the role of xylem vessel size and ray traits in dutch elm disease frequency in ulmaceae

dutch elm disease is one of the most destructive and common plant vascular diseases now which isknown as a global problem. the aim of this study was comparison of early- and late-wood vesselsdiameter and ray dimensions. in 4 species: ulmus carpinifolia, zelkova carpinifolia, ulmus glabra andceltis australis from ulmaceae. then, very thin transversal sections were prepared and after differentstages of staining, microscopic slides were prepared. the data of xylem vessel and ray attributesmeasurement among disease and healthy species analysis via one-way at level of 0.01. the comparemeans was done with duncan test. the results showed that the maximum and minimum frequency ofdisease belong to english elm and hackberry respectively. there is significant difference betweenxylem vessels and ray attributes of species. the results of light and electron microscopy showed thatthere is a change and destruction in xylem vessels and ray structure in affected trees.