EFFECT OF TEMPERATURE ON GERMINATION WITHIN AND BETWEEN DIPLOID AND TETRAPLOID POPULATIONS OF MATRICARIA-PERFORATA MERAT

Diploid (2n=18) and tetraploid (2n=36) cytotypes of Matricaria perfora ta Merat have separate geographic distributions in Canada. Since seeds are the only means of reproduction, a knowledge of the relationship b etween temperature and germination is important for an understanding o f the potential spread of these two invasive cytotypes in Canada. Germ ination response patterns of six diploid and four tetraploid populatio ns were compared at constant and alternating temperatures ranging from 0 to 45-degrees-C. Tests were performed on achenes collected from pla nts grown in a common garden for one generation at the location of one of the tetraploid sources. The general pattern of germination was sim ilar for both cytotypes. The upper and lower limits for germination we re 40-degrees-C and 5-degrees-C, respectively. Optimum germination occ urred at alternating temperatures of 30/10-degrees-C. No primary dorma ncy was found. Although the general response pattern was similar and l ittle variation existed among populations, germination did differ at s uboptimal constant temperatures; tetraploid populations germinated 28 to 39% more than the diploids within the suboptimal range. These genet ic differences may reflect adaptation to prolonged cold winters since the tetraploid populations were collected from more northern latitudes than the diploid populations.