Arthropod Demography, Distribution, and Dispersion in a Novel Trap-Cropped Cotton Agroecosystem.

Vernonia [Vernonia galamensis (Cass.) Less.] (Asterales: Asteraceae) was examined as a potential trap crop for the cotton (Gossypium hirsutum L., Malvales: Malvaceae) arthropod complex. Four rows of vernonia were embedded within a 96-row cotton field. The abundance of true bug pests, true bug predators, and spiders were determined by whole-plant and sweep net sampling procedures during the early, middle, and late phases of the cotton-growing season. The census data showed that the arthropods had a strong preference for the vernonia trap crop throughout the cotton-growing season. The movement of the arthropods from the trap crop into cotton was also measured using the protein immunomarking technique as a mark-capture procedure. The arthropods inhabiting the vernonia trap crop were marked directly in the field with a broadcast spray application of egg albumin (protein) during each phase of the study. In turn, the captured specimens were examined for the presence of the mark by an egg albumin-specific enzyme-linked immunosorbent assay. Very few marked specimens were captured beyond the vernonia trap crop 1, 3, and 6 d after each marking event. The arthropods' strong attraction and fidelity to vernonia indicate that it could serve as a trap crop for cotton pests and a refuge for natural enemies.

A greater foraging scale, not a higher foraging precision, may facilitate invasion by exotic plants in nutrient-heterogeneous conditions.

Background and Aims: Soil nutrient heterogeneity has been proposed to influence competitive outcomes among different plant species. Thus, it is crucial to understand the effects of environmental heterogeneity on competition between exotic invasive and native species. However, the effects of soil nutrient heterogeneity on the competition between invasive and native plants have rarely been linked to root foraging behaviour. Methods: In this study, a competition experiment was performed with two invasive-native species pairs (BP-VC, Bidens pilosa vs. Vernonia cinerea; MM-PS, Mikania micrantha vs. Paederia scandens) grown under homogeneous and heterogeneous conditions in a common greenhouse environment. Root activity was assessed by determining the amount of strontium (Sr) taken up by the shoot of each species. Key Results: The invasive species exhibited a greater foraging scale, whereas the native species exhibited a higher foraging precision. A trade-off between foraging scale and precision was observed within each pair of invasive-native species. Compared with soil homogeneity, soil heterogeneity significantly increased the biomass of the two invasive species, B. pilosa and M. micrantha, under competitive conditions. Within each pair, the invasive species exhibited greater relative competitive ability with respect to shoot mass, and considerably more Sr taken up by the invasive species compared with the native species. The Sr acquisition results indicate that nutrient-poor conditions may facilitate the competitive ability of the native species V. cinerea, whereas M. micrantha may possess a stronger competitive ability regardless of soil nutrient conditions. Conclusion: Soil nutrient heterogeneity has the potential to promote the invasion of these two exotic species due to their larger foraging scale, stronger competitive ability and greater root activity relative to their counterpart native species. The present work highlights the importance of soil heterogeneity in plant invasion, particularly with regards to root foraging traits and competition between invasive and native plants.

On the air cleansing efficiency of an extended green wall: a CFD analysis of mechanistic details of transport processes.

The detrimental impact of rising air pollution levels in urban landscapes has become conspicuous over the last decade, particularly in developing countries. This novel numerical study quantifies the cleansing efficiency of green façades draped with a copiously growing tropical creeper Vernonia elaeagnifolia. Turbulent transport of SO2 to the leaf boundary layer and subsequent diffusion across stomatal pores into the mesophyllic cells is modeled at the micro level, including its ionic dissociation in the leaf׳s interior. A SEM analysis indicates stomatal dimensions and density. Whilst previous studies have used either spatially averaged equations or resistance models, a spatially discretized computational approach is adopted in this study. The resulting concentration distribution is used to calculate the deposition velocity on stomatal pores, which is then extrapolated over the entire façade to yield bulk pollutant removal rates. A deposition velocity of 1.53mms(-1) and 0.72mms(-1) is obtained for open and closed pores respectively, with removal rates equal to 1.11×10(-6)s(-1) and 1.05×10(-6)s(-1) for dry and humid weather respectively. Sensitivity studies on the removal rate are carried out based on humidity, stomatal aperture and leaf temperature. The removal rate dependence on the Leaf Area Index (LAI) is also investigated. It is inferred from simulations that vegetated façades are efficient at mitigation of residual pollution.

