Morphogenetic Differences Between Nicotiana alata and N. Langsdorffii as Indicated by Their Response to Indoleacetic Acid

Abstract

An unusual opportunity for the application of the present knowledge of hormones to the investigation of morphogenetic differences between two closely related species is afforded by Nicotiana alata and Nicotiana Langsdorffii. The flowers of the two species are similar, but the difference in the size of the corolla parts suggests a possible interpretation in terms of hereditary response to growth substance. One of the chief differences lies in the constricted part of the corolla-tube (pl. 25, fig. 1). In N. alata its length is at least fifteen to twenty times that of N. Langsdorffii, whereas the whole corolla in the former is only four or five times the length of the latter. The epidermal cells of the tube of N. alata are extremely long; those of N. Langsdorffii, relatively short. The work on several known genetic dwarf races of corn by van Overbeek ('35, '38) indicates that the varietal differences are 'due to genetic differences which regulate production, use, and inactivation of auxin. The experiments on Epilobium hybrids by Schlenker and Mittman, cited by Went and Thimann ('37), suggest this same relationship. If this hypothesis holds true for species of Nicotiana and the differences between them are due to differences in amount of hormone produced, then auxin should prove to be a limiting factor in N. Langsdorffii and its application to the corollas of this species should then cause an increase in size. If differences are due to differences in ability to use growth substance, then auxin should be a limiting factor in N. alata and additional amounts should increase