Evidence that endosperm turgor pressure both promotes and restricts seed growth and size

Using computational simulations and experiments, the authors propose a mechanical model of seed growth where endosperm pressure directly induces growth but indirectly inhibits it through force-dependent testa wall stiffening. In plants, as in animals, organ growth depends on mechanical interactions between cells and tissues, and is controlled by both biochemical and mechanical cues. Here, we investigate the control of seed size, a key agronomic trait, by mechanical interactions between two compartments: the endosperm and the testa. By combining experiments with computational modelling, we present evidence that endosperm pressure plays two antagonistic roles: directly driving seed growth, but also indirectly inhibiting it through tension it generates in the surrounding testa, which promotes wall stiffening. We show that our model can recapitulate wild type growth patterns, and is consistent with the small seed phenotype of the haiku2 mutant, and the results of osmotic treatments. Our work suggests that a developmental regulation of endosperm pressure is required to prevent a precocious reduction of seed growth rate induced by force-dependent seed coat stiffening.

Automated summary

Using computational simulations and experiments, the authors propose a mechanical model of seed growth where endosperm pressure directly induces growth but indirectly inhibits it through force-dependent testa wall stiffening. By combining experiments with computational modelling, the researchers provide evidence that endosperm pressure plays a dual role in seed growth, both driving growth directly and inhibiting it indirectly. Their findings suggest that developmental regulation of endosperm pressure is necessary to prevent premature reduction in seed growth rate caused by force-dependent seed coat stiffening.