Leaf Architecture Of Genus Prunus L. Sensu Lato(s.l.) And Its Taxonomic Significance

Prunus s.l.(Rosaceae)include Amygdalus L.,Armeniaca Scop.,Cerasus Mill.,Emplectocladus Torr.,Laurocerasus Duhamel,Maddenia Hook.f.& Thomson,Padus Mill.,Persica Mill.,Prunus L.sensu stricto(s.str.).It comprises 200-250 species with most species in the temperate zone and some in the tropical and subtropical regions.Prunus s.l.is economically important because many species are sources of fruits(e.g.,P.avium,P.salicina Lindl.,P.mume,P.armeniaca),oil(e.g.,P.dulcis,P.davidiana),timber(e.g.,P.serrula,P.sibirica,P.maximowiczii)and ornamentals(e.g.,P.serrulata,P.padus).The taxonomy of Prunus are still controversial.Recent phylogenetic studies is helpful for the classification of Prunus,however,the results are also different.So,the further research of Prunus is needed.In this paper,leaves of 78 species from Prunus were studied.Integrating the geographical distribution,morphological and molecular evidences,41 leaf architectural characters were examined and conducted clustering analysis research with UPGMA method(unweighted pair-group method with arithmetic means)to discuss the intergeneric classification and definition of species.Our results are as follows:(1).Prunus has a common set of traits: simple leaf with glands;leave margins mostly has teeth;pinnate and major secondaries mostly reach the margin;areolation present;freely ending veinlets present.There are also distinctive characteristics which can be used to identify groups.The genus can be divided into 8 groups.In particular,margin type,secondary vien,tertiary vien,areole and freely ending veinlet provide valuable information for clarifying the interspecific relationships within Prunus.(2).The discussion of the taxonomic revision of subgenus.1.Subgenus Prunus and subgenus Armeniaca showed a close relationship,they should be combine into Subgenus Prunus,and divided into Sect.Prunus and Sect.Armeniaca(Lam.)Koch.;2.P.triloba is supported be a member of subgenus Prunus;3.Excluded the section Microcerasus from the subgenus Cerasus Pers.And P.glandulosa,P.pogonostyla var.obovata and P.tianshanica should belong to subgenus Amygdalus(L.)Focke,P.tomentosa should belong to subgenus Prunus;4.P.buergeriana is removed to subgenus Laurocerasus Koehne.(3).The discussion of taxonomic revision of species.1.P.sibirica and P.mandshurica is difference from P.armeniaca,so they should be treat as an independent species.P.armeniaca var.holosericea still supported be a variety.2.Maddenia hypoxantha was as conspecific with M.wilsonii,because a wide range of variation was found on the lower leaf pubescence which is the differences between two species;3.P.gongshanensis differs from P.himalayana only in its almost glabrous lower leaf surfaces,so supported that it be treated as a variety of P.himalayana;4.P.pananensis was highly similar to P.dielsiana in morphology,so it should be new distribution of P.dielsiana in Zhejiang;5.Cerasus xueluoensis also was highly similar to P.serrulata in morphology,it may be a dwarf form of P.serrulata growing at high altitude.(4).The leaf architecture is significant for evolution of Prunus.Leave tooth,glands,major secondary vein framework,areolation and freely ending veinlets complicated degrees showed leaves of Prunus is various but interrelated,reflecting the continuity of evolution.In order to adapt to the hot environment,leaves of Prunus became untoothed,at the same time the raised glands on the leaf teeth became flat glands on the abaxial surface,vein density decreased and freely ending veinlets with more branches.Padus and Laurocerasus transitional groups of temperate type to tropical type.Obviously,there are many transitional species with different degrees of evolution in Laurocerasus.Meanwhile,the temperate taxa continued to evolve,the number of orders of teeth was increased,the glands on teeth showed various types,the types of the quaternary and quinternary vein were diversity.