Contrasting Predictors of Fern versus Angiosperm Decomposition in a Common Garden

We evaluated differences in the rates and correlates of decomposition among 32 fern and angiosperm litter types collected in Hawai'i. Leptosporangiate ferns were separated into groups based on phylogeny: 'polypod' ferns, a monophyletic clade of ferns that diversified in the Cretaceous, and all other ('non-polypod') ferns that diversified earlier. We measured initial litter chemistry (nutrients and carbon chemistry), and mass loss and nitrogen (N), phosphorus (P), and calcium (Ca) of litter tissue during a 1-yr incubation in a common garden. Nutrient concentrations and carbon (C) chemistry differed significantly among litter types, and litter turnover ( k -values) ranged from 0.29 to 8.31. Decomposition rates were more closely correlated with nutrient concentration than is typically observed. Lignin:N was the best predictor of decomposition across all litter types combined; however, among plant groups different predictors of decomposition were important. Nitrogen and P concentrations best predicted fern decomposition, whereas C chemistry, particularly lignin concentration, was more important for angiosperm (monocot and dicot) decomposition. Among native plants, non-polypod ferns decomposed significantly more slowly than both polypod ferns and angiosperms. Contrary to our hypothesis, fern litter did not decompose more slowly than angiosperm litter overall. Nutrient dynamics in litter were affected by initial litter concentration more than phylogeny; low-nutrient litter immobilized more nutrients than high-nutrient litter. Systematic differences in rates of decomposition, and the importance of nutrients in predicting fern decomposition, imply that changes in species composition within ferns and between ferns and angiosperms could influence the functioning of ecosystems where ferns are important forest components.     

Variation in the shoot calcium content of angiosperms

This study describes the variation in the mean relative shoot Ca content within the angiosperms at the ordinal level. Data were derived from studies in the literature in which the shoot Ca content of two or more species had been compared, and from a hydroponic experiment in which plants were selected to represent the relative number of species within each angiosperm order. Across all angiosperms, most of the variation in shoot Ca content occurred at and above the level of the order. Relative shoot Ca contents and variances correlated between literature and experimental data. In general, orders of commelinoid monocots had lower Ca contents than other monocot or eudicot orders. These results are used to illustrate how physiological and ecological hypotheses can be formulated using literature data.     

Quantitative variability of cyanogenesis in Cathariostachys madagascariensis—the main food plant of bamboo lemurs in Southeastern Madagascar

Giant bamboo (Cathariostachys madagascariensis) is a major food plant for three sympatric species of bamboo‐eating lemurs (Hapalemur aureus, H. griseus, and Prolemur simus) in the rain forests of southeastern Madagascar. This plant species is strongly cyanogenic. However, quantitative data on cyanide concentration in C. madagascariensis are scarce. Previous studies reported 15 mg cyanide per 100 g fresh shoot material (corresponding to approx. 57 µmol cyanide per gram dry weight). However, we found mean concentrations (±SE) ranging from 139.3±19.32 in ground shoots to 217.7±16.80 µmol cyanide per gram dry weight in branch shoots. Thus, cyanogenesis of C. madagascariensis was up to four times higher than reported before. In contrast to the strongly cyanogenic shoots no cyanide could be detected in differently aged leaves of C. madagascariensis confirming earlier studies. Within individual shoots fine‐scaled analysis revealed a characteristic ontogenetic pattern of cyanide accumulation. Highest concentrations were found in youngest parts near the apical meristem, whereas concentrations decreased in older shoot parts. Beyond the general intra‐individual variability of cyanogenic features analyses indicated site‐specific variability of both, the ontogenetic pattern of cyanide concentration as well as the total amount of cyanide accumulated in shoots. Additionally, analyses of soluble proteins—one important nutritive measure affecting food plant quality—demonstrated a converse quantitative relation of protein concentrations in leaves to cyanide concentration in shoots at the site‐specific level. We, thus, suggest integrative analyses on quantitative variation of cyanogenesis together with nutritive plant parameters in future studies. This approach would allow obtaining more detailed insights into spatial variability of giant bamboo's overall browse quality and its impact on lemur herbivores. Am. J. Primatol. 71:305–315, 2009. © 2009 Wiley‐Liss, Inc.     

