Amaranthus retroflexus, A. hybridus and A. powellii were grown in a uniform garden at Ames from seed collected over a wide geographic area. Intraspecific variability in flowering response to photoperiod was studied. There was a significant correlation between date of flowering and the collection site.
Proceedings of the Iowa Academy of Science
©1966 Iowa Academy of Science, Inc.
McWilliams, E. L.; Landers, R. Q.; and Mahlstede, J. P.
"Ecotypic Differentiation in Response to Photoperiodism in Several Species of Amaranthus,"
Proceedings of the Iowa Academy of Science, 73(1), 44-51.
Available at: https://scholarworks.uni.edu/pias/vol73/iss1/10