广西多穗柯叶片性状变异及幼苗生长量研究

多穗柯是一种珍贵天然野生药用植物,可以开发出保健食品色素和天然医用药品,广西的资源较丰富,该研究采集巴马、那坡、德保及田林等4个产地的多穗柯种子进行播种育苗,并跟踪调查测定一年生幼苗的叶片性状及幼苗生长量,并进行相关性分析。结果表明:(1)不同产地间叶片性状及幼苗生长指标均存在不同程度的差异,其中巴马与那坡、德保、田林在叶长、叶宽、叶面积、叶脉间距、叶鲜重、叶片干物质含量、叶片组织密度等叶片性状上的差异均达到显著水平,在株高、地径、单株干重、主根长、单株根干重及单株叶干重等生长指标上亦存在显著差异,且生长量是后3个产地的1~2倍;通过比较各产地的叶片保水力及植株净生长量,巴马的多穗柯植株耐旱性及生长速度优于其他三地。综合各性状表现,认为巴马的多穗柯苗期表现比较好,生长速度快,长势好,抗旱性较强,可作为多穗柯优良种源的初步选择。(2)8月份是多穗柯株高、地径的生长高峰期,建议此时应加强肥水管理,调节适宜的水肥光热条件,尽量延长幼苗的快速生长时间,以获得苗木的最大累积生长量。(3)叶片性状与幼苗生长量的相关性分析结果显示,叶面积与株高、地径、单株干重、单株根干重以及单株叶干重等呈极显著正相关,叶脉间距、叶绿素相对含量(SPAD)与株高、单株干重呈显著或极显著正相关,比叶面积与株高、地径呈显著负相关。因此,在以后的优株表型选择中,要优先考虑叶子大、叶脉间距宽、中老熟叶片叶色浓绿的植株。该研究结果为多穗柯优良种质资源的早期筛选提供了一定的依据。     

Physiological comparisons of two soybean cultivars differing in canopy photosynthesis. I. Variation in vertical 14CO2 labelling and dry weight partitioning

Differences in canopy apparent photosynthesis (CAP) among soybean [Glycine max (L.) Merr.] genotypes have been shown to be correlated to seed yields. Since the physiological basis for such differences in CAP is unknown, two cultivars known to differ in CAP, Tracy and Davis, were studied during the 1978–1980 growing seasons. The CAP and dry weights of component plant parts were determined. In 1978 and 1979, ¹⁴CO₂ uptake by vertical leaf strata was determined and specific leaf weight (SLW) and leaf area index (LAI) were determined for corresponding strata in 1979 and 1980. Measurements were taken on several dates during reproductive growth. With the exception of CAP, all measurements (¹⁴C uptake, dry weights) were made in layers within the canopy. CAP on some dates were significantly higher in Tracy than in Davis and integrated CAP values from a certain growth period, labeled as R5 to R7, averaged 16 percent higher in Tracy for the three years studied. No differences in the relative recovery of ¹⁴C from different layers of leaves in the canopy were found. This indicates that variations in canopy structure or leaf orientation did not play a major role in the CAP differences between cultivars. The differences seem related to variations in leaf dry weights. Overall, Tracy exhibited 13.5, 19.2, and 13.2 percent greater leaf dry weights than Davis during 1978, 1979, and 1980, respectively. These differences in leaf dry weight seem largely due to a differences in the SLW. Data from these experiments indicate that differences in soybean CAP values were associated with differences in SLW.Abbreviations CAP Canopy Apparent Photosynthesis - CER Carbondioxide Exchange Rates - EST Eastern Standard Time - LAI Leaf Area Index - LSD Least Significant Difference - POPOP 1,4-bis-[2(5-phenyloxazdyl)]-benzene - PPO 2,5-diphenyloxazole - SLW Specific Leaf Weight     

Linking stand-level self-thinning allometry to the tree-level leaf biomass allometry

