Response of Rice Oryza sativa L to Increasing Temperature and Atmospheric CO2

S.V.K. Jagadish and Madan Pal

4.1 Introduction

Rice (O. sativa and O. glaberrima) is one of the world most important cereal food crops, particularly in Asia and increasingly so in Africa and Latin America. Rice provides a substantial portion of the dietary requirements of nearly 1.6 billion people, with another 400 million relying on rice for quarter to half of their diet (Swaminathan 1984). Rice is cultivated as far north as Manchuria in China (39c 53'N) and far south as New South Wales in Australia (28c 81'S) (Khush 2005), either as an upland (aerobic) or wetland (irrigated, rainfed and deepwater) crop. Upland rice cultivation covers 17 M ha, while wetland rice is cultivated on 131M ha, contributing about 30 and 70%, respectively, of the total rice production in the world (Dubey 2001). Rice occupies 23% of the total cultivated area under cereals in the world, of which 89% is in Asia (FAO 2003). Hence, Asia produces 523 MT of rice (91% of the world production) (Dubey 2001), on which nearly half of the world's population depend for food and livelihood (Carriger and Vallee 2007). Since the world population is increasing at 1.17% annually, an annual increase in rice production by 0.6-0.9% is required until 2050 (Carriger and Vallee 2007) to meet the anticipated demand. Previously, this demand was met by extending cultivation into marginal lands aided by advancement in irrigation facilities. In future, the reduced availability of water due to ground water depletion and competition for natural resources will render marginal lands unproductive (Young 1998). Hence, more rice will have to be cultivated on less land, with less water and labour (Khush 2005). On a global scale, nearly 60% of the rice is managed under triple cropping, 15% under double cropping and 25% cropped once a year (Matthews et al. 1991). Reduced land availability and intensive cultivation pattern have resulted in an increase in area grown under unfavourable climatic conditions e.g., hot summer seasons.

Anthropogenic activities are major contributors for increasing atmospheric CO2 concentration, from approximately 280 ^mol of CO2 mol-1 of air to a current level

Division of Plant Physiology, Indian Agricultural Research Institute, New Delhi - 110 012, India e-mail: [email protected]

S.N. Singh (ed.), Climate Change and Crops, Environmental Science and Engineering, DOI 10.1007/978-3-540-88246-6.4, © Springer-Verlag Berlin Heidelberg 2009

of 379^molmol-1 (IPCC 2007). Annual average increase of 1.9 ^molmol-1 of CO2 emission is recorded from the past 12 years and rapid economic growth of the developing countries is expected to increase CO2 concentration to 570 ^molmol-1 by 2050 (IPCC 2007). Moreover, concomitant increase in other radiatively active gases, such as methane (CH4), nitrous oxide (NO) and chloro-fluro-carbons (CFCs) will increase the pace of global warming. Considering the above, global surface mean air temperature increase by 2.0-4.5°C by 2100 (with an increased variability over this mean) is predicted by general circulation models (IPCC 2007). Rice, in the tropics, is grown at average temperatures of 28/22°C (Prasad et al. 2006), but with increasing global temperature and shift in cultivation patterns, a sustained increase in rice production will have to be obtained in a much warmer climate in the future. Both temperature and CO2 are major variables responsible for global climate change, affecting food and fodder production. Therefore, the response of rice to increasing temperature and elevated CO2 concentration is discussed in this chapter.

4.2 High Temperature and Vegetative Growth of Rice

Rice, like other crops, has an optimum temperature for growth and developmental processes (Table 4.1). Increase or decrease in optimum temperature will result in an altered physiological activity or may lead into a different developmental pathway (Downton and Slatyer 1972). A temperature gradient chamber study with increase in mean and maximum temperature by 2.0-3.6°C and 4.0-7.0°C, respectively, resulted in increased plant height and an earlier maximum tillering (Oh-e et al. 2007). High temperature (ambient +5°C) maintained throughout the crop growth period decreased the leaf photosynthetic rate by 14% (Prasad et al. 2006) and Oh-e et al. (2007), reflecting a decline of 11.2-35.6% in photosynthesis from heading to middle ripening stage. A decrease in spikelet fertility and seed yield was attributed to decline in pollen production and pollen numbers on the stigma, but not due to decrease in photosynthesis (Prasad et al. 2006). Increase in leaf temperature from 20 to 30°C differentiated O. sativa sub-spp, resulting in an increase of 18-14% and 100-150% in photosynthesis and respiration, respectively, with the increase being higher in japonica spp. than the indica spp. (Weng and Chen 1987). High temperature (36/30°C) led to an abnormal loss in chlorophyll (Thimann 1987), accelerating senescence in wheat plants (Harding et al. 1990).

Table 4.1 Optimum temperature for different growth and development stages of rice

Trait

Optimum temperature

References

Seed germination

25-35°C

Ueno and Miyoshi (2005)

Rate of leaf emergence

26° C

Ellis et al. (1993)

Days to heading

27-30°C

Horie (1994)

Rate of flowering

30°C

Nakagawa et al. (2005)

Seed-set

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