ASSESSING THE COMPETING ABILITY OF WEEDY RICE (Oryza sativa f. spontanea) WITH CULTIVATED RICE UNDER ELEVATED CO2 CONDITIONS

Climate change can adversely affect rice production, especially for weed management in the context of emergence and proliferation of newer weed species like weedy rice (Oryza sativa f. spontanea) in the rice growing tracts of Kerala. In the past decade, atmospheric carbon dioxide (CO2) has risen from 371.82 to 407.05 ppm from 2000 to 2018 which might have an impact on the competitive ability of a C3 plant like weedy rice. The competitiveness of weedy rice was studied in an open top chamber (OTC) under a CO2 concentration of 500 ppm (Chamber A), OTC without external CO2 supply (Chamber B), and open condition along with two popular cultivated rice varieties Uma and Jyothi with both air and soil temperature inside the chamber to the tune of 40-430C and 35-400C respectively. The study revealed a higher competitive potential of weedy rice in terms of tillering ability under elevated carbon dioxide as it responded well compared to cultivated rice varieties. There was a differential response of rice varieties to elevated CO2 conditions with medium duration variety responding well compared to short duration one. Compared to ambient conditions (chamber B and open condition), higher tillering was observed under elevated CO2 (chamber A) in which weedy rice tillered profusely (17.33) than cultivated rice species (9 and 11.33). There was a linear increase in plant height of weedy rice in chamber A (108.97cm) during the initial stages and in chamber B (112.77 cm) during reproductive stages. The study evidenced that in the coming future, higher CO2 levels can stimulate biomass production of C3 weed like weedy rice with a greater increase in tillering which could be an important trait affecting inter specific competition.