Thoughts on clonal integration: Facing the evolutionary context

Summary In this essay, I have pointed out that the appropriate evolutionary context for plant clonality dictates a focus on the impact of the derived trait of potential independence of subunits on the evolutionarily primitive trait of obligate interdependence of plant subunits, i.e. the advantages of independence. This fact prescribes a major shift in approach from previous lines of investigation which have assumed that clonal plants should fall apart and sought to determine the advantages of interdependence. The delineated reorientation calls for a significant change in the investigation of the ecology of clonality in higher plants, emphasizing factors that select for physical and physiological disintegration of the genet and de-emphasizing the need to derive ecological explanations for properties a plant will possess entirely by reason of its phylogenetic and developmental heritage. I suggest that (1) patterns of ramet independence may result from selective pressures on the cost of interconnections (2) programmed ramet independendence may be a response to the selective pressure of a high possibility of traumatic breakage and (3) programmed ramet independence may allow escape of the genet from mortality due to pathogen infestation.     

Can plants track changes in nutrient availability via changes in biomass partitioning?

Plant and Soil - Can old-field annuals exposed to temporally varying nutrient regimes adjust biomass partitioning programs in order to maximize growth? We grew three species of old-field annuals,...     

施肥对毛竹种群不同年龄分株间胸径大小关系的影响

克隆植物不同年龄分株间可以通过生理整合作用相互传递资源, 实现资源共享。施肥可以改变林地资源状况, 进而可能影响分株间的整合作用及不同年龄分株间的生长关系。该文采用标准主轴(SMA)估计法和多元回归分析, 对不同施肥管理下大型克隆植物毛竹(Phyllostachys edulis)种群不同年龄分株(1年生分株、3年生分株和5年生分株)间的胸径(DBH)关系进行了研究, 探讨毛竹不同年龄分株DBH大小关系对施肥的响应。结果表明: 连续5年施肥有效地增加了毛竹1年生分株的DBH, 而施肥1年处理下, 1年生分株DBH与3年生分株和5年生分株平均DBH差异不显著(p > 0.05)。1年生分株与3年生分株和5年生分株DBH之间的SMA斜率为0.88-1.10, 均与1.00不存在显著差异(p > 0.05), 表现为等速生长关系。施肥1年和连续施肥5年没有改变不同年龄分株DBH之间的SMA斜率, 但连续5年施肥导致SMA的y轴截距显著增大(p < 0.001), 即在3年生分株和5年生分株DBH相同的情况下, 连续5年施肥使1年生分株具有更大的DBH增长量。采用多元线性逐步回归分析发现, 毛竹1年生分株的DBH大小在很大程度上受3年生分株DBH大小的影响, 而连续5年施肥可增强5年生分株对1年生分株DBH大小的影响。     

外来入侵植物大狼把草种群构件生物量结构研究

大狼把草是广泛分布于我国的外来入侵植物之一,通过样方调查,从构件水平定量分析了大狼把草种群各构件的结构特征及其生物量间的关系模型,并探讨了其与入侵性的关系.结果表明:大狼把草种群各构件生物量之间的关系为茎＞花序＞根＞叶.各构件生物量所占比率表现为茎＞花序＞叶＞根.大狼把草种群各构件生物量之间及各构件生物量与植株高度之间都呈显著正相关关系,均可用幂函数模型较好地表达.大狼把草种群各构件较强的表型可塑性及其在生殖器官中较高的生物量投资分配特性,极大地提高了其入侵能力.     

A phyletic perspective on the allometry of plant biomass-partitioning patterns and functionally equivalent organ-categories

Biomass-partitioning patterns influence the functioning of aquatic and terrestrial vegetation at all levels, ranging from individual growth and reproduction to the flow of mass and energy through entire communities. For this reason, leaf, stem and root dry biomass-partitioning patterns across taxonomically and ecologically diverse seed plants (spermatophytes) have been intensively investigated, both empirically and theoretically. By contrast, phyletically disparate plants (e.g. green and brown algal macrophytes, mosses and pteridophytes) have not been examined to determine whether the partitioning of their body parts into 'leaf', 'stem' and 'root' analogs accords with that of spermatophytes. In this review, the biomass-partitioning patterns of siphonous and brown algal macrophytes, mosses and pteridophytes were compared allometrically with those of spermatophytes and were shown to be largely in statistical accordance (thus lending support to the hypothesis that a single scaling relationship exists across eukaryotic photoautotrophs). This concordance is argued to support the hypothesis of functional equivalence across analogous, but developmentally different, body parts, a feature that permits the use of simpler biological model systems with which to derive analytical explanations for the biomass-partitioning patterns reported for more complex seed plants.     

