Plant competitive ability and the transitivity of competitive hierarchies change with plant age

Plant competitive effect and response ability are known to change with plant age, however it remains unclear how competitive hierarchies among plant species change as plants age and transition between life stages. We examined the competitive interactions among seven species in all pairwise combinations in a greenhouse experiment. Competitive effect and response were measured as the relative yield (RY) for each target-neighbor species combination for both seedling and adult plants. Competitive hierarchies were constructed based on competitive effect and response scores, and we examined the degree of transitivity in the seedling and adult competitive hierarchies. The competitive effect hierarchy did not vary substantially with plant age, while the competitive response hierarchy was highly variable between juvenile and adult plants. Competitive effect and response ability were positively correlated at both plant stages. The seedling relative yield matrix was predominantly transitive, while there were far fewer transitive competitive relationships among the adult plants. The breakdown of the clear competitive hierarchy among seedlings as plants aged may explain why competition does not appear to be an active mechanism structuring some late-successional plant communities. In early-successional communities, interactions among seedlings with a clear competitive hierarchy may establish competitive ability—abundance relationships that persist as a legacy effect even though the breakdown of the competitive hierarchy among adult plants removes competition as an active mechanism structuring some late-successional plant communities.     

Plant and soil responses to defoliation: a comparative study of grass species with contrasting life history strategies

The overall aim of this study was to test for inter-species variation in plant and soil responses to defoliation among a broad range of temperate grass species and life-history strategies. We used a microcosm experiment where a range of grass species differing in life history traits were subjected to different intensities of defoliation, and a range of aboveground and belowground plant and soil responses were measured. All plant attributes, including accumulated shoot biomass, root biomass and root length, showed a strong negative response to defoliation, although plant species exhibited subtle differences in the way that they responded to increased severity of defoliation. Defoliation also exerted a strong influence on soil properties, decreasing soil microbial carbon (C) and the soil microbial C:nitrogen (N) ratio, and increasing inorganic N availability and potential N mineralisation across all species. Despite the wide range in life history strategies, plant species did not differ in their influence on most of the soil variables, except for the rate of nitrate mineralisation, which was lowest under plant species that displayed the least relative detrimental responses to defoliation. Collectively, our results suggest that plant and soil responses to defoliation are reasonably consistent across a broad range of grass species, with only subtle inter-specific differences among species.     

Plant growth and climate change

‘Climate change’ is an all-embracing subject: increasingcarbon dioxide concentration in the atmosphere, due to the insatiableappetite of our burgeoning Homo sapiens (or perhaps better H.carbonovorum) populations for energy from fossil carbon reserves,is the main driver. The consequent global warming may lead tovery complex     

Co-pigmentation and the color change with age in petals ofFuchsia hybrida

Pure or genuine malvin was isolated fromFuchsia petals for the first time and characterized as the malvin anhydro-base. The conditions for the co-pigmentation were examinedin vitro with regard to anthocyanin, co-pigment and pH, and the co-pigmentation occurred as the result of interaction between anthocyanin and co-pigment without any participation of metallic elements. The blue-violet color of youngFuchsia petals appeared at pH 4.8 in the 1∶0.6 molar ratio of anthocyanin to co-pigments. The color change from blue-violet in young petals to purple-red in old ones was caused by co-pigmentation and the pH change from 4.8 to 4.2. The decrease of pH in the old petals was due to the increase of organic acids such as aspartic, malic and tartaric acids.     

Plant systems biology comes of age

'Omics' research approaches have produced copious data for living systems, which have necessitated the development of systems biology to integrate multidimensional biological information into networks and models. Applications of systems biology to plant science have been rapid, and have increased our knowledge about circadian rhythms, multigenic traits, stress responses and plant defenses, and have advanced the virtual plant project.     

根分泌物与土壤肥力

植物生长在土壤中 ,既要从土壤中摄取营养 ,又要对土壤产生一定的响应。植物根系的生理特性和根 -土界面的营养环境是影响土壤养分有效性和植物生长的主要因素之一。根分泌物就是植物根对土壤肥力的一种响应。它是根对土壤因素的生化适应的产物。1　根分泌物的种类根分泌物是植物根系释放到周围环境中的各种物质 ,它是生物间相生相克关系不可缺少的成分。根分泌物的产生是通过代谢途径和非代谢途径。代谢途径包括初生代谢和次生代谢。根分泌物的种类繁多 ,数量各异 ,不仅有糖、有机酸和氨基酸等初生代谢物 ,还有酚类等次生代谢物 ,更有一些…     

