Leaf non-structural carbohydrates and leaf dry weight per area in three altitudinal populations ofEspeletia schultzii WEDD

The leaf non-structural carbohydrate (NSC) content and total non-structural carbohydrate content (TNC) were measured on a dry weight basis and on a leaf area basis in three altitudinal (3100, 3550 and 4200 m a.s.l.) populations ofE. schultzii. The values of leaf dry weight per area (LWA) increase with altitude. The leaf non-structural carbohydrate content (expressed as g/kg dry weight) does not show statistically significant difference among populations, but the values expressed on an area basis (g/m²) show a statistically significant increase with altitude. Significant correlations were observed between LWA and TNC (r ²=0.65); insoluble carbohydrate (r ²=0.78); total soluble carbohydrate (r ²=0.53); reducing sugars (r ²=0.47) expressed on area basis. Correlations between LWA and NSC for any fraction and TNC on a dry weight basis were not significant. It appears that along this altitudinal gradient the leaf area is more affected than the leaf dry weight. Since the NSC is known to play a role in the freezing tolerance of plants, the results indicate that the freezing tolerance does not change among the populations along the gradient.     

5个温带树种冠层枝叶非结构性碳水化合物浓度的空间变异

非结构性碳水化合物(NSC)是树木存活和生长的重要能源物质。冠层NSC不但是全树NSC的来源,也是全树NSC的重要储存库。然而,冠层NSC空间变异的研究较少,因而影响了树木NSC分配的估算精度。以红松(Pinus koraiensis)、兴安落叶松(Larix gmelinii)、水曲柳(Fraxinus mandshurica)、蒙古栎(Quercus mongolica)和白桦(Betula platyphylla)5个温带树种为研究对象,测定了不同高度冠层叶和细枝(直径≤3 cm)NSC浓度,分析了粗枝(一级侧枝)枝皮、边材和心材NSC浓度轴向变化及其与枝径的关系。结果表明:(1)除了5月末兴安落叶松树冠中层叶淀粉浓度显著高于树冠下层,以及8月中旬树冠上层叶可溶性糖浓度显著高于树冠中层之外,其他树种冠层叶NSC浓度的垂直变化不显著。常绿树种红松叶龄对NSC浓度的影响在生长季中期显著,但在生长季末期和休眠季节的影响不显著。(2)除了5月末红松树冠上层细枝可溶性糖浓度显著高于树冠中层之外,其他树种不同高度冠层间细枝NSC浓度差异不显著。(3)在纵向上,阔叶树种蒙古栎、水曲柳和白桦粗枝的枝皮、边材和心材NSC浓度多随着距树枝基部距离的增加而升高;在径向上,NSC浓度(除了水曲柳边材淀粉和白桦枝皮淀粉之外)多随着枝径增加而降低,表明树枝中的NSC浓度随着远离碳源而降低。总体上,5个温带树种冠层叶、细枝NSC浓度的空间变异不显著,但枝径和叶龄对NSC浓度的影响因树种、组织和季节而异,这在未来研究中应予考虑。     

高寒草甸小嵩草种群繁殖生态学研究

研究从繁殖生态学的角度对高寒草甸小嵩草（Kobresia pygmaea)种群进行了初步研究。结果表明：小嵩草属寒冷中生密丛短根茎地下芽植物,在高寒生境中采用以营养繁殖为主、有性繁殖为辅的繁策略,具体体现在以下几个方面：虽然小嵩草种子产量达4553.8粒／m^2,但种子萌发率较低,室内和野外萌发率分别仅有4％和1％,经氢氧化钠溶液和赤霉素溶液处理后的种子萌发率分别为1％和2％,而削去种皮后种子萌发率达52．6％,种皮坚硬是造成种子萌发率低的主要原因;进入种子库、保留至返青期且具有活性的种子仅占种子总数的24．35％,其室内萌发率仅有3％,而在野外理论实生苗仅为11．09个／m^2,与此相反小嵩草营养繁殖所形成的新个体数为6256．25个／m^2,远远多于种子萌发所形成的实生苗数。此外,小嵩草营养繁殖效力也远高于有性繁殖效力,营养繁殖效力占总繁殖效力的90．92％。     

