effect of co2 enrichment on morphophysiologycal traits in tagets spp, ageratum spp and gauilardia spp in greenhouse condition

carbon dioxide (co2) concentration of the global atmosphere has increased during the last decades. increasing global atmospheric co2 concentrations are expected to influence crop production. in order to evolution of co2 concentration effects on morphophysiologycal traits in tagets, ageratum and gauilardia, a factorial experiment based on completely randomized design with 3 replications and 12 treatments was conducted at the greenhouses of ferdowsi university of mashhad at 2009. treatments were 3 plant species (tagets spp, ageratum spp and gauilardia spp) and 4 concentrations of co2 (350, 700, 1050 and 1400 ppm). plants were placed under increasing co2 concentrations during of 30 days. day and night temperatures were 25 and 18 °c in all treatments. the number of individual plant leaf, stomatal index, stomatal diameter, plant leaf area, spad number and plant dry weight were determined. results indicated that increasing co2 concentration from 350 to 1400 ppm leading to increase of 41.6, 3.35, 61.1, 17.1 and 73.9 percentage in number of individual plant leaf, stomatal index, individual leaf area, spad number and individual dry weight, respectively. whilst increasing of co2 concentration leaded to reduce of stomatal diameter (62 percent). increasing of co2 concentration affected individual dry weight accumulation and leaf area significantly. as there was a positive relation between increasing of leaf area and dry weight accumulation, increasing of co2 concentration could have effect on production and beneficial of tagets, ageratum and gauilardia by increase leaf area and dry weight accumulation.