Journal of Threatened
Taxa | www.threatenedtaxa.org | 26 December 2024 | 16(12): 26264–26271
ISSN 0974-7907 (Online)
| ISSN 0974-7893 (Print)
https://doi.org/10.11609/jott.8243.16.12.26264-26271
#8243 | Received 29
October 2022 | Final received 12 November 2024 | Finally accepted 03 December
2024
Morpho-anatomical
characterization and conservation status of the
Whisk Fern Psilotum nudum (L.)
P.Beauv. (Polypodiopsida: Psilotaceae)
from Cooch Behar
District of West Bengal, India
Aninda Mandal
Department of Botany,
A.B.N. Seal College, Cooch Behar, West Bengal 736101, India.
Editor: Aparna Watve,
Biome Conservation Foundation, Pune, India. Date of publication: 26 December
2024 (online & print)
Citation: Mandal, A. (2024).
Morpho-anatomical characterization and conservation status of the Whisk Fern Psilotum nudum (L.)
P.Beauv. (Polypodiopsida: Psilotaceae) from
Cooch Behar District of West Bengal, India. Journal
of Threatened Taxa 16(12): 26264–26271. https://doi.org/10.11609/jott.8243.16.12.26264-26271
Copyright: © Mandal 2024. Creative Commons Attribution 4.0 International License. JoTT allows unrestricted use, reproduction, and
distribution of this article in any medium by providing adequate credit to the
author(s) and the source of publication.
Funding: This work is supported by grant (Memo No: 682/(Sanc.)/BT/ST/P/S&T/2G-01/2020, dated 04/01/2021) from the Department of Science & Technology and Biotechnology (DSTBT), Government of West Bengal, under the Research and Development Programme scheme, Gobeshonay Bangla.
Competing interests: Funding source had no role in study design, data collection, interpretation of results and manuscript writing.
Author details: Aninda Mandal is an Assistant Professor (W.B.E.S.) and Head in the Department of Botany, A.B.N. Seal College, Cooch Behar, West Bengal. He did his PhD from University of Kalyani, West Bengal. His field of interests includes pteridophytes, ecology, and ethnobotany, among others.
Acknowledgements: The author is
thankful to the divisional forest officer and range officer, Parks and Gardens,
North Division, Siliguri for their kind permission to visit the study area of
the Narendra Narayan Park and to the gardener of Madan Mohan Temple, Cooch
Behar for his valuable cooperation during the study. The author is also
thankful to the principal, A.B.N. Seal College, Cooch Behar for providing the
necessary facilities. Thanks are extended to Alamin Hoque, Student of Botany Honours of A.B.N. Seal
College for his helping hand during slide preparation. This work is supported
by a grant (Memo No: 682/(Sanc.)/BT/ST/P/S&T/2G-01/2020
dated 04/01/2021) from the Department of Science & Technology and
Biotechnology, Government of West Bengal, under the Research and Development
Programme scheme, Gobeshonay Bangla.
Abstract: The district Cooch
Behar of West Bengal, India is considered a unique zone for pteridophytes. The
Whisk Fern Psilotum nudum
(Family Psilotaceae), one of the primitive members of
living vascular plants considering its age of evolution during the Devonian, is
reported to occur in the Cooch Behar District. The present study has been
designed to investigate the current conservation status as well as to describe
the morphological and anatomical features of the epiphytic species. The present study revealed that the natural
falling of old aged host trees and cleaning and white painting of host tree
trunks lead to habitat destruction which may lead to extinction of the species
from the studied areas. During the field visits, a new site of the occurrence
(Madan Mohan Temple of Cooch Behar City) of the species has also been recorded.
Plants are perennial and pendent in nature. The rhizome is achlorophyllous,
freely branched, and covered with rhizoids. The aerial stem is up to 36 cm
long, repeatedly dichotomously branched and chlorophyllous.
Leaves are scalelike, without any midrib, lanceolate
to ovate, and without ligules. Synangiums are
composed of three connected sporangia, bearing numerous bean-shaped spores.
