种植模式和氮肥水平直接影响作物的生长和氮素的吸收,无损、即时监测大豆叶片氮素水平对大豆生产中的氮肥精确管理十分重要。本研究设置4个氮肥水平,分析单作套作下大豆在不同生育时期叶片氮素动态和光谱特征,明确对叶片氮素敏感的光谱...种植模式和氮肥水平直接影响作物的生长和氮素的吸收,无损、即时监测大豆叶片氮素水平对大豆生产中的氮肥精确管理十分重要。本研究设置4个氮肥水平,分析单作套作下大豆在不同生育时期叶片氮素动态和光谱特征,明确对叶片氮素敏感的光谱特征参数,构建单作套作大豆通用的叶片氮素积累量估测模型。结果表明,随大豆生育时期的推进,单作套作种植模式下的大豆冠层叶片氮素积累量均呈现单峰变化趋势,最大值出现在N3处理下的结荚期,两种模式两年最大值平均分别为8.70 g m^(–2)和8.38 g m^(–2);不同生育时期和种植模式的大豆冠层原始反射光谱的变化规律与冠层叶片氮素变化规律均为先增加后降低,原始反射光谱在700~1000 nm波段的反射率以结荚期为拐点先增大后减小,最大反射率达到60%~70%左右;通过对单作套作大豆冠层光谱一阶导数变换,红边幅值呈现先增加后降低的趋势,同时红边位置随叶片氮积累量的增加和减小出现"红移"与"蓝移"现象。经波段自由组合和回归分析表明,以DSI(771、755)构建的线性(y=–1.249+3.209x,R^2=0.847)和乘幂(y=–1.470x^(1.676),R^2=0.872)模型能较精确地估测不同生育时期大豆冠层叶片氮素状况。展开更多
Grain water relations play an important role in grain filling in maize. The study aimed to gain a clear understanding of the changes in grain dry weight and water relations in maize grains by using hybrids with contra...Grain water relations play an important role in grain filling in maize. The study aimed to gain a clear understanding of the changes in grain dry weight and water relations in maize grains by using hybrids with contrasting nitrogen efficiencies under differing nitrogen levels. The objectives were: 1) to understand the changes in dry matter and percent moisture content(MC) during grain development in response to different nitrogen application rates and 2) to determine whether nitrogen application affects grain filling by regulating grain water relations. Two maize hybrids, high N-efficient Zhenghong 311(ZH311) and low N-efficient Xianyu 508(XY508), were grown in the field under four levels of N fertilizer: 0, 150, 300, and 450 kg N ha;during three growing seasons. Dry weight, percent MC and water content(WC) of basal-middle and apical grains were investigated. The difference in the maximum WC and filling duration of basal-middle and apical grains in maize ears resulted in a significant difference in final grain weight. Grain position markedly influenced grain drying down;specifically, the drying down rate of apical grains was faster than that of basal-middle grains. Genotype and grain position both influenced the impact of nitrogen application rate on grain filling and drying down. Nitrogen rate determined the maximum grain WC and percent MC loss rate in the middle and the late grain-filling stages, thus affecting final grain weight. The use of high N-efficient hybrids, combined with the reduction of nitrogen application rate, can coordinate basal-middle and apical grain drying down to ensure yield. This management strategy could lead to a win-win situation in which the maximum maize yield, efficient mechanical harvest and environmental safety are all achieved.展开更多
The antioxidant effects of quercetin were studied in vitro and in vivo.In vitro,vitamin C was used as a positive control to evaluate the antioxidant capacity of quercetin in three aspects:scavenging free radicals,prot...The antioxidant effects of quercetin were studied in vitro and in vivo.In vitro,vitamin C was used as a positive control to evaluate the antioxidant capacity of quercetin in three aspects:scavenging free radicals,protecting biological macromolecules and the total reducing power.In vivo,a total of 240 AA broilers(1-day age)with similar body weight were randomly divided into four groups with six replicates in each group,and 10 broilers in each replicate.The four groups were fed with corn-soybean basal diet supplemented with 0.00%,0.02%,0.04%and 0.06%quercetin to study its effects on antioxidant indexes of AA broilers,and to explore the optimal dose of quercetin as a dietary additive.The results showed that quercetin scavenged superoxide anion,hydroxyl radical and 1,1-diphenyl-2-picrylhydrazyl(DPPH)in vitro,the scavenging effects of quercetin on O_(2)-and•OH first increased and then decreased with the increase of the concentrations(P<0.01),and its maximum scavenging effect was observed at concentrations of 40 and 300 mg·L^(-1).The scavenging effects of quercetin on DPPH was increased constantly with increasing concentrations.The scavenging effect of quercetin on three