Seed plating guide for 9 cm round Petri plates

This is a guide to plate Arabidopsis thaliana seeds on round 9 cm Petri plates (Petri dishes). The guide nicely immobilizes a plate during the procedure and indicates where to place the seeds to have even distances optimal for germination assay and root growth analysis.
This seed plating guide was originally designed to be used for automated imaging with SPIRO, but can also be implemented for other experiments.