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Effects of biochar and silicate supply on photosynthetic and fluorescence characteristics of rice leaves under nighttime warming
Received:July 28, 2020  
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KeyWord:nighttime warming;biochar;silicate;rice;photosynthesis;yield
Author NameAffiliationE-mail
XING Yu-yuan Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science and Technology, Nanjing 210044, China
Jiangsu Key Laboratory of Agricultural Meteorology, Nanjing University of Information Science and Technology, Nanjing 210044, China 
 
LOU Yun-sheng Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science and Technology, Nanjing 210044, China
Jiangsu Key Laboratory of Agricultural Meteorology, Nanjing University of Information Science and Technology, Nanjing 210044, China 
yunshlou@163.com 
WANG Kun Jiangsu Key Laboratory of Agricultural Meteorology, Nanjing University of Information Science and Technology, Nanjing 210044, China  
LIU Jian Jiangsu Key Laboratory of Agricultural Meteorology, Nanjing University of Information Science and Technology, Nanjing 210044, China  
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Abstract:
      The higher increase in temperature at nighttime than that at daytime is one of the main features of global climate warming. The effect of nighttime warming and either silicon or biochar application alone on rice production is known; however, it is unclear whether the three factors have coupled effects on the photosynthetic and fluorescence characteristics of rice under field conditions. A field simulation experiment was conducted to investigate the effects of biochar and silicate supply on photosynthetic and fluorescence characteristics of rice under nighttime warming. An orthogonal experimental design with three factors and three levels was adopted in the field experiment. The nighttime warming treatment was applied by covering the rice canopy with aluminum foil reflective film at night(19:00-6:00). The nighttime warming was set at three levels:ambient temperature control(W0), with 5 mm aluminum foil film(W1), and with 11 mm aluminum foil film(W2); biochar supply was designed at 3 levels:control(B0), 7.5 t·hm-2 biochar(B1), and 17.5 t·hm-2 biochar(B2); silicate was applied at three levels:control(Si0), steel slag powder(Si1, 200 kg·hm-2), and ore powder(Si2, 200 kg·hm-2). The results showed that 5 mm and 11 mm aluminum foil film increased the nighttime average temperature at the 5 cm soil layer by 0.72℃ and 0.28℃, and that at the 10 cm soil layer by 0.43℃ and 0.05℃, respectively. The average net photosynthetic rate(Pn), stomatal limit value(Ls), and water use efficiency(WUE) decreased, whereas the transpiration rate(Tr), intercellular CO2 concentration(Ci), and stomatal conductance(Gs)increased under nighttime warming. Nighttime warming increased the light fluorescence depletion, and inhibited PS Ⅱ original light energy conversion efficiency and photosynthetic performance. The effects on Ls, Gs, Ci, and photosynthetic performance were significant at P<0.05. The application of 7.5 t·hm-2 biochar and silicate supply improved Pn, and alleviated the inhibitory effects of nighttime warming on photosynthetic and fluorescence characteristics. Under nighttime warming and no silicate supply, photosynthesis and rice yield can be increased with the application of 7.5 t·hm-2 biochar.