A THREE YEARS PILOT STUDY TO EVALUATE FLUORESCENCE ANALYSIS IN OZONE BIOMONITORING WITH BEAN CLONES NEAR ROME, ITALY

An ozone (O3) biomonitoring experiment was conducted during the years 2008, 2009 and 2010 in a natural area inside the Castelporziano Presidential Estate (Rome, Italy), characterized by a typical Mediterranean climate (Manes et al., 1997). Following the UNECE ICP Vegetation protocols (UNECE, 2008-2010), the O3-sensitive (S156) and ozone-resistant (R123) genotypes of Phaseolus vulgaris L. were used. 10 to 12 replicates plants per clones, fully irrigated, were exposed to ambient air for approximately 60 days from mid July 2008 mid June 2009 and end of June, 2010. O3 concentrations and climatic parameters were continuously monitored in the experimental site, leaf visible injury was evaluated weekly every year and, at the end of each experiments, pods were harvested and yield evaluated. Moreover, during the years 2009 and 2010, gas exchanges and direct chlorophyll “a” fluorescence were measured on fully developed leaves, during selected phenological phases, and in particular close to the onset of flowering. AOT40 during the experimental periods (from day 0 to harvest) was 3588, 9273, and 3324 ppb in 2008, 2009 and 2010, respectively. A clear distinction in the extent of visible leaf injury symptoms between the S and R biotypes was apparent (UNECE- ICP Vegetation, 2009), although during 2010 also the R variety showed injury symptoms. However, differently from what reported in previous studies (Flowers et al., 2007) no clear relationship between the extent of leaf injury, pod yield and ozone levels were evident across years: production of developed pods was in fact higher in the R clone only in 2008 (S156/R123 = 0.86), and higher in the S clone during the years 2009 and 2010 (S156/R123 = 3.46 and 1.12 in 2009 and 2010, respectively). Stomatal conductance and net photosynthesis in the 2009 assessment were slightly lower in the S than in the R clone, while in the 2010 assessment the S clone had slightly higher gas exchange values, both before and after flowering. The chlorophyll fluorescence measurements and the application of the JIP-test (Strasser et al., 2010) give important insight for early evaluation of differences in photosynthetic efficiency between genotypes. The fluorescence transients analysis highlights a similar behaviour of both clones, and the OJIP fluorescence parameters did not show the typical ozone-induced stress response. Both clones appear instead affected by the summer climatic conditions, and particularly by high temperatures and irradiance values. Moreover, this response seems to vary with plant developmental stages (Elagöz and Manning, 2005). Further studies are therefore needed to better investigate the applicability of this biomonitoring system under environmental conditions typical of the Mediterranean area.