Long-term experimental plots of Norway spruce and European beech are investigated for a link between stand-level self-thinning and tree-level leaf biomass allometry. Self-thinning refers to the finding of Reineke (1933), who postulated for unthinned forest stands that with β = −1.605; i.e. an increase of mean (quadratic) diameter d _q by 1% results in a decrease of tree number N by 1.605%. On the individual tree level, leaf biomass (w _L) can be related allometrically to the tree diameter d: w _L = ad ^α. If we assume that (a) the stands have reached the ceiling leaf area, (b) the specific leaf area (leaf area/leaf weight) is constant, and (c) differences resulting from the use of mean quadratic diameter or individual tree diameter are negligible, then the decrease in the stands’ leaf biomass due to the trees lost in self-thinning must be compensated by an equivalent increase in the remaining trees’ leaf biomass. This means, the absolute slope of the individual trees’ leaf biomass allometry α and the self-thinning allometry β would be equal and just have the opposite sign: α = −β. The analysis of the two long-term plots reveals that α is stronger than β, both for spruce (β = −1.744, α = 1.840) and especially for beech (β = −1.791, α = 2.181). The cause is traced back to a changing average specific leaf area during stand development [assumption (b) is wrong]. The results do not only bridge a gap between tree and stand allometry, but also emphasize an important effect for the understanding and modelling of the resource allocations in trees and forests.     

<Emphasis Type="Italic"> Picea</Emphasis> seedlings show apparent acclimation to drought with increasing altitude in the eastern Himalaya

Abstract We measured plant structural and physiological responses of two sympatric Picea species, Picea likiangensis (Franchet) E. Pritzel var. balfouriana and Picea asperata Masters var. retroflexa to altitude close to the treeline in the eastern Himalaya. Most measured tree characteristics differed between different altitudes, between different ages, and between shaded and un-shaded treatments. Both P. likiangensis and P. asperata had lower foliage area/stem cross-sectional area ratios, smaller specific leaf areas, higher root mass/foliage area ratios, and less negative ¹³C at 3,900 m than at 3,600 m altitude, and in the un-shaded treatment than in the shaded treatment. The 7- and 9-year-old seedlings also showed lower foliage area/stem cross-sectional area ratios, higher root mass/foliage area ratios and less negative ¹³C than younger seedlings. Shading resulted in an increase of biomass accumulation at all altitudes. A close relationship, independent of altitude, was observed between ¹³C and specific leaf area, suggesting that internal resistance could limit CO₂ diffusion to the site of carboxylation. The results indicate that, in spite of greater water availability, trees at higher altitudes show quite a number of apparent acclimations to drought.     

光强对杉木幼苗形态特征和叶片非结构性碳含量的影响

选取南方重要的造林树种杉木(Cunninghamia lanceolata(Lamb.)Hook)幼苗为研究对象,通过搭建遮荫棚设置5个光照强度(分别为自然光照的100%、60%、40%、15%和5%),研究了幼苗在不同光照强度下的生长形态、生物量积累及分配、叶片的非结构性碳含量(NSC)特征。结果显示:(1)叶长、叶宽和叶面积在40%光照强度下最大,而比叶面积和叶片相对含水量随着光照强度的降低呈递增趋势;(2)随着光照强度的降低,杉木幼苗各器官生物量下降,根生物量比和根冠比降低,茎和叶生物量比增加;(3)杉木幼苗在60%光照强度下叶片非结构性碳含量最高,5%光照强度下含量最低;(4)杉木幼苗比叶面积与叶生物量以及与非结构性碳含量之间存在极显著的负相关关系(P0.01),叶生物量与非结构性碳含量之间存在极显著的正相关关系(P0.01)。杉木幼苗能够通过形态学上的可塑性来适应不同的光强环境,提高光竞争能力和生存适合度,但在5%光照强度下,由于较难维持碳收支平衡而不利于其生长和存活。     

The influence of ancymidol on morphology,anatomy, and chlorophyll levels in developing and mature Helianthus annuus leaves

