EPICOTYL MORPHOPHYSIOLOGICAL DORMANCY IN SEEDS OF DAPHNIPHYLLUM GLAUCESCENS, A WOODY MEMBER OF THE SAXIFRAGALES

Available information on seed dormancy for various members of the Saxifragales and phylogenetic relationships
within this order allowed us to accurately predict thatDaphniphyllumglaucescens seeds havemorphophysiological
dormancy (MPD). However, our hypothesis that seeds had deep simple epicotyl MPD, i.e., nondeep physiological
dormancy (PD) in root and deep PD in shoot, was not supported. Both the root and the shoot (cotyledons) of the
underdevelopedembryo of D. glaucescens have nondeepPD. Exposure tomoderate (15/6, 20/10C), rather than
high (25/15C), temperatures for 10–12 wk broke the PDof the hypocotyl/root. After hypocotyl emergence, seeds
with an attached developing root system did not require cold stratification to break the PD of the shoot. The PD of
the shoot was broken by an additional 10–12 wk at moderate temperatures, during which time cotyledons slowly
grew inside the seed. As cotyledons grew, all of the hypocotyl was pushed out of the seed, and the final cotyledon
length was almost twice that of the seed; at this point, the folded cotyledons emerged. Since the level of PD in root
and shoot may or may not be the same, we advocate stating the level of PD in both root and shoot when epicotyl
MPD is described in a species. Thus, seeds of D. glaucescens have nondeep simple (root)–nondeep simple (epicotyl)
MPD, which is written as C1bB(root)-C1bB(shoot) in the formula system of Nikolaeva. This is the first report of this
level of epicotyl MPD in the Saxifragales.