Integrated micrometeorology model for panicle and canopy temperature (IM2PACT) for rice heat stress studies under climate change

Abstract

Projected global warming is expected to increase the occurrence of heat-induced spikelet sterility (HISS) of rice (Oryza sativa L.). Previous chamber experiments have shown that HISS can occur where temperature at flowering time exceeds the threshold temperature of around 35 . The occurrence of HISS is, however, difficult to predict because the thermal conditions of rice canopy can be different from the air temperature under field condition. To cope with this, we developed a simple micrometeorology model focusing canopy and panicle temperatures; IM PACT was applied to the meteorology dataset based on ANEMOS in order to analyse the Tp at Kanto and Tokai regions of extremely hot summer in 2007. There was a great gap in spatial distributions between the Tp and the daily maximum air temperature which is commonly used as a measure of HISS, because the difference of meteorology, especially relative humidity, among areas altered the panicle-air temperature difference. This strongly suggests that we must refer to the Tp instead of the air temperature in daily maximum, as a measure variable for HISS. The IM 2 PACT is a powerful tool to elucidate the Tp in the climate change impact study to bridge between the responses of crop susceptible to heat and the meteorological data.

Cleistogamy Decreases the Effect of High Temperature Stress at Flowering in Rice

“…This drop of temperature may be dependent on latent heat effect by transpiration from the stoma of the glume (Nishiyama, 1981). Transpiration of panicles in the rice field reduced panicle and canopy temperature (Yoshimoto et al, 2011;Fukuoka, 2012). These data suggest that the air temperature inside the spikelet of cleistogamous rice plants at 38ºC was substantially the same as that at 36ºC.…”

Spikelet sterility of rice observed in the record hot summer of 2007 and the factors associated with its variation

“…In fact, the spatial distribution of panicle temperature estimated by using a heat balance model during the hours of flowering (10:00-12:00) does not necessarily match the distribution of daily maximum temperature . This is because the panicle temperature during flowering hours is lower than the daily maximum temperature, and other meteorological factors such as solar radiation, wind speed, and humidity also affect panicle temperature Yoshimoto et al, 2011). Matsui et al (2007) reported a similar but more extreme example in Australia, where dry and windy conditions increase transpirational cooling of the canopy, thereby reducing panicle temperature; the difference between air and panicle temperatures was as much as 6 , and this contributes to stable pollination under hot conditions.…”

Responses of spikelet fertility to air, spikelet, and panicle temperatures and vapor pressure deficit in rice

“…Recently, it is regarded that panicle temperature is better predictor variable of spikelet sterility than air temperature, because the calculated spikelet sterility with air temperature was overestimated compared to the observed (van Oort et al, 2014). Yoshimoto et al (2011) presented IM 2 PACT model using an energy balance to predict panicle temperature.…”