Abstract
The effect of high temperatures on rice production has attracted considerable research attention. It is not clear, however, whether nitrogen (N) management can be used to alleviate the damaging effects of high temperatures on flowering in rice. In this study, we compared the yields of five elite super hybrid rice varieties and examined their heat tolerance under four N treatments in two seasons with contrasting temperatures at flowering: 2015 (normal temperature) and 2016 (high temperature). The average daily temperature during the flowering stage in 2016 was 31.1°C, which was 4.5°C higher than that in 2015. There was a significant positive correlation between grain yield and N level (R2 = 0.42, P < 0.01). However, mean grain yield of the five rice varieties in 2015 was 10.5% higher than that in 2016. High N levels reduced yield losses in plants exposed to high temperature in 2016. The mean seed-set percentage in 2016 was 13.0% lower than that in 2015 at higher N levels, but spikelets per panicle increased by 7.6% at higher N levels compared with lower N levels. Higher N levels reduced the number of degenerated spikelets under high temperatures. Spikelets per panicle and N treatment level were positively correlated at high temperatures (R2 = 0.32, P < 0.05). These results confirmed that increasing N application could alleviate yield losses caused by high temperatures in super hybrid rice during the flowering stage.
Highlights
Mean global temperatures are forecast to rise by as much as 2◦C by the middle of the 21st century, with a concurrent increase in the frequency and intensity of extreme heat waves (Intergovernmental Panel on Climate Change [IPCC], 2013). Piao et al (2010) reported that temperatures have increased by 0.15–0.40◦C every 10 years over the past 50 years in China
YLY1 did not show any significant change in seed set under high temperature, which suggests that YLY1 was the most tolerant to heat stress among these cultivars
Because of a reduction in seed-set percentage caused by high temperature during the flowering stage, mean grain yield in 2016 was significantly lower than that in 2015
Summary
Mean global temperatures are forecast to rise by as much as 2◦C by the middle of the 21st century, with a concurrent increase in the frequency and intensity of extreme heat waves (Intergovernmental Panel on Climate Change [IPCC], 2013). Piao et al (2010) reported that temperatures have increased by 0.15–0.40◦C every 10 years over the past 50 years in China. Mean global temperatures are forecast to rise by as much as 2◦C by the middle of the 21st century, with a concurrent increase in the frequency and intensity of extreme heat waves (Intergovernmental Panel on Climate Change [IPCC], 2013). As the largest rice producer in the world, China contributes nearly thirty percent of global rice production (Food and Agriculture Organization [FAO], 2010; Seck et al, 2012). Rice cultivars in China are increasingly exposed to extremely high temperatures with ongoing climate change. Temperatures of 35◦C–significantly exceeding the critical threshold temperature (33◦C) for growing rice (Bheemanahalli et al, 2016; Liu et al, 2017)–that lasted for more than half a month, contributed to an estimated total yield loss of 5.18 × 107 t in the Yangtze Valley, resulting in significant economic losses in 2003 (Tian et al, 2009). The annual planting area of hybrid rice has increased to about
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