Comparative Anatomy Of The Vegetative Organs And Leaf Development Of Of Zygophyllum

Zygophyllum belongs to Zygophyllaceae.The genus consists of approxmitaly 120 species ranging from perennial herbs to shrubs which are found primarily in arid and seim-arid area of Asia,Australia,and Africa.Molecular phylogenetic analysis of Zygophyllum suggests that shrub and herbarium species in Asia evolved from the same ancestor but diverged early into two distinct subclades.However,the morphological anatomy and development of the vegetative organs were not studied.In this study,Zygophyllum xanthoxylon and Zygophyllum fabago are representative species of shrub and herbarium clades respectively.We systematically compared morphological and anatomical features of the two species.In addition,the molecular mechanism of leaf development of Z.xanthoxylon had been preliminarily explored.The results are as follows:(1)Our results show that vegetative organs of the two species display different xerophilous characteristics,suggesting environmental adaptations.Our study provides additional evidence supporting the classification of Zygophyllum.Cortex parenchyma cells were more diversified in roots and stems,and the lignification of xylem was greater in roots of Z.xanthoxylon than Z.fabago.There is more starch in the roots and stems of Z.xanthoxylon than Z.fabago.In leaves,Z.xanthoxylon had smaller leaf area and stomata density and the thicker cuticle in leaves and petiole than Z.fabago.Therefore,the Z.xanthoxylon has more remarkable xerophilic characteristics compared with Z.fabago.(2)The leaf of Z.xanthoxylon is even pinnate.The leaf consists of two leaflets.There is a apical pointlet in the position of the terminal leaf.This is obviously different from the odd pinnate compound leaf.In this study,the leaf morphological development of Z.xanthoxylon was divided into four stages,ranging from the beginning of the leaf primordium to the matunity of the leaf.From this process,it was observed that the height of the primordium was greater than that of the lateral leaves.With the development of the leaf,the terminal leaf primordium was less than the lateral leaf primordium.Finally,the terminal leaf stopped growing.Compared with the odd pinnate leaf development of Sorbaria kirilowii,it is concluded that the terminal leaf of Z.xanthoxylon was not fully developed.(3)Leaf of Z.xanthoxylon in different growth periods was studied by the transcriptomics analysis.We screened out six genes and proteins.These genes and proteins were related to the leaf development of Z.xanthoxylon,consisting of ROT3?PIF3?BZR1/2?LHCA1?LHCB6?NYC1gene.These genes have laid the foundation for the further study on the molecular mechanism of the terminal leaf development.