Responses of Rice Growth to Day and Night Temperature and Relative Air Humidity-Dry Matter, Leaf Area, and Partitioning.

Stuerz Stuerz,Asch Asch

doi:10.3390/plants8110521

Abstract

Asymmetric changes of day and night temperature have already been observed because of Climate Change. However, knowledge on environmental conditions either during day or night serving as trigger for growth processes is scarce. In this study, one rice (Oryza sativa) variety (IR64) was examined to assess the impact of varying temperatures and relative air humidities during day and night periods on biomass, leaf area, and dry matter partitioning between organs. Three different day and night temperature (30/20 °C, 25/25 °C, 20/30 °C) and relative air humidity (40/90%, 65/65%, 90/40%) regimes were established. The effect of relative air humidity on both plant dry matter and leaf area was larger than the effect of temperature, in particular low humidity had a strong negative impact during the night. With high day temperature, the shoot mass fraction increased, whereas the root mass fraction decreased. Specific leaf area increased at high night temperatures and led, along with the high leaf mass fraction at high night humidities, to higher growth rates. The results emphasize the importance of considering relative air humidity when focusing on plant responses to temperature, and strongly suggest that under asymmetric day and night temperature increases in the future, biomass partitioning rather than biomass itself will be affected.

Highlights

With climate change, temperature increases are expected in the coming decades, but have already been observed [1]
Rice plants were grown at three different temperature regimes with either “natural” (30 ◦ C/20 ◦ C; Tnat), constant (25/25 ◦ C; Tcon), or inverted (20/30 ◦ C; Tinv) day/night temperature in combination with three different relative air humidity (RH) regimes with either “natural” (40/90%; RHnat), constant
Provided that plant growth is driven by photosynthetic carbon fixation during the day [16], higher growth rates could be expected under higher day temperature, at least in the temperature range of our experiment, since maximal assimilation rates for rice were found in the range of 30–35 ◦ C irrespective of the growth temperature [17]

Summary

Introduction

Temperature increases are expected in the coming decades, but have already been observed [1]. Whereas the increase of average temperature and its negative effects on rice yields are widely accepted, there is no consensus about the effects of changes to the temperature range, the difference between day and night temperature on a daily basis. Despite high uncertainty [1], a decrease in the daily temperature range is expected in the world’s rice growing regions [4] as daily minimum temperatures increase more rapidly than daily maximum temperatures [5]. Negative yield responses of rice to a narrowing daily temperature range due to an increase in minimum temperature have been observed in field experiments in the Philippines [6]. Lobell [4] projected impacts of a narrowing daily temperature range on rice yield as positive, even if relatively small

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