Promiscuous Germination and Growth of Wildtype Pollen from Arabidopsis and Related Species on the Shoot of the Arabidopsis Mutant, fiddlehead

When pollen lands upon the stigmatic surface of a receptive flower, recognition events take place that permit germination, pollen tube growth, and tube penetration into the cell walls of the stigmatic papillae. Previously, we have described a mutant of Arabidopsis thaliana, named fiddlehead ( fdh), where noncarpel organs of the shoot fuse late in ontogeny (Lolle et al. , 1992). Here we demonstrate that wildtype Arabidopsis pollen grows on noncarpel organs of the fdh mutant. Pollen grains adhere, germinate, and emit pollen tubes when applied to vegetative and nonreproductive floral organs. Some of the emergent pollen tubes penetrate into the cell wall. Although pollen from a number of closely related species responds, tomato, tobacco, and snap-dragon pollen does not. In addition, we show that organ fusion is not a prerequisite for pollen growth and that root epidermis does not express this activity. Based on these findings we propose that the fdh mutation identifies an important regulatory gone that controls the expression of an epidermis-specific developmental program normally expressed only during gynoecial ontogeny.