Abstract
Eusporangiate fern genus Ophioglossum L. is commonly known as Adder’s tongue fern as its fertile frond gives the appearance of snake tongue. A new species in this fern genus, O. trilokinathii belonging to Ophioglossaceae family has been discovered from the plateau region of Rajasthan State of northwestern India. The new species can be distinguished from other taxa of this genus by its smaller habit, subglobose-tuberous rhizome, basipetal emergence of young roots, aggregation of old decaying roots on rhizome apex, fertile stalk as well as spike short and thick, trophophylls in rosette, ovate or orbicular and a unique sporoderm sculpture pattern under SEM having broad reticulations with thick and raised muri enclosing large hexagonal or irregular areas on the distal and proximal faces of the spores hitherto unreported in any of the presently known taxa of Ophioglossum. In addition, comparative study of stomatal structure, foliar anatomy and nucleotide sequence data of its three chloroplast DNA markers (trnL-F, rbcL and psbA-trnH) was carried out. In view of all the attributes including habitat, ecology, morphology, foliar anatomy, stomatal features, palynology and molecular phylogenetic data, the present study suggests that the Ophioglossum specimen collected from plateau region of Rajasthan represents a hitherto undescribed species thereby warranting its establishment as O. trilokinathii sp. nov. A detailed comparative account of the new taxon with its allied species has also been provided.
Highlights
Eusporangiate fern genus Ophioglossum L. is commonly known as Adder’s tongue fern as its fertile frond gives the appearance of snake tongue
Limited efforts have been made on extensive survey and detailed investigation for generating the comprehensive data pertaining to species diversity, morphology, palynology, anatomy and molecular biology of this interesting fern genus Ophioglossum
Comparison of the new species (O. trilokinathii sp. nov.) with O. gujaratense indicates that these two taxa resemble in having stoloniferous roots, subglobose tuberous rhizome, number of trophophylls which are 1–4 sometimes 5, appressed to the ground and common stalk subterranean but O. gujaratense differs from O. trilokinathii by its larger size, acropetal emergence of roots, trophophylls lanceolate, fertile stalk thin and long[20,32] and exine with muri of uneven heights along with some flat and wider areas, enclosing shallow depressions on distal face, proximal face reticulated bearing prominent triradiate ridge, laesural arms straight sometimes wavy, reaching to the margins of the central cavity of the spore (Fig. 3E,F)
Summary
Eusporangiate fern genus Ophioglossum L. is commonly known as Adder’s tongue fern as its fertile frond gives the appearance of snake tongue.
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