[Objective] This study was conducted to evaluate three training systems for Korla fragrant pear trees by comparing the characteristic parameters of light response curve and CO2 response curve, and to provide some theo...[Objective] This study was conducted to evaluate three training systems for Korla fragrant pear trees by comparing the characteristic parameters of light response curve and CO2 response curve, and to provide some theoretical basis for improving the pruning techniques of Korla fragrant pear trees. [Method] The light response curve and CO2 response curve of the trees trained to three systems were measured by LI-6400 portable photosynthesis system. The SPAD value was measured using SPAD-502 chlorophyll meter, and specific leaf weight was calculated, to evaluate the effects of the three training systems. [Result] The CO2 response curves of the three training systems were basically in agreement with their light response curves, but there were some differences in their characteristic parameters. Among the three training systems, the maximum net photosynthetic rate, apparent quantum yield and light compensation point of espalier trained trees were the highest, while their light saturation point was the lowest. The CO2 saturation point of delayed-open central leader trained trees and open center trained trees were 1 752 and 1 665 μmol/mol, both of which were much higher than that of espalier trained trees. In addition, the carboxylation efficiency and photorespiration rate of espalier trained trees were both higher than those of delayed-open central leader trained trees and open center trained trees, while the CO2 compensation point of espalier trained trees was the lowest. The leaf SPAD value of espalier trained trees was the largest, followed by that of open center trained trees, and the leaf SPAD value of delayed-open central leader trained trees was the smallest. In addition, the leaf area and specific leaf weight of espalier trained trees were both the highest, followed by those of open center trained trees. [Conclusion] Among the training systems for Korla fragrant pear trees, the espalier training system had better ability to capture light, higher photosynthetic productivity and strongest adaptability to light environment, and open center training system takes the second place. On the contrary, delayed-open central leader training system has the weakest adaptability to light environment, but it can adapt to a higher CO2 concentration. In summary, for the training of Korla fragrant pear trees, espalier training system, which has the highest theoretical yield, is the best among the three training systems, and delayed-open central leader training system is the worst.展开更多
草原植物光合作用受氮添加和刈割等草原管理措施的影响。依托内蒙古草甸草原的氮添加(0、2、5、10、20和50 g N·m^(-2)·a^(-1))和刈割(刈割和非刈割)交互处理的野外控制试验,测定其优势物种羊草的光合-CO_(2)响应过程。探究...草原植物光合作用受氮添加和刈割等草原管理措施的影响。依托内蒙古草甸草原的氮添加(0、2、5、10、20和50 g N·m^(-2)·a^(-1))和刈割(刈割和非刈割)交互处理的野外控制试验,测定其优势物种羊草的光合-CO_(2)响应过程。探究直角双曲线模型、非直角双曲线模型、直角双曲线修正模型和Michaelis-Menten模型对叶片光合-CO_(2)响应曲线的拟合效果,以及光合特性对氮添加和刈割的响应。结果表明:非直角双曲线模型拟合的初始羧化效率和光呼吸速率最接近实测值;直角双曲线修正模型对CO_(2)饱和点、CO_(2)补偿点和最大净光合速率的拟合效果最好;直角双曲线修正模型的拟合优度最高;适度氮添加能提高羊草净光合速率、水分利用效率、最大净光合速率、初始羧化效率和CO_(2)饱和点并降低CO_(2)补偿点,提升羊草对CO_(2)的利用效率;随CO_(2)浓度的升高,氮添加浓度为20 g N·m^(-2)·a^(-1)并刈割的羊草净光合速率增幅较大,具有较高的最大净光合速率、CO_(2)饱和点、水分利用效率和较低的CO_(2)补偿点。综上,非直角双曲线模型和直角双曲线修正模型较适用于氮添加和刈割条件下羊草的CO_(2)响应曲线拟合,在内蒙古草原施氮20 g N·m^(-2)·a^(-1)并刈割最有助于提高羊草光合能力,有利于增大生态系统固碳量。展开更多
Background:One-hour postprandial hyperglycemia is associated with increased risk of type 2 diabetes and cardiovascular disease.Physical activity(PA)has short-term beneficial effects on post-meal glucose response.This ...Background:One-hour postprandial hyperglycemia is associated with increased risk of type 2 diabetes and cardiovascular disease.Physical activity(PA)has short-term beneficial effects on post-meal glucose response.This study compared the oral glucose tolerance test results of 3 groups of people with habitually different levels of PA.Methods:Thirty-one adults without diabetes(age 25.9±6.6 years;body mass index 23.8±3.8 kg/m^2;mean±SD)were recruited and divided into 3 groups based on self-reported PA volume and intensity:low activity<30 min/day of moderate-intensity activity(n=11),moderately active≥30 min/day of moderate-intensity PA(n=10),and very active≥60 min/day of PA at high intensity(n=10).Participants completed an oral glucose tolerance test(50 g glucose)with capillary blood samples obtained at baseline,15 min,30 min,45 min,60 min,90 min,and 120 min post-ingestion.Results:There were no significant differences between groups for age or body fat percentage or glycated hemoglobin(p>0.05).The groups were significantly different in terms of baseline glucose level(p=0.003)and,marginally,for gender(p=0.053)and BMI(p=0.050).There was a statistically significant effect of PA on the 1-h postprandial glucose results(p=0.029),with differences between very active and low activity groups(p=0.008)but not between the moderately active and low activity groups(p=0.360),even when baseline glucose level and gender differences were accounted for.For incremental area under the curve there was no significant effect of activity group once gender and body fat percentage had been accounted for(p=0.401).Those in the low activity group took 15 min longer to reach peak glucose level than those in the very active group(p=0.012).Conclusion:The results suggest that high levels of PA have a beneficial effect on postprandial blood glucose profiles when compared to low and moderate levels of activity.展开更多
