An anatomical comparison of epidermal cells in wild-type and homeotic mutant flowers of Clarkia tembloriensis Vasek (Onagraceae) 1

Abstract

Flowers consist of four whorls of organs (sepals, petals, stamens, and carpels), each expressing unique characteristics. In floral homeotic mutants, organs develop abnormally, and floral organs of one whorl express characteristics of another whorl. Much of our current understanding of the development of floral organs has been based on studies of floral homeotic mutants. In the homeotic mutant crinkle-petal (cp) of Clarkia tembloriensis, previous investigations demonstrated that the cp petal is a hybrid organ combining characteristics of sepals and petals. This investigation extends those studies with a comparative anatomical study of trichomes, guard cells, and marginal epidermal cells in wild-type (WT) sepals, WT petals, and cp petals. The aim was to determine if cp petals exhibit a hybrid epidermal anatomy of WT sepals and WT petals. Floral buds 1 day pre-anthesis and flowers 1 day post-anthesis were collected and prepared for light microscopy or scanning electron microscopy. Trichomes and guard cell pairs were described and counted, and marginal cells were observed and described. This anatomical study of trichomes, guard cells, and marginal cells demonstrated that cp petals of C. tembloriensis combine characteristics of both WT sepals and WT petals. These results provide further support for the hybrid nature of cp petals in Clarkia tembloriensis.