高原鼠兔对小嵩草草甸的破坏及其防治

1997～2000 年在青海省果洛州达日县, 通过测定不同程度退化草地、人工草地和除杂草地中高原鼠兔种群数量的变化以及对草地的破坏程度, 分析了草地植物群落变化对高原鼠兔种群数量的影响。结果表明: 随草地退化程度的加重, 高原鼠兔种群数量相应升高, 重度退化草地中高原鼠兔种群数量降低, 是由食物资源不足引起。不同程度退化草地之间高原鼠兔种群数量差异极显著( t_{未退化与轻度}= 25.369 7 , t_{未退化与中度}= 25.55 ,t_{未退化与重度}= 36.406 0 , t_{轻度与中度}= 23.279 4 , t_{轻度与重度}= 14.343 9 , t_{中度与重度}= 20.178 5 , df = 3 , p < 0.001) 。高原鼠兔对草地的破坏面积与平均单坑面积呈显著的相关关系( F = 220146 , df = 3 , P < 0.001) 。在草地达到重度退化以前, 高原鼠兔的种群密度升高, 对草地的危害则加重。草地植物群落空间结构的变化直接影响高原鼠兔的种群数量, 当植物群落高度增加时, 其种群数量开始减少, 反之则增加。     

不同退化程度高寒草甸高山嵩草的构件变化

对不同退化程度下高山嵩草的构件变化进行了初步研究.结果表明:随着退化程度的加剧,高山嵩草无性系复合主分蘖数、单分蘖数以及构件的叶片数均明显下降,退化程度加剧不利于高山嵩草的营养生长;除极度退化草地外,其余样地各构件的生物量大小依次是:根茎>根>叶>秆,并且随退化程度的加剧,各构件生物量显著下降;重度退化草地中,莎草科植物生殖枝数占植物群落总生殖枝的比例最大,每个有效生殖枝平均产生3.4粒种子.     

Mixed reproduction strategy and polyploidy facilitate dominance of Kobresia pygmaea on the Tibetan Plateau

Aims The sedge Kobresia pygmaea is the dominant species of high-altitude pastures in Tibet, and it is the most important source of forage in animal husbandry. We present the first comprehensive reproduction study for this perennial key species that adopts a molecular approach and tests how sexual and vegetative reproduction, as well as ploidy, relate to survival and dominance under harsh conditions.Methods We assessed inflorescence numbers of K. pygmaea across two Tibetan alpine pastures with differing grazing regimes. Germination was tested in untreated diaspores and then following mechanical and chemical scarification. In a 4-year experiment, we assessed diaspore viability and seed bank formation. Using eight microsatellite markers, we recorded multilocus genotypes in hierarchical grids and measured their ploidy using flow cytometry. Adjusted analysis of variance models were used to analyse data on sexual reproduction, while the complement of the Simpson index and the Shannon diversity index were used to characterize the spatial distribution of multilocus genotypes and clonal richness.Important findings Inflorescence production was high and differed significantly between years (2010: 617±460 SD; 2012: 2015±1213 SD) but not between grazing regimes. Diaspore viability was high (94%) and gradually decreased after 3 and 4 years of storage in the soil. Diaspores not exposed to further scarification failed to germinate, while mechanical and chemical (H 2 SO 4) scarification increased germination to 9 and 44%, respectively. Clonal diversity was high, although in situ germination was rarely observed. Multilocus genotypes intersected and covered a mean area of 0.74 m 2. Most individuals were found to be tetraploid, with only 0.8% of all ramets being triploid. We conclude that K. pygmaea survives on the Tibetan Plateau by employing a mixed reproduction strategy involving both sexual and clonal propagation. The species' adaptability and dominance is further facilitated by its polyploidy. As pasture restoration using diaspores would be difficult, existing Kobresia pasture should be managed more sustainably.     

环境胁迫对海草非结构性碳水化合物储存和转移的影响

非结构性碳水化合物在海草体内的代谢对植株的生长有重要影响。为更好地跟踪非结构性碳水化合物在海草响应环境胁迫中所起的作用,根据国内外最新文献,重点综述了光强、营养盐、盐度、海洋酸化、温度、硫化物和动物摄食等环境胁迫对海草非结构性碳水化合物储存和转移的影响。光限制和富营养化均降低非结构性碳水化合物的合成,并使之从地下根茎转移到叶;而海洋酸化却促进非结构性碳水化合物合成并向地下组织转移;盐度变化改变海草体内渗透压,需要非结构性碳水化合物的新陈代谢来维持;温度通过影响光合作用、呼吸作用、氮代谢来影响非结构性碳水化合物的合成与储存;而硫化物和动物摄食则分别通过抑制海草酶的活性和啃食海草光合组织,减少非结构性碳水化合物的合成和储存。同时指出了一些今后关于海草非结构性碳水化合物的重点研究方向:(1)海草不同生命阶段(种子休眠和萌发,发育,繁殖等)非结构性与结构性碳水化合物之间,以及可溶糖与淀粉之间的转化分配机制;(2)双环境因子或者多环境因子对海草非结构性碳水化合物的耦合作用;(3)非结构性碳水化合物作为海草床生态系统健康评价指标的研究与应用。     

