A study of structural diversity of trichomes in the family fabaceae lindl and its taxonomic implication

Abstract

ABSTRACT newlineTrichomes are the outgrowths of various kinds at epidermal surfaces of plants and these microstructures are useful character in taxonomy. Fabaceae Lindl. is one of the most diversified families of flowering plants but the structural diversity of trichomes in its members is only obscurely known. Present study was conducted to study the structural diversity of trichomes in the member species of Fabaceae growing in Kumaun region of Uttarakhand, during October 2019 - September 2022. A total of 116 species, 2 subspecies belonging to 71 genera, 21 tribes and 4 subfamilies of the Fabaceae were collected and identified with the help of relevant taxonomic literature and herbarium consultation. Micro-preparations of surface peelings taken from all aerial organ surfaces were made and examined under the light microscope and photomicrographs were obtained. The illustrations were drawn using camera lucida at 10x magnification of objective lens and measurements were taken after required calibration using stage and ocular micrometers. All studied plant species invariably bear trichomes on one or more parts of plants and a total of 99 structural types of trichomes were recorded in the studied taxa. Non-glandular trichomes were more diverse with 71 types and glandular trichomes were represented by 28 types. A classification of all recorded trichomes was devised based on nature, number of cells, seriation, form and overall shape. Highest diversity of trichomes was recorded at species level in Calliandra haematocephala and Bauhinia purpurea (nine types each), at genus level in Bauhinia (18 types), at tribe level in Phaseoleae (29 types), and at subfamily level in Papilionoideae (69 types). Among different plant surfaces, petiole surface was recorded having trichomes in maximum number of taxa (106 species), followed by stem (101 spp.), abaxial surface of lamina (99 spp.), sepal and peduncle (93 spp. each). Nine different orientations or arrangement types, viz. appressed, porrect, spreading, incurved, reflexed, pendulous, ascending, descending and oriented in different directions; eight prominent positions of trichomes, viz. straight, sigmoid, arcuate, simple curved, nutant, tortuous, cochleate and furcate type; and 13 types of vestitures, viz. puberulous, puberulent, pubescent, tomentose, sericeous, hirsute, lanate, scabrid, strigose, villous, floccose, arachnoid and glabrescent were recorded on different aerial surfaces of studied taxa. Each genus, tribe, subfamily among the studied taxa has its characteristic trichomes which are useful in differentiation of it from others. Vestiture on different surfaces is a useful taxonomic character. On the basis of their structures and distribution patterns trichomes can be used for identification, differentiation and circumscription of taxa. newline newline