Na2SO4胁迫对沙枣幼苗生长和光合生理的影响

采用盆栽控制试验,研究了不同浓度(0、60、120和180 mmol·L-1)Na2SO4胁迫对沙枣幼苗生长和光合特性的影响。结果表明:(1)盐胁迫对沙枣幼苗生长具有显著的抑制效应。不同浓度Na2SO4胁迫沙枣的株高、侧枝数、总叶面积、单株叶片数、比叶面积以及各组织(除根)生物量均显著低于对照,且均随盐胁迫浓度的升高呈下降趋势,而根冠比值则由对照的0.153 1显著增加到180 mmol·L-1Na2SO4胁迫幼苗的0.348 7。(2)盐胁迫显著降低了沙枣幼苗的光合能力。随着Na2SO4胁迫的加剧,净光合速率(Pn)、气孔导度(Gs)、胞间CO2浓度(Ci)和蒸腾速率(Tr)均呈下降的趋势,而气孔限制值(Ls)和水分利用效率(WUE)则依次增加,且Pn下降主要受气孔限制;180 mmol·L-1Na2SO4胁迫沙枣幼苗的Pn、Gs、Ci和Tr分别为对照的71.57%、30.85%、67.15%和51.65%,而Ls和WUE则分别为对照的1.91、1.38倍。(3)盐胁迫强度与幼苗株高、总叶面积、单株叶片数、比叶面积、茎生物量、叶生物量、总生物量等生长指标以及Pn、Gs、Ci、Tr等光合参数呈极显著负相关,叶片的光合参数与总叶面积、单株叶片数呈显著或极显著正相关,而叶片的生长指标、光合参数与幼苗的株高生长和生物量累积也呈显著或极显著正相关。     

Structure analysis of water-soluble polysaccharide CPPS3 isolated from Codonopsis pilosula

Codonopsis pilosula is a perennial species of flowering plants propagated in Northeast Asia. A water-soluble polysaccharide, CPPS₃, was extracted from the root of Codonopsis pilosula by boiled water extraction and ethanol precipitation. The molecular weight was estimated to be 7.4 × 10⁴ Da determined by using Gel permeation chromatography. Monosaccharide composition and the structure of the polysaccharide were determined by gas spectroscopy, Fourier transform IR (FT-IR) spectroscopy, NMR spectroscopy and mass spectroscopy and some chemical method analysis was made. The components were galactose, arabinose and rhamnose in the molar ratio of 1.13:1.12:1. The main chain of CPPS₃ is illustrated to be (1→3)-linked-β-GalpNAc, (1→3)-linked-α-Rhap and (1→2,3)-β-Galp.     

O_3胁迫对三种楠木幼苗光合作用的影响及伤害症状

[目的]随着全球O_3浓度升高,O_3胁迫对植物影响的研究已成为研究的热点之一。我国的相关研究较少,主要以农作物为主,且大多局限在北方地区。本研究探讨O_3胁迫下,亚热带三种楠木幼苗光合作用的变化规律及其可见伤害症状,以期为后续研究提供理论依据。[方法]以一年生亚热带乡土树种桢楠、闽楠和刨花楠幼苗为材料,采用开顶式气室(OTCs),研究低浓度O_3、环境大气、100 n L·L-1O_3、150 n L·L-1O_3处理对光合作用的影响及伤害症状。[结果]研究表明:(1)O_3胁迫下,三种楠木幼苗的光合作用受到一定的抑制,气孔导度和净光合速率的相关性降低,对光合有效辐射的利用范围整体减小,出现了明显的光抑制现象。O_3浓度越高,对桢楠和刨花楠光合作用的抑制效果越明显,而100 n L·L-1O_3处理对闽楠光合作用的抑制效果较150 n L·L-1O_3处理明显。环境大气中的O_3浓度均值较低,但由于其较高的O_3浓度峰值,仍对三种楠木幼苗的光合作用产生了一定的抑制。与环境大气相比,低浓度O_3处理通过消除较高的O_3浓度峰值从而缓解了O_3对光合作用的不利影响。(2)O_3胁迫下,桢楠叶片出现褪绿、黄斑和坏死斑的症状,闽楠叶片出现褪绿、黄斑和水渍的症状,刨花楠叶片出现红褐色斑、水渍、坏死斑、卷曲皱缩、失水萎蔫的症状。三种楠木幼苗叶片的伤害症状随O_3浓度的增加而更明显。[结论]三种楠木幼苗叶片的光合作用均受到O_3的抑制,并出现了伤害症状,可作为O_3污染的指示树种。光合作用对O_3敏感性的关系为:刨花楠闽楠桢楠,其中刨花楠对O_3更敏感,伤害症状也较多样,因此指示O_3污染的效果更好。     

