Relationship Between Root Morphology And Physiology Of Rice And Methane Emission From Paddy Field

China is the world's largest producer and consumer of rice.Increasing rice yield is the top priority for rice production in China.However,the rice paddy ecosystem is also an important source of methane emissions.The CH4 emission problem in paddy fields has been receiving widespread international attention.There are many studies on rice methane emissions from rice varieties,but there are relatively few studies on the mechanism of differences in methane emissions among rice varieties.The research on the relationship between the root morphology and physiology of rice cultivars and the methane emissions from paddy fields has important implications for high-yielding cultivation of rice and reduction of methane in paddy fields.In this study,four rice varieties with large differences in methane emissions were selected as materials to study the basic changes of methane emissions from rice fields,and the relationship between root morphology and physiology among varieties and methane emissions from paddy fields.The main results are as follows:Methane emissions from paddy fields.The methane emission fluxes of paddy fields in the four rice varieties were similar during the whole growth period.Methane emissions from paddy fields began to rise rapidly after transplanting,reaching the first peak at about 20 days after transplanting,and there was no significant difference in the types of rice varieties.Mid-term drainage of methane emissions from the field is almost zero,after which methane emissions begin to rise again and reach a second peak before and after the booting stage.There are significant differences between the varieties.The methane fluxes of Yangdao 6 and Yanjing 2 were significantly higher than those of Liangyoupeijiu and Zhendao 88.Methane emissions from rice fields after heading are gradually reduced until the difference in harvest changes is not significant.Compared with the same type of rice,the total methane emission of the japonica rice Liangyoupeijiu during the whole growth period was significantly lower than that of the Yangdao 6,and the japonica rice 88 was significantly lower than the japonica rice.From the panicle initiation to the heading stage,the high methane flux and the large amount of accumulation are the important reasons for the total methane emissions of Yangdao 6 and Yanjing 2 is higher than that of Liangyoupeijiu and Zhendao 88.The main agronomic characteristics and root morphology of rice in booting stage.There were no significant differences in the main agronomic traits such as number of stems,leaf area index and dry matter weight at the booting stage between the same types of rice varieties.However,the root dry weight,root length,number of roots,root diameter,root oxidative force,total root-absorbed surface area,root active surface area,root-injury flow rate and malic acid concentration in root exudates of japonica rice Liangyoupeijiu during booting stage were significantly higher than that of Yangdao 6.The above mentioned main physiological and physiological indexes of 88 roots of japonica rice were also significantly higher than that of Yanjing 2.Correlation analysis showed that the root dry weight,root length,number of roots and root diameter of rice were significantly negatively correlated with the methane flux of rice fields during booting stage;root oxidative power,root flow rate,and malic acid concentration in root exudates Methane emissions from rice fields during booting also showed extremely significant negative correlations.Effects of nitrogen rate and alternate wet-drying irrigation on root morphogenesis and methane emission in rice at booting stage.Under the experimental conditions,increasing the nitrogen application rate at the root stage can significantly increase the root dry weight,root oxidative power,root flow rate,and malic acid concentration in the root exudates of the rice during the booting stage,and reduce the methane flux in the paddy field at booting stage.Compared with conventional water-irrigation(FI),mild dry-wet alternate irrigation(AWD)improved the root morphological and physiological indexes and the concentration of malic acid in root exudates,and reduced the methane flux in paddy field at booting stage..These results further confirmed that large root volume,strong root activity,and high malic acid concentration secreted from roots are beneficial to reducing methane emissions from rice fields.