sakha 101 after detillering resulted from both improved water status and

higher Rubisco contents whereas in IR64, increasing the Rubisco content did

not contribute to improving photosynthesis. Detillering did not increase the

carbohydrate contents of leaves but prevented starch depletion at the end

of grain filling. The leaf protein content during vegetative and reproductive

stages, the grain filling rate, the number of filled grains per paniclewere greatly

improved, bringing about 38.3 and 35.9% increase in the harvested grain dry

weight per panicle in Sakha 101 and IR64, respectively.We provide evidence

that improving the root performance by increasing the root/shoot ratio would

eliminate the current limitations to photosynthesis and growth in rice.