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Alterations in Source-Sink Relations Affect Rice Yield Response to Elevated CO₂: A Free-Air CO₂ Enrichment Study.

ABSTRACT: To understand the effects of source-sink relationships on rice yield response to elevated CO₂ levels (eCO₂), we conducted a field study using a popular japonica cultivar grown in a free-air CO₂ enrichment environment in 2017-2018. The source-sink ratio of rice was set artificially via source-sink treatments (SSTs) at the heading stage. Five SSTs were performed in 2017 (EXP1): cutting off the flag leaf (LC1) and the top three functional leaves (LC3), removing one branch in every three branches of a panicle (SR1/3) and one branch in every two branches of a panicle (SR1/2), and the control (CK) without any leaf cutting or spikelet removal. The eCO₂ significantly increased grain yield by 15.7% on average over all treatments; it significantly increased grain yield of CK, LC1, LC3, SR1/3, and SR1/2 crops by 13.9, 18.1, 25.3, 12.0, and 10.9%, respectively. The yield response to eCO₂ was associated with a significant increase of panicle number and fully-filled grain percentage (FGP), and the response of crops under different SSTs was significantly positively correlated with FGP and the average grain weight of the seeds. Two SSTs (CK and LC3) were performed in 2018 (EXP2), which confirmed that the yield response of LC3 crops (25.1%) to eCO₂ was significantly higher than that of CK (15.9%). Among the different grain positions, yield response to eCO₂ of grains attached to the lower secondary rachis was greater than that of grains attached to the upper primary rachis. Reducing the source-sink ratio via leaf-cutting enhanced the net photosynthetic rate response of the remaining leaves to eCO₂ and increased the grain filling ability. Conversely, spikelet removal increased the non-structural carbohydrate (NSC) content of the stem, causing feedback inhibition and photosynthetic down-regulation. This study suggests that reducing the source-sink ratio by adopting appropriate management measures can increase the response of rice to eCO₂.

SUBMITTER: Gao B

PROVIDER: S-EPMC8283783 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Evaluating the impact of increasing CO2 on rice quality is becoming a global concern. However, whether adjusting the source-sink ratio will affect the response of rice grain quality to elevated CO2 concentrations remains unknown. In 2016-2018, we conducted a free-air CO2 enrichment experiment using a popular japonica cultivar grown at ambient and elevated CO2 levels (eCO2, increased by 200 ppm), reducing the source-sink ratio via cutting leaves (LC) at the heading stage, to investigate the effects of eCO2 and LC and their interactions on rice processing, appearance, nutrition, and eating quality. Averaged across 3 years, eCO2 significantly decreased brown rice percentage (-0.5%), milled rice percentage (-2.1%), and head rice percentage (-4.2%) but increased chalky grain percentage (+ 22.3%) and chalkiness degree (+ 26.3%). Markedly, eCO2 increased peak viscosity (+ 2.9%) and minimum viscosity (+ 3.8%) but decreased setback (-96.1%) of powder rice and increased the appearance (+ 4.5%), stickiness (+ 3.5%) and balance degree (+ 4.8%) of cooked rice, while decreasing the hardness (-6.7%), resulting in better palatability (+ 4.0%). Further, eCO2 significantly decreased the concentrations of protein, Ca, S, and Cu by 5.3, 4.7, 2.2, and 9.6%, respectively, but increased K concentration by 3.9%. Responses of nutritional quality in different grain positions (brown and milled rice) to eCO2 showed the same trend. Compared with control treatment, LC significantly increased chalky grain percentage, chalkiness degree, protein concentration, mineral element levels (except for B and Mn), and phytic acid concentration. Our results indicate that eCO2 reduced rice processing suitability, appearance, and nutritional quality but improved the eating quality. Rice quality varied significantly among years; however, few CO2 by year, CO2 by LC, or CO2 by grain position interactions were detected, indicating that the effects of eCO2 on rice quality varied little with the growing seasons, the decrease in the source-sink ratios or the different grain positions.