去叶对青杨雌雄植株生长和非结构性碳水化合物的影响

近年来,森林食叶害虫在全世界呈爆发趋势.树木的非结构性碳水化合物(NSC)如何响应叶片损失对其生长和生存至关重要.雌雄异株植物在维持森林生态系统稳定性方面扮演着重要角色.然而,目前对该类植物性别之间如何响应去叶的研究还比较少.本文以我国重要的经济和生态恢复树种青杨(Populus cathayana)为研究材料,比较了...     

干旱对兴安落叶松枝叶非结构性碳水化合物的影响

降水格局的变化以及极端干旱的频繁发生是全球气候变化的重要特征之一。为了揭示干旱对树木碳代谢的影响,通过控雨试验研究兴安落叶松(Larix gmelinii Rupr.)枝叶的非结构性碳水化合物(NSC)及其组分(可溶性糖和淀粉)的浓度对降水减少的响应,探索枝叶NSC浓度与土壤含水率的关系。控雨试验包括减雨100%(100%RE)、减雨50%(50%RE)和对照(CK)3个处理;控雨时期为2012年生长季(6月至8月)。结果表明,叶NSC浓度对干旱处理的响应比枝更显著。控雨处理对枝叶总NSC浓度影响不显著(P0.05),试验期间叶总NSC平均浓度变化在9.45—14.12 mg/g范围内;枝总NSC平均浓度变化在7.72—9.26 mg/g之间。然而,不同处理之间的叶片可溶性糖浓度差异显著。100%RE最高(8.98±0.31)mg/g、50%RE次之(8.45±0.13)mg/g、CK最低(7.73±0.32)mg/g。相反,叶淀粉浓度以CK最高(2.99±0.22)mg/g、50%RE次之(2.68±0.32)mg/g、100%RE最低(2.63±0.17)mg/g。叶可溶性糖与淀粉浓度的比值的大小顺序为:CK(2.27)50%RE(2.51)100%RE(3.70)。叶可溶性糖浓度、可溶性糖浓度和淀粉浓度的比值与土壤含水率呈显著的负相关关系(P0.05),而叶淀粉浓度有随土壤含水率升高而增高趋势,但相关关系不显著(P0.05)。叶NSC总浓度、枝NSC及其组分浓度与土壤含水率的关系均不显著(P0.05)。研究表明,短期干旱对兴安落叶松树体内总NSC浓度的影响不显著,树木可以通过将淀粉转化成可溶性糖的方式维持其正常的呼吸作用等生理活动。     

氮添加与降雨变化对红砂幼苗非结构性碳水化合物的影响

非结构性碳水化合物(NSC)在植物体内的含量及分配对植物生长和存活至关重要。开展氮沉降和降雨变化对幼苗NSC影响的研究,为揭示干旱导致幼苗死亡机理及预测气候变化背景下幼苗自然更新及培育提供依据。本研究以1年生红砂幼苗为对象,测定了不同降雨(降雨减少(W-)、自然降水(W)和降雨增多(W+))和氮添加(N0(0 g N·m-2·a-1)、N1(4.6 g N·m-2·a-1)、N2(9.2 g N·m-2·a-1)、N3(13.8 g N·m-2·a-1))条件下红砂幼苗各器官NSC及其组分含量。结果表明:红砂幼苗各器官NSC含量为28.8～71.8mg·g-1,叶片含量最高,茎含量最低。氮添加和降雨变化对红砂幼苗叶片和根系淀粉及总NSC含量有显著影响,而对茎无显著影响。各降雨条件下,氮添加均促进了红砂幼苗叶片淀粉和总NSC累积,在降雨增加30%的条件下氮的促进效应更显著,中高氮(N2和N3)叶片淀粉与总NSC含量显著高于低氮水平(N1和N0);在低氮降雨减少30%(N1W-)处理下,红砂叶片淀粉和NSC含量最小,而根系淀粉和NSC含量最大,即低氮干旱胁迫下红砂可通过NSC在不同器官的重...     

