Tobacco [For Jean Nicot, 1530–1600, French ambassador at Lisbon, who sent tobacco plants and/or seeds to French court ca. 1560]

Sandra Knapp

Herbs, shrubs, or small trees, with soft wood, annual, biennial, or short-lived perennial, often rosette-forming, from taproot or rarely horizontal rootstock (forming colonies), sparsely to densely viscid-pubescent with simple hairs, rarely glabrous. Stems usually erect, sometimes branching from base. Leaves alternate, densely clustered in rosette-forming species, sessile or petiolate; petiole often winged; blade simple, margins entire or irregularly and obscurely crenate and sometimes undulate. Inflorescences terminal or apparently axillary, cymose, usually forming false racemes, or glomerulate. Flowers bisexual, 5-merous (fasciated with increased parts only in cultivars), radially symmetric or somewhat bilaterally symmetric, especially in androecium; calyx tubular or narrowly campanulate, 5-lobed, lobes persistent, usually deltate or triangular, equal or unequal, usually slightly accrescent and mostly enclosing capsule; corolla white to cream, variously marked or tinged with pink or purple, or yellow-green, radial or more commonly at least somewhat bilateral, tubular, funnelform, or salverform, limb deeply 5-lobed to ± entire, lobes, if present, rounded to deltate, sometimes emarginate; stamens 5, inserted variously from near base of corolla tube to near apex, sometimes unequal (2 + 2 + 1), on equal filaments or filaments of unequal length with one inserted at a different level and usually shorter than the other 4; anthers dorsifixed (or appearing basifixed), ellipsoid to globose, dehiscing by longitudinal slits; ovary 2-carpellate (irregularly more in some cultivars); style filiform, straight or curved; stigma capitate or slightly 2-lobed. Fruits capsules, usually ovoid, sometimes narrowly so, 2–4-valved (occasionally many-valved in cultivars), dehiscent apically with long septicidal cleft and shorter loculicidal cleft. Seeds angular to oblong (minute), occasionally somewhat reniform. x = (9, 10), 12, (16, 18, 19), 24.

Species ca. 75 (12 in the flora): North America, Mexico, West Indies, Central America, South America, s Africa, Australia; introduced widely.

Species of Nicotiana that bloom in the evening usually have white or cream flowers and are pollinated by moths, while day-flowering species have yellow, pink, or cream flowers and are pollinated by bees; however, this overall pattern does not hold strictly true. Nicotiana attenuata has become a model system for the study of the complex interplay between pollinators and herbivores in the evolution of floral and other traits (for example, C. Diezel et al. 2011; D. Kessler et al. 2015).

Nicotiana is recognizable by its tubular flowers and usually sticky pubescence. Of the species occurring in North America, only N. glauca is not sticky-pubescent. The genus has long been of interest due the high number of allopolyploid species (T. H. Goodspeed 1954; M. W. Chase et al. 2003; E. W. McCarthy et al. 2015).

Most species of Nicotiana in the flora area have distinct basal rosettes until flowering occurs, and cauline leaves usually differ in morphology from those in the basal rosette. Many species occur as short-lived perennials in areas without frost, but occur as annuals where winters are harder. The tree tobacco (N. glauca) is the only truly woody species occurring in North America.

Nicotiana species are often cultivated and occur occasionally as garden or greenhouse escapes. Nicotiana alata Link & Otto and N. × sanderae W. Watson have been reported for the flora area but are known only as ephemerals or from cultivation. Some records of N. alata are possible misidentifications for N. longiflora, from which N. alata differs in its strongly decurrent cauline leaves and larger corollas with wider tubes. Nicotiana × sanderae has striking red salverform corollas; various horticultural hybrids of this long-flowered species are possible ephemeral occurrences on waste heaps.

The two tobaccos of commerce, Nicotiana rustica and N. tabacum, are cultivated as orna­mentals or as sources of leaves for human use. Although most herbarium specimens from the flora area are clearly from cultivation, both taxa are sometimes adventive.

The small seeds and weedy habits of Nicotiana species predispose them to become invasive; for example, the non-native species N. glauca is a common component of ecosystems in western North America. This propensity to grow in disturbed areas means cultivated species are likely to become established briefly in areas where soil is loose or in old garden sites.

SELECTED REFERENCES Chase, M. W. et al. 2003. Molecular systematics, GISH and the origin of hybrid taxa in Nicotiana (Solanaceae). Ann. Bot. (Oxford) 92: 107–127. Clarkson, J. J. et al. 2004. Phylogenetic relationships in Nicotiana (Solanaceae) inferred from multiple plastid DNA regions. Molec. Phylogen. Evol. 33: 75–90. Goodspeed, T. H. 1954. The genus Nicotiana. Chron. Bot. 16. Knapp, S., M. W. Chase, and J. J. Clarkson. 2004. Nomenclatural changes and a new sectional classification in Nicotiana (Solanaceae). Taxon 53: 73–82. McCarthy, E. W. et al. 2015. The effect of polyploidy and hybridization in the evolution of flower colour in Nicotiana (Solanaceae). Ann. Bot. (Oxford) 115: 1117–1131.