Ancymidol foliar spray at 132 mg·liter^–1 a.i. modified leaf anatomy of developing Helianthus annuus L. Mammoth Russian leaves, but not of mature leaves. Ancymidol was effective in retarding plant growth when applied at the young seedling or at a more mature stage of growth. Ancymidol increased leaf weight per unit area and chlorophyll content on an area and unit weight basis, regardless of stage of leaf development. Total chlorophyll per leaf was also increased in mature leaves. Thus, darker green foliage due to increased chlorophyll content and modified leaf anatomy responses were determined to be independent effects.Texas Agricultural Experiment Station paper no. 22927.     

野外土壤增温对胡桃楸幼苗生长和生理特性的影响

全球气候变化将增加地表土壤温度,从而影响植物幼苗生长和种群动态。本研究以温带地带性顶极植被——阔叶红松林的优势树种胡桃楸为对象,研究野外土壤增温2 ℃对1年生和2年生胡桃楸幼苗生长与生理特性的影响。结果表明: 与对照相比,土壤增温使1年生胡桃楸幼苗的基径、根长、总叶面积、叶干重、根干重、总生物量、表观光合电子传递速率(ETR)、PSⅡ实际光化学效率(Φ_PSⅡ)和表观光合电光化学淬灭系数(q_P)分别显著增加18.3%、66.7%、 94.4%、105.9%、 95.8%、37.8%、89.5%、100.0%和71.4%;土壤增温使2年生幼苗的基径、总叶面积、叶干重、总生物量、叶片超氧化物歧化酶活性、过氧化物酶活性、过氧化氢酶活性和游离脯氨酸含量、ETR、Φ_PSⅡ和q_P分别显著增加12.5%、180.5%、97.3%、42.5%、23.9%、20.4%、14.9%、20.7%、66.7%、283.3%和284.6%。苗龄和增温对幼苗的根冠比以及叶绿素荧光参数中的Φ_PSⅡ、q_P存在交互作用,表现为土壤增温显著降低了2年生幼苗的根冠比,2年生幼苗叶绿素荧光参数的增幅(4.1～4.6倍)远高于1年生幼苗(1.5～1.8倍)。野外土壤增温2 ℃有利于1年生和2年生胡桃楸幼苗生长,提高胡桃楸幼苗的更新潜力,尤其是2年生胡桃楸幼苗通过大幅增大叶面积、提高叶片光化学效率和提升体内的保护酶活性产生抗逆性来应对土壤增温。     

Acclimation of a dominant mangrove plant (<Emphasis Type="Italic">Kandelia candel</Emphasis>) to soil texture and its response to canopy shade

Kandelia candel, a dominant plant species in Hong Kong mangroves, had different growth strategies during its seedling stage for acclimation to various soil types. Leaves of the seedlings grown in sandy soils (coarse texture) were significantly thicker than those in loamy–sandy and silty soils (fine texture). However, leaf weight per unit leaf area of seedlings grown in sandy soils was similar to that in loamy-sandy soils and was 1.60 times that in silty soils. These indicate that K. candel in sandy soils had developed a more loose leaf structure and a xerophilous characteristic during its seedling stage for acclimation to the features of coarse textured soils, which were low water holding capacity and low mineral content. In addition, for young seedlings grown in sandy and loamy–sandy soils, more biomass was allocated to roots than in silty soils, indicating that K. candel seedlings in sandy soils developed stronger roots for anchorage and water absorption; another xerophilous characteristic to acclimate to loose and coarse textured soils. As the plants became more mature, no significant difference in leaf thickness of the saplings was found between loamy-sandy and sandy soils. In order to acclimate to the low water holding capacity in sandy soils, K. candel seedlings had lower physiological activities including lower chlorophyll content; lower activities of root oxidase, nitrate reductase, peroxidase and superoxide dismutase but higher malonaldehyde contents than those in silty soils. Canopy shade is an important factor affecting the growth and physiology of K. candel. The seedling grew worse under the mangrove canopy than that in the open gap, with smaller leaf area, specific leaf area, leaf number and biomass. The seedlings under the canopy eventually died and no saplings were found under canopy shade, implying K. candel is a shade intolerant species and canopy shade might force its newly recruited individuals to expand out of the forest.     