地涌金莲及红苞地涌金莲对光和CO2的响应

比较分析了地涌金莲原种及红苞地涌金莲变种的光响应和CO2响应特征以及叶绿素含量等指标.结果表明:(1)在Pn-PAR中,地涌金莲原种的最大光饱和净光合速率、光补偿点和暗呼吸速率分别较红苞变种高20.42％、34.88％、31.95％,而光饱和点却较红苞变种低4.95％;Pn-Ci响应的各参数中,原种的光呼吸速率、CO2饱和最大净光合速率以及羧化效率分别高于红苞变种2.73％、14.79％、21.35％,说明地涌金莲的光合能力要强于红苞地涌金莲;(2)地涌金莲具有典型的C3植物特征;(3)地涌金莲为阳性耐荫植物;(4)地涌金莲的叶绿素a、b以及a/b的含量分别高于红苞地涌金莲22.60％、32.46％、25.06％.     

Effects of winter selective tree harvest on soil microclimate and surface CO2 flux of a northern hardwood forest

Soil surface CO₂ flux (S_flux) is the second largest terrestrial ecosystem carbon flux, and may be affected by forest harvest. The effects of clearcutting on S_flux have been studied, but little is known about the effect of alternative harvesting methods such as selective tree harvest on S_flux. We measured S_flux before and after (i) the creation of forest canopy gaps (simulating group tree selection harvests) and (ii) mechanized winter harvest but no tree removal (simulating ground disturbance associated with logging). The experiment was carried out in a sugar maple dominated forest in the Flambeau River State Forest, Wisconsin. Pre-treatment measurements of soil moisture, temperature and S_flux were measured throughout the growing season of 2006. In January–February 2007, a harvester created the canopy gaps (200–380 m²). The mechanization treatment consisted of the harvester traveling through the plots for a similar amount of time as the gap plots, but no trees were cut. Soil moisture and temperature and S_flux were measured throughout the growing season for 1 year prior to harvest and for 2 years after harvest. Soil moisture and temperature were significantly greater in the gap than mechanized and control treatments. Instantaneous S_flux was positively correlated to soil moisture and soil temperature at 2 and 10 cm, but temperature at 10 cm was the single best predictor. Annual S_flux was not significantly different among treatments prior to winter 2007 harvest, and was not significantly different among treatments after harvest. Annual (+1 std. err.) S_flux averaged 967 + 72, 1011 + 72, and 1012 + 72 g C m⁻² year⁻¹ in the control, mechanized and gap treatments, respectively, for the 2-year post-treatment period. The results from this study suggest selective group tree harvest significantly increases soil moisture and temperature but does not significantly influence S_flux.     

The effect of safranal on histamine (H1) receptors of guinea pig tracheal chains

The effect of three concentrations of safranal on histamine (H₁) receptors was tested on two groups of tracheal chains incubated with: 1) indomethacin, and 2) indomethacin, propranolol and atropine (n = 6). The EC₅₀ (effective concentration of histamine causing 50% of maximum response) obtained in the presence of chlorpheniramine and all concentrations of safranal in both groups were significantly greater than those of saline (p < 0.05 to p < 0.001). The EC₅₀ obtained in the presence of all concentrations of safranal and maximum response of its two higher concentrations (1.25 and 2.5 μg/mL) in group 2 were greater than in group 1 (p < 0.05 to p < 0.001).     

