Monitoring of pollen rain in moss polsters and mats in view of their suitability as controls for determining the air-borne component of pollen spectra in herbivore faeces

Pollen has been extracted from six bryophyte and two lichen taxa, sampled from three habitats: upland heath, lowland bog and mixed woodland, in both west and east Scotland. The highest number of pollen taxa was recorded in bothSphagnum andThuidium; the lowest numbers of pollen taxa were recorded in two of the mosses and both lichens. For pollen rain control purposes in herbivore faecal studies, woodland species of bryophytes are not suitable due to the sheltering effects from rain provided by the overhead canopy. Open habitats such as moorland heath and bog provide polsters/mats which normally trap pollen rain more effectively for control purposes. The aim of this study was twofold: to observe the effectiveness of selected polsters and lichens as traps for pollen rain and to establish eventually, whether or not such vegetative traps could be used as controls in pollen spectra analyses of herbivore faeces for the determination of nutritional regime and habitat. From a comparison with recent studies in north west Spain of three taxa in common with Scottish samples,Polytrichum demonstrated a consistently higher number of pollen taxa trapped.Thuidium andCladonia all yielded between one and a half and three times the number of pollen taxa as in the same three bryophyte/lichen taxa sampled in Scotland. Investigation relating the pollen rain trapped in polsters to that in faecal material are continuing, and will be reported in due course. This paper is based on one given by E.C. at the 5th International Aerobiology Conference, held at Bangalore, India, August 1994.     

Revelation of ancestral roles of KNOX genes by a functional analysis of <Emphasis Type="Italic">Physcomitrella</Emphasis> homologues

KNOX genes are indispensable elements of indeterminate apical growth programmes of vascular plant sporophytes. Since little is known about the roles of such genes in non-vascular plants, functional analysis of moss KNOX homologues (MKN genes) was undertaken using the genetically amenable model plant, Physcomitrella patens. Three MKN genes were inactivated by targeted gene knockout to produce single, double and triple mutants. MKN2 (a class 1 KNOX gene) mutants were characterised by premature sporogenesis, abnormal sporophyte ontogeny and irregular spore development. MKN4 (a second class 1 gene) mutants were phenotypically normal. MKN1-3 (a class 2 KNOX gene) mutants exhibited defects in spore coat morphology. Analysis of double and triple mutants revealed that the abnormal sporophytic phenotype of MKN2 mutants was accentuated by mutating MKN4 and to a lesser degree by mutating MKN1-3. The aberrant spore phenotype of MKN1-3 and MKN2 mutants was exacerbated by mutating MKN4. This study provides the first instance in which an abnormal phenotype has been associated with the disruption of a class 2 KNOX gene as well as the first demonstrated case of functional redundancy between a class 1 and a class 2 KNOX gene. We conclude that KNOX genes play significant roles in programming sporophytic development in moss and we provide evidence that ancestral function(s) of this gene family were instrumental in the successful transition of plants to a terrestrial environment.     

Cryptogams on decaying wood in old-growth forests of southern coastal British Columbia

Abstract. We studied the floristic composition of lignicolous cryptogams (i.e. bryophytes and lichens inhabiting decaying wood) in the old-growth coniferous forests of southern coastal British Columbia. The composition of the cryptogams was related to forest communities (described by vegetation units using forest floor cryptogams and vascular plants) and regional climates (described by biogeoclimatic zones). The study is based on a total of 247 sample plots, each of 0.04 ha in size. The plots were located in three different biogeoclimatic zones and were classified into 12 alliances and four orders in a previous study. We used indicator species analysis to determine cryptogam indicator species for each vegetation unit and biogeoclimatic zone, and used similarity analysis and multi-variate analyses (discriminant analysis and detrended correspondence analysis) to detect differences in the floristic composition of the cryptogams among sample plots, vegetation units, and biogeoclimatic zones. Most of the cryptogams in this study had a narrow distribution, and only < 5% of the species were present across all the vegetation units and biogeoclimatic zones. The overall means of Jaccard coefficients between two sample plots from the same vegetation unit (alliance or order) or biogeoclimatic zone were significantly higher (P < 0.05) than those from different vegetation units or biogeoclimatic zones. The difference in the mean Jaccard coefficients within- and between-units was highest for zones. The results of detrended correspondence analysis and discriminant analysis suggest that the composition of lignicolous cryptogams changes with the change in the floristic composition of forest floor vegetation. When the first axes of detrended correspondence analysis were compared, the Pearson's correlation coefficients between the first axes of lignicolous cryptogams and forest floor vascular plants and between the first axes of lignicolous cryptogams and forest floor cryptogams were 0.78 and 0.87, respectively. The degree of correspondence in the composition of lignicolous cryptogams and forest floor vegetation increased from alliance to order to biogeoclimatic zone. This trend suggests that the floristic composition of lignicolous cryptogams is influenced at the community level mainly by edaphic conditions and at the regional level by climatic conditions.     