壳斗科五树种幼苗叶片结构型性状及其相关关系

通过种子的人工采集、低温沙藏和温室培育后,将幼苗移栽到环境条件相同的同质园中自然生长,研究了中亚热带壳斗科丝栗栲(Castanopsis fargesii)、苦槠(C.sclerophylla)、锥栗(Castanea henryi)、板栗(C.mollissima)和麻栎(Quercus acutissima)2年生幼苗生长季节的叶面积、叶厚度、比叶面积、叶干物质含量、叶氮浓度、叶磷浓度和叶氮磷比7种结构型性状的差异及其相关关系。结果表明:(1)在5树种幼苗中,锥栗幼苗的叶面积和比叶面积最大、叶氮浓度最高,其叶干物质含量最低;丝栗栲幼苗的叶面积最小、叶氮浓度和叶磷浓度最低;苦槠幼苗的叶厚度和比叶面积最小,其叶干物质含量最高;板栗幼苗则是叶厚度最小;同时5树种幼苗叶片的氮磷比均无显著差异(P0.1)。(2)Pearson相关和线性回归分析表明,壳斗科5树种幼苗的叶面积与叶氮浓度极显著正相关(P0.01),并与比叶面积显著正相关(P0.05);叶厚度与比叶面积极显著负相关(P0.01),其与叶干物质含量显著正相关(P0.05);比叶面积与叶干物质含量极显著负相关(P0.01),并与叶氮浓度极显著正相关(P0.01),同时与叶磷浓度显著负相关(P0.05);叶氮浓度与叶干物质含量、叶磷浓度分别为显著负相关(P0.05)和显著正相关(P0.05)。该研究结果表明壳斗科5树种幼苗叶片的7种结构型性状表现出了一定的种间差异性,但同一结构型性状的大小顺序和种间差异的显著性不同;同时所有树种幼苗叶片各结构型性状间的相关性及其显著程度不同。     

Seedlings of temperate rainforest conifer and angiosperm trees differ in leaf area display

Background and Aims

The contemporary relegation of conifers mainly to cold or infertile sites has been ascribed to low competitive ability, as a result of the hydraulic inefficiency of tracheids and their seedlings'' initial dependence on small foliage areas. Here it is hypothesized that, in temperate rainforests, the larger leaves of angiosperms also reduce self-shading and thus enable display of larger effective foliage areas than the numerous small leaves of conifers.

Methods

This hypothesis was tested using 3-D modelling of plant architecture and structural equation modelling to compare self-shading and light interception potential of seedlings of six conifers and 12 angiosperm trees from temperate rainforests. The ratio of displayed leaf area to plant mass (LAR_d) was used to indicate plant light interception potential: LAR_d is the product of specific leaf area, leaf mass fraction, self-shading and leaf angle.

Results

Angiosperm seedlings self-shaded less than conifers, mainly because of differences in leaf number (more than leaf size), and on average their LAR_d was about twice that of conifers. Although specific leaf area was the most pervasive influence on LAR_d, differences in self-shading also significantly influenced LAR_d of large seedlings.

Conclusions

The ability to deploy foliage in relatively few, large leaves is advantageous in minimizing self-shading and enhancing seedling light interception potential per unit of plant biomass. This study adds significantly to evidence that vegetative traits may be at least as important as reproductive innovations in explaining the success of angiosperms in productive environments where vegetation is structured by light competition.     

