ANGIOSPERMIC FLORA OF GAFARGAON UPAZILA OF MYMENSINGH DISTRICT FOCUSING ON MEDICINALLY IMPORTANT SPECIES

Gafargaon upazila has been floristically explored to identify and assess the angiospermic flora that resulted in occurrence of 203 taxa under 174 genera and 75 families. Magnoliopsida is represented by 167 taxa under 140 genera and 62 families, while Liliopsida is constituted by 36 taxa belonging to 34 genera and 13 families. Vegetation analysis shows that herbs are represented by 106 taxa, shrubs 35, trees 54, and climbers by 8 species. In Magnoliopsida, Solanaceae is the largest family possessing 10 species, whereas in Liliopsida, Poaceae is the largest family with 12 species. The study has identified 45 medicinal plants which are used for treatment of over 40 diseases including diabetes, ulcer, diarrhoea, dysentery, fever, cold and cough, menstrual problems, blood pressure and urinary disorders by the local people. Some noticeable medicinal plants used in primary healthcare are Abroma augusta (L.) L.f., Coccinia grandis (L.) Voigt., Commelina benghalensis L., Cynodon dactylon (L.) Pers., Holarrhena antidysenterica Flem., Glycosmis pentaphylla (Retz.) A. DC., Mikania cordata (Burm. f.) Robinson, Ocimum tenuiflorum L. and Rauvolfia serpentina (L.) Benth. A few number of species are also employed in cultural festivals in the study area. Cardamine flexuosa With., Oxystelma secamone (L.) Karst., Phaulopsis imbricata (Forssk.) Sweet, Piper sylvaticum Roxb., Stephania japonica (Thunb.) Miers and Trema orientalis L. have been found to be rare in the investigated area. In order to preserve botanical resources of Gafargaon upazila, particularly the rare, threatened and medicinal plants, conservation measures need to be undertaken through both in-situ and ex-situ methods for their sustainable use. Introduction Gafargaon upazila under Mymensingh district is located in 24o15' to 24o33'N and 90o27' to 90o39'E with an area of 401.16 sq. km. The upazila is bounded by Trishal and Nandail upazilas on the north, Kapasia and Sreepur upazilas on the south, Hossainpur and Pakundia upazilas on the east, and Trishal, Bhaluka, and Sreepur upazilas on the west (Fig. 1). The climate of Gafargaon is moderate as other parts of the district, as it is closer to the Himalayas and in the tropical monsoon zone. The temperature of the area varies from 9oC to 37oC. The maximum monthly average humidity ranges from 81 to 97%, while the minimum monthly average humidity ranges from 47 to 79% illustrates the monthly variations of humidity in the area (BBS, 2018). The Gafargaon upazila presents diverse habitats and ecosystems comprising wetland, cultivated land, char, homestead area, scrub jungles, fallow lands, etc. which support dense formation of angiosperms and play a pivotal role in the local economy, environment and primary healthcare system. However, the ecosystems of Gafargaon have been depleted due to anthropogenic interferences over the years. As a result, many plant species have become rare and Corresponding author. Email: oliur.bot@du.ac.bd; prof.oliurrahman@gmail.com


