臭氧胁迫对水稻生长以及C、N、S元素分配的影响

采用开顶式气室(Open-top Chamber, OTC),对水稻"3694繁"(Oryza sativa L., 3694 Fan)在浙江嘉兴进行田间原位臭氧(O₃)熏气实验,研究不同臭氧浓度熏气对水稻生长以及C、N,S元素分配的影响。实验设置分4个水平:过滤大气组(CF,10 nL/L)、自然大气组(NF,40 nL/L)和两个不同浓度的臭氧处理组(O₃-1:100 nL/L; O₃-2:150 nL/L)。主要结果表明:(1)开始臭氧熏气时,各个处理组单茎水稻各组分生物量没有差异. 在熏气后期(水稻成熟期),臭氧处理使单茎水稻根、茎和穗生物量显著下降,根冠比降低,株高显著降低,表明臭氧胁迫增加水稻地上部分的干物质分配,且对株高的影响可能大于对地上生物量的影响;(2)臭氧处理使水稻根和茎C元素含量下降,叶C元素含量上升,表明臭氧胁迫提高了叶片中碳分配,而降低了根和茎的碳分配;(3)各个组分N元素含量上升和碳氮比下降;(4)茎、叶和穗S元素含量上升,可能会增强水稻抗氧化系统的作用,从而抵抗臭氧胁迫。所有实验结果表明臭氧浓度升高会对水稻生长产生严重不利影响,从而导致水稻各个组分的C、N、S元素分配格局发生改变。

Influences of elevated ozone on growth and C, N, S allocations of rice

The effects of elevated ozone (O₃) concentrations on the growth and C, N, S allocations of rice (Oryza sativa L., 3694 Fan) were investigated with Open-top chambers (OTCs) in situ in Jiaxing, Zhejiang Province. Four treatments with three replicates for each treatment were deployed: charcoal-filtered air (CF, 10 nL/L), unfiltered air (NF, 40 nL/L), and charcoal-filtered air with ozone addition (100 nL/L for O₃-1 and 150nL/L for O₃-2). Rice was planted on May. 26 then transplanted into the OTCs on Jul. 4 and harvested on Nov.12, 2008. The ozone exposure started on Jul. 25 and ended on Oct. 19, 2008 at 9:00 17:00 (Chinese standard time) except raining days and the actual exposure was 69 days. We determined the component biomass (root, stem, foliage, panicle) of rice on Jul.27, Aug.14, Sep.18, Oct.17 and the C, N, S concentrations in root, stem, foliage, panicle and grain of rice when the rice was harvested. The main results showed that: (1) At the beginning of the ozone exposure, there were no significant differences in the biomass of rice components among the treatments. However, in maturing stage, the root, stem and panicle biomass of rice, as well as the root-shoot ratio and plant height, were significantly lower under the elevated ozone concentrations. During the whole experimental period, the differences in component biomass and plant height of rice between CF and NF treatments were not significant. The percentage of dry matter of aboveground biomass increased under elevated ozone concentrations and plant height was more sensitive to ozone than the aboveground biomass, which indicated that ozone stress might have much more effect on the cell elongation than on the cell division; (2)Under O₃-1 and O₃-2 treatments, the C concentrations reduced in root and stem but increased in foliage, which meant that the C allocation to foliage increased but reduced to root and stem under elevated ozone concentrations; (3) The N concentrations in all components of rice increased and it might be a adaptive strategy to resist the ozone stress. The C/N ratios reduced in all rice components under elevated ozone concentration and it revealed that the vegetative growth was inhibited under ozone stress; (4) The S concentrations in stem, foliage and panicle increased in O₃-1 and O₃-2 treatments, which would enhance the antioxidant capacity of rice under ozone stress. All the results indicated that elevated ozone concentrations had significant unfavorable influence on rice growth and it led to the obvious changes in the allocations of C, N and S in different rice components.