Photosynthetic response to dynamic changes of light and air humidity in two moss species from the Tibetan Plateau

Bryophytes are widely distributed in alpine meadow and wetlands on the Tibetan Plateau, where light intensity and air moisture are highly variable in time. To address how bryophytes respond to their light and moisture environments, we examined dynamic photosynthesis in two moss species, Distichium inclinatum common in meadow, and Encalypta alpine frequently found in wetland. Photosynthetic induction response was faster in the two moss species than in most vascular species. In both species the 90% induction time after a sudden light increase from 50 to 600 μmol m⁻² s⁻¹ was within 3 min. The induction was faster in mosses experiencing a period of weak light than in those in total darkness. E. alpina, the wetland species, showed more rapid induction response and shorter post-illumination CO₂ fixation to sunflecks than D. inclinatum, the meadow species. Photosynthetic rate (A _max) under saturated light in the two species increased linearly with increasing air relative humidity (RH). The meadow species D. inclinatum showed higher A _max under low RHs, but exhibited lower A _max under high RHs in comparison with the wetland moss E. alpina. Moreover, the quantum efficiency increased linearly with increasing RH, indicating that air humidity plays a critical role in photochemical activities in the alpine mosses. The study suggests that there are acclimations in dynamic photosynthesis in response to light and humidity, and the acclimations would benefit a high leaf carbon gain in the two alpine moss species in their common habitats.     

Targeted knock-out of a gene encoding sulfite reductase in the moss Physcomitrella patens affects gametophytic and sporophytic development

A key step in sulfate assimilation into cysteine is the reduction of sulfite to sulfide by sulfite reductase (SiR). This enzyme is encoded by three genes in the moss Physcomitrella patens. To obtain a first insight into the roles of the individual isoforms, we deleted the gene encoding the SiR1 isoform in P. patens by homologous recombination and subsequently analysed the ΔSiR1 mutants. While ΔSiR1 mutants showed no obvious alteration in sulfur metabolism, their regeneration from protoplasts and their ability to produce mature spores was significantly affected, highlighting an unexpected link between moss sulfate assimilation and development, that is yet to be characterized.     

城市生态基础设施及其构建原则

城市生态基础设施是一个综合的概念,不仅包含了绿色植被、河网水系,也包括了大尺度地貌格局;不但突出强调了基于这些生态用地的网络体系构建,还着重强化了城市生态建设的作用和意义。城市生态基础设施可以维系城市生物多样性、土壤侵蚀及水文循环等自然生态过程的稳定,并可以通过缓解交通污染,调节空气质量,增进休闲文化和生态教育,促进社会经济发展,以及约束和导向城市扩张等方面改善和保障城市人居环境质量。城市生态基础设施的构建中应高度重视其整体性和系统性:(1)在城市总体规划中要注重生态规划先行,对重要生态区域进行重点保护和永久保留,并将其纳入城市整体生态网络体系,提高整体稳定性;(2)在社区尺度上,应重视公众在社区生态基础设施构建中的作用,引导公众参与社区生态基础设施规划的制定,鼓励公众及企事业单位参与社区生态基础设施的构建和保护,努力提高城市整体的人居环境质量。     

