Leaf Midrib Anatomy of Palmyra Palm (Borassus flabellifer L.) - structural differentiation, adaptive features, and micro morphological insights

Abstract

Palmyra palm is a multipurpose tree due its wide range of economical uses to the poor and Palmyra
dwellers. The biology of Palmyra palm is being studied in justifying the usage of every part of the
plant. Besides leaf, the midrib of palm leaf lamina is specifically used for making certain
handicrafts and toys. The craftsmen and palm dependents have identified the flexible nature of leaf
midribs (Eierkku in Tamil) and make unique objects only with midribs like tea/coffee cup holders,
garlands and many other products which have elastic nature. The present study aims at
understanding the anatomy and tissue properties which are responsible for such flexible nature of
the products. The investigation elaborates on description and characterization of fibro vascular
bundles, fibrous sheaths and flexible collenchyma from midribs. Comparative anatomical studies
are carried out on basal, middle and apical regions of leaf laminal midrib with reference to diversity
and arrangement of fibro vascular bundles and other tissues. For anatomical and histochemical
studies free hand sections of the Palmyra leaf laminal midrib were made and studied with
florescence, light and polarized microscopic facilities. Midribs were macerated for studying
occurrence of stomata, typifying of fibres and for micrometry. Parameters such as micrometrics of
all type of cells, and wall thickness were made and the results were statistic ally analyzed. The
midrib epidermis is covered by thick cuticle layer of waxes followed hypodermis. Variety of fibro
vascular bundles, fibre sheaths, peculiar collenchymas and other tissue characteristics were
recorded. The flexible nature of the objects made out of midrib is mainly due to the presence of
highly thick walled fibro vascular bundles, patches of fibre sheaths and elastic collenchyma with
their well evolved architectural design. The findings on midrib anatomy would be useful in
comparative studies of other species and genera of Palmae. The midrib anatomical characteristics
justify that Palmyra palms are well evolved species to adapt themselves to dynamic environmental
factors like heavy wind coupled with dry and high temperatures. Thus, the findings of this
investigation are unique and shed more light on the evolutionary and adaptation features of Palmyra
Palm.