The effect of samara wing presence on predation of Acer pseudoplatanus (Sapindaceae) seeds on the ground

The key selective pressure shaping the morphology of samaras is seen as enhancing primary wind-borne dispersal from the parent plant to the ground. However, the consequences of the samara wing of primarily wind-dispersed tree species for post-dispersal processes has not been well studied. We explored whether the presence of this wing in Acer pseudoplatanus either deters or promotes predation after dispersal, either by increasing the time and energy required to predate the seed or by increasing the seed's visibility to predators. We found that wing-removed fruits were preferred, suggesting that the presence of samaras makes seed handling more expensive for granivores. Further, we found that fewer seeds were consumed from treatments that contained the most winged seeds, thus there was no evidence of the samaras making seed finding easier for granivores. We conclude that the presence of the wing may offer an anti-predatory benefit as well as aiding primary dispersal.     

Filtration stress-induced variations of peroxidase activity in cell suspension cultures of sycamore (Acer pseudoplatanus) cells

Filtration stress, consisting in the rapid filtration of Acer pseudoplatanus L. cell suspension cultures, resulted in significant differences between the peroxidases (EC 1.11.1.7) released during cell growth and those released after filtered cells were resuspended in fresh medium (recovery medium). These differences concerned mainly modifications of (i) the pH optimum of peroxidase activity (guaiacol as electron donor), (ii) the number and the pI values of the peroxidase isoenzymes as shown by isoelectric focusing, and (iii) the molecular weights of the different peroxidase fractions determined by gel filtration chromatography. The presence of 1 m M Li⁺ in the recovery medium inhibited the release of peroxidase and this effect was partially reversed by K⁺. The release of peroxidase by stressed cells was also strongly inhibited by Na₂CO₃ in the recovery medium. The results presented are consistent with the proposal that the characteristic isoperoxidase patterns induced by filtration stress might be used as a model to study the response of plant cells to stress.     

Intra-crown variation in leaf herbivory and seed production in striped maple,Acer pensylvanicum L. (Aceraceae)

Summary Patterns of spatial variation in leaf herbivory and the effects of this variation on seed production and twig growth were studied in striped maple, Acer pensylvanicum (Aceraceae). Experimental removal of 25% of the leaf area from each of four leaves directly subtending a developing infructescence significantly reduced seed number in that infructescence. When leaf area was removed from leaves neighboring to, but not directly subtending developing infructescences, no reduction in seed production occurred. Together, these results suggest that only photosynthate from leaves directly subtending infructescences contributes to seed production in nearby infructescences. Effects of the experimental removal of leaf area did not persist the second year, suggesting that mobilization of storage products the following spring occurred independent of prior treatment. There was probably little negative impact of leaf herbivores on this plant species during the study year due to (1) low occurrence of localized damage within the crowns of censused trees and (2) delay of leaf area loss until completion of fruit development.     

东北槭属的花粉形态及其在分类上的意义

本文采用光学显微镜和扫描电镜,对我国东北地区械属10种变1种的花粉形态进行了观察。本属花粉近球形式长球形,赤道面观为近圆形或窄椭圆形,极面观为3裂圆形,极轴长2.-40μm;具3沟,沟明显;外壁通常具条纹状纹饰,稀具网状纹饰。从观察材料看,本属花粉可归之为2个类型:(1)色木槭型:(Mono maple type):外壁具条纹状纹饰,条纹宽0.250.50μm;(2)梣叶槭型(Ash-leaved maple type):外壁具条网状纹饰,网眼形状不规则,多为长形,长约3μm;网脊宽0.7μm,这正好与分类学家根据形态划分的个亚属相吻合。花粉形态所提供的资料,也支持色木槭(Acermono Maxim.)和平基槭(A.truncatum Bge.)作为两个独立种的处理意见。     

A theoretical model of hydraulic conductivity recovery from embolism with comparison to experimental data on Acer saccharum