文摘[Objective] This study was conducted to evaluate three training systems for Korla fragrant pear trees by comparing the characteristic parameters of light response curve and CO2 response curve, and to provide some theoretical basis for improving the pruning techniques of Korla fragrant pear trees. [Method] The light response curve and CO2 response curve of the trees trained to three systems were measured by LI-6400 portable photosynthesis system. The SPAD value was measured using SPAD-502 chlorophyll meter, and specific leaf weight was calculated, to evaluate the effects of the three training systems. [Result] The CO2 response curves of the three training systems were basically in agreement with their light response curves, but there were some differences in their characteristic parameters. Among the three training systems, the maximum net photosynthetic rate, apparent quantum yield and light compensation point of espalier trained trees were the highest, while their light saturation point was the lowest. The CO2 saturation point of delayed-open central leader trained trees and open center trained trees were 1 752 and 1 665 μmol/mol, both of which were much higher than that of espalier trained trees. In addition, the carboxylation efficiency and photorespiration rate of espalier trained trees were both higher than those of delayed-open central leader trained trees and open center trained trees, while the CO2 compensation point of espalier trained trees was the lowest. The leaf SPAD value of espalier trained trees was the largest, followed by that of open center trained trees, and the leaf SPAD value of delayed-open central leader trained trees was the smallest. In addition, the leaf area and specific leaf weight of espalier trained trees were both the highest, followed by those of open center trained trees. [Conclusion] Among the training systems for Korla fragrant pear trees, the espalier training system had better ability to capture light, higher photosynthetic productivity and strongest adaptability to light environment, and open center training system takes the second place. On the contrary, delayed-open central leader training system has the weakest adaptability to light environment, but it can adapt to a higher CO2 concentration. In summary, for the training of Korla fragrant pear trees, espalier training system, which has the highest theoretical yield, is the best among the three training systems, and delayed-open central leader training system is the worst.
文摘草原植物光合作用受氮添加和刈割等草原管理措施的影响。依托内蒙古草甸草原的氮添加(0、2、5、10、20和50 g N·m^(-2)·a^(-1))和刈割(刈割和非刈割)交互处理的野外控制试验,测定其优势物种羊草的光合-CO_(2)响应过程。探究直角双曲线模型、非直角双曲线模型、直角双曲线修正模型和Michaelis-Menten模型对叶片光合-CO_(2)响应曲线的拟合效果,以及光合特性对氮添加和刈割的响应。结果表明:非直角双曲线模型拟合的初始羧化效率和光呼吸速率最接近实测值;直角双曲线修正模型对CO_(2)饱和点、CO_(2)补偿点和最大净光合速率的拟合效果最好;直角双曲线修正模型的拟合优度最高;适度氮添加能提高羊草净光合速率、水分利用效率、最大净光合速率、初始羧化效率和CO_(2)饱和点并降低CO_(2)补偿点,提升羊草对CO_(2)的利用效率;随CO_(2)浓度的升高,氮添加浓度为20 g N·m^(-2)·a^(-1)并刈割的羊草净光合速率增幅较大,具有较高的最大净光合速率、CO_(2)饱和点、水分利用效率和较低的CO_(2)补偿点。综上,非直角双曲线模型和直角双曲线修正模型较适用于氮添加和刈割条件下羊草的CO_(2)响应曲线拟合,在内蒙古草原施氮20 g N·m^(-2)·a^(-1)并刈割最有助于提高羊草光合能力,有利于增大生态系统固碳量。
文摘Background:One-hour postprandial hyperglycemia is associated with increased risk of type 2 diabetes and cardiovascular disease.Physical activity(PA)has short-term beneficial effects on post-meal glucose response.This study compared the oral glucose tolerance test results of 3 groups of people with habitually different levels of PA.Methods:Thirty-one adults without diabetes(age 25.9±6.6 years;body mass index 23.8±3.8 kg/m^2;mean±SD)were recruited and divided into 3 groups based on self-reported PA volume and intensity:low activity<30 min/day of moderate-intensity activity(n=11),moderately active≥30 min/day of moderate-intensity PA(n=10),and very active≥60 min/day of PA at high intensity(n=10).Participants completed an oral glucose tolerance test(50 g glucose)with capillary blood samples obtained at baseline,15 min,30 min,45 min,60 min,90 min,and 120 min post-ingestion.Results:There were no significant differences between groups for age or body fat percentage or glycated hemoglobin(p>0.05).The groups were significantly different in terms of baseline glucose level(p=0.003)and,marginally,for gender(p=0.053)and BMI(p=0.050).There was a statistically significant effect of PA on the 1-h postprandial glucose results(p=0.029),with differences between very active and low activity groups(p=0.008)but not between the moderately active and low activity groups(p=0.360),even when baseline glucose level and gender differences were accounted for.For incremental area under the curve there was no significant effect of activity group once gender and body fat percentage had been accounted for(p=0.401).Those in the low activity group took 15 min longer to reach peak glucose level than those in the very active group(p=0.012).Conclusion:The results suggest that high levels of PA have a beneficial effect on postprandial blood glucose profiles when compared to low and moderate levels of activity.
