Pollen Morphology of Lactuca L. (s. lat.) (Cichorieae - Asteraceae) from Hindukush, Western Himalyan and Karakorum Ranges and its taxonomic significance

Abstract

ABSTRACT Pollen morphology of 15 species of the genus Lactuca L. (s. lat.) of the tribe Cichorieae from the Hindukush, Western Himalayan and Karakorum Ranges has been studied using Light microscope (LM) and Scanning Electron Microscope (SEM). Pollen morphology of six species viz., L. erostrata Bano & Qaiser, L. glaucifolia Boiss., L. persica Boiss., L. crambifolia (Bunge) Boiss., L. chitralensis (Tuisl.) Ghafoor, Qaiser & Roohi Bano and L. picridiformis Boiss., was never studied before. Pollen were found to be isopolar, spheroidal to oblate-spheroidal, elliptic to rarely circular in equatorial view, hexagonal in polar view, trizonocolporate and echinolophate with 15 lacunae. Morphometric analysis of the pollen characters was conducted using Agglomerative cluster analysis with Euclidean distance and Ward’s method to compute the dissimilarity matrix, and a dendogram was prepared. Two pollen-types primarily based on the diameter of polar and equatorial axis of the pollen grain were recognized. Keys to the pollen types, subtypes and to the species are provided. The present palynological findings to a greater extent are in agreement with the results of current phylogenetic studies based on molecular evidences. Moreover, both the pollen types are well correlated with the general morphology of the investigated species of the genus Lactuca L. (s.lat) and provided additional micromorphological characters for the delimitation of the species.