The Effects Of O₃, Seedling Quality And Transplanting Density To The Quality Of Rice Grain

Tropospheric ozone concentration [O3] continues to rise, which is projected to increase20-25%by2050and as much as40-60%by2100. Rice is one of the most important food crops in the world. Increased concentration of tropospheric ozone decreases grain yield of rice, however, little information is available on the impact of elevated [O3] on grain quality and its relationship with cultivation conditions. In order to investigate the interactive effects of ozone with seedling quality and trasplanting density on processing, appearance, cooking/eating and nutritional quality, we conducted a unique Free Air ozone Concentration Enrichment (FACE) experiment at Jiangdu County, China in2011. A three-line hybrid India rice Shanyou63was grown under two levels of [O3](ambient and elevated by60%), seedling quality (normal seedlings and strong seedlings), and transplanting density (constant density and high density). The results obtained here could provide important implications on rice cultivation measure under future high ozone environments. The main findings are as follows:1.Elevated [O3] decreased brown, milled and head rice rates slightly, and a significant O3effect was observed for brown rice rate; No O3×seedling quality or O3×density interaction was detected for brown, milled and head rice rates.2.Averaged across all levels of seedling quality and planting density, elevated [O3] increased chalky grain percentage by3.3%(P<0.01), while no significant O3effect was observed for chalkiness area or chalkiness degree; No O3×seedling quality or O3×density interaction was detected for these three parameters.3.On average, elevated [O3] decreased amylose content and gel consistency by4.4%(P<0.01) and3.6%(P<0.01), respectively, while gelatinization temperature was decreased by1.5%; No O3×seedling quality or O3×density interaction was detected for these three parameters. 4. On average, elevated [O3] decreased peak viscosity and breakdown of ground rice by2.7%and10.9%, respectively, increased setback and peak time by5.6%and0.8%, respectively, while no significant O3effect was observed for hot paste viscosity, final viscosity and consistency; No O3×seedling quality or O3×density interaction was detected for all RVA profile characteristics.5. One average, elevated [O3] increased concentrations of protein, K, Mg, Zn, Mn and Cu by2%,15%,17%,9%,16%,19%, respectively; while no O3effect was observed for Ca, Na and Fe concentration; No interaction between O3and density was found for concentrations of protein and all measured elements except Zn; With the exception of Mg and Mn, no interaction between O3and seedling quality was found for the concentrations of other six elements and protein.To sum up, as for Shanyou63, long-term exposure to ozone-enriched atmospheres projected in2050tended to increase the nutritional quality, but decrease the processing, appearance, especially cooking/eating quality. In most cases, no interaction between treatment variables was detected for grain quality of hybrid rice.