Morpho-Palynological and Seed Diversity of Invasive Plants in Lesser Himalaya Pakistan

Abstract

The present study planned to the systematic investigation of invasive floral diversity in Lesser Himalaya Pakistan using qualitative and quantitative micromorphological characterization of pollen and seeds. Plants were collected, dried, preserved, identified, mounted on herbarium sheets and deposited in the herbarium of Pakistan (ISL), Quaid-I Azam University, Islamabad. A total of 52 invasive species belonging to 31 families were reported in this study. The most dominant family was Asteraceae (11 species) followed by Fabaceae (04 species), Amaranthaceae, Verbenaceae (03 species each) and rest of the families contain each species respectively. The first section is confined to morpho-palynological characters studied using light and scanning electron microscope. The second section of this study is confined to macro and micro-morphological characters of seeds of invasive plants. The data analysis regarding invasiveness revealed that 29 species were introduced or established unintentionally, 13 species as ornamental, 1 species as food, 1 as fodder, 5 as plantation, and 3 for medicinal purposes. The findings indicates that most dominant life form was herb (31 species) followed by shrubs (11 species) and trees (8 species) while grasses and under shrubs were represented by only 1 species each i.e. Sorghum halepense (L.) Pers. and Cassia occidentalis L. The pollen micromorphological variations were observed for pollen shape and size, polar equatorial diameter, pore size, P/E ratio, aperture and exine thickness. The tricolporate pollen were most dominant and reported in Ageratum conyzoides L., Anagallis arvensis L., Bidens pilosa L., Brachychiton acerifolius (A.Cunn. ex G.Don) F.Muell., Broussonetia papyrifera (L.) L'Hér. ex Vent., Carthamus oxyacantha M.Bieb., Cassia occidentalis L., Callistemon citrinus (Curtis) Skeels, Commelina benghalensis L., Lantana camara L, Melilotus indicus (L.) All., Oxalis corniculata L., Parthenium hysterophorus L., Prosopis juliflora (Sw.) DC., Quisqualis indica L., Ranunculus muricatus L., Ricinus communis L., Taraxacum officinale (L.) Weber ex F.H.Wigg., Tecoma stans (L.) Juss. ex Kunth., Tropaeolum majus L., Verbena officinalis L., Verbesina encelioides (Cav.) Benth. & Hook.f. ex A.Gray. The tricolpate pollen were repprted in Bryophyllum pinnatum (Lam.) Oken., Cannabis sativa L., Convolvulus arvensis L., Datura innoxia Mill., Digera muricata (L.) Mart. and Jasminum humile L. The third dominant pollen type was pantoporate which were observed in Achyranthes aspera DRSML QAU XIV L., Chenopodium ambrosioides L., Eucalyptus camaldulensis Dehnh., Malvestrum coromandelianum (L.) Garcke., Tribulus terrestris L. Similarly, remarkable variation regarding exine sculpturing was observed among invasive plant species from Psilate, echinate, reticulate, psilate-perforate to scabrate. As far as size of pollen is concerned 45% pollen were moderate size, followed by the small (34%) and small to medium (13%). In polar view circular shape was shown by most of the plant species while equatorial view the dominant shape was prolate- spheroidal represented by 54% of collected plant species. Remarkable variations about seeds morphology were reported for seed inner and outer color, seed shape, seed surface/texture, hilum position, seed length and width, and length to width ratio. Most of the seeds were spheroidal followed by obovate and elliptical. Seeds of 12 invasive plants were found with smooth surface followed by 6 with rough surface while ridges with furrows were observed in only one species. As far as position of hilum is concerned 15 invasive plants showed terminal while in 5 plants it was not clear. The seed of Xanthium strumarium L. was observed with maximum length of 13mm with width of 8mm. Length by width ratio of seeds were also calculated, it was found that maximum L/W ratio was observed in Sonchus oleraceus L. i.e. 2.66. Based on above findings regarding palyno-morphological and seed morphological features, this study is useful addition for write up of invasive flora Atlas for ecologists, botanists and taxonomists. Furthermore this systematic study will provide a base line data for molecular biologists for the better and correct identification of invasive plants. This study further recommends to work on invasive plants with special reference to their management and their impacts on natural biodiversity, economy, human health and environment and conservation of indigenous flora of Lesser Himalaya particularly and world generally .