Maize plant growth and accumulation of photosynthetic pigments at short- and long-term exposure to cadmium

A wide range of cadmium concentrations (from 4 to 200 μM for seedlings and up to 2 mM for germinating kernels) was used to assess Cd toxic effects on maize (Zea mays L.) plants at the different developmental stages: germinating kernels, seedlings (4–9 days), and juvenile plants (34 days). Cd accumulation in plant organs was followed, and its lethal concentration was elucidated. In maize, cadmium was accumulated predominantly in roots; in shoots it was mainly accumulated in the lower leaves, and the higher was leaf position the lower was Cd content in it. At high concentrations (80 and 200 μM), kernels became the substantial cadmium depot. Germinating kernels manifested the lowest sensitivity to cadmium; seedlings were more sensitive; the inhibition of juvenile plant growth attained 90% and more. In the tested range of concentrations, cadmium suppressed shoot mass accumulation harder than that of roots. In 34-day-old plants, water content in shoots was stronger reduced than in roots. Plant death was also manifested earlier in shoots. It was concluded that maize plant sensitivity to cadmium increases with plant growing and that, under conditions of normal mineral nutrition, cadmium inhibits shoot growth more severe than root growth.     

The plant vigour hypothesis revisited – how is browsing by ungulates and elephant related to woody species growth rate?

The way herbivores select what to eat is of considerable practical and theoretical interest, and has given rise to different theories and hypotheses. The plant vigour hypothesis predicts that herbivores feed preferentially on vigorous, i.e., large and/or fast-growing plants or plant parts. These predictions have previously primarily been tested on variation within plant species. Here we test whether differences in vigour among plant species in the same environment can explain differences in herbivore attack. We studied variation in browsing pressure by a guild of large herbivores on different woody species in an African savanna ecosystem. Shoot growth rate, annual shoot length, basal shoot diameter and annual shoot volume of 14 woody plant species were measured in the field. Plant species’ shoot vigour represented by the first PCA axis scores generated from the four shoot variables were then related to browsing pressure (% utilisation) on each of the species by native ungulates and elephant. Nutrient and fibre concentrations and tannin activity were also determined for the 14 woody plant species. We found ungulate browsing pressure to show a unimodal relationship with plant species’ shoot vigour. The heaviest browsing pressure was on plant species with shoots of intermediate vigour. We suggest that species with less vigorous shoots had low nutrient and high fibre concentrations and offered small bite sizes, whereas species with vigorous shoots had high nutrient concentrations but larger shoot diameters than the bite diameters of browsing ungulates. Elephant browsing pressure was not related to plant species’ shoot vigour.     

Testing the distinctness of shoot ionomes of angiosperm families using the Rothamsted Park Grass Continuous Hay Experiment

? The ionome is the elemental composition of a tissue or organism. Phylogenetic variation in the ionomes of plant shoots has been widely reported based on controlled experiments, vegetation surveys and literature meta-analyses. However, environmental effects on phylogenetic variation in shoot ionomes have not been quantified. This study tests the hypothesis that phylogenetic variation in shoot ionomes is robust to environmental perturbation and that plant families can be distinguished by their shoot ionomes. ? Herbage was sampled from six subplots of the Rothamsted Park Grass Experiment. Subplots had received contrasting fertilizer treatments since 1856. Herbage was separated into its constituent species (n?=?21) and concentrations of eleven mineral elements were determined in dried shoot material. ? Shoot concentrations of calcium (Ca), zinc (Zn), manganese (Mn), magnesium (Mg) and sodium (Na) showed significant variation associated with plant species, and responded similarly to fertilizer treatments in diverse plant species. Species?×?treatment interactions were indicated for phosphorus (P), potassium (K), nickel (Ni), copper (Cu) and iron (Fe). Plant families could be distinguished by their shoot ionomes. The most informative elements for discriminant analysis were Ca?>?Mg?>?Ni?>?S?>?Na?>?Zn?>?K?>?Cu?>?Fe?>?Mn?>?P. ? Whilst shoot ionomes were sensitive to fertilizer treatment, phylogenetic variation in a subset of the shoot ionome (Ca, Zn, Mn, Mg) was robust to this environmental perturbation.     