A theoretical model of bubble dissolution in xylem conduits of stems was designed using the finite differential method and iterative calculations via computer. The model was based on Fick's, Henry's and Charles' laws and the capillary equation. The model predicted the tempo of recovery from embolism in small diameter branches of woody plants with various xylem structures under different xylem water pressures. The model predicted the time required to recover conductivity in any position in the stem. Repeated iterative solution of the model for different situations yielded an empirical formula to calculate the time for complete recovery of conductivity in stems from a fully embolised initial state. The time, t_p, is given by: where α is a temperature coefficient; D is the coefficient of diffusion of air in wood at 25°C; r_cs is the ratio of the area of total conduit cross section to the stem cross section; Ψ_xp is the stem xylem pressure potential (Pa, where 0 Pa equals atmospheric pressure); τ is solution surface tension (0.072 N m^?1); and D_c and D_s are diameters of the conduits and the stem, respectively (m). The equation is valid only when Ψ_xp > –4τ/D_c. The model predicts no recovery of conductivity when Ψ_xp≤–4τ/D_c. The model agreed with experiments.     

珍稀濒危植物梓叶槭种群径级结构与种内种间竞争关系

该研究对四川省珍稀濒危植物梓叶槭(Acer catalpifolium)种群的主要分布区进行调查,分析梓叶槭种群径级结构与种内和种间的竞争关系,探讨竞争强度与径级和距离之间的关系。结果表明:(1)梓叶槭胸径与树高之间存在显著的幂函数关系;种群径级结构呈正态分布,中小径级树木较多,高径级树木较少。(2)梓叶槭种内和种间竞争强度分别占总竞争强度(222.87)的15.16%和84.84%,说明竞争主要来自种间。(3)梓叶槭与主要伴生种之间的竞争强度大小依次为柳杉桢楠白栎刺楸灯台树桦木杉木厚朴光皮桦;对象木和竞争木距离与竞争指数之间较好地服从指数函数关系,当对象木与竞争木距离小于1m时,竞争指数可达到5.5,随着距离逐渐增加,其竞争指数相应降低,并最终趋于平缓。(4)竞争强度随对象木胸径的增大而减小,当对象木胸径小于20cm时,受到的竞争压力最大,竞争指数最大的分别是梓叶槭与整个林分(234.98)以及梓叶槭与种间(184.01);当对象木胸径小于10cm时,竞争指数均可以达到18;当对象木胸径大于20cm时,竞争强度变化很小且竞争指数较低;竞争强度与对象木胸径服从幂函数关系(CI=AD-B)。(5)模型预测结果表明,随着梓叶槭胸径的增加,竞争指数均越来越小,竞争强度呈降低趋势;当梓叶槭胸径为0~5cm时,梓叶槭与整个林分受到的竞争强度最大,竞争指数为7.14,占总竞争强度的50%;当胸径大于20cm时,竞争指数变化不大;该模型能很好的预测梓叶槭种内和种间竞争强度。     

Seasonality of cavitation and frost fatigue in Acer mono Maxim.

Although cavitation is common in plants, it is unknown whether the cavitation resistance of xylem is seasonally constant or variable. We tested the changes in cavitation resistance of Acer mono before and after a controlled cavitation–refilling and freeze–thaw cycles for a whole year. Cavitation resistance was determined from ‘vulnerability curves’ showing the percent loss of conductivity versus xylem tension. Cavitation fatigue was defined as a reduction of cavitation resistance following a cavitation–refilling cycle, whereas frost fatigue was caused by a freeze–thaw cycle. A. mono developed seasonal changes in native embolisms; values were relatively high during winter but relatively low and constant throughout the growing season. Cavitation fatigue occurred and changed seasonally during the 12‐month cycle; the greatest fatigue response occurred during summer and the weakest during winter, and the transitions occurred during spring and autumn. A. mono was highly resistant to frost damage during the relatively mild winter months; however, a quite different situation occurred during the growing season, as the seasonal trend of frost fatigue was strikingly similar to that of cavitation fatigue. Seasonality changes in cavitation resistance may be caused by seasonal changes in the mechanical properties of the pit membranes.     