Physiological basis of differential response to salinity in rice cultivars

Growth analyses of rice Oryza sativa L. seedlings in salinized nutrient solution condition were conducted with 24 cultivars and lines after genetic purification. Cultivar differences in relative growth rate in salinized conditions were chiefly dependent on differences in shoot Na content. The shoot Na content was affected by Na selectivity in the root and by the leaf area ratio (LAR, leaf area per total dry weight). The contribution of LAR was equally important to that of root cultivar selectivity against Na uptake under a higher salinization condition where root selectivity against Na may be decreased due to reduced root activity. Cultivar differences in salt tolerance in highly salinized conditions were mainly attributed to differences in these two factors. A more convenient and efficient screening method for salt tolerance is proposed.     

Spatial variation in sapwood area to leaf area ratio and specific leaf area within a crown of silver birch

Spatial variation in sapwood area to leaf area ratio (Huber value, HV) and specific leaf area (SLA) was examined in branches of closed-canopy trees of silver birch (Betula pendula Roth). HV increased basipetally within a crown and decreased with increasing branch order, but exhibited no significant radial trend along a primary branch. HV was primarily determined by branch position in a crown and branch diameter at the sampling point, being independent of the size of the tree and branch. Greater HV in the lower-crown branches is considered a means to mitigate differences in hydraulic transport capacity between the branches located in different canopy layers. Beside branch position and sampling location on a branch, SLA depended significantly on several other variables characterising tree and branch size. SLA increased basipetally within a crown and along a primary branch, but exhibited no significant trend with branch orders. Because height caused leaf area (A_L) to diminish more rapidly than leaf dry weight, A_L primarily determined the vertical variation in SLA.     

Growth and nutrition of birch seedlings in relation to potassium supply rate

Summary Growth of hydroponically cultivated birch seedlings (Betula pendula Roth.) at sub- and supra-optimum potassium supply rates was investigated. Potassium was supplied either as a relative addition rate (r _k = 5, 10, 15 and 20% increase day^-1) or as fixed concentrations (0.2, 3, 6, 12 and 15 mM) in the culture solution. After an acclimation period the growth rate of the seedlings in the suboptimum treatments reached values close to the treatment variable, the relative rate of K-addition. Deficiency symptoms, in the form of chlorosis and necroses along the leaf margins, developed initially in all suboptimum treatments, but very few new symptoms appeared once the seedlings had reached the phase of steady-state nutrition and growth. At supra-optimum K-supply levels, i.e. at 0.2–15 mM K in the culture solution, no symptoms of deficiency or toxicity developed, and the relative growth rate of the seedlings remained maximum. The relative growth rate of the seedlings was linearly related to the plant K-status for K contents ranging from 0.2 to 1.0% of dry weight (DW). At higher internal K-concentrations, 1.0–3.0% DW, no further increase in relative growth rate was achieved. A shortage of K resulted in a decrease in the net assimilation rate. This effect was counterbalanced by the absence of shift in he leaf weight ratio as well as by the production of relatively thin leaves. The fraction of dry matter allocated to roots decreased in K-limited plants, as did the leaf contents of soluble carbohydrates and starch.     

A Comparison of Photosynthesis in Endangered and Non-Endangered Plants Changium smyrnioides and Anthriscus sylvestris

Changium smyrnioides Wolff. and Anthriscus sylvestris (L.) Hoffm. have similar photosynthetic characters; they use radiant energy in winter and early spring effectively, but cannot take full advantage of higher irradiance after spring. The specific leaf area (SLA), leaf area ratio (LAR), and leaf mass ratio (LMR) of C. smyrnioides were lower than those of A. sylvestris. The photosynthetic period of C smyrnioides was about 160 d shorter than that of A. sylvestris, causing the total photosynthetic production of C. smyrnioides to be lower than that of A. sylvestris. Hence if C. smyrnioides is disturbed, it could not recover within a short period.     

