Ag. Thomas et al., EFFECT OF TEMPERATURE ON GERMINATION WITHIN AND BETWEEN DIPLOID AND TETRAPLOID POPULATIONS OF MATRICARIA-PERFORATA MERAT, Weed Research, 34(3), 1994, pp. 187-198
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.