Photoperiod in Three Xanthium Populations from the Tropic of Cancer in Mexico

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Science  18 Jul 1969:
Vol. 165, Issue 3890, pp. 292-294
DOI: 10.1126/science.165.3890.292


Diverse photoperiodic responses were shown by three populations of Xanthium strumarium L. originating between 22° and 25°N on the western coast near Culiacán, Sinaloa; in the Chihuahuan Desert near Matehuala, San Luis Potoś; and on the Gulf Coast near Ciudad Mante, Tamaulipas, respectively. A combination of differences in critical night length and in ripeness-to-flower response (maturity) appears to be the basis for reproductive adaptation of these populations to different climatic regimes that prevail at the same latitude (and photoperiodic regime).