Elevated Carbon Dioxide Level Suppresses Nutritional Quality of Lettuce and Spinach

Rising global CO2 levels are a major factor that impacts not only the environment but also many plant functions including growth, productivity and nutritional quality. The study examined the impact of elevated [CO2] on nutritional quality and growth characteristics of lettuce (Lactuca sativa) and spinach (Spinacia oleracea). Elevated [CO2] decreased the concentration of many important nutrients including nitrogen (protein), potassium and phosphorus in the edible parts of both lettuce and spinach. The nitrogen concentration in lettuce shoots was reduced by more than 30% at elevated [CO2] compared to the plants grown at ambient level of CO2. Similarly the concentration of a number of micronutrients including sulfur, zinc, copper and magnesium, was depressed in lettuce shoots. Although the total phenolic content and antioxidant capacity were higher in lettuce at elevated CO2, they were not affected in spinach. The photosynthetic activity was variable among the plant species while there was no increase in the carbon accumulation in these plants at elevated [CO2]. However, there was significant reduction in the leaf stomatal conductance in both lettuce and spinach in response to higher [CO2], which is likely affect both water loss from the leaves and their photosynthetic activity. The results indicate a broad adverse impact of rising [CO2] on the nutritional quality of commonly consumed leafy vegetables namely, lettuce and spinach.

Transcriptome response of wheat Norin 10 to long-term elevated CO_2 under high yield field condition

The increasing atmospheric carbon dioxide concentration, caused by fossil fuel combustion and deforestation, plays an important role in plant growth and development. Wheat, as a major staple crop, adapts to climate change by tuning its inherent molecular mechanism, which is not well understood. The present study employed the RNA-Seq method to generate transcriptome profiles of the wheat Norin 10 in response to elevated CO_2 in comparison with ambient CO_2. The 10 895 787 high-quality clean reads of Norin 10 were assembled de novo using Trinity（without a reference genome） resulting in a total of 18 206 candidate transcripts with significant BLAST matches. GO enrichment analysis of Norin 10 at different CO_2 concentrations showed that some functional genes related to plastids, precursor metabolites, and energy, thylakoid and photosynthesis were apparently enriched at elevated CO_2（550 μmol mol^–1） in contrast to that at ambient CO_2（400 μmol mol^–1）; these findings were further confirmed by RT-PCR analysis. The findings demonstrated the specific effects of elevated CO_2 during long-term period in free air CO_2 enrichment（FACE） on transcriptome response of the high yielding wheat variety, Norin 10, which has a large spike.

Legacy effect of elevated CO_(2) and N fertilization on mineralization and retention of rice (Oryza sativa L.) rhizodeposit-C in paddy soil aggregates

Rhizodeposits in rice paddy soil are important in global C sequestration and cycling.This study explored the effects of elevated CO_(2) and N fertilization during the rice growing season on the subsequent mineralization and retention of rhizodeposit-C in soil aggregates after harvest.Rice(Oryza sativa L.)was labeled with ^(13)CO_(2) under ambient(400 ppm)and elevated(800 ppm)CO_(2) concentrations with and without N fertilization.After harvest,soil with labeled rhizodeposits was collected,separated into three aggregate size fractions,and flood-incubated for 100 d.The initial rhizodeposit-^(13)C content of N-fertilized microaggregates was less than 65%of that of non-fertilized microaggregates.During the incubation of microaggregates separated from N-fertilized soils,3%–9%and 9%–16%more proportion of rhizodeposit-^(13)C was mineralized to ^(13)CO_(2),and incorporated into the microbial biomass,respectively,while less was allocated to soil organic carbon than in the non-fertilized soils.Elevated CO_(2) increased the rhizodeposit-^(13)C content of all aggregate fractions by 10%–80%,while it reduced cumulative ^(13)CO_(2) emission and the bioavailable C pool size of rhizodeposit-C,especially in N-fertilized soil,except for the silt-clay fraction.It also resulted in up to 23%less rhizodeposit-C incorporated into the microbial biomass of the three soil aggregates,and up to 23%more incorporated into soil organic carbon.These results were relatively weak in the silt-clay fraction.Elevated CO_(2) and N fertilizer applied in rice growing season had a legacy effect on subsequent mineralization and retention of rhizodeposits in paddy soils after harvest,the extent of which varied among the soil aggregates.