Soil CO2 efflux in an Afromontane forest of Ethiopia as driven by seasonality and tree species

Variability of soil CO₂ efflux strongly depends on soil temperature, soil moisture and plant phenology. Separating the effects of these factors is critical to understand the belowground carbon dynamics of forest ecosystem. In Ethiopia with its unreliable seasonal rainfall, variability of soil CO₂ efflux may be particularly associated with seasonal variation. In this study, soil respiration was measured in nine plots under the canopies of three indigenous trees (Croton macrostachys, Podocarpus falcatus and Prunus africana) growing in an Afromontane forest of south-eastern Ethiopia. Our objectives were to investigate seasonal and diurnal variation in soil CO₂ flux rate as a function of soil temperature and soil moisture, and to investigate the impact of tree species composition on soil respiration. Results showed that soil respiration displayed strong seasonal patterns, being lower during dry periods and higher during wet periods. The dependence of soil respiration on soil moisture under the three tree species explained about 50% of the seasonal variability. The relation followed a Gaussian function, and indicated a decrease in soil respiration at soil volumetric water contents exceeding a threshold of about 30%. Under more moist conditions soil respiration is tentatively limited by low oxygen supply. On a diurnal basis temperature dependency was observed, but not during dry periods when plant and soil microbial activities were restrained by moisture deficiency. Tree species influenced soil respiration, and there was a significant interaction effect of tree species and soil moisture on soil CO₂ efflux variability. During wet (and cloudy) period, when shade tolerant late successional P. falcatus is having a physiological advantage, soil respiration under this tree species exceeded that under the other two species. In contrast, soil CO₂ efflux rates under light demanding pioneer C. macrostachys appeared to be least sensitive to dry (but sunny) conditions. This is probably related to the relatively higher carbon assimilation rates and associated root respiration. We conclude that besides the anticipated changes in precipitation pattern in Ethiopia any anthropogenic disturbance fostering the pioneer species may alter the future ecosystem carbon balance by its impact on soil respiration.     

非生长季刺槐林土壤CH4通量的变化特征及其影响因子

[目的]探讨在非生长季不同天气条件下45年生刺槐林土壤CH₄通量的日变化和季节变化特征,并确定其主要影响因子.[方法]2014年10月-2015年4月(非生长季),在华北低山丘陵区黄河小浪底森林生态系统定位研究站,利用基于离轴积分腔输出光谱技术的土壤CH₄通量自动观测系统,对土壤CH₄通量进行连续观测,同步观测林内大气温度和相对湿度、5 cm深处土壤温度和土壤湿度、林内总辐射以及降雨量,分析各因子间的相互关系并确定影响土壤CH₄通量的主要因子.[结果]表明:(1)在非生长季,刺槐人工林土壤为大气CH₄重要的汇,变化范围为-0.15~-2.34 nmol·m^-2·s^-1 .晴天的林地土壤吸收CH₄能力 (-0.78 nmol·m^-2·s^-1) 明显高于阴天(-0.61 nmol·m^-2·s^-1)、降雨或降雪天气 (-0.58 nmol·m^-2·s^-1),而且呈"V"型日际变化特征;在2014年11月-2015年1月,土壤吸收CH₄能力逐渐下降,并维持相对较低的水平,直至2015年3月达到最大值 (-2.34 nmol·m^-2·s^-1);(2)土壤CH₄通量与大气温度、5 cm深处土壤温度呈显著负相关,与相对湿度呈正相关;在2015年1月,土壤CH₄通量与总辐射呈正相关;(3)在生长末期土壤上冻阶段和冬季土壤冻结阶段,大气温度和相对湿度为影响土壤CH₄通量的主要因子;而在生长季初期,主要的影响因子为大气温度和5 cm深处土壤温度.[结论]非生长季刺槐林土壤表现为大气CH₄的汇,在非生长季初期土壤吸收CH₄的能力最弱,主要受大气温度和相对湿度的影响,而在非生长季末期土壤吸收CH₄的能力逐渐增加,主要受大气温度和土壤温度的影响.     