Stele in rhizome is haplostelic type; while, it is actinostele in the aerial stem. Morpho-anatomical description
of the species has been documented for the first time from West Bengal and has
enriched the botanical information of the species. Proper conservation of the
taxa is utmost necessary in order to maintain their population in natural
habitat.
Keywords: Anatomy, eastern indo-himalaya, ecology, epiphyte, habitat loss, living
fossil, morphology, pteridophytes.
INTRODUCTION
The genus Psilotum (belonging to the primitive family Psilotaceae), with its two Indian species, i.e., P. nudum (L.) P.Beauv.
and P. complantum Sw. (Pande
2002; Chauhan et al. 2003; Muthukumar et al. 2009),
is often grouped with the extinct psilophytes, the Rhyniales, and Zosterophyllales
dating from the Devonian some 400 million years ago (Roux 2003). Many
paleobotanists and plant morphologists considered the members under Psilotum as ‘living fossils’ or ‘living
rhyniophytes’ (Kidston & Lang 1917; Banks 1975; Kaplan 1977; Wagner 1977;
Rothwell 1999); but unfortunately, no fossils of psilophytes
are known to exist. Recent morpho-anatomical studies (Bell & Hemsley 1992;
Stewart & Rothwell 1993) suggest that the genus is not closely related to
rhyniophytes; rather, the primitive characters present in living psilophytes represent a reduction from a more typical
modern fern plant. Similarly, according to molecular data, it is evident that Psilotum is a fern and that psilophytes
are sister to ophioglossoid ferns (Qiu & Palmer 1999; Pryer et
al. 2001; Smith et al. 2006; Schneider et al. 2009).
Psilotum nudum (Greek—‘psilos’ means smooth or naked
and Latin—‘nudus’ means naked, and both referring to
the smooth and naked character of the stems; commonly known as whisk fern - Qiu & Palmer 1999), one of the two species in the genus
Psilotum, is widely distributed across
tropical and sub-tropical areas of both hemispheres (Zhang & Yatskievych 2013). In India, the species is reported to be
found in Andaman Islands, Nicobar Islands, Western Ghats, Eastern Ghats,
central India, eastern India, northwestern India (Thothathri
et al. 1970; Pande 2002; Chauhan et al. 2003; Valavan et al. 2016; Kanivalan
& Rajendran 2017) with its first report in Barren Island, an isolated one
in the Andaman group of
islands (Prain 1893). In West Bengal,
the species is reported to occur in Darjeeling (Pande
2002), Cooch Behar (Biswas 1956; Bandyopadhyay et al. 2006; Mandal 2023) and Jhargram (Sen & Bhakat 2021)
districts. P. nudum has most recently been
assessed for The IUCN Red List of Threatened Species in 2020 and is listed as
‘Least Concern’ (Bárrios & Copeland 2021).
The whisk fern became
a popular pot plant in Japan during the Edo Period (1603–1867), leading to the
selection of slightly over 100 ornamental garden varieties, most of which are
illustrated in the ‘Matsubaran fu’
(Hoshizaki & Moran 2001; Chernova et al. 2020).
The plant is also reported to be used for different medicinal purposes in India
and Hawaii (Foster & Gifford 1974; Benjamin & Manickam 2007; Mannan et
al. 2008; Karthik et al 2011; Kumari et al. 2011;
Revathi et al. 2013; Valavan et al. 2016, Mandal
2023).
Until now, several
morpho-anatomical studies of P. nudum have
been published from the different parts of the world (Ford 1904; Sporne 1962; Schulte et al. 1987; Nazarian et al. 2010; Vahdati et al. 2014; Rahman et al. 2015; Valavan et al. 2016); as per literature survey, detailed
morpho-anatomical studies of the species from India especially from the state
of West Bengal is lacking.
Keeping all these in
mind, the present study has been designed to investigate the present
conservation status and to describe the morpho-anatomical characters of the
species from the Cooch Behar District of West Bengal, India for the first time
which will enrich the botanical information of the species. The current study
will also report a new site of the occurrence of the species.
