Left-right asymmetry causes twisting in rice (Oryza sativa) leaves via physical interaction between organs

Shape of plant organs is constrained by other organs within the same plant, yet these constraints remain under-reported. In grasses, new leaves typically develop inside the space formed by the older leaf, which imposes spatial restrictions on the developing leaf. This study focused on the rice (Oryza sativa) mutant, DSK115, which exhibits twisted leaf blades to understand how constraints affect leaf development. We quantified 3D shapes of twisted and nontwisted leaves developing inside the cylindrical space formed by the older leaf sheath by micro X-ray computed tomography (micro-CT). We also used computational modelling for qualifying leaf phenotype. CT scanning showed physical contact between the inner and outer edges of a leaf blade due to left-right asymmetry in leaf width, and physical inhibition of leaf growth due to reduced space within the enclosing leaf sheath. The simulation models demonstrated these factors could produce a twisted structure like DSK115. The study revealed the twisting of leaf blades is consistent with a mechanical explanation by physical contact between the inner and outer edges of a leaf blade and physical inhibition of leaf growth.