Cottonwoods (Populus spp.) are dioecious phreatophytes of hydrological and ecological importance in riparian woodlands throughout the Northern Hemisphere. In streamside zones of southern Alberta, groundwater and soil water typically decline between May and September. To understand how narrowleaf cottonwoods (Populus angustifolia James) are adapted to this seasonal decrease in water availability, we measured photosynthetic gas exchange, leaf reflectance, chlorophyll fluorescence and stable carbon isotope composition (delta(13)C) in trees growing in the Oldman River valley of southern Alberta during the 2006 growth season. Accompanying the seasonal recession in river flow, groundwater table depth (Z(gw)) declined by 1.6 m, but neither mean daily light-saturated net photosynthetic rate (A(max)) nor stomatal conductance (g(s)) was correlated with this change. Both A(max) and g(s) followed a parabolic seasonal pattern, with July 24 maxima of 15.8 micromol m(-2) s(-1) and 559 mmol m(-2) s(-1), respectively. The early summer rise in A(max) was related to an increase in the chlorophyll pool during leaf development. Peak A(max) coincided with the maximum quantum efficiency of Photosystem II (F(v)/F(m)), chlorophyll index (CI) and scaled photochemical reflectance index (sPRI), but occurred one month after maximum volumetric soil water (theta(v)) and minimum Z(gw). In late summer, A(max) decreased by 30-40% from maximum values, in weak correlation with theta(v) (r(2) = 0.50). Groundwater availability limited late-season water stress, so that there was little variation in mean daily transpiration (E). Decreasing leaf nitrogen (% dry mass), CI, F(v)/F(m) and normalized difference vegetation index (NDVI) were also consistent with leaf aging effects. There was a strong correlation between A(max) and g(s) (r(2) = 0.89), so that photosynthetic water-use efficiency (WUE; A(max)/E) decreased logarithmically with increasing vapor pressure deficit in both males (r(2) = 0.75) and females (r(2) = 0.95). The male:female ratio was unequal (2:1, chi(2) = 16.5, P < 0.001) at the study site, but we found no significant between-sex differences in photosynthetic gas exchange, leaf reflectance or chlorophyll fluorescence that might explain the unequal ratio. Females tended to display lower NDVI than males (P = 0.07), but mean WUE did not differ significantly between males and females (2.1 +/- 0.2 versus 2.5 +/- 0.2 mmol mol(-1)), and delta(13)C remained in the -28.8 to -29.3 per thousand range throughout the growth season, in both sexes. These results demonstrate changes in photosynthetic and water-use characteristics that collectively enable vigorous growth throughout the season, despite seasonal changes in water supply and demand.

通过树木年轮学方法, 研究了树木性别、大小、邻体竞争和气候因子(温度和降水)对东北红豆杉(Taxus cuspidata)径向生长的影响。研究表明, 性别和树木大小对东北红豆杉径向生长影响显著, 雄株的径向生长速率显著大于雌株(p=0.023)。东北红豆杉雌、雄植株径向生长速率均与邻体竞争强度显著负相关(p&lt;0.05), 并且邻体竞争对雌株径向生长的负效应更大。树木气候学分析表明, 东北红豆杉雌、雄植株径向生长对气候因子的响应不同。雌株径向生长量与前一年8月、前一年10月平均温度显著负相关, 雄株径向生长量与月平均温度不显著相关。雌株径向生长量与当年1月的降水量显著负相关, 而雄株径向生长量与当年8月的降水显著负相关。

为了更好地理解温带阔叶红松原始林群落主要树种的生理生态学特征,为森林生态系统碳动态的模拟预测提供基础数据,本研究依托中国科学院长白山森林生态系统定位站,首次利用冠层塔吊原位测定了阔叶红松原始林群落4个主要树种成熟大树的CO₂响应曲线,并利用FvCB模型计算了一些重要的光合生理参数.结果表明: 红松的光合速率(A)、最大羧化速率(V_{c max})和气孔导度(g_s)均最小,而其气孔对光合的限制性(L_s)最大.水曲柳、蒙古栎和紫椴这3个阔叶树种的光合特征也存在显著差异.基于叶片面积的V_{c max}大小顺序为:水曲柳(83.2 μmol·m^-2·s^-1)、蒙古栎(89.3 μmol·m^-2·s^-1)&gt;紫椴(68.4 μmol·m^-2·s^-1)、红松(68.8 μmol·m^-2·s^-1)(P&lt;0.05),而基于叶片质量的V_{c max}大小顺序为:水曲柳(1.36 μmol·g^-1·s^-1)&gt;蒙古栎(1.03 μmol·g^-1·s^-1)&gt;紫椴(0.90 μmol·g^-1·s^-1)&gt;红松(0.42 μmol·g^-1·s^-1)(P&lt;0.05).7—9月,水曲柳和蒙古栎的A值显著降低,而紫椴和红松的A值变化不显著;所有树种V_{c max}都随季节发生显著下降.在温带阔叶红松林生态系统碳动态的模拟预测中,应该考虑V_{c max}的季节变化.