Project description:BackgroundBeing a promising tropical woody oilseed crop, the evergreen and recurrent plants of Sacha Inchi (Plukenetia volubilis L.) has complex phenology and source-sink interactions. Carbon source-sink manipulations with control and two treatments (reduce source, ca. 10% mature leaf pruning; reduce sink, 10% fruitlet thinning) were conducted on 2.5-year-old field-grown P. volubilis plantation during the early-wet season in a seasonal tropical area.ResultsLeaf photosynthetic rate and specific leaf area largely remained unchanged in response to defoliation or defloration. Compared with control, higher N contents on average were observed in both remaining leaves and branches of the defoliated plants, suggesting that N-mobilization was mainly due to the enhanced N uptake from soil. Carbon, but not N, is a source-driven growth process of P. volubilis plants, as defoliation reduced the contents of non-structural carbohydrates (especially sugar) in branches, although temporally, whereas defloration increased available C reserve. The seasonal dynamic pattern of fruit ripening was altered by source-sink regulations. Total seed yield throughout the growing season, which depends on fruit set and retention (i.e., number of matured fruit) rather than individual fruit development (size), was slightly increased by defloration but was significantly decreased by defoliation. Compared with control, defloration did not enrich the KEGG pathway, but defoliation downregulated the TCA cycle and carbohydrate and lipid metabolisms in fruitlets after 24 days of the applications of source-sink manipulation.ConclusionCarbohydrate reserves serve to buffer sink-source imbalances that may result from temporary adjustment in demand for assimilates (e.g., defloration) or shortfalls in carbon assimilation (e.g., defoliation). Defoliation is disadvantageous for the yield and also for carbohydrate and lipid accumulation in fruits of P. volubilis plants. Although more studies are needed, these results provide new insights to the further improvement in seed yield of the strong source-limited P. volubilis plants by source/sink manipulations.

Project description:Within the Australian Grains Free Air CO2 Enrichment (AGFACE) research program, several facilities were established at different field sites near the towns of Horsham (36.752 S, 142.114 E; 127 m elevation), and Walpeup (35.121 S, 142.005 E; 94 m elevation) in the state of Victoria Australia from 2007 - 2017. These included: TraitFACE, SoilFACE, WalpeupFACE, VegeFACE, and NFACE. These facilities were designed to answer a range of research questions to understand the impacts of elevated CO2 (e[CO2]) on crop physiology and production. To this end, FACE 'rings' (octagons) were built to elevate atmospheric CO2 to 550 µmol/mol expected by 2050. These rings were open structures allowing crops to grow freely, without enclosures. Each side of an octagonal ring was individually controlled by a ring-side controller that injected CO2 over crops as per the control program. Infrared Gas Analysers (IRGAs) placed at ring centres sampled air continuously from 10 cm above the crop canopy, while CO2 was injected at a height 15 cm above the crop canopy. Infrared Gas Analysers (IRGAs) measured atmospheric CO2 concentration ([CO2]) during the cropping season and provided feedback to the controller to maintain ring-centre [CO2] at 550 µmol/mol. The [CO2] data were collected from the centre of each FACE ring from 2007 until 2017. The [CO2] within a ring was measured each second using calibrated IRGAs. Wind direction and speed were monitored continuously at 2 m above the soil surface at the centre of each ring. These measurements were also collected at the centres of a couple of ambient experimental areas (control - no rings) using the same IRGA and wind sensors. A wireless ethernet local area network (LAN) and a Visual Basic program were used to monitor and transmit data from the individual rings and control areas for data logging. Data at every 4th second and one-minute average (A_MN_CO2) from each ring were logged to daily files, and only A_MN_CO2 data were combined into a seasonal cumulative file. All data recorded during the IRGA warmup period and due to equipment malfunction were removed from cleaned data files. Only A_MN_CO2 data from the rings are uploaded in the Mendeley Data Repository for this article because these data are principally used by scientists and researchers. Data columns in an individual clean file are labelled with abbreviated column names and each file includes: 1) RING, 2) DATE, 3) TIME, 4) A_MN_CO2, 5) REGULAT, 6) WIND_SPD, 7) WIND_DIR and 8) RING_SEC. A limited amount of data (2007 CO2 data at ring centres from 8 TraitFACE rings) was published previously [1].

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Alterations in Source-Sink Relations Affect Rice Yield Response to Elevated CO₂: A Free-Air CO₂ Enrichment Study.

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Alterations in Source-Sink Relations Affect Rice Yield Response to Elevated CO2: A Free-Air CO2 Enrichment Study.

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OmicsDI is part of the ELIXIR infrastructure

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Alterations in Source-Sink Relations Affect Rice Yield Response to Elevated CO₂: A Free-Air CO₂ Enrichment Study.