Use of Ethylenediurea (EDU) in identifying indicator cultivars of Indian clover against ambient ozone.

Three clover (Trifolium alexandrium L.) cultivars (Bundel, Wardan and JHB-146) were assessed for their responses to ambient ozone (O3 ) with respect to growth, physiological and biochemical parameters at two rural sites (R1 and R2) using ethylenediurea (EDU). EDU solution (300ppm) was applied as soil drench, 10 days after germination (DAG) at an interval of 10 days up to 80 DAG. The average O3 concentrations were 52.76 and 60.86 ppb at R1 and R2 sites, respectively during the experimental period. Ambient O3 induced visible symptoms in all the cultivars at both the sites, with more at R2 site having high ambient O3 levels. Visible injury was observed first in non-EDU treated plants of Wardan at R2 site. Wardan also showed maximum reduction in leaf injury under EDU treatment at both the sites with more at R2. Under EDU treatment, better adaptation to ambient O3 at initial age of observation and higher acquisition of resources at later ages of observation at both the sites led to better physiological and biochemical adaptations in Wardan. Bundel retained more biomass in shoot as is reflected with higher shoot/root ratio and thus focused more on repair and defense. Shoot/root ratio of JHB-146 did not respond to EDU treatment and thus showed insignificant variations except at initial age of observation at R1 site. This study clearly suggests that Wardan and Bundel are sensitive to ambient O3 and can be used as bioindicator species in areas having higher O3 levels using EDU as a research tool.