Biomass allocation in old-field annual species grown in elevated CO2 environments: no evidence for optimal partitioning

Increased atmospheric carbon dioxide supply is predicted to alter plant growth and biomass allocation patterns. It is not clear whether changes in biomass allocation reflect optimal partitioning or whether they are a direct effect of increased growth rates. Plasticity in growth and biomass allocation patterns was investigated at two concentrations of CO₂ ([CO₂]) and at limiting and nonlimiting nutrient levels for four fast‐ growing old‐field annual species. Abutilon theophrasti, Amaranthus retroflexus, Chenopodium album, and Polygonum pensylvanicum were grown from seed in controlled growth chamber conditions at current (350 μmol mol^?1, ambient) and future‐ predicted (700 μmol mol^?1, elevated) CO₂ levels. Frequent harvests were used to determine growth and biomass allocation responses of these plants throughout vegetative development. Under nonlimiting nutrient conditions, whole plant growth was increased greatly under elevated [CO₂] for three C3 species and moderately increased for a C4 species (Amaranthus). No significant increases in whole plant growth were observed under limiting nutrient conditions. Plants grown in elevated [CO₂] had lower or unchanged root:shoot ratios, contrary to what would be expected by optimal partitioning theory. These differences disappeared when allometric plots of the same data were analysed, indicating that CO₂‐induced differences in root:shoot allocation were a consequence of accelerated growth and development rates. Allocation to leaf area was unaffected by atmospheric [CO₂] for these species. The general lack of biomass allocation responses to [CO₂] availability is in stark contrast with known responses of these species to light and nutrient gradients. We conclude that biomass allocation responses to elevated atmospheric [CO₂] are not consistent with optimal partitioning predictions.     

东北样带上的克隆植物及其重要性与环境的关系

1997年野外调查资料,对中国东北样带克隆植物沿样带的分布,克隆植物在群落中的重要性以及其与环境因子之间的关系进行了研究,结果表明;克隆植物相对种数（C/Pt)和克隆植物相对重要值（IV）随样带上环境梯度变化呈增加的趋势,群落中克隆植物相对种数与土壤全氮含量负相关,与海拔高度正相关,与年平均温度和年降水相关不显著;克隆植物相对重要值与土壤全氮含量负相关,与海拔高度正相关,与年平均温度和年降水相关不显著,研究还发现,群落中克隆植物种数与非克隆植物种数随样带上海拔高度、年平均温度、年降水梯度变化相关性较差,而克隆植物种数与土壤全氮含量负相关不显著,非克隆植物物种数与土壤全氮含量正相关不显著,根茎型、分蘖型及鳞茎球茎型克隆植物在土壤湿度较差的生境中出现频率较高,而匍匐茎型、根茎鳞茎及根茎球茎型克隆植物在土壤湿度较好的生境中出现频率较高。     

Clonal variation in above- and below-ground growth responses of Populus tremuloides Michaux: Influence of soil warming and nutrient availability

Trembling aspen (Populus tremuloides Michx.) is the most widely distributed tree species in North America making it important to terrestrial carbon and nutrient cycles. Due to anthropogenic climate change high latitude temperatures are expected to increase, making it necessary to assess the feedback between above- and below-ground carbon pools to increased temperature at sites of both high and low N-availability. We grew four clones of aspen at two levels of soil temperature and two levels of soil N-availability for 98 days and quantified photosynthesis, growth, biomass allocation, and root length production and mortality. High soil temperature increased rates of photosynthesis (65%), resulting in greater whole-plant growth (37%) through increases in roots, stems, and foliage; however these increases generally occurred only in soil of high N-availability. Root:shoot biomass allocation varied between clones but was unaffected by the soil temperature or N-availability treatments. Root length production and mortality increased at elevated soil temperature, but this response was modified by soil N-availability. At high soil temperature, soil N-availability had little effect on root dynamics, while at low soil temperature, high soil N-availability increased both the production and mortality (turnover) of roots. We conclude that trembling aspen has the potential for substantially greater growth and root turnover under conditions of warmer soil at sites of both high and low N-availability, but that allometric patterns of growth are under strong genetic, rather than environmental control. This revised version was published online in June 2006 with corrections to the Cover Date.     