Correlation analysis between arbuscular mycorrhizal fungal community and host plant phylogeny

 为弄清丛枝菌根(arbuscular mycorrhiza, AM)真菌群落随宿主植物演化的变异规律,通过对MaarjAM数据库进行数据挖掘, 根据每个分子虚拟种(virtual taxa, VT)包含的DNA序列不少于5条的标准, 筛选出188种菌根植物。通过分析植物与其根内AM真菌的关系发现: AM真菌的物种丰富度随着寄主植物的分化而增加; 在不同的植物系统类群中, AM真菌的物种丰富度显著不同; 在起源时间较晚的被子植物和裸子植物中, AM真菌的物种丰富度显著高于起源较早的苔类、角苔类和蕨类植物类群, 而与寄生植物共生的AM真菌物种丰富度与早期植物无显著差异; 不同寄主植物进化类群间AM真菌组成差异显著。以上结果表明: AM真菌群落随着寄主植物进化而发生变化。在进化过程中, 寄主植物倾向于选择保留共生效率较高的AM真菌。     

南昌市不同植物类群叶片氮磷浓度及其化学计量比

对南昌大学前湖校区89种主要植物叶片的N、P浓度及其化学计量比进行了研究,结果表明:乔灌、常绿、针叶、种子、裸子和单子叶植物类群的N浓度分别低于相对应的草本、落叶、阔叶、蕨类、被子和双子叶植物类群,而C3和C4植物差异不显著;乔灌、常绿和裸子植物类群的P浓度含量分别低于相对应的草本、落叶和被子植物类群,而针叶和阔叶、蕨类和种子、单子叶和双子叶、C3和C4植物类群间差异不显著;乔木、阔叶、被子和双子叶植物类群叶片N/P分别高于相对应的灌草、针叶、裸子和单子叶植物类群,而常绿和落叶、蕨类和种子、C3和C4植物类群之间差异不显著.可见,不同类型植物对N和P的吸收利用存在差异,且对不同养分供应采取不同的适应对策.结合研究区土壤养分现状,建议优先选择常绿、针叶、裸子和单子叶植物类群作为城市园林植物.     

Large-area experiment on uptake of metals by twelve plants growing in soils contaminated with multiple metals

A site in central Taiwan with an area of 1.3 ha and contaminated with Cr, Cu, Ni, and Zn was selected to examine the feasibility of phytoextraction. Based on the results of a preexperiment at this site, a total of approximately 20,000 plants of 12 species were selected from plants of 33 tested species to be used in a large-area phytoextraction experiment at this site. A comparison with the initial metal concentration of 12 plant species before planting demonstrated that most species accumulated significant amounts of Cr, Cu, Ni, and Zn in their shoots after growing in this contaminated site for 31 d. Among the 12 plant species, the following accumulated higher concentrations of metals in their shoots; Garden canna and Garden verbena (45-60 mg Cr kg(-1)), Chinese ixora and Kalanchoe (30 mg Cu kg(-1)), Rainbow pink and Sunflower (30 mg Ni kg(-1)), French marigold and Sunflower (300-470 mg Zn kg(-1)). The roots of the plants of most of the 12 plant species can accumulate higher concentrations of metals than the shoots and extending the growth period promotes accumulation in the shoots. Large-area experiments demonstrated that phytoextraction is a feasible method to enable metal-contaminated soil in central Taiwan to be reused.     

