Spatial heterogeneity in the determinants of woody plant invasion of lowland heath

Questions: 1. What is the scale and extent of spatial variability in factors affecting Betula invasion of heaths? 2. How much effect does each factor have on within‐patch patterns of invasion? 3. How can this understanding aid in managing Betula invasions? Location: Lowland heath of southern England. Methods: Determinants of Betula (both B. pubescens and B. pendula) invasion: biomass density, necromass density, mean vegetation height, P‐availability, soil water content and total Betula seed bank density, were measured at two sites on a 5‐ha sampling grid. Spatial pattern was assessed using geostatistics. Contributions of each determinant to within‐site heterogeneity in predicted Betula seedling densities were estimated by varying variables over their full and interquartile ranges in a statistical model derived from experimental data. Results: Salient spatial trends were revealed: strong autocorrelation over distances of < 50 m for soil factors and more extensive autocorrelation (0 to > 150 m) in vegetation variables and Betula seed bank densities. The latter resulted in single across‐site gradients, the former small, distinct patches. All patterns were overlain with variance that was present at distances of < 17.6 m. Variables displaying spatial pattern also accounted for within‐site heterogeneity in predicted Betula seedling densities but their relative contribution to this varied between sites. Conclusions: Identifiable spatial autocorrelation in factors controlling patch‐scale invasion patterns allows managers to target invasion prone patches, potentially reducing management intensities. Furthermore, management effort may be optimised by spatially de‐coupling Betula seed from safe‐sites. This plan may adaptable to the management of other weeds and open‐land ecosystems.     

Development and persistence of sandsheaths of Lyginia barbata (Restionaceae): relation to root structural development and longevity

Background and Aims

Strongly coherent sandsheaths that envelop perennial roots of many monocotyledonous species of arid environments have been described for over a century. This study, for the first time, details the roles played by the structural development of the subtending roots in the formation and persistence of the sheaths.

Methods

The structural development of root tissues associated with persistent sandsheaths was studied in Lyginia barbata, native to the Western Australian sand plains. Cryo-scanning electron microscopy CSEM, optical microscopy and specific staining methods were applied to fresh, field material. The role of root hairs was clarified by monitoring sheath development in roots separated from the sand profile by fine mesh.

Key Results and Conclusions

The formation of the sheaths depends entirely on the numerous living root hairs which extend into the sand and track closely around individual grains enmeshing, by approx. 12 cm from the root tip, a volume of sand more than 14 times that of the subtending root. The longevity of the perennial sheaths depends on the subsequent development of the root hairs and of the epidermis and cortex. Before dying, the root hairs develop cellulosic walls approx. 3 µm thick, incrusted with ferulic acid and lignin, which persist for the life of the sheath. The dead hairs remain in place fused to a persistent platform of sclerified epidermis and outer cortex. The mature cortex comprises this platform, a wide, sclerified inner rim and a lysigenous central region – all dead tissue. We propose that the sandsheath/root hair/epidermis/cortex complex is a structural unit facilitating water and nutrient uptake while the tissues are alive, recycling scarce phosphorus during senescence, and forming, when dead, a persistent essential structure for maintenance of a functional stele in the perennial Lyginia roots.     

Increasing maize seed weight by enhancing the cytoplasmic ADP-glucose pyrophosphorylase activity in transgenic maize plants

ADP-glucose pyrophosphorylase (AGPase) plays a key role in regulating starch biosynthesis in cereal seeds and is likely the most important determinant of seed strength. The Escherichia coli mutant glgC gene (glgC16), which encodes a highly active and allosterically insensitive AGPase, was introduced into maize (Zea mays L.) under the control of an endosperm-specific promoter. Developing seeds from transgenic maize plants showed up to 2–4-fold higher levels of AGPase activity in the presence of 5 mM inorganic phosphate (Pi). Transgenic plants with higher cytoplasmic AGPase activity under Pi-inhibitory conditions showed increases (13–25%) in seed weight over the untransformed control. In addition, in all transgenic maize plants, the seeds were fully filled, and the seed number of transgenic plants had no significant difference compared with that of untransformed control. These results indicate that increasing cytoplasmic AGPase activity has a marked effect on sink activity and, in turn, seed weight in transgenic maize plants.     

虎皮鹦鹉耳蜗感觉细胞的发育与听觉的关系

选用18d、38d、成鸟(3月以上)三种年龄的雄性虎皮鹦鹉作为实验材料,采用测量脑干听觉诱发电位和制作内耳的石蜡切片两种方法,研究了鸟类在发育时期耳蜗感觉上皮细胞的变化以及听觉功能的发育状况。鸟的听觉能力在出生后不断得到提高,38d基本达到成鸟的水平;耳蜗毛细胞的形态、内部结构逐渐趋于成熟,其灵敏度不断提高,感受听觉的能力也在增强,38d基本与成鸟的发育程度相同。耳蜗感觉上皮细胞的发育对听觉行为产生的时间和发展具有极为重要的影响。     

Genetic structure of <Emphasis Type="Italic">Cerasus jamasakura</Emphasis>, a Japanese flowering cherry,revealed by nuclear SSRs: implications for conservation

The genetic resources of a particular species of flowering cherry, Cerasus jamasakura, have high conservation priority because of its cultural, ecological and economic value in Japan. Therefore, the genetic structures of 12 natural populations of C. jamasakura were assessed using ten nuclear SSR loci. The population differentiation was relatively low (F _ST, 0.043), reflecting long-distance dispersal of seeds by animals and historical human activities. However, a neighbor-joining tree derived from the acquired data, spatial analysis of molecular variance and STRUCTURE analysis revealed that the populations could be divided into two groups: one located on Kyusyu Island and one on Honshu Island. Genetic diversity parameters such as allelic richness and gene diversity were significantly lower in the Kyushu group than the Honshu group. Furthermore, STRUCTURE analysis revealed that the two lineages were admixed in the western part of Honshu Island. Thus, although the phylogeographical structure of the species and hybridization dynamics among related species need to be evaluated in detail using several marker systems, the Kyusyu Island and Honshu Island populations should be considered as different conservation units, and the islands should be regarded as distinct seed transfer zones for C. jamasakura, especially when rapid assessments are required.     

