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 perforata Merat have separate geographic distributions in Canada. Since seeds are the only means of reproduction, a knowledge of the relationship between temperature and germination is important for an understanding of the potential spread of these two invasive cytotypes in Canada. Germination response patterns of six diploid and four tetraploid populations were compared at constant and alternating temperatures ranging from 0 to 45-degrees-C. Tests were performed on achenes collected from plants grown in a common garden for one generation at the location of one of the tetraploid sources. The general pattern of germination was similar for both cytotypes. The upper and lower limits for germination were 40-degrees-C and 5-degrees-C, respectively. Optimum germination occurred at alternating temperatures of 30/10-degrees-C. No primary dormancy was found. Although the general response pattern was similar and little variation existed among populations, germination did differ at suboptimal constant temperatures; tetraploid populations germinated 28 to 39% more than the diploids within the suboptimal range. These genetic differences may reflect adaptation to prolonged cold winters since the tetraploid populations were collected from more northern latitudes than the diploid populations.