Germination characteristics and ecological significance of dimorphic seeds of Viola philippica

Viola philippica has dimorphic seeds which come from chasmogamous flowers and cleistogamous flowers. Based on the morphology observation of CH and CL seed, we compared the germination characteristics of the two types of seeds at different temperatures, light conditions and the storage time. The results showed that: 1) The length, width and weight of CL seeds were significantly lighter (P<0.05) than CH seeds. 2) The optimum germination temperatures of CH and CL seeds were 20 ℃, and both the germination rates were above 95%. Both of the two types of seeds did not germinate at a low temperature (10 ℃), but germination rate of CH seeds was significantly lower (P<0.05) than CL seeds at a high temperature (30 ℃). As to the moderate temperature (15-25 ℃), the germination rates of CH and CL seeds did not differ significant(P>0.05). 3) CH seeds were sensitive to light and its germination rate would be inhibited in the dark (P<0.01), but the germination rate of CL seeds had no significantly difference at 12 h light and full dark conditions(P>0.05). 4) Compared with the control, the germination rates of CH and CL seeds significantly decreased after 210 d and 510 d storage (P<0.05), respectively. CH seeds maturing in the spring can quickly germinate. CL seeds germinated later in the season than CH seeds. The part of CL seeds could germinate, another part became transient soil seed bank and could germinate next spring. The differences in germination characteristics between dimorphic seeds of V. philippica improved the species’ fitness to heterogeneous habitats.