为了明确直播条件下软米粳稻与常规粳稻食味品质与淀粉结构差异特征及其对氮肥和密度的响应变化。本研究以软米粳稻南粳9108和常规粳稻丰粳3227为供试材料,设置3个施氮量(0、150和300 kg hm^(-2))和3个密度(90×10^(4)、180×10...为了明确直播条件下软米粳稻与常规粳稻食味品质与淀粉结构差异特征及其对氮肥和密度的响应变化。本研究以软米粳稻南粳9108和常规粳稻丰粳3227为供试材料,设置3个施氮量(0、150和300 kg hm^(-2))和3个密度(90×10^(4)、180×10^(4)和360×10^(4)hm^(-2)),研究施氮量和密度及其互作对水稻食味品质和淀粉结构的影响。结果表明,与常规粳稻相比,软米粳稻直链淀粉含量低,蛋白质含量低,胶稠度长,米饭硬度低和黏度大,淀粉RVA谱中崩解值大、消减值小和糊化温度低,淀粉相对结晶度、有序度和峰强度较高,而片层距离较短,稻米食味品质优。随着施氮量增加,稻米直链淀粉含量降低,蛋白质含量提高,胶稠度变短,米饭硬度增加,稻米食味值下降。相关分析表明,施氮量与蛋白质含量和硬度呈极显著正相关,与米饭食味值、黏度、峰值黏度、热浆黏度、最终黏度和片层距离呈极显著负相关。而密度与稻米食味品质和淀粉结构相关指标均无显著相关性。展开更多
Glycerol dialkyl glycerol tetraethers(GDGTs) in lake sediments are useful biomarkers for the continental paleoclimatic reconstruction. However, the environmental controls on the distribution of these compounds, in par...Glycerol dialkyl glycerol tetraethers(GDGTs) in lake sediments are useful biomarkers for the continental paleoclimatic reconstruction. However, the environmental controls on the distribution of these compounds, in particular the 6-methyl isomers of bacterial branched GDGTs(bGDGTs), in the lakes with contrasting pH, are still unknown, hindering their application for paleo-reconstructions. Here, we investigated the environmental impacts on the distribution of GDGTs in 17 alkaline lakes and 1 acid lake in China. It was found that the dissolved oxygen content in water column may have an impact on the distribution of archaeal isoprenoid GDGTs(iGDGTs) by causing the change in archaeal communities. The ratio of GDGT-0/crenarchaeol increases with decreasing oxygen content, indicating that the relative abundance of anaerobic methanogenic archaea or Miscellaneous Crenarchaeotic Group(MCG) vs. aerobic Thaumarchaeota is controlled by the oxygen content dissolved in water of these lakes. Thaumarchaeota are likely to contribute only a small proportion of iGDGTs in the relatively oxygen-depleted lakes, and thus TEX_(86) is not suitable for the reconstruction of the surface temperature of these lakes. The abundance ratio of iGDGTs to bGDGTs(R_(i/b)) appears to show no relationship with water pH in all the lakes, but exhibits a significant positive correlation with the water depth of the acid Lake Qinghai in Tengchong. As expected, the methylation degree of bGDGTs(MBT′) was found to correlate with both mean annual air temperature(MAT) and water pH, and the cyclization degree of bGDGTs(CBT) correlates only with water pH in these lakes. However, the MBT′_(5ME), an index to measure the methylation degree of 5-methyl bGDGTs, exhibits no relationship with MAT, whereas MBT′_(6ME), the methylation degree of 6-methyl bGDGTs, was found to correlate significantly with MAT. This is opposite to the situation observed in the global soils, pointing to a different adaptation of b GDGT-producing bacteria to environmental variables or different microbial sources of bGDGTs in these lakes. The relative abundance of 6- vs. 5-methyl bGDGTs is controlled by pH in these lakes, similar to that observed in worldwide soils. Hence, the isomer ratio(IR) of 6-methyl bGDGTs or CBT′ can be used as a proxy for water pH, although they might be influenced by other environmental factors including temperature in the lakes with a narrow range of pH.展开更多
