22. Petunia Jussieu, Ann. Mus. Natl. Hist. Nat. 2: 215, plate 47. 1803. name conserved.
[I]
[Tupi-Guarani (Brazilian) petun, tobacco, alluding to affinity with Nicotiana]
Kathryn L. Fox
Janet R. Sullivan
Stimoryne Rafinesque
Herbs, annual [perennial], taprooted, sparsely to densely viscid-glandular pilose. Stems erect or ascending to decumbent [prostrate], branched at base and distal nodes. Leaves alternate, geminate subtending flowers at distal nodes, petiolate. Inflorescences axillary, solitary flowers. Flowers 5-merous, radially symmetric; calyx campanulate, lobes 5, linear [lanceolate], not accrescent (lobes erect or reflexed); corolla white to rose-purple (drying deep violet) [red], throat reticulated rose-purple or greenish white, radial, salverform to funnelform with shallow, rounded lobes; stamens slightly unequal (2 long, 2 medium, 1 short [4 equal, 1 longer]), inserted at base or near midpoint of corolla tube; anthers ventrifixed, oblong to elliptic, dehiscing by longitudinal slits; ovary 2-carpellate; style slender to thick, curved to straight; stigma obconic to capitate-truncate, 2-lobed. Fruits capsules (2-valved, apex bidentate or entire, dehiscence septicidal), ovoid, length 1/2–3/4 calyx lobes. Seeds globose-reniform (red-brown; foveolate-reticulate with coarse, wavy middle lamellae and anticlinal walls). x = 7.
Species 17 (3, including 1 hybrid, in the flora): introduced; South America (Argentina, Bolivia, Brazil, Paraguay, Uruguay); introduced also widely.
The hybrid of Petunia axillaris and P. integrifolia, P. × atkinsiana, is one of the most popular ornamental garden plants today and has been grown in cultivation since its creation around 1834 (T. Ando et al. 2005). Natural hybridization does not occur, even in the species’ native ranges, due to differences in pollination syndrome (Ando et al. 1999, 2001; M. E. Hoballah et al. 2007; T. Gübitz et al. 2009). Artificial hybridization results in viable seed when the carpellate parent is P. axillaris (Ando et al. 1999, 2001, 2005b; Gübitz et al. 2009; T. L. Sims and T. P. Robbins 2009).
Since the late eighteenth century, the parent species have been popular garden plants in their own rights; today, they are grown much less commonly than the hybrid. Three species occur in the flora area as naturalized populations in disturbed areas; they probably do not persist for more than a few years.
SELECTED REFERENCES Ando, T. et al. 2005. Phylogenetic analysis of Petunia sensu Jussieu (Solanaceae) using chloroplast DNA RFLP. Ann. Bot. (Oxford) 96: 289–297. Stehmann, J. R. et al. 2009. The genus Petunia. In: T. Gerats and J. Strommer, eds. 2009. Petunia: Evolutionary, Developmental and Physiological Genetics, ed. 2. New York. Pp. 1–28. Watanabe, H. et al. 1999. Three groups of species in Petunia sensu Jussieu (Solanaceae) inferred from the intact seed morphology. Amer. J. Bot. 86: 302–305.
