Ranunculaceae Carpel Diversity And Its System Studies

Carpel characterizes the angiosperm,and it is the most important organ in the flower of angiosperms,it has four primary functions:embracing and protecting the ovules,accepting the pollen grains and conducting the pollen tube to grow so as to guarantee the eggs to finish the fertilization,the place in which the new sporophytes arise and develop,protecting and spreading the seeds.So it is very important to know the structure of the carpels to help to delimit the relationship of the plants among families and genera.Rannuculaceae,which is one of the key groups in the basal eudicots,is the bridge of the basal angiosperms and the core eudicots.As the speciality of its systematic position,abundance of variations exist in this group.People hold different ideas towards its classification before.A lot of new challenges are put forward based on the study of molecular results.They consider that there are several paths within this group from which the achene evolved from follicle.The traditional morphological studies are based mainly on fruit type and the vascular bundle in the carpels,and little attention are paid to other morphological features.The mature carpels of 3 subfamilies,11 families,24 genuses,38 species in Ranunculaceae, Circaeaster agrestis Maxim.and Kingdonia uniflora Balf.f.et W.W.Smith in Circaeasteraceae,as well as Akebia trifoliate(Yhunb.) Koidz in Lardizabalaceae were studied in this paper.Also the carpel vascular bundles of 3 subfamilies,10 families,19 genuses,27 species of Ranunculaceae were observed.In our result,we found there are abundant variations in the mature carpels of Ranunculaceae,which has systematic significance,meanwhile,according with that of molecular systematics.The basal carpel nunber in Ranunculaceae maybe small(4-9),and increased or decreaed in two directions.The multiovular conduplicate carpel maybe primitive.The multiovular berry and follicle and the athene with single ovule all derived from this type of carpel.During the evolutionary trend with follicles to achenes,the three carpel traces often decreaed to single carpel trace,and the transitional vascular supply can be observed.The size of the carpels also evolved in two directions. The achenes can be long in size as well as the follicles.Both the multiovular and singleovular carpel has remarkable relationship with the elongation of styles.The sizes of stomata and ovarian cells are relative to the chromosomal type.But the size of cells also has something to do with their maturity.The pattern that the stomata are distributed in the upside of the carpel may be primive in Ranunculaceae.The stigma defferentiation pattern can be classified into four types,which indicate the specialization degree within this group.The unicellular-papilla can be grouped into three types.The unicellular hair on carpel surface can be classified into five types.The type of the hair and its distribution have systematic significance.As the conservative structure,vascular supply in carpels is vital in systematics.It is often considered that the follicular group has three carpel traces.The single carpel trace in this group is considered to be the occasional case.But we only found single carpel traces in Trollius and Caltha.It is worthy of being confirmed that whether single carpel trace exists within other follicular groups of Ranunculaceae.The carpel morphology studies support the results of recent studies based on the molecular systematics:support the view that Coptis is basal in Ranunculaceae;the affinity between Trollius and Adonis is approved;approve the treatment of the genera in Tribe Cimicifugeae;Nigella should be isolated from Tribe Deiphineae,and treated as a tribe Nigelleae;Callianthemum has more similarities with Adonis than with Tribe Ranunculeae;support the result that Oxygraphis has close relationship with other genera within Tribe Ranunculeae as well as some dissimilarities.