Mechanical conflicts control fruit morphogenesis in Arabidopsis.

Plant organ shape emerges from coordinated growth between adjacent tissues and from the mechanical conflicts that arise when growth rates differ. In Arabidopsis, the gynoecium, the female reproductive organ that develops into the fruit, consists of fast-growing valves flanking the slowly expanding replum, a medial domain that supports ovule formation. Yet how differential growth between these tissues influences gynoecium and fruit development remains unclear. Using quantitative live imaging, mechanical perturbations, and modeling, we show that growth differences between these tissues generate mechanical conflicts that shape their morphogenesis. During gynoecium development, the rapid valve expansion mechanically stretches the replum, amplifying its elongation, whereas reducing valve growth diminishes replum anisotropy and limits ovule production. Disrupting this balance by removing one valve causes reproducible bending toward the slower-growing replum. After fertilization, intrinsic elongation of replum cell files increases relative to the valves, and when this elongation is mechanically constrained, the replum buckles, leading to a reorientation of growth at the tissue level. Together, our results demonstrate that growth-derived mechanical interactions between tissues feed back on growth patterns to coordinate organ geometry and reproductive capacity, demonstrating that mechanical conflict regulates fruit morphogenesis.