蛋白质水平解析高山嵩草对青藏高原昼夜环境的响应（英文）

高山嵩草(Kobresia pygmaea)是高寒草甸的重要建群种,其生长发育同时受到年际、季节和昼夜环境变化的影响,但目前对高山嵩草响应昼夜环境变化的研究很少。本研究通过差异蛋白质组学的方法,结合抗氧化酶活性测定和蛋白质免疫印迹技术,分析了高山嵩草在一天中每4个小时的蛋白质表达变化。结果表明:在白天的高温、强光和紫外辐射,以及夜里的低温等不利条件下,高山嵩草体内的抗氧化酶、热休克蛋白和脱落酸代谢相关的蛋白质等能够被大量诱导表达,从而对细胞和机体起到保护作用。同时,受蛋白质调控的一些生命活动如光合作用会集中在较为适宜的时间段进行。通过体内蛋白质表达的可塑性和灵活性,高山嵩草能够有效地应对短时间里环境的变化。     

Pools of non-structural carbohydrates in soybean root nodules during water stress

The aim of this study was to examine how the pools of non-structural carbohydrates in soybean nodules are affected under water stress conditions depending on the nature of the symbiont strains with particular emphasis on the plant-borne carbohydrates sucrose and pinitol, and on trehalose, a compatible solute synthesized by the bacteroids. Soybean ( Glycine max [L.] Merr. cv. Maple Arrow) plants were inoculated with the nitrogen-fixing strains Bradyrhizobium japonicum 61-A-101 or USDA 110 spc4 and cultivated axenically under conditions in which nodules formed in an upper soil compartment while roots for water supply grew into a compartment filled with nutrient solution. When the nodules were well established (1 month post inoculation), 10% (w/v) PEG 6000 was added to the nutrient solution. This led to a slowly progressing, moderate water stress, as determined by measuring the decrease of transpiration, and to a decrease in nitrogen fixation. The pool sizes of the major non-structural nodule carbohydrates changed during progression of water stress. Sucrose, the major soluble carbohydrate in nodules of unstressed plants (2 and 4%, respectively of nodule dry weight depending on symbiont strain), strongly increased in nodules of stressed plants, reaching nearly 10% of dry weight. The activities of two major sucrose-consuming enzymes, sucrose synthase and alkaline invertase, decreased markedly in nodules of stressed plants. Starch decreased only transiently upon water stress. Pinitol, a cyclitol serving as compatible solute in many plants, increased more than 4 times, reaching about 1% of nodule dry weight during the stress. Trehalose, the major soluble carbohydrate synthesized by the bacteroids, increased in nodules colonized by USDA 110 spc4 from about 0.2 to 0.8% of nodule dry weight, while in nodules colonized by 61-A-101 it amounted to more than 1.5% of dry weight both with and without stress.     

Changes in plant biomass and species composition of alpine Kobresia meadows along altitudinal gradient on the Qinghai-Tibetan Plateau

Alpine Kobresia meadows are major vegetation types on the Qinghai-Tibetan Plateau. There is growing concern over their relationships among biodiversity, productivity and environments. Despite the im-portance of species composition, species richness, the type of different growth forms, and plant bio-mass structure for Kobresia meadow ecosystems, few studies have been focused on the relationship between biomass and environmental gradient in the Kobresia meadow plant communities, particularly in relation to soil moisture and edaphic gradients. We measured the plant species composition, her-baceous litter, aboveground and belowground biomass in three Kobresia meadow plant communities in Haibei Alpine Meadow Ecosystem Research Station from 2001 to 2004. Community differences in plant species composition were reflected in biomass distribution. The total biomass showed a de-crease from 13196.96±719.69 g/m2 in the sedge-dominated K. tibetica swamp to 2869.58±147.52 g/m2 in the forb and sedge dominated K. pygmaea meadow, and to 2153.08±141.95 g/m2 in the forbs and grasses dominated K. humilis along with the increase of altitude. The vertical distribution of below-ground biomass is distinct in the three meadow communities, and the belowground biomass at the depth of 0-10 cm in K. tibetica swamp meadow was significantly higher than that in K. humilis and K. pygmaea meadows (P<0.01). The herbaceous litter in K. tibetica swamp was significantly higher than those in K. pygnaeca and K. humilis meadows. The effects of plant litter are enhanced when ground water and soil moisture levels are raised. The relative importance of litter and vegetation may vary with soil water availability. In the K. tibetica swamp, total biomass was negatively correlated to species richness (P<0.05); aboveground biomass was positively correlated to soil organic matter, soil moisture, and plant cover (P<0.05); belowground biomass was positively correlated with soil moisture (P<0.05). However, in the K. pygnaeca and K. humilis meadow communities, aboveground biomass was posi-tively correlated to soil organic matter and soil total nitrogen (P<0.05). This suggests that the distribu-tion of biomass coincided with soil moisture and edaphic gradient in alpine meadows.     

