Elsevier

European Journal of Agronomy

Volume 99, September 2018, Pages 21-29
European Journal of Agronomy

Elevated CO2 cannot compensate for japonica grain yield losses under increasing air temperature because of the decrease in spikelet density

https://doi.org/10.1016/j.eja.2018.06.005Get rights and content

Highlights

  • We applied T-FACE to evaluate whether elevated CO2 could offset rice yield losses by increased temperature.

  • Elevated CO2 cannot alleviate the rice yield losses by increased temperature.

  • Yield losses under combination of elevated CO2 and increased temperature was attributed to spikelet density.

  • Dry matter per unit area before heading is the crucial physiological parameter accounting for spikelet density losses.

Abstract

Extensive evidence shows that elevated carbon dioxide (CO2) stimulates rice yield, but increasing global surface temperature decreases it. However, few studies have been conducted to evaluate whether elevated CO2 compensates for the rice yield losses induced by increased air temperature under field conditions. Here, we report the effects of four treatments, namely, ambient condition (ACAT), CO2 enrichment (590 ppm, ECAT), canopy air warming (1 °C above the ambient temperature, ACET), and combined CO2 enrichment and warming (ECET) on leaf photosynthesis, nitrogen (N) uptake, spikelet architecture and yield components over two rice growing seasons using a free-air CO2 enrichment facility. We found that elevated CO2 cannot compensate for the negative impacts of increased air temperature on rice yield, especially in the warmer season. Compared to ACAT, ECAT increased the rice grain yield by 14.8% in 2015 and 12.9% in 2016. ACET decreased the rice grain yield by 8% in 2015 and 21% in 2016. Similarly, ECET decreased the rice grain yield by 4% in 2015 and 14% in 2016. Spikelet density was the dominant factor accounting for the yield losses under increased temperature alone or combined with elevated CO2, and spikelet density was mainly affected by the dry matter per unit area before heading. The decrease in the number of spikelets per panicle in ECET was attributed to the differentiation of primary branches and the corresponding spikelets, which was caused by the reduction in nitrogen uptake per culm before the booting stage. However, the decrease in the number of panicles per hill under ECET was related to the reduction in dry matter per culm before jointing. Overall, the dry matter per unit area before the heading stage will be important for alleviating rice yield loss under future climate changes. These results provide a better understanding of the rice growth responses to future climate conditions.

Introduction

Rice (Oryza sativa L.) is an important staple food throughout the world. The productivity of rice needs to be increased by nearly 30% by 2050 to satisfy the demands of the growing global population (Alexandratos and Bruinsma, 2012). Crop production will be significantly affected by changes in the growth environment that are projected to occur in the future, including carbon dioxide (CO2) and temperature changes. Therefore, it is crucial to evaluate the response of rice growth to these two factors of climate change to assess food security.

Numerous studies have shown that elevated CO2 generally increases rice yield mainly by improving the leaf photosynthesis rate and the number of panicles per unit area (Clough et al., 1981; Kim et al., 2003a,b; Yang et al., 2006; Hasegawa et al., 2013; Chen et al., 2014). In general, global temperature increases have negative effects on rice growth (Wang et al., 2016; Wu et al., 2016). When high temperature occurs during temperature-sensitive stages of rice growth (panicle initiation and anthesis), the number of spikelets per panicle and the number of panicles per unit area significantly decrease, but the percentage of infertile spikelets increases (Madan et al., 2012; Wu et al., 2016; Xiong et al., 2017). The results of a crop growth model indicated that crop yield will increase as the global temperature slightly increases but will significantly decrease when the temperature change exceeds 0.8 °C (De Vries, 1993). Researchers found similar results for crops grown under combination of elevated CO2 and temperature in chamber and greenhouse experiments (Frank and Bauer, 1996; Rowland-Bamford et al., 1996; Matsui et al., 1997; Vu et al., 1997; Ziska et al., 1997; Thomas et al., 2003; Roy et al., 2012; Pereira-Flores et al., 2016). When using a crop growth model to evaluate the effects of elevated CO2 and high temperature, researchers predicted that elevated CO2 may alleviate the negative effects of increased temperature if the increase in temperature is no more than 2 °C (Krishnan et al., 2007). Long et al. (2006) reported that an increase in crop yields at a free-air CO2 enrichment (FACE) site was much lower than the increase predicted by a crop growth model and believed that elevated CO2 would not offset the negative effects of high global temperatures. However, few studies have focused on the combined effects of elevated CO2 and temperature on rice growth at field sites. Japonica rice is broadly cultivated in Asia because of its outstanding grain qualities, such as its taste and cooking characteristics. Wang et al. (2015) summarized the effects of elevated CO2 on rice with a meta-analysis and indicated that the average rice yield increased by 20%. However, our previous studies showed that the response of japonica rice yield to elevated CO2 at a field site was nearly 1/2 that of indica rice (Yang et al., 2006; Liu et al., 2008; Zhu et al., 2014). We inferred that japonica rice may be severely affected by increased air temperature under elevated CO2 conditions in the future. Therefore, it is necessary to evaluate the response of japonica rice to the combined influence of elevated CO2 and increased air temperature.