Differences in meristems between monocots and dicots and susceptibility to attack by gall-inducing insects

We used comparative methods that account for the phylogenetic correlations among species to test hypotheses about the community of gall-inducing insects on dicotyledonous and monocotyledonous plants and woody and herbaceous angiosperms in the UK. We found that the species richness of gall-inducing insects on dicots was greater than on monocots and that the odds of a dicot having an associated gall-inducing insect is 42% higher than for a monocot. Woody angiosperms have higher species richness of associated gall-inducing insects than do herbaceous angiosperms. Furthermore, using a Monte Carlo analysis we found that attacks by gall-inducing insects on monocot families were phylogenetically clustered in the order Poales, particularly within the grass family Poaceae. We suggest that the higher risk of attack on dicots and higher species richness of gall-inducing insects on woody angiosperms, which are exclusively dicots, arises because of differences in the abundance or susceptibility of dicot meristems to attack by gall-inducing insects. Architectural and anatomical differences between monocots and dicots that give rise to differences in meristem abundance and anatomy appear to play an important role in determining the occurrence and richness of associated gall-inducing insects on host plants.     

Silicon does not always mitigate zinc toxicity in maize

We have investigated the influence of silicon on higher zinc concentration reducing the growth of aboveground parts by ca 50 % in young maize plants (hybrid Novania) grown in hydroponics. Eight different treatments were used: control, Zn (800 μM ZnSO₄·7H₂O), Si1/Si2.5/Si5 (1/2.5/5 mM Na₂SiO₇) and Zn+Si (combination of zinc and all silicon concentrations). The concentration of Zn and Si and their distribution in plants was determined. The growth parameters (length of primary seminal root, leaf area of first and second leaves, fresh and dry weight of below- and above-ground plant parts) of plants grown in various Zn+Si treatments were significantly decreased in comparison to all other treatments. Increasing concentration of Si in combination with Zn treatment and selected hybrid (Novania) resulted in increased physiological stress in comparison to Zn treatment. However, roots and shoots of all Zn+Si treated plants contained significantly lower amount of Zn than Zn treatment. The Si concentration in roots was the same in Si and Zn+Si plants. In general, higher amount of Si was observed in shoots than in roots of Si1- and Si2.5-treated plants and opposite was observed in Si5-treated plants. In spite of significantly decreased root and shoot accumulation of Zn in the presence of Si, no positive effect of Si on Zn toxicity in young maize plants under experimental conditions used in this work and used maize hybrid was observed.     

世界上已知维管植物有多少种? 基于多个全球植物数据库的整合

维管植物是地球上生物多样性的重要组成部分, 拥有超过200年的研究历史。然而, 世界上有多少种维管植物, 其中有多少种已被发现和描述等问题迄今仍未很好回答。本文整合分析了全球4个主要植物数据库, 以期回答全球已发现和描述了多少物种的问题。结果表明, 全球已发现和描述的维管植物有376,366种(包括自然杂交种)。排除自然杂交种后, 全球共包含369,054种维管植物, 其中广义蕨类植物13,810种, 裸子植物1,172种, 被子植物354,072种。我们的结果比已有的4个数据库中的任何一个的物种数都至少要多17,700种。     

KNOX homeobox genes potentially have similar function in both diploid unicellular and multicellular meristems, but not in haploid meristems

Members of the class 1 knotted-like homeobox (KNOX) gene family are important regulators of shoot apical meristem development in angiosperms. To determine whether they function similarly in seedless plants, three KNOX genes (two class 1 genes and one class 2 gene) from the fern Ceratopteris richardii were characterized. Expression of both class 1 genes was detected in the shoot apical cell, leaf primordia, marginal part of the leaves, and vascular bundles by in situ hybridization, a pattern that closely resembles that of class 1 KNOX genes in angiosperms with compound leaves. The fern class 2 gene was expressed in all sporophyte tissues examined, which is characteristic of class 2 gene expression in angiosperms. All three CRKNOX genes were not detected in gametophyte tissues by RNA gel blot analysis. Arabidopsis plants overexpressing the fern class 1 genes resembled plants that overexpress seed plant class 1 KNOX genes in leaf morphology. Ectopic expression of the class 2 gene in Arabidopsis did not result in any unusual phenotypes. Taken together with phylogenetic analysis, our results suggest that (a) the class 1 and 2 KNOX genes diverged prior to the divergence of fern and seed plant lineages, (b) the class 1 KNOX genes function similarly in seed plant and fern sporophyte meristem development despite their differences in structure, (c) KNOX gene expression is not required for the development of the fern gametophyte, and (d) the sporophyte and gametophyte meristems of ferns are not regulated by the same developmental mechanisms at the molecular level.     