Seasonal changes in non-structural carbohydrates and sucrose metabolism enzymes in two Sabina species

Evergreen plants need to store reserves to allow for their survival during the winter months and for new leaf growth in the following spring. In many of the tree species, these reserve functions are mainly carried out by starch, which is degraded to soluble carbohydrates during the dormant season to maintain active respiration and provide protection against freezing. In the present study, two evergreen woody plants, S. przewalskii Kom. (SP) and S. chinensis (Lin.) Ant.(SC), were used to investigate the patterns of seasonal variation in the concentrations of soluble sugars, sucrose, fructose and starch, and the activities of sucrose-phosphate synthase (SPS), sucrose synthase (SUSY), neutral invertase (NI) and soluble acid invertase (SAI). Foliar soluble sugar, sucrose, fructose, and starch concentrations were markedly higher in SC than in SP; moreover, the activities of SPS, SUSY, NI and SAI were also higher in SC than in SP. There were generally higher concentrations of soluble sugars, sucrose and fructose and SPS activities in the winter than in the summer for both Sabina trees, which was consistent with the necessity for protection against freezing; however, opposite results were found with regards to starch concentrations and the activities of SUSY, NI and SAI. In contrast with the activities of SUSY, NI and SAI, the negative correlation observed between SPS and air temperature was likely a reflection of its crucial role in the acquisition of freezing tolerance by sucrose metabolism in the winter. These results suggest that higher carbon reserves do not give S. chinensis (Lin.) Ant. a competitive advantage in tolerating cold temperatures and that only SPS, but not SUSY, NI and SAI, may play a positive role in freezing tolerance by increasing soluble sugar.     

Spatial variations in non-structural carbohydrates in stems of twelve temperate tree species

The radial, axial and inter-specific variations in concentrations and contents of non-structural carbohydrates (NSC) in stems were investigated for 12 Chinese temperate tree species. These species had contrasting leaf phenology (evergreen and deciduous) and wood types (non-, ring- and diffuse-porous wood). For each species, we sampled bark (periderm and phloem), outer wood (light-colored) and inner wood (dark-colored) at four heights along the stem (stump, breast height, crown base and mid-crown). Concentrations of total NSC (TNC, sum of sugars and starch), sugars and starch were much higher in bark than those in wood. On average, contents of sugars and starch accounted for 48 and 52 % of the TNC, respectively, and contents of TNC in bark, outer wood, and inner wood accounted for 34, 38, and 28 % of the stem total, respectively. Bark was the major pool of sugars in the stem (accounting for 50 % of the stem total on average), while outer wood was the major pool of starch (41 %). The concentration of sugars varied axially for all the conifers but did not for the broadleaved species. Mean concentrations of TNC, sugars and starch in stem varied by more than twofold among the species. However, there were no significant differences in these values for the species groups with different leaf phenology or wood types. Ignoring the radial, axial and inter-specific variations in NSC in stem would introduce large bias in estimating NSC storage at tree or ecosystem levels.     