Eco-evolutionary vs. habitat contributions to invasion in salmon: experimental evaluation in the wild

Although trait evolution over contemporary timescales is well documented, its influence on ecological dynamics in the wild has received much less attention particularly compared to traditional ecological and environmental factors. For example, evolution over ecologically relevant timescales is expected in populations that colonize new habitats, where it should theoretically enhance fitness, associated vital rates of survival and reproduction, and population growth potential. Nonetheless, success of exotic species is much more commonly attributed to ecological aspects of habitat quality and 'escape from enemies' in the invaded range. Here, we consider contemporary evolution of vital rates in introduced Chinook salmon (Oncorhynchus tshawytscha) that quickly colonized New Zealand and diverged over c. 26 generations. By using experimental translocations, we partitioned the roles of evolution and habitat quality in modifying geographical patterns of vital rates. Variation in habitat quality within the new range had the greatest influence on broad geographical patterns of vital rates, but locally adapted salmon still exhibited more than double the vital rate performance, and hence fitness, of nonlocal counterparts. The scope of this fitness evolution far exceeds the scale of divergence in trait values for these populations, or even the expected fitness effects of particular traits. These results suggest that contemporary evolution can be an important part of the eco-evolutionary dynamics of invasions and highlight the need for studies of the emergent fitness and ecological consequences of such evolution, rather than just changes in trait values.     

基于植株拓扑结构的生物量分配的玉米虚拟模型

依据植物结构—功能相互作用机理,建立了能模拟玉米生长发育与形态结构建成的虚拟模型。该模型的重要部分为基于植株拓扑结构的生物量分配模块。叙述了该模块的构建原理,以2000年田间试验数据提取了玉米的发育、生物量生产和生物量分配参数。模型模拟了2001年的玉米生长发育与生物量分配过程,模拟结果与田间试验结果比较吻合。应用该模型模拟了2001年玉米不同生育阶段植株的生物量分配和各器官生物量积累动态。     

底泥高磷浓度提高了喜旱莲子草的入侵性

植物通过改变自身的形态和生态生理特征对多变的环境因素做出响应,这种表型可塑性能增强外来物种的入侵能力。该文研究了入侵植物喜旱莲子草(Alternanthera philoxeroides)对底泥磷浓度、植株密度以及二者间交互作用的可塑性响应,探讨可塑性是否能使其获得更高的入侵能力。结果表明:低密度×底泥高磷浓度处理条件下的叶重、茎重、总重、叶数、分枝数和茎长等明显高于低、中磷浓度处理;高密度×底泥高磷浓度条件下的叶数、茎长和比茎长的值最大;植株的含磷量随底泥磷浓度的升高显著增加,说明喜旱莲子草响应底泥磷浓度变化时改变了自身的形态与生态生理性状。泥底含磷量对叶重比、叶数、茎长、茎磷含量、叶磷含量和植株总含磷量的影响都达到显著水平(p<0.05);植株密度对茎重、比茎长、叶磷含量和植株总磷含量的影响达到显著水平(p<0.05)。与入侵能力相关的叶重比、叶数、茎长在底泥高磷浓度处理中显著增加,说明底泥的高磷浓度增强了喜旱莲子草的入侵能力。     

Carbon Balance of a Winter Wheat-Root Microbiota System Under Elevated CO2

We examined the carbon budget of young winter wheat plants and their associated microorganisms as affected by a doubling of the atmospheric CO₂ concentration (700 μmol mol^-1). Plants were grown hydroponically in pre-sterilised sand at a controlled irradiance and temperature regime. Net photosynthesis (P_N) and respiration (R_D) rates of roots and shoots were measured continuously, plant growth and carbon distribution in the plant-root medium-associated microorganism system were determined destructively in interval-based analyses. P_N in elevated CO₂ grown plants (EC) was 123% of that in the control (AC) plants when averaged over the whole life span (39-d-old plants, 34 d in EC), but the percentage varied with the developmental stage being 115, 88, and 167% in the pretillering, tillering, and posttillering phase, respectively. There was a transient depression of P_N, higher amplitude of day/night fluctuations of the chloroplast starch content, and depression of carbon content in rhizosphere of EC plants during the period of tillering. After 34 d in EC, carbon content in shoots, roots, and in rhizodepositions was enhanced by the factors 1.05, 1.28, and 1.96, respectively. Carbon partitioning between above and belowground biomass was not affected by EC, however, proportionally more C in the belowground partitioning was allocated into the root biomass. Carbon flow from roots to rhizodepositions and rhizosphere microflora was proportional to P_N; its fraction in daily assimilated carbon decreased from young (17%) to order (3-4%) plants. This revised version was published online in June 2006 with corrections to the Cover Date.