The interaction of soil biota and soil structure under global change

The structural framework of soil mediates all soil processes, at all relevant scales. The spatio-temporal heterogeneity prevalent in most soils underpins the majority of biological diversity in soil, providing refuge sites for prey against predator, flow paths for biota to move, or be moved, and localized pools of substrate for biota to multiply. Just as importantly, soil biota play a crucial role in mediating soil structure: bacteria and fungi aggregate and stabilize structure at small scales (μm–cm) and earthworms and termites stabilize and create larger-scale structures (mm–m). The stability of this two-way interaction of structure and biota relations is crucial to the sustainability of the ecosystem. Soil is constantly reacting to changes in microclimates, and many of the soil–plant–microbe processes rely on the functioning of subtle chemical and physical gradients. The effect of global change on soil structure–biota interactions may be significant, through alterations in precipitation, temperature events, or land-use. Nonetheless, because of the complexity and the ubiquitous heterogeneity of these interactions, it is difficult to extrapolate from general qualitative predictions of the effects of perturbations to specific reactions. This paper reviews some of the main soil structure–biota interactions, particularly focusing on soil stability, and the role of biota mediating soil structures. The effect of alterations in climate and land-use on these interactions is investigated. Several case studies of the effect of land-use change are presented.     

Nitrogen turnover in soil and global change

Nitrogen management in soils has been considered as key to the sustainable use of terrestrial ecosystems and a protection of major ecosystem services. However, the microorganisms driving processes like nitrification, denitrification, N-fixation and mineralization are highly influenced by changing climatic conditions, intensification of agriculture and the application of new chemicals to a so far unknown extent. In this review, the current knowledge concerning the influence of selected scenarios of global change on the abundance, diversity and activity of microorganisms involved in nitrogen turnover, notably in agricultural and grassland soils, is summarized and linked to the corresponding processes. In this context, data are presented on nitrogen-cycling processes and the corresponding microbial key players during ecosystem development and changes in functional diversity patterns during shifts in land use. Furthermore, the impact of increased temperature, carbon dioxide and changes in precipitation regimes on microbial nitrogen turnover is discussed. Finally, some examples of the effects of pesticides and antibiotics after application to soil for selected processes of nitrogen transformation are also shown.     

Plant pathogens but not antagonists change in soil fungal communities across a land abandonment gradient in a Mediterranean landscape

We assessed whether the presence and abundance of plant pathogens and antagonists change in soil fungal communities along a land abandonment gradient. The study was carried out in the Cilento area (Southern Italy) at a site with three different habitats found along a land abandonment gradient: agricultural land, Mediterranean shrubland and woodland. For all microbiological substrates the colony forming units were about 3.1 × 10⁶ g⁻¹ soil for agricultural land and about 1.1 × 10⁶ g⁻¹ soil for Mediterranean shrubland and woodland. We found the following genera in all habitats: Cladosporium, Mortierella, Penicillium and Trichoderma. In agricultural land, the significantly most abundant fungus genera were Aspergillus, Fusarium, Cylindrocarpon and Nectria; in Mediterranean shrubland, Rhizopus and Trichoderma; and in woodland, Bionectria, Mortierella, Cladosporium, Diplodia, Paecilomyces, Penicillium and Trichoderma. We found a total of 8, 8 and 9 species of fungal antagonist, and 16, 6 and 6 species of fungal plant pathogens in agricultural land, Mediterranean shrubland and woodland respectively. Fungal plant pathogens decreased significantly over a land abandonment gradient, while we no found significant differences among fungal antagonists in the three habitats. We conclude that a decrease in the number of fungal pathogen species occurs when formerly cultivated areas are abandoned. On the other hand, fungal antagonists seem not to be affected by this process.     

Plant parasite control and soil fauna diversity

The use of pesticides to control plant parasites and diseases has generated serious problems of public health and environmental quality, leading to the promotion of alternative Integrated Pest Management strategies that tend to rely more on natural processes and the active participation of farmers as observers and experimenters in their own fields. We present three case studies that point at different options provided by locally available populations of soil organisms, the maintenance of diverse populations of pests or increased resistance of plants to pest attacks by their interactions with earthworms and other useful soil organisms. These examples demonstrate the diversity of options offered by the non-planned agro-ecosystem diversity in pest control and the need to identify management options that maintain this biodiversity.     

Stress-induced change in cerebral ATP+ubiquitin-dependent proteinase activity vary with age.

Stress-induced changes in cerebral ATP+ubiquitin-dependent proteinase activity were studied and the effect of age on it was checked. For that purpose 23,000 g supernatant prepared from whole brain of 3- and 7-month-old rats after 6h long immobilization stress were used. With azocasein as substrate, at pH 8.0 values of ATP+ubiquitin-dependent proteinase activity increased for 20% and 10% in 3- and 7-month-old animals respectively. Following 24 h long immobilization, values of cerebral ATP + ubiquitin-dependent activity in 3-month-old animals dropped by 16%. Data obtained indicate that immobilization stress affects ATP+ubiquitin-dependent proteinase activity and point to the contribution of age in the modulation of enzyme response to stress.