The Impact Of Free-air CO₂ Enrichment (FACE) On Yield Formation And Grain Quality Of Yangmai14 And Its Causes

Limited studies have been conducted on the Free Air CO₂ Enrichment (FACE) on growth and development of spring wheat (Triticum aestivum L.) (USA)or weak gluten wheat (China). However, no information is available on the effects of FACE on growth and development of medium gluten wheat. In order to elucidate the effects of FACE on growth duration, plant height, grain yield and its components, dry matter production and distribution, nitrogen (N) uptake and utilization, root growth and grain quality of wheat under different N rates, we conducted a free-air CO₂ enrichment (FACE) experiment which was located at the Jiangdu, Yangzhou, China (32°35,N,119°42,E). A medium gluten wheat cultivar Yangmai14 was grown at ambient or elevated (570μL·L-1) [CO₂]. The results obtained here could be helpful in providing some guidelines on high-yielding and fine-quality cultivation of wheat under future elevated [CO₂] conditions.1.Compared with ambient (AMB), the duration from sowing to heading, from heading to maturity and the whole growth duration of wheat shrank 0.1, 0.3, 0.4 days , respectively, in the FACE vs ambient plots, with no significant effect. The duration from sowing to heading, from heading to maturity and the whole growth duration of wheat increased significantly (P < 0.01 or P < 0.05) with increasing N application rate, while [CO₂]×N interactions were not detected on wheat phenology.2.FACE significantly increased the plant height (+4.21%) at harvest. N fertilization, as well as interaction between CO₂ and N, had no influence on plant height of wheat.3. The wheat yield showed 68.08 and 106.09 g m^-2 higher (relative increases 9.88% and 18.61%, P < 0.05) in FACE vs AMB in 2004-2005 and 2005-2006 wheat growth seasons, respectively. And averaged across the two year, 87.09 g m^-2 higher yield (relative increases 13.83%, P < 0.05) was detected due to FACE. Grain yield increased significantly (P < 0.05) with increasing N application rate, while no interaction between CO₂ and N was observed on grain yield.4. FACE significantly increased ear number per unit area, grain number per ear and 1000-grain weight by 8.14%, 5.39% and 2.70%, respectively. The magnitude of the contributions to yield enhancement was in the order of ear number > grain number per ear > 1000-grain weight.5.Dry matter accumulation under FACE was enhanced by 1.35%, 17.26%, 24.39% and 13.13% at seeding, elongation, heading and grain maturity stages, respectively; FACE increased economic coefficient by 8.77%; Under FACE the leaves or ears decreased significantly in proportion to the total above-ground DM over the season (except grain maturity), the stems (include sheaths) showed an opposite trend. Interactions between CO₂ and N were not observed for these parameters.6.FACE decreased shoot N concentration significantly, averaging 2.26%, 9.37%, 11.46% and 11.46% at seeding, elongation, heading and grain maturity, respectively; N accumulation under FACE was enhanced by -1.39%, 6.43%, 0.91% and 1.96%, showing no significant effect. FACE treatment resulted in the non-significant increases in both nitrogen use efficiency for grain output (NUEg) (+11.28%) and nitrogen harvest index (NHI) (+3.68%). the interaction between CO₂ and N was not detected for all N parameters measured.7.On averaged, cumulative adventitious root number per plant was greater under FACE by 2.04%, 2.23%, 6.89% and 11.24% at seedling, elongation, booting and heading stage, respectively.FACE treatment also showed an increase in adventitious root length per plant, averaging -2.75%, 1.41%, 16.2% and 10.67% at seedling, elongation, booting and heading stage, respectively. As for adventitious root dry weight per plant, it was enhanced due to FACE by -0.91%, 8.25%, 6.86% and 17.51% at seedling, elongation, booting and heading stage. Concerning amount ofα-NA oxidation per plant, the figures were 4.33%, 8.84%, 20.9% and 14.66% at respective growth stages, respectively. No interaction between CO₂ and N was detected for all root parameters mentioned above.8. FACE increase grain test weight, amylopectin content, starch content, ratio of amylase to amylopectin and flour extraction rate by 0.2% (P > 0.05), 4.72% (P < 0.05), 3.61% (P > 0.05), 4.86%(P > 0.01) and 3.67% (P > 0.05), respectively, while it decreased amylose content, wet gluten content, dry gluten content and grain protein content by 1.27% (P>0.05), 3.81% (P < 0.01), 3.53% (P < 0.01) and 6.86% (P < 0.01), respectively. No interaction between CO₂ and N was found for all quality attributes.