Non-deep complex morphophysiological dormancy in seeds of the Iberian Peninsula endemic geophyte Merendera montana (Colchicaceae)

Heretofore, no detailed account was available on seed dormancy and germination of a member of the Colchicaceae (Liliales). Thus, the primary aim of this study was to do an in-depth investigation of the temperature requirements for dormancy break and germination in seeds of Merendera montana (Colchicaceae) at the embryo and whole-seed levels under near-natural temperatures in a non-heated frame shade-house and under controlled conditions in the laboratory. Mean embryo length in fresh seeds was c. 0.57mm and embryos had to grow to at least 1.30 mm before radicle emergence. Embryos grew to full size and seeds completed germination (radicles emerged) when they were stratified at 28/14 degrees C for 60 d followed by a cool temperature for 60 d and then incubated at a cool temperature for 30 d. The optimum cool stratification temperature for dormancy-break was 10 degrees C. Thus, after the moist pretreatment at 28/14 degrees C + 10 degrees C, radicle emergence was > 93% at all incubation temperatures (5, 15/4 and 20/7 degrees C). In its natural habitat, M. montana seeds are dispersed in June, the embryo elongates to full size in autumn and radicles emerge from early November to early February. Although the shoot does not emerge until March and April, it is not physiologically dormant. The shoot emerged from 80% of the radicle-emerged seeds in 13 d at 20/7 degrees C without a previous cold pretreatment. Seeds of M. montana have non-deep complex morphophysiological dormancy, C1b1aB-C-1a. This is the first study on seeds with complex MPD to show a delay in shoot emergence following root emergence despite the shoot being physiologically non-dormant.