郑州市数码公园不同植物群落对PM2.5和PM10浓度的影响研究

以郑州市数码公园为例,研究不同植物群落对大气颗粒物污染的影响。2020年4月—2021年3月,监测郑州市数码公园内不同植物群落结构(乔灌草、乔草、乔灌、灌草、草坪)在春夏秋冬四季的PM_2.5和PM₁₀浓度以及温度、湿度和风速等气象因子,分析不同植物群落PM_2.5、PM₁₀浓度的变化规律,并研究其与气象因子的相关性。研究结果表明,不同样地内PM_2.5和PM₁₀浓度日变化基本一致,呈早高晚低趋势。不同样地内PM_2.5和PM₁₀浓度均表现为秋冬季高,春夏季低;PM_2.5和PM₁₀浓度高低依次为草坪和广场样地>灌草和乔草结构样地>乔灌草和乔灌结构样地;复合群落结构绿地对颗粒物滞尘能力大于单一群落结构。乔灌草、乔灌结构样地对PM_2.5和PM₁₀的阻滞率较高。PM_2.5和PM₁₀浓度...     

大气中O3与CO2浓度升高对植物影响研究进展

由于工业的快速发展,大气中的O₃和CO₂浓度有逐年上升的趋势,对植物产生了很大的影响。目前,植物对O₃和CO₂浓度变化的复合作用的响应机制研究已经成为生态学研究的热点问题。文中阐述了O₃和CO₂浓度升高及其复合作用对植物的形态特征、光合作用、抗氧化系统及生物量等生理生化机制的影响,指出目前研究中存在并有待进一步研究的问题,以期为进一步开展高浓度O₃和CO₂对植物生理生态学影响研究提供科学参考和理论依据。     

Effects of [CO2] and nitrogen on morphological and biomass traits of white birch (Betula papyrifera) seedlings

To investigate the interactive effects of CO₂ concentration ([CO₂]) and nitrogen supply on the growth and biomass of boreal trees, white birch seedlings (Betula papyrifera) were grown under ambient (360 μmol mol⁻¹) and elevated [CO₂] (720 μmol mol⁻¹) with five nitrogen supply regimes (10, 80, 150, 220, and 290 μmol mol⁻¹) in greenhouses. After 90 days of treatment, seedling height, root-collar diameter, biomass of different organs, leaf N concentration, and specific leaf area (SLA) were measured. Significant interactive effects of [CO₂] and N supply were found on height, root-collar diameter, leaf biomass, stem biomass and total biomass, stem mass ratio (SMR), and root mass ratio (RMR), but not on root mass, leaf mass ratio (LMR), leaf to root ratio (LRR), or leaf N concentration. The CO₂ elevation generally increased all the growth and biomass parameters and the increases were generally greater at higher levels of N supply or higher leaf N concentration. However, the CO₂ elevation significantly reduced SLA (13.4%) and mass-based leaf N concentration but did not affect area-based leaf N concentration. Increases in N supply generally increased the growth and biomass parameters, but the relationships were generally curvilinear. Based on a second order polynomial model, the optimal leaf N concentration was 1.33 g m⁻² for height growth under ambient [CO₂] and 1.52 g m⁻² under doubled [CO₂]; 1.48 g m⁻² for diameter under ambient [CO₂] and 1.64 g m⁻² under doubled [CO₂]; 1.29 g m⁻² for stem biomass under ambient [CO₂] and 1.43 g m⁻² under doubled [CO₂]. The general trend is that the optimal leaf N was higher at doubled than ambient [CO₂]. However, [CO₂] did not affect the optimal leaf N for leaf and total biomass. The CO₂ elevation significantly increased RMR and SMR but decreased LMR and LRR. LMR increased and RMR decreased with the increasing N supply. SMR increased with increase N supply up to 80 μmol mol⁻¹ and then leveled off (under elevated [CO₂]) or stated to decline (under ambient [CO₂]) with further increases in N supply. The results suggest that the CO₂ elevation increased biomass accumulation, particularly stem biomass and at higher N supply. The results also suggest that while modest N fertilization will increase seedling growth and biomass accumulation, excessive application of N may not stimulate further growth or even result in growth decline.     

