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Dry matter production and partitioning in rice in response to elevated temperature

Estela M. Pasuquin1,2, Phil Eberbach1, Tanguy Lafarge2, Toshihiro Hasegawa3 and Len Wade1

1 Charles Sturt University, E H Graham Centre for Agricultural Innovation, Wagga Wagga NSW 2678;
www.csu.edu.au; Email: epasuquin@csu.edu.au; peberbach@csu.edu.au; lwade@csu.edu.au
2
Crop and Environmental Sciences Division, IRRI, Philippines; Email: t.lafarge@cgiar.org
3
National Institute of Agro-Environmental Sciences, Tsukuba, Japan; Email: thase.affrc.go.jp

Abstract

Atmospheric temperature is predicted to rise by 1-6C over the next century, with adverse consequences for rice productivity. Rice is the main source of food for half of the world’s population, so avenues are needed to understand the basis for improvement of yield under the predicted temperature rise. This PhD study will examine the responses of rice to elevated temperature, focusing on the partitioning of dry matter to grain from current assimilate during grain-filling, and from assimilate accumulated prior to anthesis, under different temperature regimes. Experiments will be conducted in controlled environments and in the field in order to quantify source and sink size and source-sink interactions in grain fill, and how the plant and its management may be changed to stabilise or even improve rice productivity under the elevated temperatures expected under future climates.

Key Words

Atmospheric temperature, climate change, controlled environment, dry matter partitioning, plant development, plant growth

Introduction

The changes in our climate condition are happening faster than was predicted earlier, and with negative impacts predicted in agricultural production including the world’s most important cereal, rice (Darwin, 2001). Grain yield of rice was reported to start to decline when daily mean temperature exceeds 29C (Oh-e et al., 2004). Experiments conducted under prevailing temperatures in the field in Kyoto, Japan during 1995 and 2001 showed strong evidence that yield variation among rice cultivars was highly correlated with source; dry matter production during grain filling (Lubis et al., 2003), carbohydrates accumulated in rice stems during the pre-heading period (Song et al. 1990, Sumi et al., 1996), or the non-structural carbon accumulated prior to heading (Lubis et al., 2003). The levels of pre-anthesis assimilates were positively correlated with grain yield (Samonte et al., 2001). On the other hand, several authors have reported that high yield in rice is supported by a large sink size (Saitoh et al., 1991; Shi et al., 1996). Over 157 field experiments in Japan showed a highly significant correlation between total nitrogen accumulated at panicle formation stage and spikelet number (Hasegawa et al., 1994). Within maturity groups, Pasuquin et al. (2008) showed that higher grain yield was related to higher shoot dry weight, but when temperatures were higher by 2C, grain yield was more closely related to number of filled grains per panicle, implicating the balance between source and sink. Thus, rice responses to elevated temperature are highly dynamic in terms of source-sink relationships, and there is a need to explore their expression based on the temperature responses of their components over growth stages. The objectives of this study are (1) to determine the responses in rice dry matter accumulation and partitioning to elevated temperature relative to current conditions in Australia and the Philippines and cardinal temperatures for rice, (2) to examine how changes in source or sink size at elevated temperature can alter patterns of dry matter production and partitioning, and (3) to consider the implications for rice improvement and management in order to maintain or even increase rice productivity under climate change.

Methods

Controlled-environment experiments (CSU, Australia and NIAES, Japan) and field experiments (IRRI, Philippines and CSU, Australia) are planned.

The first controlled-environment experiment in Australia aims to characterise the dry matter production and partitioning responses of rice cultivars to a range of temperatures. Two or more cultivars reported to differ in their temperature sensitivity will be used, with data collected on plant development and growth, C assimilation, leaf conductance and respiration. These data will provide a background to how the plants respond to increasing temperature.

The second experiment will be conducted in large trays placed in environment-controlled enclosures in the field in Australia, where mini-paddies of rice can be grown. Two contrasting cultivars will be grown in two temperature regimes chosen from the results of the previous experiment. The same measurements will be taken, and in addition, subplots will be manipulated in order to limit the sizes of the assimilate source, the grain sink, or both. These data should allow consideration of how source-sink interactions at different temperatures alter dry matter partitioning and components of yield.

The third experiment, utilising precise growth chambers in Japan, will test sensitivity to selected temperatures and other environmental parameters, to determine how sensitive are the temperature responses to changes in relative humidity and vapour pressure deficit, when the plants are grown in flooded soils.

The fourth experiment will assess the consistency of the controlled-environment responses with those in the field in the Philippines, and in addition, will permit an evaluation of the genotypic variation among cultivars.

Discussion

This PhD study will provide a better understanding of how rice responds to elevated temperature, and what opportunities may arise to develop better cultivars or management practices to maintain or increase rice productivity at elevated temperatures. The parameters measured will allow consideration of how cultivars differed in their ability to produce dry matter as temperature increased, and which parameters were responsible for any differential behaviour observed. Likewise, variation in size of source and sink and their timing may alter sink priority, and assimilates that can be directed to grain, even if dry matter production is altered. This thesis will provide evidence to allow consideration of plant design for elevated temperature, and whether rice management may also assist in stabilizing yields in elevated temperature.

References

Darwin, R. (2001). Climate change and food security. In: Food Security Issues. Agric. Info. Bull. No. 765-8, USDA. Economic Res. Service.

Hasegawa, T., K. Yasou, N.G. Seligman and T. Horie (1994). Response of spikelet number to plant nitrogen concentration and dry weight in paddy rice. Agron. J. 86:673-676.

Lubis, I., S. Tatsuhiko, M. Ohnishi, T. Horie and N. Inoue (2003). Contribution of sink and source sizes to yield variation among rice cultivars. Plant Prod. Sci. 6(2): 119-125.

Oh-e, I., K. Saitoh and T. Kuroda. (2004). Effects of rising temeprature on growth, yield and dry matter production of rice grown in the paddy field. In: Proc. of the 4th Int. Crop Science Congress, Brisbane, Australia, Sept 26-Oct 2.

Pasuquin, E., T. Lafarge and B. Tubana (2008). Tranpslanting young seedlings in irrigated rice fields: Early and high tiller production enhanced grain yield. Field Crops Res. 105:141-155

Saitoh, K., S. Kasiwagi, T. Kinosita and K. Ishihara (1991). Characteristics of dry matter production process in high yield rice varietites. IV. Dry matter accummulation in the panicle. Jpn. J. Crop Sci. 60:255-263.

Samonte, S.O. PB., L.T. Wilson, A.M. McClung and L. Tarpley (2001). Seasonal dynamics of nonstructural-carbohydrate partitioning in 15 diverse rice genotypes. Crop Sci. 41:902-909.

Shi, C., D.L. Qin, M. Tsuda and Y. Matsumoto (1996). High-yielding performance of paddy rice achieved in Yunnan province, China: II. Spikelet production of Japonica F1 hybrid rice, Yu-Za 29. Jpn. J. Crop Sci. 65:22-28.

Song, X. F., W. Agata and Y. Kawamitsu (1990). Studies on dry matter and grain production of F1 hybrid rice in China. III. Grain-production character from the view point of time changes in non-structural carbohydrate and nitrogen contents during yield production. Jpn. J. Crop Sci. 59:107-112.

Sumi, A., S. Hakoyama, J.H. Weng, W. Agata and T. Takeda (1996). Analysis of plant characteristics determining ear weight increase during the ripening period in rice (Oryza sativa L.) II. The role of reserved carbohydrate at heading stage upon the receptive efficiency of assimilation products in spikelets. Jpn. J. Crop Sci. 65:214-221.

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