Fig. 1
The dispersal units of Lepidium didymum are fruit valves each harbouring a single seed encased in a hard pericarp (fruit coat). a Oblate spheroid-shaped fruits each consisting of two fruit valves attached to the replum. b Detachment from the fruit’s replum at maturity provides two dispersed fruit valves. The mature fruit valves have a hard pericarp and a ‘Natural Pericarp Opening’ (NPO) that permits water uptake and gas exchange. c Dry fruit valve, cracked open, exposing the encased single dry seed that fills almost the entire pericarp cavity. The seed is always positioned inside the cavity with the radicle (embryonic root) directed towards the distal pericarp region adjacent to the NPO. The pericarp layers and the ‘Predetermined Breaking Zone’ (PBZ) along the distal and dorsal pericarp regions are indicated. d Germinating fruit valve with pericarp rupture initiated in the distal pericarp region (crack initiation point) adjacent to the NPO. e Germinated fruit valve opened like a shell by progressed pericarp rupture to facilitate radicle emergence