Seasonal and species variation in the content of cadmium and associated metals in pasture plants at Shipham

Summary Very high Cd and Zn concentrations exist in soils reclaimed from old mine workings at Shipham but little of the metal is transferred into the pasture herbage. The amount of metal in the soil therefore only influences the amount in the aerial part of the plant to a small degree. It would appear to be the plant species which to a large extent governs its metal burden: grasses accumulating the least Cd and members of the Compositae the most.Within this species variation exists a change in metal content that corresponds to the time of year, setal levels in plants peaking in the winter between January and March. This increase in the metal content of the shoot reflects the redistribution of metal previously bound within the root. The movement of Pb may be associated with changes in the phosphate status of the plant. In grasses it would appear that the root possesses the highest metal burden, and forHolcus lanatus, tolerance to both Cd and Zn has been established. The ammonium-acetate and DTPA-extractable Zn/Cd ratio in soils corresponds closely to that found in the roots of both ryegrass and Yorkshire fog. A much higher ratio was observed in the shoots of these plants.     

The invention of WUS-like stem cell-promoting functions in plants predates leptosporangiate ferns

The growth of land plants depends on stem cell-containing meristems which show major differences in their architecture from basal to higher plant species. In Arabidopsis, the stem cell niches in the shoot and root meristems are promoted by WUSCHEL (WUS) and WOX5, respectively. Both genes are members of a non-ancestral clade of the WUS-related homeobox (WOX) gene family, which is absent in extant bryophytes and lycophytes. Our analyses of five fern species suggest that a single WUS orthologue was present in the last common ancestor (LCA) of leptosporangiate ferns and seed plants. In the extant fern Ceratopteris richardii, the WUS pro-orthologue marks the pluripotent cell fate of immediate descendants of the root apical initial, so-called merophytes, which undergo a series of stereotypic cell divisions and give rise to all cell types of the root except the root cap. The invention of a WUS-like function within the WOX gene family in an ancestor of leptosporangiate ferns and seed plants and its amplification and sub-functionalisation to different stem cell niches might relate to the success of seed plants, especially angiosperms.     

Vascular plant diversity in eastern Asia and North America: historical and ecological explanations

Taxonomic diversity of vascular plants (ferns, gymnosperms and angiosperms) was compared between eastern Asia and North America. Eastern Asia has significantly higher species richness in all three classes but the difference was greatest in ferns and least in angiosperms. Differences in taxonomic treatments between the two continents are not likely contributors to these patterns. The relationship of regional to global species richness across the three plant classes suggested that diversity patterns were relatively homogeneous at three taxonomic levels. Thus, differences in species richness are established at the family level and are therefore relatively old. The previously noted fact that eastern Asia has a higher proportion of primitive taxa was shown by analyses both among and within plant classes. Diversity patterns across three taxonomic levels (i.e. family, genus and species) of the three classes may reflect the relative historical positions of the two continents (following continental drift) to the centre(s) of their origin, neighbouring land masses, differential speciation/extinction rates, and switches in dominance levels associated with climate change (including glaciation), as well as reproductive/dispersal mechanisms of the three plant classes.     

Anatomical patterns of aerenchyma in aquatic and wetland plants

A well-developed aerenchyma is a major characteristic of aquatic plants. However, because such tissues are also found in wetland and terrestrial plants, it is not always possible to use their presence or absence to distinguish aquatic species. Whereas patterns of aerenchyma in roots have been studied in detail, those of the shoots have not. We collected and tested 110 species of various aquatic and wetland plants, including ferns (5), basal angiosperms (5), monocots (65), and eudicots (35). Three common and two rare types of aerenchyma were observed in their roots (three schizogeny and two lysigeny), plus five types of schizogeny in their shoots. We re-confirmed that, although a well-developed aerenchyma is more common in most organs of aquatic plants than in wetland plants, this presence cannot be used as strict evidence for the aquatic quality of vascular plants. Here, aerenchyma patterns were stable at the genus level, and the consistency of pattern was stronger in the roots than in the shoots. Furthermore, significant trends were verified in several higher taxa, and those consistencies of patterns partially coincided with their phylogeny.     