新疆额尔齐斯河流域苦杨与欧洲黑杨遗传多样性分析

应用SSR标记技术,对新疆额尔齐斯河流域河谷分布的苦杨(Populus laurifoli)和欧洲黑杨(Populus nigra)天然居群的遗传多样性和遗传分化进行了研究。结果显示:苦杨和欧洲黑杨的天然居群具有较高的遗传多样性,且苦杨明显高于欧洲黑杨。与苦杨居群相比,欧洲黑杨居群间基因流较高,居群间的遗传分化程度较小,变异主要源于居群内。苦杨和欧洲黑杨居群内的杂合度较高,各个居群的各项遗传参数都要小于物种水平。苦杨和欧洲黑杨均偏离Hardy-Weinberg平衡,表现为杂合子过量的现象。     

30个桉树无性系人工林碳储量分析

通过对国营雷州林业局30个5年生桉树无性系人工林的调查、试验,旨在阐明不同桉树无性系人工林碳储量的变化规律及营建桉树碳汇林的合理措施.结果表明:30个桉树无性系人工林生态系统平均碳储量为148.743 t·hm-2,高于之前学者研究的桉树人工林碳储量,其中,乔木层和土壤层分别占34.39％、61.88％;乔木层平均碳储量达51.948 t·hm-2,不同无性系间差异极显著(p＜0.01),其中,23(101-1)、25(179-1)、4(BU1)、26(184-1)号无性系表现最优;土壤层的平均碳储量为92.033 t·hm-2,不同无性系土壤层碳储量差异不明显;灌木层、草本层、凋落物层碳储量分别是2.430、0.731、1.592 t·hm-2,占比例较小.营建桉树碳汇林关键在于无性系的正确选择.     

Comparison of soil CO2 flux between uncleared and cleared windthrow areas in Estonia and Latvia

Storms can turn a great proportion of forests’ assimilation capacity into dead organic matter because of windthrow and thus its role as a carbon sink will be diminished for some time. However, little is known about the magnitude or extent to which storms affect carbon efflux. We compared soil CO₂ fluxes in wind-thrown forest stands with different time periods since a storm event, and with different management practices (deadwood cleared or left on-site). This study examined changes in soil CO₂ efflux in two windthrow areas in north-eastern Estonia and one area in north-western Latvia, which experienced severe wind storms in the summers of 2001, 2002 and 1967, respectively. We measured soil CO₂ fluxes in stands formerly dominated by Norway spruce (Picea abies L. Karst.) with total and partial canopy destruction (all trees or roughly half of the trees in stand damaged by storm), in harvested areas (material removed after the wind storm) and in control areas (no damage by wind). Removal of wind-damaged material decreased instantaneous CO₂ flux from the soil surface. The highest instantaneous fluxes were measured in areas with total and partial canopy destruction (0.67 g CO₂ m⁻² h⁻¹ in both cases) compared with fluxes in the control areas (0.51 g CO₂ m⁻² h⁻¹), in the new storm-damaged areas where the material was removed (0.57 g CO₂ m⁻² h⁻¹) and in the old storm-damaged area where wood was left on site (0.55 g CO₂ m⁻² h⁻¹). The only factor affecting soil CO₂ flux was location of the measuring collar (plastic collar with diameter 100 mm, height 50 mm) - either on undamaged forest ground or on the uprooted tree pit, where the mineral soil was exposed after disturbance. New wind-thrown stands where residues are left on site would most likely turn to sources of CO₂ for several years until forest regeneration reaches to substantial assimilation rates. New wind-thrown stands where residues are left on site would most likely tend to have elevated CO₂ fluxes for several years until forest regeneration reaches to substantial assimilation rates. However, forest managers might be concerned about the amounts of CO₂ immediately released into the atmosphere if the harvested logs are burned.     

