Comparison of petiole anatomy in Flemingia and its potential for delimitation of species

Abstract

Socio-economically, different species of Flemingia are used worldwide for various purposes like food, folk medicine to cure various ailments, as a source of non-timber products (e.g., resin, dye, host for lac insect, toothbrush, etc.). Therefore, species level identification is important even in the absence of reproductive structures as it will help to avoid adulteration. In this context, petiole anatomy may be effectively employed since it is considered to be one of the diagnostic characters for the discrimination of taxa at species level. Thus, in the present study, petiole anatomy of 16 species of Flemingia is investigated to find additional diagnostic features for species level identification. Amongst these 16 species, 13 had trifoliolate leaves whereas three, F. strobilifera, F. chappar and F. paniculata possessed unifoliolate leaves. The petiole was winged except for F. chappar and F. vestita. The wings were much larger in F. nana, F. paraecox and F. sootepensis while in F. paniculata, F. strobilifera and F. wightiana they were just a small outgrowth/projection. The number of vascular bundles in wings varied from 1 to 5. The cortex was composed of palisade and spongy cells which were restricted to the wing region of F. praecox and F. sootepensis. Cortical fibres formed a cap like structure external to the vascular bundle in F. angustifolia, F. nana, F. procumbens, F. sootepensis, F. strobilifera and F. vestita whereas a complete ring was formed in the remaining species. Besides these features, outline of the stem and presence or absence of wing on the dorsal side of the petiole is another important character of taxonomic value. Histological structure and the composition of the petiole of all the species is described in detail and discussed in relation to its diagnostic significance.