Competition between <Emphasis Type="Italic">Eucalyptus victrix</Emphasis> seedlings and grass species

Competition in a natural system may be interspecific or intraspecific. In semiarid ecosystems, competition for resources between established neighboring grass species and newly recruited seedlings is very high. To examine the effects of grass species density, growing space and time of establishment on Eucalyptus victrix seedlings (interspecific competition), and the effect of density and growing space within E.victrix (intraspecific competition) we conducted an experiment under controlled conditions. We tested four hypotheses (i) E.victrix seedling growth is not affected by grass density; (ii) there is no difference in E.victrix survival and growth between early and later grass establishment; (iii) interspecific competition is not more intense than intraspecific competition in E.victrix; and (iv) growth of E.victrix seedlings is not dependent on available growing space. In a monoculture of E.victrix, seedling mortality was higher (10%) in large pots. In mixed culture pots, where E.victrix seedlings and grass seedlings were planted on the same day, E.victrix seedlings survived for up to 4weeks, but started to die after week five in the smallest pots. However, mortalities occurred in pots of all sizes when grass was established before E.victrix seedlings. Results also indicated that the resources necessary for the growth of individual E.victrix seedlings were more limiting under conditions of increased density of neighboring grass species rather than intraspecific competition. In particular, photosynthetic area of E.victrix seedlings was drastically reduced in mixed cultures. Although density, pot size and time of planting had impacts on E.victrix seedlings, the patterns of these impacts were variable.     

喀斯特高原峡谷优势种叶片功能性状分析

该研究对喀斯特石漠化高原峡谷地区优势种的叶片功能性状进行了分析,调查了17种植物的叶片厚度、叶面积、叶片鲜重、叶片干重、叶干物质含量、比叶面积、叶组织密度等能反映植物生存策略且易于测量的叶片功能性状,并采用逐步回归的方法探究了叶片功能性状与土壤养分之间的关系。结果表明:(1)不同优势种叶片功能性状差异明显,叶片的厚度为0.18～0.78 mm、鲜重为0.07～6.51 g、干重为0.04～3.19 g、叶面积为3.07～325.64 cm~2、叶干物质含量为318.61～573.22 mg·g~(-1)、比叶面积为60.98～236.90 cm~2·g~(-1)、叶组织密度为0.022 1～0.036 g·cm~(-3)。(2)植物通过较小的比叶面积与较大的叶干物质含量来减少水分散失、增加养分储存,以适应高温、缺水少土的环境。(3)叶片功能性状之间存在广泛的相关关系,且均达到极显著水平。叶片厚度对鲜重、干重均表现为促进效应,比叶面积与叶干物质含量及叶组织密度之间均存在极显著的抑制效应。(4)叶片功能性状随土壤养分的变化产生规律性变化。土壤全氮、全钾和有机碳对叶片功能性状产生显著影响,尤以土壤有机碳的影响更为显著。进一步分析发现,喀斯特高原峡谷地区植被恢复及重建的优势种或建群种为翅荚香槐、清香木、枇杷等;施用有机肥能够提高花椒、金银花等经济林树种的适应能力。     

Compensatory photosynthesis as a response to partial debudding in ezo spruce, <Emphasis Type="Italic">Picea jezoensis</Emphasis> seedlings

The effects of partial debudding on photosynthesis, stomatal conductance and nitrogen contents of 1-year-old needles and newly grown needles were studied in Picea jezoensis (Sieb. et Zucc.). Seventy-five percent of the buds of P.jezoensis seedlings were removed soon after bud break. Gas exchange was measured three times for 1-year-old needles and twice for current-year needles. The photosynthetic rates of 1-year-old needles were greater in debudded seedlings than in control seedlings, and the difference increased as the growing season progressed. This greater photosynthetic rate in debudded seedlings was accompanied by greater stomatal conductance. However, neither the photosynthetic rates nor the stomatal conductance of current-year needles differed between debudded and control seedlings after the needles had fully expanded. Debudding also had no effect on mass-based nitrogen contents in either the 1-year-old or the current-year needles. Area-based nitrogen in the 1-year-old needles did not differ between debudded and control seedlings, but was greater in debudded seedlings than in control seedlings in current-year needles. These results suggest that the enhanced photosynthetic rate is more likely a result of an increased root/leaf ratio that reduces the stomatal limitation of photosynthetic rate than a result of altered sink-source relationships or increased leaf nitrogen content.     