文摘为了明确直播条件下软米粳稻与常规粳稻食味品质与淀粉结构差异特征及其对氮肥和密度的响应变化。本研究以软米粳稻南粳9108和常规粳稻丰粳3227为供试材料,设置3个施氮量(0、150和300 kg hm^(-2))和3个密度(90×10^(4)、180×10^(4)和360×10^(4)hm^(-2)),研究施氮量和密度及其互作对水稻食味品质和淀粉结构的影响。结果表明,与常规粳稻相比,软米粳稻直链淀粉含量低,蛋白质含量低,胶稠度长,米饭硬度低和黏度大,淀粉RVA谱中崩解值大、消减值小和糊化温度低,淀粉相对结晶度、有序度和峰强度较高,而片层距离较短,稻米食味品质优。随着施氮量增加,稻米直链淀粉含量降低,蛋白质含量提高,胶稠度变短,米饭硬度增加,稻米食味值下降。相关分析表明,施氮量与蛋白质含量和硬度呈极显著正相关,与米饭食味值、黏度、峰值黏度、热浆黏度、最终黏度和片层距离呈极显著负相关。而密度与稻米食味品质和淀粉结构相关指标均无显著相关性。
基金supported by the Fundamental Research Funds for the Central Universities (Grant No. CUGL150812)the National Natural Science Foundation of China (Grant No. 41330103)the Programme of Introducing Talents of Discipline to Universities Project (Grant No. B08030)
文摘Glycerol dialkyl glycerol tetraethers(GDGTs) in lake sediments are useful biomarkers for the continental paleoclimatic reconstruction. However, the environmental controls on the distribution of these compounds, in particular the 6-methyl isomers of bacterial branched GDGTs(bGDGTs), in the lakes with contrasting pH, are still unknown, hindering their application for paleo-reconstructions. Here, we investigated the environmental impacts on the distribution of GDGTs in 17 alkaline lakes and 1 acid lake in China. It was found that the dissolved oxygen content in water column may have an impact on the distribution of archaeal isoprenoid GDGTs(iGDGTs) by causing the change in archaeal communities. The ratio of GDGT-0/crenarchaeol increases with decreasing oxygen content, indicating that the relative abundance of anaerobic methanogenic archaea or Miscellaneous Crenarchaeotic Group(MCG) vs. aerobic Thaumarchaeota is controlled by the oxygen content dissolved in water of these lakes. Thaumarchaeota are likely to contribute only a small proportion of iGDGTs in the relatively oxygen-depleted lakes, and thus TEX_(86) is not suitable for the reconstruction of the surface temperature of these lakes. The abundance ratio of iGDGTs to bGDGTs(R_(i/b)) appears to show no relationship with water pH in all the lakes, but exhibits a significant positive correlation with the water depth of the acid Lake Qinghai in Tengchong. As expected, the methylation degree of bGDGTs(MBT′) was found to correlate with both mean annual air temperature(MAT) and water pH, and the cyclization degree of bGDGTs(CBT) correlates only with water pH in these lakes. However, the MBT′_(5ME), an index to measure the methylation degree of 5-methyl bGDGTs, exhibits no relationship with MAT, whereas MBT′_(6ME), the methylation degree of 6-methyl bGDGTs, was found to correlate significantly with MAT. This is opposite to the situation observed in the global soils, pointing to a different adaptation of b GDGT-producing bacteria to environmental variables or different microbial sources of bGDGTs in these lakes. The relative abundance of 6- vs. 5-methyl bGDGTs is controlled by pH in these lakes, similar to that observed in worldwide soils. Hence, the isomer ratio(IR) of 6-methyl bGDGTs or CBT′ can be used as a proxy for water pH, although they might be influenced by other environmental factors including temperature in the lakes with a narrow range of pH.