A previous field experiment revealed that the filled grain number per unit area was the key factor accounting for the effects of elevated CO2 and temperature on rice (Cai et al., 2015). An increase in grain number per unit area is always associated with rice yield improvements (Sheehy et al., 2001). The filled grain number per unit area consists of panicles per unit area and filled spikelets per panicle. Cai et al. (2015) showed that increased temperature had a minor effect on the panicles per unit area regardless of whether the CO2 was elevated. In contrast, Wang et al. (2016) indicated that high temperature alone or combined with elevated CO2 significantly decreased the number of panicles per plant. Therefore, the effect of elevated CO2 and temperature on the number of panicles per unit area is not clear. Although Cai et al. (2015) primarily evaluated the combined effect of elevated CO2 and temperature on the number of spikelets per panicle, they did not explore the response of the spikelet architecture. The number of surviving spikelets is related to nitrogen (N) accumulation during panicle initiation (Yao et al., 2000; Yang et al., 2006; Wang et al., 2012). Spikelet degeneration is related to the availability of photoassimilates nearly two weeks before anthesis (Kobayasi et al., 2001). Therefore, the changes in N uptake and dry matter related to spikelet architecture under elevated CO2 and increased temperature conditions need to be explored to further understand the corresponding mechanisms.

In this study, we hypothesized that elevated CO2 would compensate for the japonica rice yield losses caused by rising air temperature. The first objective of this study was to evaluate whether elevated CO2 would offset the negative effects caused by increased air temperature. For this purpose, we detected the yield and yield components of japonica rice under these two conditions of climate change over two growth seasons. The second objective was to explore the response of panicle formation to temperature and CO2 changes. Leaf photosynthesis, N uptake, and spikelet architecture of rice from the jointing to the heading stage were assessed in 2016 to answer this question. Air temperature (Ta) is difficult to control under open-field conditions, and researchers have widely used infrared heaters to explore the effect of increased temperature on crop growth and physiology (Nijs et al., 1996, 1997; Cai et al., 2015; Ding et al., 2016; Wang et al., 2017). In this study, we directedly increased the air temperature to evaluate the combined effect of temperature and CO2 on rice growth under field conditions.

Section snippets

Free-air CO2 enrichment (FACE) facility

The FACE facility was established in Zongchun village (119°42′0′′E, 32°35′5′′N), Yangzhou city, Jiangsu Province. Detailed descriptions of the design and operation of the FACE facility can be found elsewhere (Yang et al., 2006). In brief, three uniform rectangular fields were selected at the FACE experimental site. There was a distance of 90 m between the centre of the CO2 treatment plot and the ambient plot to avoid CO2 contamination. Each octagonal FACE plot was encircled by tubes that

Growth duration

Elevated CO2 alone shortened the pre-heading phase by 2 days, and increased air temperature alone notably shortened the pre-heading phase by 2.5 days on average, as measured in calendar days (Table 1). The combination of elevated CO2 and temperature further exacerbated this phenological tendency by shortening the pre-heading phase by 4 days (Table 1).