树木光合作用的测定常因植株高大而难以开展, 其中离体测定是解决途径之一。但离体测定的方法及其可靠性因树种而异。选取东北东部温带森林中特性各异的7种主要树种: 针叶树(红松(Pinus koraiensis)、长白落叶松(Larix olgensis))、散孔材(白桦(Betula platyphylla)、胡桃楸(Juglans mandshurica))和环孔材(水曲柳(Fraxinus mandshurica)、黄榆(Ulmus macrocarpa)、蒙古栎(Quercus mongolica)), 首先采用光合速率恢复到光合诱导前稳定值90%的时间(T₉₀)长短和叶片蒸腾速率(E)的大小评估离体叶片水分供应状况及其光合活力, 以此确定较优的离体测定方案; 同时, 观测离体叶片的光合活力稳定时间; 最后通过比较原位测定和采用所确定的较优离体方案测定的各树种叶片气体交换参数, 论证采用离体测定光合作用的可靠性。结果表明: 除蒙古栎外的6个树种的离体叶片均具有较高、较稳定的水分供应和光合活力。离体枝条或复叶插入水中, 环剥去除切口处3 cm左右的韧皮部和剩余叶片的方法, 是这6个温带树种叶片光合能力的较优离体测定方法。6个树种叶片的T₉₀受树木特性的影响而差异显著(p T₉₀显著高于散孔材和针叶树种。6个树种离体叶片在1 h内均有较高、较稳定的水分供应和光合活力。在此期间离体所测得的绝大多数叶片的气体交换参数与其原位测定值之间的差异不显著。该研究提出了可行的树木叶片光合作用的离体测定方案, 适用于蒙古栎以外的其他6个温带树种。

<p><em>Aims</em> Tree leaf photosynthesis is often difficult to measure <em>in situ</em> because of the physical inaccessibility of the tree canopy. One simple, inexpensive solution is to measure photosynthesis <em>in vitro</em>, but its validity and reliability for specific tree species need verification. Our goals were to determine (a) which <em>in vitro</em> measurement methods would result in detached leaves maintaining as high photosynthetic activity as<em> in situ</em>, (b) how long the photosynthetic activity of detached leaves can be sustained and (c) the reliability and feasibility of<em> in vitro</em> measurements. <em>Methods</em> We selected seven major tree species with divergent ecophysiological characteristics in the temperate forest of northeastern China: coniferous (<em>Pinus koraiensis</em> and<em> Larix olgensis</em>), diffuse-porous (<em>Betula platyphylla</em> and <em>Juglans mandshurica</em>) and ring-porous (<em>Fraxinus mandshurica</em>, <em>Ulmus macrocarpa</em> and <em>Quercus mongolica</em>) species. We used the time for the photosynthetic rate to recover 90% of its pre-photoinducement value (<em>T</em>₉₀) and leaf transpiration rate (<em>E</em>) to assess the water supply and photosynthetic activity of detached leaves. Based on this, we determined an optimal <em>in vitro</em> protocol for measuring photosynthesis of detached leaves. We simultaneously monitored the duration of relatively stable photosynthetic rates after leaves had been detached. We then compared the differences in gas exchange parameters between<em> in situ</em> and <em>in vitro</em> measurements with the chosen protocol to determine the reliability of the protocol for each tree species. <em>Important findings</em> The detached leaves of all measured tree species except for<em> Q. mongolica</em> had the potential to maintain relatively high, stable water supply and photosynthetic activity. The optimal protocol of <em>in vitro</em> photosynthesis measurements for the other six tree species was to insert the twigs or compound leaves into water immediately following detaching, girdle phloem about 3 cm from the cut and remove all leaves except the target ones. <em>T</em>₉₀differed significantly among the six tree species (<em>p</em> < 0.05), and the ring-porous tree species had significantly greater <em>T</em>₉₀ than the other species. The leaf water supply and photosynthetic activity for the six species was effectively maintained for one hour following detachment, during which most of the gas exchange parameters measured did not differ significantly between <em>in situ</em> and <em>in vitro</em> measurements. Therefore, this study provided a feasible protocol of <em>in vitro</em> measurement of leaf photosynthesis for the six temperate tree species.</p>

光合作用对光和CO2响应模型是研究植物生理和植物生态学的重要工具, 可为植物光合特性对主要环境因子的响应提供科学依据。该文综述了当前光合作用对光和CO2响应模型的研究进展和存在的问题, 并在此基础上探讨了这些模型的可能发展趋势。光合作用涉及光能的吸收、能量转换、电子传递、ATP合成、CO2固定等一系列复杂的物理和化学反应过程。光合作用由原初反应、同化力形成和碳同化3个基本过程构成, 任一个过程均可对光合作用速率产生直接的影响。光合作用对光响应模型只涉及光能的转换, 而光合作用的生化模型包含了同化力形成和碳同化这两个基本过程。把光合作用的原初反应, 即把参与光能吸收、传递和转换的捕光色素分子的物理参数(如捕光色素分子数、捕光色素分子光能吸收截面、捕光色素分子处于激发态的平均寿命等)结合到生化模型中, 可能是今后光合作用对光响应机理模型的发展方向。

