Asymmetric warming effects on N dynamics and productivity in rice (Oryza sativaL.)

Abstract

Climate warming exhibits strong diurnal variations, with higher warming rates being observed at nighttime, which significantly affects rice (Oryza sativa L.) growth and grain yield. The objective of this study was to determine the effects of asymmetric warming (all-day warming, AW; daytime warming from 07:00 to 19:00, DW; nighttime warming from 19:00 to 07:00, NW, and a control, CK) on rice nitrogen (N) dynamics and productivity. Two rice bucket warming experiments were performed in Nanjing in Jiangsu Province, China, using the free air temperature increase (FATI) technique. The daily mean temperatures in the rice canopy in the AW, DW and NW plots were 2.0, 1.1 and 1.3ºC higher than those in the rice canopy in the CK plots, respectively. The results indicated that the total N accumulation of rice was 8.27-40.53% higher in the warming treatment than in the control during the jointing, anthesis and maturity stages. However, there was no significant difference detected among the three warming treatments. The warming treatment substantially decreased N translocation efficiency, leading to the retention of more N in the plant stems during grain filling. The warming treatment also decreased the N harvest index, N utilization efficiency based on grain yield and N utilization efficiencies based on biomass in both growing seasons. The warming treatment significantly increased the aboveground biomass (9.26-16.18%) in the jointing stage but decreased it (2.75-9.63%) in the maturity stage. Although DW increased the carbon (C) gain by photosynthesis and NW increased the C loss by night respiration, the daytime higher-temperature treatment affected rice photosynthesis and reduced its photosynthetic rate and product. This effect may be one of the primary reasons for the insignificant difference in the aboveground biomass between the DW and NW treatments. In the AW, DW and NW plots, the grain yield was reduced by an average of 10.07, 5.05 and 7.89%, respectively, across both years. The effective panicles and grains per spike tended to decrease in the warmed plots, whereas irregular changes in the 1000-grain weight were observed. Our results suggest that under the anticipated climate warming, rice productivity would further decline in the Yangtze River Basin.

Prediction model of rice crude protein content, amylose content and actual yield under high temperature stress based on hyper-spectral remote sensing

“…Crude protein is a conventional expression of the total content of N compounds of the analysed product, calculated by multiplying the corresponding N content by a conversion factor. N content was measured according to micro-Kjeldahl method provided by Xie et al (2018), and the conversion factor for rice grain is 5.95. Amylose content was measured according to the method provided by Hong et al (2004).…”

Nonuniform Time-Lag Effects of Asymmetric Warming on Net Primary Productivity across Global Terrestrial Biomes

“…Apart from these model-based studies, there still exist many in situ studies. For example, Wan et al (2009) revealed that the nocturnal-warming-derived carbon losses in the temperate steppe ecosystem can be compensated by stimulating the following daytime photosynthesis through the depletions of leaf carbohydrates in grassland (Grass) at night; Xie et al (2014) revealed that the increases in the aboveground biomass of rice will be significantly enhanced by asymmetric warming in the jointing stage, but suppressed in the maturity stage; and Phillips et al (2016) suggested that this warming asymmetry would turn the grassland ecosystems into a carbon source, mainly by enhancing the warming-induced carbon losses from unprotected soil.…”

“…Increasing bodies of evidence have shown the common existence of significant timelag effects of climate factors on vegetation growth (Braswell et al 1997;Kuzyakov and Gavrichkova 2010;Sherry et al 2008;Wu et al 2015;Zhang et al 2015;Zhao et al 2015). The asymmetric warming is projected to be reinforced (IPCC 2014), which is anticipated to generate enormous effects on the terrestrial green plants' growth (Matiu et al 2016;Peng et al 2013;Su et al 2015;Xie et al 2014). However, little is known about the time-lag effects that asymmetric warming have on different plant biomes.…”