free radicals was DPPH>•OH>O_(2)-.The inhibition of vitelline lipoprotein peroxidation by quercetin was increased with increasing concentrations(P<0.01)and the inhibitory effect was higher than that of vitamin C.The inhibition of red blood cell hemolysis by quercetin was increased with increasing concentrations at 0.05-1.25 mg·L^(-1)(P<0.01);however,the inhibition tended to decrease when the concentration was too high(31.25 mg·L^(-1)),and the inhibitory effect was higher than that of vitamin C.The inhibition of mitochondrial expansion by quercetin was increased with increasing concentrations,according to the degree of mitochondrial expansion at 60 min,the integrity of mitochondria in the experimental groups was significantly higher than that in the model group(P<0.01).The total reducing power of quercetin was increased with increasing concentrat展开更多
牧区合理载畜量的确定是进行草畜平衡评价的核心工作之一,对指导牧区经济、社会和生态环境的可持续发展具有重要意义。中国西北干旱风沙草原受不合理放牧的影响,草地退化、沙化、盐碱化问题突出,为保护草原生态系统而实施的季节性间歇...牧区合理载畜量的确定是进行草畜平衡评价的核心工作之一,对指导牧区经济、社会和生态环境的可持续发展具有重要意义。中国西北干旱风沙草原受不合理放牧的影响,草地退化、沙化、盐碱化问题突出,为保护草原生态系统而实施的季节性间歇放牧制度使得牧区草畜供需关系进一步复杂化,牧区合理载畜量的确定缺乏有效的计算方法,草畜平衡评价的指导意义不强。该研究选取鄂托克旗牧区作为典型研究区,引入载畜量年内波动系数和草地生产力丰平枯系数2个动态参数,构建了一种基于改进关键场的牧区合理载畜量计算方法,并结合草畜平衡指数(Balance of Grassland and LivestockIndex,BGLI)对鄂托克旗牧区的草畜平衡状况进行了分析。结果表明,干旱风沙草原牧区草畜供需过程非一致性显著,牧业年度内形成了包含5个子过程的动态周期;改进关键场方法充分考虑了这一供需节律匹配关系,对传统和关键场方法进行了改进和完善,其在干旱风沙草原牧区合理载畜量计算中更具适用性,合理载畜量计算结果表明牧区各分区的冷季草场占比过高,现状年桌子山及山前平原分区、都斯图流域分区以及内流河分区的全年合理载畜量分别为8.60、53.49和27.66万羊单位;基于改进关键场方法对鄂托克旗牧区进行草畜平衡评价可知,现状年内流河分区超载最为严重,牧区各草场及全年的BGLI值均在105%左右,桌子山及山前平原分区次之,均在40%以上,而都斯图流域分区草畜平衡状况相对良好。展开更多
文摘种植模式和氮肥水平直接影响作物的生长和氮素的吸收,无损、即时监测大豆叶片氮素水平对大豆生产中的氮肥精确管理十分重要。本研究设置4个氮肥水平,分析单作套作下大豆在不同生育时期叶片氮素动态和光谱特征,明确对叶片氮素敏感的光谱特征参数,构建单作套作大豆通用的叶片氮素积累量估测模型。结果表明,随大豆生育时期的推进,单作套作种植模式下的大豆冠层叶片氮素积累量均呈现单峰变化趋势,最大值出现在N3处理下的结荚期,两种模式两年最大值平均分别为8.70 g m^(–2)和8.38 g m^(–2);不同生育时期和种植模式的大豆冠层原始反射光谱的变化规律与冠层叶片氮素变化规律均为先增加后降低,原始反射光谱在700~1000 nm波段的反射率以结荚期为拐点先增大后减小,最大反射率达到60%~70%左右;通过对单作套作大豆冠层光谱一阶导数变换,红边幅值呈现先增加后降低的趋势,同时红边位置随叶片氮积累量的增加和减小出现"红移"与"蓝移"现象。经波段自由组合和回归分析表明,以DSI(771、755)构建的线性(y=–1.249+3.209x,R^2=0.847)和乘幂(y=–1.470x^(1.676),R^2=0.872)模型能较精确地估测不同生育时期大豆冠层叶片氮素状况。
基金funding support from the National Key Research and Development Program of China(2018YFD0301206,2016YFD0300209,2016YFD0300307,and 2017YFD0301704)。
文摘Grain water relations play an important role in grain filling in maize. The study aimed to gain a clear understanding of the changes in grain dry weight and water relations in maize grains by using hybrids with contrasting nitrogen efficiencies under differing nitrogen levels. The objectives were: 1) to understand the changes in dry matter and percent moisture content(MC) during grain development in response to different nitrogen application rates and 2) to determine whether nitrogen application affects grain filling by regulating grain water relations. Two maize hybrids, high N-efficient Zhenghong 311(ZH311) and low N-efficient Xianyu 508(XY508), were grown in the field under four levels of N fertilizer: 0, 150, 300, and 450 kg N ha;during three growing seasons. Dry weight, percent MC and water content(WC) of basal-middle and apical grains were investigated. The difference in the maximum WC and filling duration of basal-middle and apical grains in maize ears resulted in a significant difference in final grain weight. Grain position markedly influenced grain drying down;specifically, the drying down rate of apical grains was faster than that of basal-middle grains. Genotype and grain position both influenced the impact of nitrogen application rate on grain filling and drying down. Nitrogen rate determined the maximum grain WC and percent MC loss rate in the middle and the late grain-filling stages, thus affecting final grain weight. The use of high N-efficient hybrids, combined with the reduction of nitrogen application rate, can coordinate basal-middle and apical grain drying down to ensure yield. This management strategy could lead to a win-win situation in which the maximum maize yield, efficient mechanical harvest and environmental safety are all achieved.
