Domestic Aristolochiaceae Family (aristolochiaceae) Plant Morphology

Aristolochiaceae consists of 4-8 genera and ca.500 species.There are 4 genera in China,viz. Saruma Oliv.,Asarum L.,Aristolochia L.and Thottea Rottb.The floral morphogenesis,the variation of vessel perforation plates and the palynology of representative species of Saruma,Asarum,and Aristolochia were described in the present paper.Based on above researches,we discussed the intergenerical relationships in Aristolochiaceae.The observation results as follows:1 Floral Morphogenesis and DevelopmentThere are six whorls of floral organs in aspect of morphogenesis in Saruma henryi Oliv..The first whorl is three sepals that initiate successively.After that,the floral apex becomes cup-shaped and the petals and the stamens appear simultaneously in each whorl on the margin of the cup.The second whorl is three petals alternating to the sepals.The third whorl is three stamens opposite to the sepals.The fourth whorl is six stamens in double position opposite to sepals.The fifth whorl is three stamens opposite to petals.Six separate carpels initiate in two whorls and arrange in one whorl later to form the sixth whorl.The carpels initiate on the receptacle cup wall as a conduplicate structure and are hypogynous in this stage and then become perigynous ovary due to the fast growth of carpel apex.Floral morphogenesis of Asarum himalaicum Hook.f.et Thoms.ex Klotzsch.is similar to that of Saruma,but the second whorl is three stamens,the fifth whorl is absent,six adnate carpels initiate simultaneously,and the carpels are epigynous.In Aristolochia contorta Bge.,the initiation of the sepal resembles to the bract,four in the six stamens initiate firstly and the other two slightly later, then six placentas intrude into the ovary representing the initiation of the carpel and finally fuse in the center of the ovary to form an axial placenta.A protuberance appears in ventral base of each anther and joins with the expanding placenta in the following developmental stages.Each of the protuberance forms a gynostemium lobe.2 Vessel Perforation plates in Secondary XylemIn Saruma,the vessel end-walls include reticulate,reticulate-scalariform,reticulate -scalariform-simple,reticulate-simple,scalariform-simple and simple perforation plates;In Asarum the vessel end-walls include scalariform,reticulate-simple,scalariform-simple and simple perforation plates;But only simple perforation plates were oberved in the species of Aristolochia.3 Palynology charactersSaruma has semitectate,reticulate,monosulcate pollen.Asarum himalaicum pollen is inaperturate,and has a surface composed of tectate with strumae.Pollen ofAristolochia contorta is monosulcate,tectate,approximately psilate. 4 Intergenerical relationships of AristolochiaceaeAccording to the foral morphogenesis and morphological characters of Aristolochiaceae,then compared with former research results by other scholars,we considered that the floral organs in the second whorl in Saruma,Asarum,and Thottea may be homeotic shift from stamens to petals or degenerate petals,and the pefigynous ovary is derived in Saruma;the gynostemium lobes origin from the stamens in Aristolochia contorta,and the axial placenta is derived.The floral morphogenesis features support the opinion that Saruma and Asarum are closely related and should be placed in Subfam.Asaroideae.The initiation and development pattern of sepals,petals(if present), and the stamens of Saruma and Asarum is similar to that of Thottea,the initiation and development of the placenta and gynostemium lobes of Aristolochia is similar to that of Thottea.In aspects of floral morphogenesis features,Subfam.Asaroideae and Subfam.Aristolochioideae might be phylogenetically related through Thottea.According to the types of the vessel perforation plates in Aristolochiaceae,there are various types of perforation plates on the end-walls of vessel elements in Saruma and Asarum;but those of Aristolochia have only simple perforation plates,and are evolutional.Therefore,we considered that the relationship between Saruma and Asarum is so closer,yet ulterior with Aristolochia.The floral morphogenesis and development,and the vessel perforation plate support the opinion that Saruma and Asarum should be placed in Subfam.Asaroideae and Aristolochia in Subfam. Aristolochioideae.