The fate of sheep-dispersed seeds: Plant species emergence and spatial patterns

Sheep epizoochory has often been proposed as an important vector which can help to overcome the dispersal limitation of plants in fragmented landscapes. In order to evaluate the contribution of herbivores to recruitment especially of target species, the dispersal and post-dispersal fate of such seeds must be known. In a field experiment sheep with seeds of mainly target species (experimentally attached to their coats) were present at three sand plots for 24 h. Natural epizoochorous dispersal was already shown for most of the species in our study area. Seed detachment, trampling intensity and seed shadow were measured; seedling emergence and survival were recorded over an 8-month period. In addition, the effect of sheep trampling on seedling emergence and survival of two threatened species, Jurinea cyanoides and Koeleria glauca, were studied.     

藏羚冬季绒毛的形态结构

哺乳动物被毛的作用在于发挥其保温、缓冲和隔离的功能,而这些功能会因动物分布地域、不同季节、不同身体部位等的毛形态结构差异,发生适应性变化(Johnson and Homby,1980;Moen and Severing.haus,1984;Chen and Wang,1991;张伟等,1997;汪玺,1998;徐正强等,2006;张伟等,2008).     

芒果核仁的化学成分及其抑菌活性

从杧果(Mangifera indica L.)果实核仁中分离得到6种化合物。经光谱分析及与文献对照,分别鉴定为没食子酸(1)、没食子酸甲酯(2)、没食子酸乙酯(3)、间-二没食子酸甲酯(4)、对羟基苯甲酸(5)和丁二酸单甲酯(6),它们均为首次从芒果核中获得。用琼脂平板稀释法测定了化合物1~5对7种细菌和4种真菌生长的抑制活性。结果表明,化合物1对金黄色葡萄球菌(Staphylococcus aureus)、表皮葡萄球菌(S. epidermidis)、干燥棒状杆菌(Corynebacterium xerosis)和藤黄微球菌(Micrococcus luteus)的最小抑制浓度(MIC)为50~100 µg mL-1,化合物4对绿脓杆菌(Pseudomonas aeruginosa)有抑制活性。     

Screening of rice cultivars for Cr-stress response by using the parameters of seed germination,morpho-physiological and antioxidant analysis

Rice is the most important crop for the majority of population across the world with sensitive behavior toward heavy metals such as chromium (Cr) in polluted regions. Although, there is no information on the Cr resistance phenotyping in rice. Herein, two different groups of rice cultivars (normal, and hybrid) were used, each group with 14 different rice cultivars. Firstly, seed germination analysis was conducted by evaluating various seed germination indices to identify the rice cultivars with greatest seed germination vigor. Furthermore, exposure of chromium (Cr) toxicity to 28 different rice varieties (NV1-NV14, HV1-HV14) caused noticeable plant biomass reduction. Subsequently, NV2, NV6, NV10, NV12, NV13 (normal type), HV1, HV4, HV8, and HV9 (hybrid types) were pragmatic as moderately sensitive varieties, while NV3, NV4, NV9, and NV14 (normal type), HV3, HV6, HV7, and HV13 were observed as moderately tolerant. Although, NV7, and HV10 were ranked most sensitive cultivars, and NV11, and HV14 were considered as most tolerant varieties as compared to the other rice (both groups) genotypes. Afterward, Cr induced reduction in chlorophyll pigments were significantly lesser in HV14 relative to NV11, NV7, and especially HV10, and as a result HV14 modulated the total soluble sugar level as well as reduced ROS accumulation, and MDA contents production by stimulating the antioxidant defense mechanism conspicuously which further reduced the electrolyte leakage as well. Our outcomes provide support to explore the Cr tolerance mechanism in cereal crops as well as knowledge about rice breeding with increased tolerance against Cr stress.     

Purification and partial characterisation of two abscisic-acid-responsive proteins induced in cultured embryos ofPisum sativum L.

When pea (Pisum sativum L.) embryos were cultured on low osmotica, with or without added abscisic acid (ABA), there was very little change in the total mRNA translation products resolved by one-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The only marked alteration was an increase in production of two low-molecular-weight proteins. The purification and partial characterisation of these two ABA-responsive seed proteins (ABR17 and ABR18) is described. Both proteins were purified to homoeneity, as judged by SDS-PAGE, from embryos cultured in the presence of ABA. Antisera were raised against both proteins. Each serum cross-reacted with the other protein, indicating that the proteins are closely related. Their apparent molecular masses (M_rs) were estimated to be 17200 (ABR17) and 18100 (ABR18) by SDS-PAGE, and 26000 by gel filtration. Both proteins were heterogeneous on isoelectric focusing. Neither protein was detected (by immunoblotting or immunoprecipitation of cell-free translation products) in embryos grown in vivo at early to mid-development stages but both were present in embryos late in development. These proteins appear to be produced late in seed development but are capable of being induced early in development by culturing embryos in vitro and are markedly enhanced by ABA.