Impacts of warming and fertilization on nitrogen-fixing microbial communities in the Canadian High Arctic

The impacts of simulated climate change (warming and fertilization treatments) on diazotroph community structure and activity were investigated at Alexandra Fiord, Ellesmere Island, Canada. Open Top Chambers, which increased growing season temperatures by 1-3 degrees C, were randomly placed in a dwarf-shrub and cushion-plant dominated mesic tundra site in 1995. In 2000 and 2001 20N:20P2O5:20K2O fertilizer was applied at a rate of 5 gm(-2) year(-1). Estimates of nitrogen fixation rates were made in the field by acetylene reduction assays (ARA). Higher rates of N fixation were observed 19-35 days post-fertilization but were otherwise unaffected by treatments. However, moss cover was significantly positively associated with ARA rate. NifH gene variants were amplified from bulk soil DNA and analyzed by terminal restriction fragment length polymorphism analysis. Non-metric multidimensional scaling was used to ordinate treatment plots in nifH genotype space. NifH gene communities were more strongly structured by the warming treatment late in the growing season, suggesting that an annual succession in diazotroph community composition occurs.     

Distichophyllum chenii B.C.Ho sp. nov. (Daltoniaceae) from Southeast China

Abstract

Despite the genus Distichophyllum having been revised recently for the Moss Flora of China, upon examination of a wide range of both Chinese and non-Chinese material a distinct new species was found among existing specimens collected from China. The new species, Distichophyllum chenii, is described based on specimens previously misidentified and reported as Distichophyllum cirratum var. cirratum. Published illustrations of D. cirratum var. cirratum based on a misidentified collection of D. collenchymatosum are highlighted to avoid further future taxonomic confusion.     

Forced calcium entry and polarized growth of Funaria spores

We have used both steady electric fields, and gradients of the divalent ionophore, A23187, to control the point at which rhizoids emerge from spores of the common moss Funaria hygrometrica. The spores were grown in a medium containing calcium nitrate as the only major salt. Spores tend to form rhizoids towards the positive electrode, with a half maximal response to a difference of 4–8 mV across each cell. They also tend to form rhizoids towards the end of higher ionophore concentration in response to A23187 gradients. Both of these responses are the same at pH 5.5 and 8.0. Our tentative explanation is that Funaria spores tend to form rhizoids where most calcium enters. However, the point of chloronema emergence is scarcely affected by steady fields of up to 45 mV/cell. Moreover, when steady fields are applied across already developed rhizoids or chloronemata, their subsequent growth is directed towards the negative electrode in both cases, with rhizoids giving a 50% response at only 3—5 mV/cell, and chloronemata being less responsive.From Tsung-Hsien Chen's Ph.D. thesis, Purdue University     

Molecular and chemical characterization of a Sphagnum palustre clone: Key steps towards a standardized and sustainable moss bag technique

This work aimed to define the molecular and chemical signature of a S. palustre clone developed in the framework of the EU-FP7 Mossclone project to improve the standardization and reliability of the moss-bag technique. The molecular characterization was performed by a set of DNA molecular markers (RAPD, ISJ, PCR-RFLP, sequencing and microsatellites) to tag the clone produced within the project. Molecular characterization also provided new DNA markers that can be applied in systematic analyses of Sphagnum, and gave new insights to implement well established techniques. The elemental composition of the clone was measured by ICP-MS analysis of 54 major and trace elements, with and without commonly applied pre-exposure treatments (oven devitalization and EDTA washing). Concentrations of almost all analyzed elements were significantly lower (from 10 to 100 times) in the clone than in conspecific field moss, apart from some elements (K, Mo, P and Na) deriving from the culture medium or EDTA treatment. Oven devitalization and EDTA washing did not significantly affect the clone composition. A comparison between the elemental composition of the clone with that of naturally growing Sphagnum species proved the particularly low elemental content of the clone. Therefore, in view of a rigorously standardized moss-bag protocol for the monitoring of persistent atmospheric pollutants, the use of the S. palustre clone, a biomaterial with very low and constant element composition, and homogenous morphological characteristics is strongly recommended.