胡杨(Populus euphratica)叶形多变, 随个体生长发育, 植株出现条形、卵形和锯齿阔卵形叶。在新疆塔里木河上游人工胡杨林内选择具有此3种叶形的成年标准株, 将枝条拉至同一高度, 通过活体测定, 比较其光合作用-光与CO₂响应及叶绿素荧光响应特征。结果表明: 胡杨异形叶光合速率对光强/CO₂浓度与电子传递速率对光强的响应曲线均可用直角双曲线修正模型来拟合, 得出的主要光合参数与实测值较吻合。胡杨卵形叶、锯齿阔卵形叶光合速率-光响应参数与生化参数及快速光响应参数与条形叶差异显著, 而光合速率-CO₂响应参数则无显著差异。胡杨异形叶CO₂饱和浓度下的最大净光合速率(P_nmax)较饱和光强下的P_nmax高, 表明胡杨强光下光合速率在很大程度上受CO₂供应和1,5-二磷酸核酮糖(RuBP)再生能力的限制。卵形叶、锯齿阔卵形叶的初始量子效率(α)、初始羧化效率(CE)、P_nmax、光合能力(A_max)与最大羧化速率(V_cmax)均显著高于条形叶; 锯齿叶光饱和点(LSP)、最大电子传递速率(ETR_max)与光呼吸速率(R_p)高于卵形叶, 条形叶光补偿点(LCP)与LSP、α、CE最低。表明荒漠干旱环境下胡杨锯齿叶最耐强光, 高R_p可能是其耗散过剩光能、保护光合机构免于强光破坏的重要途径; 卵形叶高的α、CE、磷酸丙糖利用效率(TPU)、PSII实际光化学效率(Φ_PSII)与低LCP及叶氮分配策略是其保持高光合速率的原因; 条形叶Φ_PSII、ETR、P_n低, 因其制造光合产物不足而难以满足树体生长逐渐减少并处于树冠下部。可见, 胡杨条形叶光合效率低、抗逆性差, 主要以维持生长为主; 随着树体长大, 条形叶难以适应荒漠环境来维系其生长, 出现了卵形叶; 卵形叶光合效率高, 易于快速积累光合产物而加快树体生长, 但其LSP低和耐光抑制能力弱, 逐渐被更耐强光、高温与大气干旱的锯齿叶所取代, 从而使胡杨在极端逆境下得以生存, 这是胡杨从幼苗到成年叶形变化及异形叶着生在树冠不同高度的原因。

This review reports on the processes associated with costs of reproduction, including some theoretical considerations, definitions and methodological aspects, followed by a list of the situations where costs are difficult to find. Despite some exceptions, case studies, examined by trade-offs between reproduction and other life-history traits, generally support the predictions of the cost of reproduction hypothesis. The cost of reproduction as an evolutionary determinant of sexual dimorphism in life history traits in dioecious species was specifically tested, considering that the higher cost of reproduction in females has driven the life history traits related to sexual dimorphism. Females of woody dioecious species were consistently smaller than males supporting the costs of reproduction hypothesis. By contrast, females of herbaceous perennials were generally the larger sex, which did not fit the expectations of the hypothesis. Finally, the mechanisms that enable the compensation of the reproductive costs are detailed, including the plastic responses of photosynthesis and growth, the effects of the timing of investment, plant architecture and plant physiological integration. Contents Summary 321 I. Introduction 321 II. Theory on costs of reproduction 322 III. Methodological aspects 324 IV. Empirical evidence 328 V. Plant size and costs of reproduction 330 VI. Costs of reproduction in sexually dimorphic plants 331 VII. Compensation of the costs 333 VIII. Concluding comments and future perspectives 336 Acknowledgements 337 References 337.

根据74条样带、436.872 hm2抽样面积的调查结果，对黑龙江穆棱东北红豆杉(Taxus cuspidata)自然保护区内天然东北红豆杉种群数量、种群分布与生态因子的相互关系进行了研究，结果表明：在保护区34 544 hm2范围内天然东北红豆杉种群数量庞大，个体数高达179 613株。天然东北红豆杉种群的分布对海拔、坡向、坡位和坡度等生态因子具有选择性。700～800 m是种群的最适海拔范围；分布在阴坡的天然种群数量明显高于阳坡；山地的中部和上部更适合东北红豆杉生长；东北红豆杉种群多数分布在坡度15度以下的山地，随着坡度的增加，天然种群的数量明显减少。