不同种源五角枫幼苗叶片N、P化学计量学特征对氮添加的响应

不同土壤氮环境下植物对氮沉降的响应趋势不同,因此研究不同种源地的五角枫(Acer mono)对氮沉降的响应机理具有重要的意义。为了深入了解不同种源五角枫对氮沉降的适应和响应机制,主要通过3个种源的五角枫幼苗氮添加控制实验,分析不同种源的五角枫幼苗比叶面积(SLA)和叶片干物质含量(LMDC)以及叶片N、P含量和N∶P对氮添加的响应规律。结果表明:(1)不同氮添加处理下,内蒙古种源五角枫幼苗(NW)和山西种源五角枫幼苗(SW)的LDMC均显著低于对照,NW和SW在N4条件下表现为显著的促进作用。随着氮添加浓度的增加,NW与北京种源的五角枫幼苗(BW)的SLA在N4条件下显著增加;SW的SLA在N2的水平下显著增加。(2)氮添加下,只有SW的P_(mass)在N1水平下显著增加,N_(mass)在N1和N3水平下表现为显著增加。说明在低氮水平下,能够促进SW对P的吸收,从而增加植物体内对P的积累。同时在低氮和中高氮条件下,能够促进SW对N的吸收,说明SW能较好的适应低氮和高氮环境,使其生存能力更强。(3)分析变异来源及各指标的相关性得出,氮添加条件下,五角枫的SLA、LDMC、P_(area)及N∶P与氮添加处理呈显著的相关关系,而SLA、LDMC、N_(mass)、P_(mass)、Narea、P_(area)和N∶P对氮添加处理和种源的交互作用均未表现出相关关系,说明引起五角枫各性状主要受氮添加处理影响。(4)综合各指标的变化,氮添加条件下,NW的LDMC显著降低,SLA显著增大,同时叶N含量、叶P含量以及N∶P比较高;SW的LDMC显著降低,SLA增大,同时叶N含量、叶P含量表现为显著增大,结合叶经济谱理论分析得出,SW和NW属于"快速投资-收益"型,而BW倾向于"缓慢投资-收益"型。因此,不同种源的五角枫对于氮沉降的响应存在差异,并且持续的氮添加已经改变了五角枫的适应性。     

濒危树种庙台槭种群数量特征及动态分析

庙台槭(Acer miaotaiense Tsoong)为我国三级保护植物,是秦岭特有的濒危树种,具有重要的经济价值和观赏价值。通过对庙台槭主要分布区野生资源进行调查,研究其种群的年龄结构、静态生命表、存活曲线和死亡曲线,用动态指数(Vpi、Vpi')和时间序列模型预测其种群发展趋势。结果显示,庙台槭种群幼龄个体多,中龄和老龄个体少,其生存曲线呈Deevey-Ⅲ型;静态生命表及相关曲线分析显示,庙台槭种群的存活率与径级表现出显著负相关,而种群死亡率曲线总体呈先下降后增加的趋势;种群数量动态分析显示,庙台槭种群整体结构处于增长型,在缺乏成年个体的情况下,种群对外部环境的抗干扰能力下降;时间序列预测发现,经过幼苗、幼树阶段,同一时间曲线的庙台槭种群数量在高径级所占比例略有增加,但高龄级个体相对较少;庙台槭分布地区的主要植被类型为落叶阔叶林和常绿阔叶林,但庙台槭个体受保护较少,人为活动及病虫害影响较大,天然更新困难,生存和保护状况不容乐观。     

槭属的一个系统

对槭属的研究历史作了简要的回顾。详细地论述了槭属植物的芽、花序、性别分花,花,果实、胚、叶等的形态特征及其演化关系。在上述论述的基础上提出槭属的一个系统。这个系统包括４亚属２３组３３系２００种。