Stomatal characteristics of ferns and angiosperms and their responses to changing light intensity at different habitats

气孔是植物与大气环境进行气体交换的重要通道, 在调控植物碳水平衡方面发挥着重要作用。为探讨生境和植物类型对气孔形态特征的影响以及气孔对光强变化的响应格局在不同植物间和不同生境条件下的变异, 选取开阔生境和林下生境的5种蕨类植物和4种被子植物, 测定了它们的气孔形态特征和气孔导度对光强变化的响应。此外, 还收集了8篇文献中开阔和林下生境的45种蕨类植物和70种被子植物的气孔密度和气孔长度数据, 以增大样本量从而更好地探讨不同生境条件下蕨类和被子植物气孔密度及长度的变异格局, 并通过分析生境和植物类型对气孔形态特征的影响来推测生境和植物类型对气孔响应行为的可能影响。实验结果表明, 与林下植物相比, 开阔环境下的植物气孔密度更大, 气孔长度更小, 气孔对光强降低的响应更敏感; 但植物类型对气孔形态特征的影响以及对气孔响应光强的敏感程度的影响均不显著。对文献数据的分析表明, 生境和植物类型对气孔形态特征均有显著影响。考虑到气孔响应快慢与气孔形态特征密切相关, 与蕨类植物相比, 被子植物小而密的气孔可能为其更快地响应环境变化提供了基础。研究表明生境和植物类型对气孔响应行为均有显著影响。     

不同生境条件下蕨类和被子植物的气孔形态特征及其对光强变化的响应

气孔是植物与大气环境进行气体交换的重要通道, 在调控植物碳水平衡方面发挥着重要作用。为探讨生境和植物类型对气孔形态特征的影响以及气孔对光强变化的响应格局在不同植物间和不同生境条件下的变异, 选取开阔生境和林下生境的5种蕨类植物和4种被子植物, 测定了它们的气孔形态特征和气孔导度对光强变化的响应。此外, 还收集了8篇文献中开阔和林下生境的45种蕨类植物和70种被子植物的气孔密度和气孔长度数据, 以增大样本量从而更好地探讨不同生境条件下蕨类和被子植物气孔密度及长度的变异格局, 并通过分析生境和植物类型对气孔形态特征的影响来推测生境和植物类型对气孔响应行为的可能影响。实验结果表明, 与林下植物相比, 开阔环境下的植物气孔密度更大, 气孔长度更小, 气孔对光强降低的响应更敏感; 但植物类型对气孔形态特征的影响以及对气孔响应光强的敏感程度的影响均不显著。对文献数据的分析表明, 生境和植物类型对气孔形态特征均有显著影响。考虑到气孔响应快慢与气孔形态特征密切相关, 与蕨类植物相比, 被子植物小而密的气孔可能为其更快地响应环境变化提供了基础。研究表明生境和植物类型对气孔响应行为均有显著影响。     

Transfer factors for Sr as influenced by species Ca uptake and soil Ca availability

Strontium (Sr) and calcium (Ca) concentrations were studied in different plant species grown in five soil treatments. For either shoots or roots, a positive linear relationship was found between Sr and Ca concentrations in different plant species grown in the same soil treatment. Strontium and calcium concentrations of different species were related to the soil selectivity coefficient for Sr and Ca, defined as the ratio of CH₃COONH₄-extractable Sr and Ca to the ratio of Sr and Ca in the soil solution. For the species used in all soils, transfer factors (TF) for Sr, defined as the ratios of the Sr amount per g of dry plant material and the Sr amount per g of dry soil, were negatively correlated with extractable Ca of the soil. Transfer factors for Sr varied greatly among species or between roots and shoots. This variation of transfer factor was reduced when transfer factor values were divided by the shoot or root Ca concentration of each species. The proposed index TF for Sr per Ca concentration could be used to compare various soils according to their ability to supply plants with Sr when different plant species are grown in these soils.