基金Supposed by the National Natural Science Foundation of China(32072749)。
文摘The antioxidant effects of quercetin were studied in vitro and in vivo.In vitro,vitamin C was used as a positive control to evaluate the antioxidant capacity of quercetin in three aspects:scavenging free radicals,protecting biological macromolecules and the total reducing power.In vivo,a total of 240 AA broilers(1-day age)with similar body weight were randomly divided into four groups with six replicates in each group,and 10 broilers in each replicate.The four groups were fed with corn-soybean basal diet supplemented with 0.00%,0.02%,0.04%and 0.06%quercetin to study its effects on antioxidant indexes of AA broilers,and to explore the optimal dose of quercetin as a dietary additive.The results showed that quercetin scavenged superoxide anion,hydroxyl radical and 1,1-diphenyl-2-picrylhydrazyl(DPPH)in vitro,the scavenging effects of quercetin on O_(2)-and•OH first increased and then decreased with the increase of the concentrations(P<0.01),and its maximum scavenging effect was observed at concentrations of 40 and 300 mg·L^(-1).The scavenging effects of quercetin on DPPH was increased constantly with increasing concentrations.The scavenging effect of quercetin on three free radicals was DPPH>•OH>O_(2)-.The inhibition of vitelline lipoprotein peroxidation by quercetin was increased with increasing concentrations(P<0.01)and the inhibitory effect was higher than that of vitamin C.The inhibition of red blood cell hemolysis by quercetin was increased with increasing concentrations at 0.05-1.25 mg·L^(-1)(P<0.01);however,the inhibition tended to decrease when the concentration was too high(31.25 mg·L^(-1)),and the inhibitory effect was higher than that of vitamin C.The inhibition of mitochondrial expansion by quercetin was increased with increasing concentrations,according to the degree of mitochondrial expansion at 60 min,the integrity of mitochondria in the experimental groups was significantly higher than that in the model group(P<0.01).The total reducing power of quercetin was increased with increasing concentrat
文摘牧区合理载畜量的确定是进行草畜平衡评价的核心工作之一,对指导牧区经济、社会和生态环境的可持续发展具有重要意义。中国西北干旱风沙草原受不合理放牧的影响,草地退化、沙化、盐碱化问题突出,为保护草原生态系统而实施的季节性间歇放牧制度使得牧区草畜供需关系进一步复杂化,牧区合理载畜量的确定缺乏有效的计算方法,草畜平衡评价的指导意义不强。该研究选取鄂托克旗牧区作为典型研究区,引入载畜量年内波动系数和草地生产力丰平枯系数2个动态参数,构建了一种基于改进关键场的牧区合理载畜量计算方法,并结合草畜平衡指数(Balance of Grassland and LivestockIndex,BGLI)对鄂托克旗牧区的草畜平衡状况进行了分析。结果表明,干旱风沙草原牧区草畜供需过程非一致性显著,牧业年度内形成了包含5个子过程的动态周期;改进关键场方法充分考虑了这一供需节律匹配关系,对传统和关键场方法进行了改进和完善,其在干旱风沙草原牧区合理载畜量计算中更具适用性,合理载畜量计算结果表明牧区各分区的冷季草场占比过高,现状年桌子山及山前平原分区、都斯图流域分区以及内流河分区的全年合理载畜量分别为8.60、53.49和27.66万羊单位;基于改进关键场方法对鄂托克旗牧区进行草畜平衡评价可知,现状年内流河分区超载最为严重,牧区各草场及全年的BGLI值均在105%左右,桌子山及山前平原分区次之,均在40%以上,而都斯图流域分区草畜平衡状况相对良好。
