Patterns of flower morphology and structural changes during interconversion between chasmogamous and cleistogamous flowers in Viola philippica
LI Qiao-Xia;HUANG Xiao-Xia;CHEN Wen;WANG Yong;SUN Kun;College of Life Sciences,Northwest Normal University;
Aims Viola philippica is a species with a typical chasmogamous-cleistogamous(CH-CL) mixed breeding system.It provides a flower model system to investigate floral organs development under different photoperiods.Morphological changes of intermediate cleistogamous(in CL) flowers have been observed,the trends in variation of changes from CH flowers to CL flowers or from CL flowers to CH flowers have been analyzed,the localized effects of poorly developed stamens and petals in CL and in CL flowers have been identified.This research provided morphology and structural changes with implication for the evolutionary significance of the dimorphic flower formation for further study in dimorphic flower development.Methods We used methods of anatomy and structural analysis to observe the morphological structures of flowers under different photoperiods.Important findings Photoperiod played an important role in the development of CH and CL flowers in V.philippica.Under short-day light and intermediate-day light,both CH and in CL flowers developed simultaneously.Most of the floral buds were CH flowers under a photoperiod of short-day light,but most of the floral buds were in CL flowers under mid-day light.Complete CL flowers formed under long-day lights.However,there were a series of transitional types in the number and morphology of stamens and petals among in CL flowers,including five stamens with three petals related to CH flowers and two stamens with one petal related to CL flowers.The former type was dominant under short-day light conditions,and the latter type was dominant under mid-day light.Further more,there were localized effects in stamen and petal development for CL and in CL flowers.The development of ventral lower petal(corresponding to the lower petal with spur of CH flower) and the adjacent two stamens in in CL flowers were best,and the back petal was similar to that of CL flowers,an organ primordium structure.The adjacent stamens with the back petals tended to be poorly developed.In extreme cases,these stamens in in CL flowers had no pollen sac,only a membranous appendage or even a primordium structure.When the plants with CL or CH flowers were placed under short-day light or long-day light,the newly induced flowers all showed a series of in CL flower types,finally the CL flowers transformed into CH flowers,and the CH flowers transformed into CL flowers.This result indicates the gradual effects of different photoperiods on dimorphic flowers development of V.philippica.A long photoperiod could inhibit the development of partial stamens and petals,and a short photoperiod could prevent the suppression of long-day light and promote the development of stamens and petals.
【CateGory Index】： Q944.58
【CateGory Index】： Q944.58