Genetics of mutations affecting the development of a barley floral bract

Two groups of mutants that affect the morphology of the lemma, a floral bra ct of bar-ley, are described. The fir st comprises phenotypes associated wi th mutant alleles of calcaroides loci. On the lemma of these mutants, a wel l-organized neomorphic structure is formed, tel-med the sac. We provide a m orphological description of wild-type (WT) and mutant lemmas, based on scan ning electron microscopy (SEM),showing that both consist of similar tissues , but that the mutant is characterized by reversed growth polarity. The sac is a unique structure among grasses, and it is remarkable that recessive m utations at five different generic loci lead to the same organ. The second group of mutants carry recessive alleles of two leafy lemma genes, both of which ar-e necessary to cause the transformation of the lemma into a struct ure having all characteristics of a vegetative leaf, as shown by SEM analys is. The presence of sheath, blade, and ligule in the mutant lemma suggests that wild-type lemma development is interrupted at a leaf-like stage. The g enes cal a, b, C, d, 23, lel1, and lel2 have no cz; been mapped at precise positions on linkage groups 2, 7, 7, 3, 7, 5, and 7, respectively. The muta nts considered in this article are unaffected in other floral organs. A mod el for lemma development is suggested.