Mat rush (Juncos effusus L.) is a cosmopolitan, emergent macrophyte inhabits fresh to brackishmarshes, wetlands and meadows．1t is an economical as well as ecologically important plant grownfor reclamations of land, mitigation and construction of wetlands, while its stem is used as rawmaterial for production of various products．Keeping in view the importance of mat rush plant aseries of experiments was conducted to induce genetic variations and to improve the quality of plantusing in vitro mutagenesis techniques．An efficient tissue culture protocol was developed in the firststep as a prerequsite of in vitro mutagenesis experiment．Plants were grown on MS (Murashige andSkoog, 1962) medium and effects of hormonal combinations and medium innovation on tissueculture system were investigated．Positive effects of additional benzylaminopurine (BA) in themedium were observed on callus proliferation, plant regeneration and its multiplication．0.5 mg/L concentration of BA in combination with 4mg/L of 2,4-dichlorophenoxyacetic acid (2,4-D) in themedium resulted in the highest callus induction (90.48％)．The effects of various growth regulatorsand their combinations with successive subculturing (medium replacement) were found to beessential to develop embryogenic calli and to regenerate shoots．Among different combinations ofgrowth regulators tested in the study, the combination of 0.1mg/L BA and 2mg/L 2,4-D in MSmedium was determined to be the best for callus proliferation．Medium innovation was also foundnecessary for successful plant regeneration．Our results suggested the importance of the ratio ofauxin (IAA) to cytokinin (BA and KT) in the manipulation of shoot regeneration in this plant．Themaximum plant survival frequency and multiplication rate (90.97％)were recorded in the presenceof 0.5mg/L BA in the 1/2 MS multiplication medium for the plant. An in vitro mutagenesis study was carried out using the tissue culture protocol developed in thefirst study to induce genetic variability in mat rush and to unveil the mutagenic effects ofethylmethane sulfonate (EMS at 0.1-1.0％for 12 and 24 h) and ultraviolet radiations (UV for 15, 30and 45 min) on physiological characteristics and ultra-structural responses of the plant．The basalculms of plants were treated with EMS and UV radiations and then transferred to 1/2 MS media togrow and multiply．Physiological and ultra-structural alterations of leaf were observed in the leavesof treated plants．A large number of mutants with changes in leaf colour, length, size and growth rates were found．With the increase in the level of mutagens, the activities of antioxidant enzymesincreased invariably, however, at their higher level these activities showed downward trend．Plantgrowth and biomass significantly reduced at the higher doses of both mutagens．Further study of theselected mutants showed greater reduction in chlorophyll contents as well as noticeable changes atthe ultra-cellular levels．Over all reduction in the size of cell and chloroplast, appearance of largenumber of oil bodies in chloroplasts and disruption of the thylakoid integrity were some of theobvious changes in resultant mutants．Present study suggested that both EMS and UV mutagenscaused mutation at functional and ultra-structural levels that can be effectively used to create geneticvariations in mat rush (Juncus effuses L.).