Effect Of The Expected Increase In Tropospheric Ozone Concentration On Element Absorption And Alocation Of Rice (Oryza Sativa L.)

At present, the wordwide average tropospheric ozone concentration ([O3]) has been increased from an estimated pre-industrial level of 38 to approximately 50 nl L-1. According to IPCC, tropospheric [O3] is projected to increase by 23% by 2050 and to reach the level of 80 nl L-1 by 2100 based on most pessimistic. Elevated [O3] not only influences the growth, yield and quality of plants, but also changes the patterns of element uptake and allocation. Rice is the most important food crop in the world, however, to date, no information is available on the seasonal responses of element (include macro-elements and micro-elements) concentration, uptake and allocation of rice to elevated [O3] and whether the ozone effect was modified by cultivars grown or developmental stages. In order to investigate the effects of elevated [O3] on seasonal changes in nine element (i.e., K, Ca, Mg, Cu, Fe, Mn, Zn, B and S) concentration, absorption and allocation at different growth stages of rice (including tillering, jointing, heading, 20 days after heading (DAH) and maturity stage), we conducted a unique free-air O3 enrichment (FACE) experiment in a rotation system of rice and wheat at Jiangdu, Jiangsu Province, China (32°35.5'N,119°42'E) in 2008-2009. Four rice cultivars: Wu Yunjing 21 (WYJ21), Yangdao 6 (YD6), Shanyou 63 (SY63) and Liangyoupeijiu (LYPJ) were grown at ambient (AMB) or elevated [O3] (FACE, 50% above ambient). The results obtained here could provide important implications on fertilizer management and strategies of rice in a future elevated [O3] world.1. In most cases, significant differences (P < 0.01 or P < 0.05) existed among the cultivars for concentrations of all elements in aboveground at all growth stages of rice (i.e. tillering, jointing, heading, 20 DAH and maturity stage), however, no effect of elevated [O3] was detected for concentrations of the all elements in aboveground across the season. Analysis of variance (ANOVA) indicated no significant O3×cultivar and O3×year interaction for above parameters.2. The differences among the rice cultivals for dry matter accumulation were significant (P < 0.01) at different growth stages. The negative effect of elevated [O3] on dry matter accumulation of rice tended to increase with crop development: averaged across the two growing seasons, dry matter accumulation of rice plant was lower under FACE by 4%, 6%, 9%, 7% and 10% at tillering, jointing, heading, 20 DAH and maturity stage, respectively, with the effect being significant at jointing (P < 0.05), heading, 20 DAH and maturity stage (P < 0.01). In most cases, there was no siginificant interaction between O3×cultivar or O3×year for dry matter accumulation of rice plant at all sampled stages.3. Significant differences (P < 0.01 or P < 0.05) existed among the cultivars for accumulations of all elements in aboveground at different growth stages, and elevated [O3] was detected for concentrations of all elements in aboveground across the season, the rate of decrease had increased with the growth stages, but not significantly. there was no siginificnat interaction beween O3×cultivar or O3×year for dry matter accumulation of rice plant at all sampled stages.4. In most cases, significant differences (P < 0.01 or P < 0.05) existed among the cultivars for distribution of all elements in green leaves, yellow leaves, stem and panicle at different growth stages, however, no effect of elevated [O3] was detected for distribution of the all elements. there was no siginificnat interaction beween O3×cultivar or O3×year for the proportion of elements distribution in different parts of rice at all sampled stages.5. In maturity stage, significant differences (P < 0.01 or P < 0.05) existed among the cultivars for the concentration of the elements in seeds of rice. But the elevated O3 almost had no effect on the concentration of elements. There was no siginificnat interaction beween O3×cultivar or O3×year for the concentration of the elements of rice plant at all sampled stages.6. Significant differences (P < 0.01 or P < 0.05) existed among the cultivars for the accumulation of various elements of seeds in different cultivars of rice. the accumulation of K, Ca, Mg, Cu, Fe, Mn, B and S was lower under FACE by 2%, 2%, 1%, 4%, 1%, 9%, 11% and 1%, respectively, but did not reach significant level. There was no siginificnat interaction beween O3×cultivar for the accumulation of various elements of seeds at all sampled stages. But there was siginificnat interaction beween O3×year for the accumulation of various elements of seeds at all sampled stages.