桑苗非结构性碳水化合物和生长激素对水淹胁迫的响应

桑(Morus alba)具有较强的耐水淹特性, 为了探究水淹胁迫对其非结构性碳水化合物和生长激素的影响, 揭示变化规律, 该研究采取室内模拟水淹实验, 以三年生盆栽桑苗作为研究对象, 设置对照组(CK)、根淹组(GY)、浅淹组(QY)、深淹组(SY)等4个不同水淹胁迫的处理, 定期观测并记录桑苗叶片非结构性碳水化合物(可溶性糖和淀粉)含量、内源生长激素(乙烯、脱落酸、赤霉素)含量变化情况。研究结果表明: (1)水淹胁迫会促进桑苗叶片内的生化反应, 造成叶片可溶性糖含量增加。水淹75天, GY、QY、SY桑苗叶片可溶性糖含量较水淹前分别增加182.18%、170.21%和94.16%, 差异显著, 且显著高于CK。水淹胁迫下桑苗叶片淀粉含量在水淹0-50天无显著变化, 水淹75天, GY、QY、SY桑苗叶片淀粉含量较水淹50天分别增加290.84%、244.65%和130.04%, 差异显著, 且显著高于CK。(2)水淹胁迫下桑苗叶片乙烯和赤霉素含量均显著增加, 水淹75天, GY和SY桑苗乙烯含量较水淹前分别增加62.80%和26.78%, 差异显著; GY、QY和SY桑苗赤霉素含量分别增加27.48%、18.02%和25.04%, 差异显著。随着水淹时间增加, GY和SY桑苗乙烯和赤霉素含量总体均呈增加趋势, QY桑苗乙烯和赤霉素含量先增后减, 但仍高于水淹前。水淹胁迫下水淹各组桑苗叶片脱落酸含量随着水淹深度的增加而增加, 水淹75天, QY和SY桑苗叶片脱落酸含量较水淹前分别增加19.20%和36.16%, 差异显著; GY桑苗脱落酸含量无显著变化。上述研究结果表明桑苗可通过调整体内非结构性碳水化合物(可溶性糖和淀粉)的含量和分配, 同时通过积累乙烯、赤霉素、脱落酸等内源激素以适应水淹环境, 具有较强耐淹能力。     

Seasonal dynamics of non-structural carbohydrates in bulbs and shoots of the geophyte Galanthus nivalis

Seasonal dynamics of non-structural carbohydrates were studied in Galanthus nivalis L. over a 2-year period. The plants were collected in the field and separated into above- and below-ground biomass. The polysaccharide fraction of the bulbs consisted of fructans and starch. Seasonal variations suggest that the polysaccharides were utilized for carbon and energy supply for re-growth and flower development. With the re-sprouting of the bulbs in autumn the fructans within the bulbs were depolymerized and an increase of low degree of polymerization fructans as well as sucrose was observable. Within shoots the major polysaccharides were fructans, the starch content was much lower. Gas liquid chromatography and high-performance, anion-exchange chromatographyanalysis of the fructan fraction revealed that the fructans within the shoots were predominantly those with a low degree of polymerization. In addition to the two polysaccharides the other dominant sugar in shoots was sucrose. During the period of slow re-growth and flowering, fructan and starch pools were depleted to different degrees. Calculation of the difference between the carbohydrate content at the start of visible growth and at the time of lowest content revealed that the starch pool showed a higher depletion than the fructan pool. During the re-growth periods in 1996/97 and 1997/98 fructans were catabolized by 39 and 32% only, whereas the starch pool was depleted by 92% (1996/97) and 79% (1997/98), respectively. During rapid shoot growth and fruiting, the bulbs and above-ground organs appeared to be competing sinks for the photosynthetically fixed carbon. Refilling of the bulbs carbohydrate reserve started in February/March In shoots, the period of refilling the bulbs was characterized by a low content of oligosaccarides and a high content of hexoses.     

Variation of non-structural carbohydrates in silver birch (Betula pendula Roth) wood

Non-structural carbohydrates in silver birch (Betula pendula Roth) wood were analysed in a 7-year-old clone and in five mature stems. The analysis was conducted to obtain more detailed information on seasonal fluctuation of these components and of the tree-to-tree variation and within stem variation. The sugars were analysed by GLC-MS. The smallest total soluble sugar amounts (consisting of sucrose, fructose, glucose, raffinose and myo-inositol) in young trees were measured during mid-summer (ca. 0.3%) and the largest while in dormancy (ca. 1.6% on wood dry weight basis). Raffinose was detected in autumn as a minor component. The proportion of monosaccharides and the amount of myo-inositol were largest during growth. Compared to other studies silver birch showed more evident seasonal fluctuation in soluble sugars than evergreen tree species. The sugar amount in mature stems was approximately at the same level as in young trees that had the same felling time. Tree-to-tree variation in the non-structural carbohydrates in the mature wood was fairly large. However, the amount of total soluble sugars, sucrose and glucose showed significant variation within the stem. The amount of these sugars was largest in samples that were taken close to the cambium. Starch was also detected close to pith. According to the heartwood definition and starch measurement results in this paper, it could be stated that silver birch does not form heartwood.