喜旱莲子草对喀斯特三种不同生境的可塑性反应

喜旱莲子草自入侵以来在我国各地广为传播蔓延,对人们生产生活产生了重要影响。该研究通过野外采样和室内理化指标分析,探讨喀斯特不同生境中喜旱莲子草的可塑性。结果表明:(1)在三种生境中喜旱莲子草的节间长度、叶面积、单株重和叶干重差异显著。(2)在岩石环境中其无性繁殖器官——茎的投入比例占其生物量的比例最大,其次是行道生境和湘江河道。(3)节间距随环境因子从岩石环境、绿化行道和水生生境的变化,依次增加,叶质比(叶面积/质量)也随水分环境的增加而增加;(4)在岩石环境中,喜旱莲子草通过缩短节间距并增加无性繁殖器官——茎的质量来增加其在水分匮乏生境的繁殖能力。该研究结果为喜旱莲子草今后的防治对策提供了科学依据。     

Relationships between early vigour, grain yield, leaf structure and stable isotope composition in field grown barley

Fast growth and early development in barley are used in breeding programmes to improve the water use efficiency and transpiration efficiency of this crop in Mediterranean conditions. Here, we examine the use of several simple traits based on the structure and stable isotope composition of seedling leaves to assess differences in early vigour, phenology and grain yield, and also the interaction with low temperatures in barley. A set of 260 F₈ lines of two-row barley (Hordeum vulgare L.) derived from the cross of Tadmor and WI 2291 were cultivated in two locations in northwest Syria. Total chlorophyll content on an area basis (SPAD) and specific leaf dry weight (SLDW) were measured in recently fully expanded intact leaves of seedlings. Total leaf area and total dry weight per seedling were evaluated in the same seedlings. The stable isotope compositions of carbon and nitrogen (δ¹³C and δ¹⁵N, respectively) were analyzed in the same leaves on a subset of 75 genotypes. Number of days from planting to heading and grain yield were recorded at both sites. The grain yield measured at both locations was positively correlated with the SPAD value of seedlings, but showed no relationship with SLDW. Days to heading was negatively correlated with SPAD values. Regarding early vigour, a negative relationship between the SLDW and the total leaf area of seedlings was observed. However, no relationship between the δ¹³C of seedlings and early vigour was observed, except when only the genotypes most resistant to low temperatures (i.e. showing the highest SPAD values) were considered. This subset of genotypes showed negative relationships between δ¹³C and either total leaf area or total dry weight. In addition, δ¹⁵N was negatively correlated with SPAD only within the high-SPAD genotypes. This suggests that within the genotypes resistant to low temperatures, those with higher chlorophyll content assimilate more nitrogen from nitrate.     

Influence of insect-infested cotyledons on early seedling growth of Mongolian oak, <Emphasis Type="Italic">Quercus mongolica</Emphasis>

Insect-infested (II) acorns germinated 3 d earlier than the healthy (H) ones. However, germination ratio of II-acorns was strongly decreased compared with H-acorns and there were great differences in activities of amylase. We found an apparently lower net photosynthetic rate and total chlorophyll contents of the first true leaf of II-acorns than of the H-ones. Maximal photochemical efficiency of photosystem 2 (PS2, F_v/F_m) decreased in seedlings germinated from II-acorns than from the H-ones. Infestation of insects, especially for weevil (Curculio spp.) had significantly negative effects on length of taproots, height of plants, dry mass (DM) of roots and the first fully expanded true leaf. Leaf area and total N content of the first true leaf declined due to limitation of resource reserves in cotyledons. Damage of cotyledons caused by weevil accounted much for poor development of seedlings germinated from II-acorns. A mutual relationship between seedling establishment and seed-infesting insects may exist due to high predation on H-acorns by small rodents. An erratum to this article is available at .