Grain yield and yield components

Significant interactions of the grain yield and 1000 grain weight between years were observed in this study (Table 2). There were significant

Discussion

Researchers have used closed- or open-top chambers (Ziska et al., 1997; Cheng et al., 2009) and FACE systems (Cai et al., 2015) to investigate the independent or combined effects of elevated CO2 and increased global surface temperature on rice yield. However, the yield responses to elevated CO2 reported from FACE experiments were half of or less than those reported from enclosure experiments (Long et al., 2006). Our study showed that CO2 elevated by 200 ppm significantly increased rice yield by

Conclusions

The findings obtained in this study have important implications for adaptive strategies for future rice production systems. This study showed that the decrease in japonica rice yield induced by increased air temperature could not be alleviated by elevated CO2. Spikelet density was the factor that determined the rice yield and was most affected by the interaction between elevated CO2 and increased temperature. The dry matter per unit area before heading was the crucial factor that accounted for

Acknowledgements

This work was supported by the National Natural Science Foundation of China (Grant No. 31261140364, 31370457). The authors express their thanks to Shah Fahad for comments on the manuscript. The FACE system instrument was supplied by the National Institute of Agro-Environmental Sciences and the Agricultural Research Center of Tohoku Region (Japan).

References (58)

  • K. Roy et al.

    Combined effect of elevated CO2 and temperature on dry matter production, net assimilation rate, C and N allocations in tropical rice Oryza sativa L

    Field Crops Res.

    (2012)
  • J. Sheehy et al.

    Spikelet numbers, sink size and potential yield in rice

    Field Crops Res.

    (2001)
  • Y. Wang et al.

    Investigations on spikelet formation in hybrid rice as affected by elevated tropospheric ozone concentration in China

    Agric. Ecosyst. Environ.

    (2012)
  • T. Wang et al.

    Simultaneous rough rice drying and rice bran stabilization using infrared radiation heating

    LWT-Food Sci. Technol.

    (2017)
  • D. Xiong et al.

    Meta-analysis and dose-response analysis of high temperature effects on rice yield and quality

    Environ. Exp. Bot.

    (2017)
  • L. Yang et al.

    The impact of free-air CO2 enrichment (FACE) and N supply on yield formation of rice crops with large panicle

    Field Crops Res.

    (2006)
  • E.A. Ainsworth et al.

    What have we learned from 15 years of free‐air CO2 enrichment (FACE)? A meta‐analytic review of the responses of photosynthesis, canopy properties and plant production to rising CO2

    New Phytol.

    (2005)
  • N. Alexandratos et al.

    World agriculture towards 2030/2050: the 2012 revision

    ESA Working Paper No. 12-03

    (2012)
  • C. Cai et al.

    Responses of wheat and rice to factorial combinations of ambient and elevated CO2 and temperature in FACE experiments

    Glob. Change Biol.

    (2015)
  • C. Cai et al.

    Do all leaf photosynthesis parameters of rice acclimate to elevated CO2, elevated temperature, and their combination, in FACE environments?

    Glob. Change Biol.

    (2018)
  • C.P. Chen et al.

    Do the rich always become richer? Characterizing the leaf physiological response of the high-yielding rice cultivar Takanari to free-air CO2 enrichment

    Plant Cell Physiol.

    (2014)
  • J.M. Clough et al.

    Effects of high atmospheric CO2 and sink size on rates of photosynthesis of a soybean cultivar

    Plant Physiol.

    (1981)
  • F.P. De Vries

    Rice production and climate change

    Systems Approaches for Agricultural Development

    (1993)
  • C. Ding et al.

    Nitrogen fertilizer increases spikelet number per panicle by enhancing cytokinin synthesis in rice

    Plant Cell Rep.

    (2014)
  • C. Ding et al.

    Improvement in storage stability of infrared-dried rough rice

    Food Bioprocess Technol.

    (2016)
  • A. Frank et al.

    Temperature, nitrogen, and carbon dioxide effects on spring wheat development and spikelet numbers

    Crop Sci.

    (1996)
  • T. Hasegawa et al.

    Response of spikelet number to plant nitrogen concentration and dry weight in paddy rice

    Agron. J.

    (1994)
  • T. Hasegawa et al.

    Rice cultivar responses to elevated CO2 at two free-air CO2 enrichment (FACE) sites in Japan

    Funct. Plant Biol.

    (2013)
  • S. Jagadish et al.

    High temperature stress and spikelet fertility in rice (Oryza sativa L.)

    J. Exp. Bot.

    (2007)
  • Cited by (49)

    View all citing articles on Scopus
    View full text