不同施肥措施臭氧浓度升高对不同水稻品种光合特性的影响

近地层臭氧(O₃)已严重威胁到作物生产,而施肥可以调节土壤的养分平衡,进而促进作物生长。以两个水稻品种(徽两优898和南粳9108)为研究对象,利用开顶式气室,设置2个O₃浓度处理(NF:环境大气为对照;NF40:环境大气+40 nmol/mol O₃),每个O₃处理下嵌套设置3个肥料处理(Ino:施无机肥处理,270 kg N hm^-2 a^-1;Red:减施无机肥30%处理,189 kg N hm^-2 a^-1;Com:有机无机肥配施处理,Red+有机肥鸡粪5000 kg hm^-2 a^-1),通过测定不同生育期水稻光合参数,探究不同肥料处理下O₃对水稻不同生育阶段光合生理的影响。结果表明,NF40对水稻营养生长阶段的饱和光合速率(A_sat)没有显著影响,而显著地降低了水稻灌浆期的A_sat。基于两个水稻品种的A_sat和相对叶绿素含量(SPAD)相对减少量与O₃累积剂量关系的斜率,发现杂交稻徽两优898(A_sat和SPAD的斜率:-1.55和-0.98)比常规稻南粳9108(A_sat和SPAD的斜率:-0.92和0.06)对O₃更敏感。此外,基于不同O₃处理下水稻的气孔导度(g_s)和胞间二氧化碳浓度(C_i),可以看出O₃造成南粳9108光合速率降低的主要是非气孔因素,而徽两优898光合的降低是由气孔因素和非气孔因素共同限制。与Ino处理相比,Red处理主要通过降低叶片SPAD进而显著地抑制两种水稻品种的A_sat,但Ino处理和Com处理间A_sat没有显著差异,说明有机无机肥配施能部分缓解减施无机肥造成水稻光合的降低。O₃和肥料处理对两个水稻的所有光合参数都没有显著的交互影响,表明短期有机无机肥配施并不能有效缓解O₃对作物造成的负面影响。在O₃污染背景下,研究结果可以为通过合理的农田氮肥管理措施减缓O₃造成的作物减产提供理论依据。

Effects of elevated ozone on the photosynthesis of different rice cultivars under different fertilization measures

Ground-level ozone (O₃) has seriously threatened crop production in China, and the fertilization can regulate soil nutrient balance, thereby promoting crop growth. This study was conducted in open top chambers, using two O₃ treatments (ambient air (NF) as control; ambient air+40 nmol/mol O₃ (NF40)). Three fertilizer treatments were nested under each O₃ treatment, including conventional application of inorganic fertilizer (Ino, 270 kg N hm^-2 a^-1), 30% reduction of inorganic fertilizer (Red, 189 kg N hm^-2 a^-1), and combination of organic and inorganic fertilizer (Com, Red+5000 kg hm^-2 a^-1 chicken manure). The photosynthetic parameters of two rice cultivars (HLY898 and NJ9108) at different growth stages were measured, which mainly explored the effects of O₃ on the photosynthetic and physiological processes of rice at different growth stages under different fertilizer treatments. The results showed that NF40 had no significant effect on the saturated photosynthetic rate (A_sat) during the vegetative growth stage of rice, but it significantly reduced the A_sat during the filling stage of rice. Based on the slopes of the relationship between the relative reduction of A_sat and SPAD of two rice cultivars with the O₃ cumulative index, it was found that the hybrid rice cultivar HLY898 (slopes of A_sat and SPAD: -1.55 and -0.98,respectively.) was more sensitive to O₃ than the conventional rice cultivar NJ9108 (slopes of A_sat and SPAD: -0.92 and 0.06,respectively.). In addition, based on the results for the stomatal conductance (g_s) and intercellular carbon dioxide concentration (C_i) of rice under different O₃ treatments, we found that the decrease photosynthesis caused by O₃ in NJ9108 was mainly attributed to non-stomatal limitations, while the decrease in photosynthesis of HLY898 was limited by both stomatal and non-stomatal factors. Compared with the Ino treatment, the Red treatment significantly inhibited A_sat in the two rice cultivars by reducing leaf SPAD, but there was no significant difference in A_sat between the Ino and Com treatments. This suggested that the combined application of organic and inorganic fertilizers could partially alleviate the decrease in rice photosynthesis caused by reduced application of inorganic fertilizers. There was no significant interactive effect of O₃ and fertilizer treatment on all photosynthetic parameters of the two rice cultivars, indicating that short-term combination of organic and inorganic fertilizers could not effectively alleviate the negative effects of O₃ on crops. The research results can provide a theoretical basis for mitigating crop yield reduction caused by O₃ through reasonable nitrogen fertilizer management measures in farmland under O₃ pollution.