Fig 8. Model of interactions among Hd, B1 and B2 for development of the hooded phenotype.

The dominant Hd allele is necessary for development of the membranous lateral expansion at the base of awns. Presence of the dominant B2 allele and other factors contribute to the formation of this ectopic tissue. In contrast, presence of the dominant B1 allele suppresses its formation, leading to a complete lack of the hooded phenotype or to a broadening of the base of awn, depending probably on the genetic background.