MATERIALS AND METHODS
The Cooch Behar
District (Image 1), situated in the foothills of the eastern Indo-Himalaya, is
known for its rich floristic composition. Field visits have been conducted
across different seasons during January 2021 to September 2022 to observe the
habitat and population growth pattern. The plant, P. nudum
has been collected from the previously reported study area (Biswas 1956;
Bandyopadhyay et al. 2006), i.e., Narendra Narayan Park (26.325 0N,
89.450 0E; elevation 14.5 m; Image 1), Cooch Behar for morphological
and anatomical studies. Morphological description has also been done from the
new site of occurrence of the species, i.e., Madan Mohan Temple (26.320 0N,
89.444 0E; elevation 14.5 m; Image 1), Cooch Behar based on the
available plant specimens. Geographical locations of the study areas were
recorded using the device GARMIN® eTrex®
22x. Anatomical studies have been performed through hand–sectioning of rhizome,
aerial shoot of different orders and synangium.
Slides were prepared after double staining and photographs were taken for
photographic documentation. Spore morphology was examined under a light
microscope (10X × 40X) and described as per Erdtman
(1945, 1971). Identification of the plant specimen was made using relevant
floras (Chinnock 1998; Diggs et al. 2006) and proper
nomenclature was maintained following POWO (2022). Voucher specimens were
deposited in the Department of Botany, A.B.N. Seal College, Cooch Behar.
RESULTS AND
DISCUSSION
Habitat, ecology and
conservation status
The plant population
of Psilotum nudum
recorded from the new site of occurrence (Madan Mohan Temple) was found to grow
on the tree trunk base (up to 1.5 m) of an old katgolap
tree (Plumeria sp.) in association with Drynaria
quercifolia (L.) J.Sm.,
Pyrrosia lanceolata
(L.) Farw. and some species of orchids and mosses
(Image 2). Approximately, 35 Psilotum plants
were found to be grown in the tree trunk of which only a few with sporangium.
The host tree is very old and eventually dying day by day as per the information
provided by the gardener of the temple. Cleaning and white painting of the tree
trunks of the temple before the ancient and traditional Rash Utsav is a very
common practice for the beautification of the garden and may harm the concerned
species and lead to loss from the site. Hence, in situ and ex situ conservation
strategies should be taken to protect the species. The author made the gardener
aware of the importance of the species and suggested barricading the tree and
not to paint the tree trunk so that the species can grow in its natural
habitat.
Biswas (1956) only
reported a few plants of the species growing on Polyalthia
longifolia along with an orchid (Dendrobium
sp.) in the main park (now named Narendra Narayan Park) and predicted the
species has been introduced from south India along with the orchid collection.
Later on, a team from ENVIS, Botanical Survey of India, Kolkata visited the
same park and reported that the species on the trunk of five very old trees
(out of six trees) of P. longifolia in
association with D. quercifolia and some
orchid species (Bandyopadhyay et al. 2006). The present study revealed that
approximately 15 plant species are found to be grown in the first tree; the
second tree becomes dead and only the remnants of trunk remains without having Psilotum plant; the third tree also contains no Psilotum species as reported earlier; more than 50
plant species are found to be grown in the fourth tree (Image 2); there is no
trace of the fifth tree and no plants are found to be grown on the tree number
six, though the previous authors reported that many plants were found to be
grown in fifth and sixth trees. From the current study it is clear that the
plant population decreased day by day which may be due to the natural falling
of host plants and or cleaning and painting of the tree trunks. The park
authority made aware by the present author regarding the present status of this
significant plant species in the park with a suggestion for taking necessary
measures to protect this declining species.
Morphological
description
Plants are perennial
medium-sized herbs, that grow as an epiphyte and pendent in nature (Image 3).