Seasonal soil CO2 efflux dynamics after land use change from a natural forest to Moso bamboo plantations in subtropical China

Moso bamboo plantations (Phyllostachys pubescens) are one of the most important forest types in southern China, but there is little information on the effects of their establishment and silvicultural practices on soil CO₂ efflux. The objectives of this study were to evaluate the effect of land use change from a natural broadleaf evergreen forest to Moso bamboo plantations and their management practices on soil CO₂ efflux in a subtropical region of China using static closed chamber method. Regardless of the land uses or management practices, the effluxes over a 12-month period had a seasonal pattern, with the maximum effluxes observed in summer and the minimum in winter. Whereas there was no significant difference in the total annual soil CO₂ efflux between the natural broadleaf evergreen forest (BL) and the conventionally managed bamboo forests (CM), soil CO₂ efflux in the intensively managed bamboo forest (IM) was significantly higher. Soil temperature was the most important environmental factor affecting soil CO₂ efflux rates for all three land uses. Soil moisture also had a significant positive correlation with soil CO₂ efflux rates. Soil temperature and moisture had greater influence on soil CO₂ efflux rate in the IM than the CM and BL forests. Soil dissolved organic C had a positive correlation with soil CO₂ efflux rate in the CM, but had no significant correlation with that in the IM or the BL forests. Our study for the first time demonstrated that conversion of the natural subtropical broadleaf evergreen forest to Moso bamboo does not increase soil CO₂ efflux. However, when bamboo forests are under intensive management with regular tillage, fertiliser application and weeding, significantly more soil CO₂ emission occurs. Therefore, best management practices should be developed to reduce soil CO₂ efflux in Moso bamboo plantations in the subtropical regions of China.     

O_3浓度升高对桢楠和闽楠幼苗光合作用、抗氧化能力及生物量的影响

[目的]探讨O_3浓度升高对两种亚热带树木幼苗的影响,并分析其敏感性差异及原因。[方法]本试验以1年生桢楠和闽楠幼苗为材料,采用开顶式气室(OTCs),研究未过滤大气、100 nmol·mol-1(E1)、150 nmol·mol-1(E2)O_3处理对光合作用、抗氧化能力和生物量的影响。[结果]研究表明:(1) O_3熏蒸主要通过非气孔限制因素降低了两树种的净光合速率(Pn)。其中对于桢楠,E2对Pn的不利影响大于E1。而对于闽楠,8月份E2的Pn大于E1,而9月份和10月份小于E1。(2) O_3熏蒸提高了两树种的抗氧化能力,表现为总酚含量和总抗氧化能力随着O_3浓度的升高逐渐升高,而E2的还原型抗坏血酸含量低于E1。(3) O_3熏蒸降低了两树种根、茎、叶及总干质量,及降低了闽楠的根茎比。[结论]O_3熏蒸降低了两树种的光合作用,提高了抗氧化能力,最终减少了生物量。根据Pn和生物量,确定闽楠较桢楠对O_3浓度升高更加敏感。两树种间的O_3敏感性差异与气孔导度和抗氧化物质的背景水平及其对O_3浓度升高的响应有关。     

Triterpenes and steroids from the leaves of Aglaia exima (Meliaceae)

A study on the leaves of Aglaia exima led to the isolation of one new and seven known compounds: six triterpenoids and two steroids. Their structures were elucidated and analyzed mainly by using spectroscopic methods; 1D and 2D NMR, mass spectrometry, UV spectrometry and X-ray. All the triterpenoids and steroids were measured in vitro for their cytotoxic activities against eight cancer cell lines; lung (A549), prostate (DU-145), skin (SK-MEL-5), pancreatic (BxPC-3), liver (Hep G2), colon (HT-29), breast (MCF-7) and (MDA-MB-231). The new cycloartane triterpenoid, 24(E)-cycloart-24-ene-26-ol-3-one 1, showed potent cytotoxic activity against colon (HT-29) cancer cell line (IC₅₀ 11.5 μM).     

