Fruit Polymorphism And Plasticity In Two Species Of Lappula

Lappula duplicicarpa and L.semiglabra (Boraginaceae) are early-spring ephemerals distributing in the Junggar Desert. We determined the ratio of nutlets with long (LN) and short (SN) glochids produced by individual flowers and compared their morphology, anatomy, dispersal, germination and plasticity characteristics. The main results are described as follows:(1) Morphology and dispersal ability: In both species, LN and SN had significant difference in morphology. The dimorphic nutlets of both species had different dispersal abilities, LN was much more easily detached from the mother plant and dispersed further than SN.(2)Dormancy and germination characteristics: Germination and germination rates of LN and of SN were significantly higher at 20/10°C than those at other temperatures. Germination of both species was significantly affected by seed type, temperature, light condition and their interactions. The germination rate in both species also increased with the increase of storage time. Dimorphic nutlets of both species stored in the open field had the same dormancy cycle. The germination temperature range of dimorphic nutlets descreased with increasing storage time. Germination of LN was higher than that of SN at the same condition.(3)Phenotypic plasticity characteristics: Dimorphic nutlets of both species could germinate in autumn and in spring. The plants formed by dimorphic nutlets of both species presented various plasticity changes in size and shape, fruit and nutlet and biomass allocation under different environment conditions. The small plants (under unpredictable environment) increased the number of 4SN or 3SN/LN, of 2SN/2LN and of SN, which would stay in the"safe"habitat of the mother plant and make population stable. The big plants produced more number of SN/3LN, of 4LN and of LN to long-distance dispersal to other sites, which was benefit to the rapid growth and expansion of population and increased fitness of species.