Developmental ultrastructure of cells and plastids in the petals of wallflower (Erysimum cheiri)

An ultrastructural study of petal cells of wallflower (Erysimum cheirii) of the family Brassicaceae shows that the adaxial epidermal cells are of the conical papillate type whereas the cells of the abaxial epidermis are lenti cular in shape. The abaxial epidermis contains stomata, which are solitary and lack any obvious subsidiary cells. Pigmentation is apparent in both epi dermal and internal mesophyll cells and results from the presence of both c hromoplasts and large cytoplasmic vesicles containing pigment. These pigmen ted vesicles are very obvious in preparations of fixed isolated petal cells . Chromoplasts are of the globular type and are present in significant numb ers in both epidermal and mesophyll cells. Division of chloroplasts in youn g petals prior to bud break appears to give rise to the populations of chro moplasts observed in mature petals since there was no evidence of chromopla st division itself. The development of wallflower petals and their chromopl asts is discussed in relation to development of petals in the related speci es Arabidopsis thaliana. (C) 1999 Annals of Botany Company.