| A non-crystalline silica structure with different shapes in plant,which is also called phytolith,is formed during the process of silicon absorption,During the formation of phytolith,some organic substances are always carried in,including some organic carbon matters.This part of organic carbon is very stable and can survive for thousands of years due to the outer layer of silicon,thereby being of great archeological and ecological implications.Many environmental researchers believe that the total amount of carbon storage in the phytolith is relatively large,which makes phytolith a way to relieve the stress on carbon emissions in the ecological environment,and meanwhile promotes ecological balance,and meets the demand for environmental protection.Rice,a typical silicon-accumulating crop,is the most widely grown crop in China,and in the world as well.It is very helpful to study the carbon sequestration of rice plant for environmental protection.Twenty four kinds of early season rice and late rice plant were collected in the Hunan and Jiangxi provinces of China where rice is the major crop species.At the same time,the paddy soils were also collected for the extraction and analysis of silicon,phytolith,and PhytOC concentrations.The main results obtained are presented as follows:1.The analysis of plant samples in early season rice and late rice showed that the silicon content,phytolith content,and phytolith carbon content were all higher in late rice than in early rice,and were higher in stem than in grain,and in late rice than in the early rice as well.The silicon content of rice stem in early rice ranged from 17.73 to 46.20 g/kg,compared to 65.18 to 83.01 g/kg in late rice;the phytolith content ranged from 73.60 to 108.80 g/kg in early rice,and 133.60 to 176.00 g/kg in late rice.The PhytOC content of rice stem in early rice ranged from 52.19 to 77.19 g/kg,compared to 83.78 to 96.83 g/kg in late rice.And the silicon content of rice grain in early rice ranged from 26.47 to 35.92 g/kg,compared to 40.32 to 49.04 g/kg in late rice;the phytolith content ranged from 15.12 to 24.60 g/kg in early rice,and 23.56 to 28.88 g/kg in late rice the PhytOC content ranged from 43.93 to 59.08 g/kg in early rice,and 53.31 to 68.46 g/kg in late rice.2.The carbon sequestration capacity was calculated from the PhytOC/dry biomass,which ranged from 4.14 to 16.41 g/kg in plant stem,and from 0.78 to 1.94 g/kg in rice grain.Our study showed the previous studies ignored the carbon sequestration capacity in rice grain,but actually the carbon sequestration capacity in rice grain,was also abundant,and thus worthy of attention.Based on the average yield of rice in China(6.3 ton per ha),it could be calculated that carbon sequestration capacity per hectare of rice could reach about 6.3 kg of carbon in rice grain during one growing season.The total PhytOC storage in rice stem of China was 70.56-284.66×104 T C/yr,compared to 18.82×104 T C/yr in rice grain.3.There existed significant positive correlations between silicon content,phytolith content,and PhytOC/dry biomass;for example,a significant positive correlation was found between silicon content in rice stem and phytolith content was R2=0.59(P<0.01),and the correlation between silicon content in rice grain and phytolith content was R2=0.89(P<0.01).Besides,significant correlation between the carbon content of phytolith and the PhytOC/dry biomass in the soil was noted.The correlation between phytolith content in rice stem and PhytOC content was R2=0.95(P<0.01),and the correlation between phytolith content in rice grain and PhytOC was R2=0.80(P<0.01).However,those correlations are relatively smaller in soil.4.PhytOC content in soil ranged from 0.17 to 0.65 g/kg;according to the estimated total rice planting area of China,the total PhytOC storage in the plough layer of paddy soils was 1.34-4.97×104 T C/yr.Our study showes that adopting rice cultivars which are rich in phytolith and PhytOC content can help improve plant carbon sequestration and contribute to mitigating against global warming. |
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