Rhizome is brown (achlorophyllous), cylindrical, slender, freely branched,
2.0–3.0 cm long, 1.5 mm in diameter, and covered with hair-like structures,
called rhizoids. The rhizome merges above the surface with the aerial part of
the plant. The aerial stem is 16–36 cm in long and 0.5–2.0 mm in diameter,
repeatedly dichotomously branched above with 30–42 branches, often pentagonal
towards the main stem, first and second dichotomy, quadrangular towards the
third and fourth dichotomy and triangular in the most distal portions (fifth
dichotomy), glabrous and green in color (chlorophyllous),
with longitudinal parallel lines twisted slowly around the stem. Leaves are scale-like
(Image 3), lacking a midrib, 1.5–2.0 mm long, spirally arranged on the stem,
lanceolate to ovate in outline, pointed, and without any ligules. Synangia (Image 3) is 2.5–3.0 mm in diameter, orbicular,
smooth, light green during young stages, become yellowish when mature and composed of
three fused sporangia (Image 3) separated by three longitudinal and arched
depressions, bearing numerous kidney or bean-shaped spores, a dichotomous bract
is present around the synangium. Spores are homosporous, monad, bilaterally symmetrical, monolete,
prolate to per–prolate in shape, large sized (polar axis: 76.68–88.52 µm,
equatorial diameter: 36.42–45.92 µm), exine thick
(3.26–4.98 µm), exine ornamentation verrucate-tuberculate (Image 3).
Anatomical
description
A model plant drawing
of P. nudum has been displayed in the image
(Image 3) to show the scheme of sampling sites for transverse sections (T.S.)
of rhizome and aerial stem of different dichotomies.
Rhizome
The T.S. of the
rhizome is more or less circular in shape (Image 3). Epidermis is thin,
inconspicuous and single layered. Most of the epidermal cells extend into two
celled absorptive rhizoids. Below the epidermal layer, there is a broad cortex
of thin-walled cells. Stele is protostele (haplostele) in nature. Pith is absent
and the xylem mass is usually chain- like / rod- like in outline and without
any protoxylem. The xylem is surrounded by uniform layers of phloem which in
turn is surrounded by the pericycle. Outside the pericycle, a distinguishable
endodermal layer is present with conspicuous Casparian
strips on radial walls. Vahdati et al. (2014) have
also reported the presence of haplostele in the rhizome; Nazarian et
al. (2010) have reported the stellar type as actinostele.
Aerial stem
In T.S., the aerial
stem appeared pentagonal towards the main stem (Image 3), first (Image 3) and
second (Image 3) dichotomy, quadrangular towards the third (Image 3) and fourth
(Image 3) dichotomy and triangular in the most distal portions (fifth
dichotomy; Image 3). The aerial stem shows a well-marked single- layered
cuticularized epidermis, and large numbers of stomata are found to be present
in the grooves of the stem. The cortex is broad and is differentiated into
three zones. The outermost zone is 3-layered, cells are thin- walled,
vertically elongated with intercellular spaces, parenchymatous, nucleated, and
contain chlorophyll. The middle cortex is 3–4 layered, and cells are
thick-walled and sclerenchymatous. The inner cortex
is 5–7 layered, cells are thin-walled, parenchymatous, and without any
intercellular spaces. The stele is surrounded by well-marked endodermis.
Pericycle is not distinguishable. The stele in the aerial stem is of actinostele type. Xylem is star-shaped and the protoxylem
lies at the tip of each ray. Presence of actinostele
has also been reported earlier by different authors (Schulte et al. 1987; Khoshravesh et al. 2009; Vahdati
et al. 2014); however, Gifford & Foster (1989) and Nazarian et al. (2010)
interpreted the stele as siphonostele.
CONCLUSION
Psilotum nudum is one of the
primitive vascular plants still living and often considered as ‘living fossil’.
In the present study, the species is found to grow as an epiphyte in the tree
trunks of very old aged plants in the studied areas. The host trees are
gradually falling down due to their very old age. Cleaning and sometimes white
painting of host tree trunk for beautification of park and garden lead to
habitat destruction. Continuous habitat loss may lead to extinction of the
species from the studied areas. So, necessary measures should be taken
immediately for in situ and ex situ conservation of the botanically interesting
species. Detailed morpho–anatomical description of the species is also carried
out for the first time from the district Cooch Behar of West Bengal, India
which will enrich the botanical information of the species.
For
images – click here for full PDF
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