Shared and Unique Gene Ontology Terms. S15 = 18 unique gene ontology terms; S21 = 23 unique gene ontology terms; S27 = 1 unique gene ontology term. There is no gene ontology term that is shared among all the three stages, between S15 and S27 and between S21 and S27.
Teoh et al. BMC Plant Biology 2013 13:19 doi:10.1186/1471-2229-13-19