ANATOMICAL CHARACTERIZATION OF PARASITIC PLANTS OF PAKISTAN

The gross anatomical characteristics of 5 parasitic plant species, viz., Cuscuta reflexa Roxb. (Cuscutaceae), Orobanche aegyptiaca Pers. (Orobanchaceae), Korthalsella opuntia (Thomb.) Merrill, Viscum album L., and Viscum cruciatum Seib. Ex. Spreng. (Viscaceae) were investigated. The vascular bundles of all these parasitic plants were less developed having poorly developed phloem but well developed xylem. The most interesting features were the presence of terminal sclereids in Viscum cruciatum and brachysclereids in Korthalsella opuntia. Terminal sclereids have not been reported previously in the genus. These parasitic species show variation in the invasiveness of endophytic tissue of haustorium into the host vascular tissue. Haustorium of Cuscuta reflexa forms connection to the phloem of the host. The haustorium was consisting of few threads of xylem and phloem which penetrate only to the phloem tissue of the host. In Korthalsella opuntia and Viscum cruciatum haustoria form connection to the xylem of the hosts. The haustorium of Korthalsella opuntia is well developed and surrounds the host xylem in the form of cup.