赣县稀土采矿区巨桉林地土壤抗蚀性评价

通过野外调查与室内分析相结合,应用主成分分析法,从衡量土壤抗蚀性的16个指标中,优化得到赣县稀土采矿区巨桉林地土壤抗蚀性7个最佳评价指标：分散系数（X₁）、团聚度（X₂）、>0.25 mm水稳性团聚体含量（X₃）、>0.5 mm水稳性团聚体含量（X₄）、<0.05 mm粉黏粒含量（X₅）、>0.25 mm团聚体破坏率（X₆）和<0.001 mm黏粒含量（X₇）,并以此为变量分析比较不同林龄巨桉林地土壤抗蚀性变化规律。结果表明：不同林龄巨桉林地土壤抗蚀性综合指数大小为：1年生林地>2年生林地>4年生萌芽1 a林地>裸露地。在此基础上,以上述7个评价指标为自变量,以土壤抗蚀性综合指数（Y）为因变量,进行回归分析,得出稀土采矿区土壤抗蚀性综合评价方程为：Y=0.309 X₁+0.038 X₂ -0.161 X₃ -0.643 X₄ +0.491 X₅ -0.032 8 X₆ +0.129 X₇ +41.637,因子决定系数R²=0.991 5,F=49.84,各因子间显著相关,方程拟合较好,可为构建稀土采矿区土壤抗蚀性评价指标体系提供依据。     

12个楸树无性系叶片多酚含量与抗氧化活性

自由基具有强氧化性,机体衰老及多种疾病如肿瘤、炎症、神经退行性疾病、动脉粥样硬化等的诱发促进机制都与自由基有关[1]。自由基的减少,不仅要靠自身的清除系统,还需要外部抗氧化剂的协助。近年来,关于合成抗氧化剂的副作用受到人们更多的关注,因此,寻找安全、高效的植物源类抗氧化剂,已成为食品领域研究的热点。楸树(Catalpa bungei C.A.Mey.)为紫葳科(Bignoniaceae)梓属植物,落叶乔木,《本草纲目》记载楸树树皮、叶具有药     

MALDI-TOF/MS analyses of decomposition behavior of beech xylan as treated by semi-flow hot-compressed water

Japanese beech (Fagus crenata) was treated with semi-flow hot-compressed water at various temperatures of 150–230 °C under 10 MPa. The obtained various products were then analyzed with matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF/MS). In a temperature range of 150 °C up to 210 °C, however, no hydrolyzed products were found, and at 210 °C/10 MPa, O-acetyl-4-O-methylglucuronoxylo-oligosaccharides (X _n Ac _m MG _i ) and O-acetyl-xylo-oligosaccharides (X _n Ac _m ) were obtained, indicating the first cleavage of native xylan β-1,4-glycosidic linkages followed by a cleavage of α-1,2-glycosidic linkage in 4-O-methylglucuronic acid (MG) residue at mainly 220–230 °C under 10 MPa. At subsequent stage of 230 °C/10 MPa, X _n Ac _m were predominantly recovered. As the treatment was prolonged at 230 °C, X _n Ac _m were reduced, but remained to some extent, indicating that the acetyl group which is hydrolyzed to be acetic acid is more resistant than MG residue. In such a stage of treatment, cellulose started to hydrolyze to cello-oligosaccharides. These lines of evidence can clearly indicate the hydrolysis pathway of native O-acetyl-4-O-methylglucuronoxylan as treated by hot-compressed water. Thus, xylo-oligosaccharides recovered in a very early stage of the semi-flow hot-compressed water treatment preserve native O-acetyl-4-O-methylglucuronoxylan.