Introduction
Gafargaon upazila under Mymensingh district is located in 24º15' to 24º33'N and 90º27' to 90º39'E with an area of 401.16 sq. km. The upazila is bounded by Trishal and Nandail upazilas on the north, Kapasia and Sreepur upazilas on the south, Hossainpur and Pakundia upazilas on the east, and Trishal, Bhaluka, and Sreepur upazilas on the west (Fig. 1). The climate of Gafargaon is moderate as other parts of the district, as it is closer to the Himalayas and in the tropical monsoon zone. The temperature of the area varies from 9ºC to 37ºC. The maximum monthly average humidity ranges from 81 to 97%, while the minimum monthly average humidity ranges from 47 to 79% illustrates the monthly variations of humidity in the area (BBS, 2018).
The Gafargaon upazila presents diverse habitats and ecosystems comprising wetland, cultivated land, char, homestead area, scrub jungles, fallow lands, etc. which support dense formation of angiosperms and play a pivotal role in the local economy, environment and primary healthcare system. However, the ecosystems of Gafargaon have been depleted due to anthropogenic interferences over the years. As a result, many plant species have become rare and threatened. Therefore, it is indispensable to explore, identify, document and preserve the plant wealth of the area for the betterment of mankind especially those plant resources which are used for primary healthcare. In the recent past, several attempts have been made on floristic studies in different parts of the country alongside with some protected areas (Khan and Huq, 2001;Alam et al., 2006;Tutul et al., 2010;Rahman et al., 2015;Arefin et al., 2017;Haque et al., 2018;Rashid et al., 2018). Despite sporadic studies on the flora of some upazilas of the country were carried out earlier (Moniruzzaman et al., 2012;Rahman and Alam, 2013;Rahman et al., 2012Rahman et al., , 2019, the flora of Gafargaon upazila has never been explored and the potential of its existing flora has not been evaluated. Therefore, the present study aimed at exploring and identifying the angiosperm flora of Gafargaon upazila, and to focus on the medicinally important plant resources for meeting up the primary healthcare demand of the local people. The study has the potential to collate primary data on the plant diversity of the upazila which will eventually contribute towards logical understanding and conservation of the biodiversity of this region.

Materials and Methods
Taxonomic inventories were conducted in Gafargaon upazila of Mymensingh district through five botanical expeditions covering all seasons from April 2017 to March 2018. Plant specimens with flowers and/or fruits were collected, critically studied and preserved following standard herbarium technique (Bridson and Forman, 1989;Singh and Subramaniam, 2008). The collected specimens were identified by experts, consulting standard literature, viz., Hooker (1872Hooker ( -1897, Prain (1903), Khan (1972Khan ( -1987, Dassanayake andFosberg (1980-1985), Rahman (1989-2002), and by matching with already identified specimens housed at Dhaka University Salar Khan Herbarium (DUSH). Nomenclature of each taxon has been updated following recent literatures (Ahmed et al., 2008(Ahmed et al., -2009, the nomenclatural databases of The Plant List (2013) and TROPICOS (2017). The recognized families are arranged following Cronquist (1981), and the genera and species under each family have been placed in an alphabetical order (Table 1). Bengali name have been cited based on interview with local people, and Huq (1986). Each species is supplemented by its habit, phenology and representative voucher specimen. The information on the uses of medicinal plants has been gathered through interview of the local people. The voucher specimens are preserved at DUSH.

Results and Discussion
The present study revealed the occurrence of 203 taxa under 174 genera and 75 families in Gafargaon upazila of Mymensingh district. Among them, Magnoliopsida is represented by 62 families, 140 genera and 167 taxa, while Liliopsida (Monocots) is represented by 13 families, 34 genera and 36 taxa. The identified taxa with their Bangla name, family name, habit, status of occurrences and voucher specimen are presented in Table 1.

Potential of the angiospermic flora Medicinal Plants
Potential of plant species of Gafargaon upazzila has been assessed and medicinal uses of the angiospermic flora by the local people have been recorded during field investigation. The study has identified 45 medicinal plants used for treatment of several diseases by the local people. The medicinal plant species with their part(s) used and uses are presented in Table 2.

Economically and culturally important plant species
The present study shows the role of angiospermic flora in the local communities. The local people rely on surrounding plant wealth not only for their health care, but also for food and other life accessories. Apart from medicinal uses several species are economically and culturally important. The species having economic and cultural importance are documented in Table 3. The present study revealed a number of threats based on the observations and group discussion with local people which might lead to cause angiospermic flora to diminish. Some of the important threats to the flora are habitat degradation, modern agriculture, urbanization, overexploitation of medicinal plants, lack of knowledge of collection technique, lack of awareness on biodiversity, and exotic plantation. Consequently, some species are extinct in the wild and many of them are at the verge of extinction. In order to save the plant resources from further annihilation urgent measures to be adopted for their conservation and sustainable uses including protection of habitats, public awareness on biodiversity conservation, and applying both ex-situ and in-situ conservation approaches for the medicinal and threatened species.