Concentrações de BAP sobre a proliferação in vitro de brotos de Lippia alba [(Mill. )N. E. Brown] / BAP concentrations on in vitro proliferation of Lippia alba [(Mill. ) N. E. Brown] shoots

Lippia alba é uma planta de origem brasileira, pertencente à família Verbenaceae. É conhecida por combater a insônia e a asma, além de possuir ação anticonvulsivante e antifúngica. A micropropagação tem sido utilizada para multiplicação de várias espécies com propriedades medicinais, e o BAP é a citocinina sintética mais utilizada para a multiplicação in vitro. O objetivo deste trabalho foi estabelecer a concentração adequada de BAP na multiplicação in vitro de L. alba. Explantes constituídos de segmentos nodais provenientes de plântulas já estabelecidas in vitro com aproximadamente 0,5 cm foram inoculados em meio MS, suplementado com 0,0; 0,5; 1,0 e 1,5 mg L-1 de BAP em adição de 30 g L-1 de sacarose. A utilização de 1,5 mg L-1 de BAP promove a multiplicação in vitro de L. alba. A ausência deste regulador propicia maior número de folhas e o uso na concentração de 0,5 mg L-1 aumentou as massas fresca e seca de parte aérea nesta espécie.

Lippia alba is a Brazilian plant, belonging to the Verbenaceae family. It is known to combat insomnia and asthma, also has antifungal and anticonvulsant actions. Micropropagation has been used for propagation of various species with medicinal properties, and BAP is the most widely used synthetic cytokinin for in vitro multiplication. The aim of this study was to determine the appropriate concentration of BAP on in vitro multiplication of L. alba. Explants consisting of nodal segments from seedlings already established in vitro with approximately 0.5 cm were inoculated on MS medium supplemented with 0; 0.5; 1.0 and 1.5 mg L-1 of BAP and 30 g L-1 of sucrose. The use of 1.5 mg L-1 of BAP promotes the in vitro multiplication of L. alba. The absence of this regulator provides a greater number of leaves and its use at the concentration of 0.5 mg L-1 increased shoots' fresh and dry weights in this specie.

Linking water uptake with rooting patterns in grassland species.

Water availability strongly governs grassland primary productivity, yet this resource varies dramatically in time (seasonally) and space (with soil depth and topography). It has long been assumed that co-occurring species differ in their partitioning of water use by depth, but direct evidence is lacking. We report data from two growing seasons (2004-2005) in which we measured the isotopic signature of plant xylem water from seven species (including C(3) forbs and shrubs and C(4) grasses) growing along a topographic gradient at the Konza Prairie Biological Station. Plant xylem stable oxygen isotope ratio (delta(18)O) values were compared to soil water delta(18)O profiles, recent rainfall events, and groundwater. Species varied in both their temporal patterns of water use and their responses to seasonal droughts in both years. During wet periods, species differences in water use were minimal, with common dependency on recent rainfall events stored in the upper soil layers. However, during dry periods, most C(3) species used proportionally more water from deeper portions of the soil profile relative to the C(4) grasses. Plants in uplands used more shallow soil water compared to those in lowlands, with the greatest differences across the topographic gradient occurring during dry periods. While the documented vertical root distribution varies by species and growth form in this grassland, each of the species we measured appeared to compete for the same surface layer soil moisture when water was not limiting. Thus, our results suggest that variation in precipitation history and landscape positions are greater determinants of water-use patterns than would be expected based on absolute rooting depth.

Fructan metabolising enzymes in rhizophores of Vernonia herbacea upon excision of aerial organs.

The activities of fructan metabolising enzymes and fructan contents are reported for rhizophores of Vernonia herbacea (Vell.) Rusby induced to sprouting by shoot excision. The activities of fructan exohydrolase (1-FEH), sucrose: sucrose fructosyltransferase (1-SST), fructan: fructan fructosyltransferase (1-FFT) and invertase (INV) and the fructan contents were analysed every 3-4 days for 1 month by colorimetric and chromatographic methods. Sprouting of new shoots started on day 9. 1-FEH activity increased after day 13 and reached its maximum value 20 days after shoot excision. A gradual decrease in 1-SST activity was detected between days 3 and 9. 1-FFT activity exhibited fluctuations throughout the experimental period and a peak of activity for invertase was detected 9 days after shoot excision. Variation in fructan contents in vivo included a decrease until day 13 after which, levels remained practically unchanged. Fructan depolymerization and sprouting are concomitant processes in V. herbacea and can be induced by shoot excision at any phenological phase. 1-FEH and 1-FFT seemed to act in a concerted way to catalyse fructan depolymerization, while 1-SST was inhibited, possibly due to interruption of sucrose supply to rhizophores from the aerial organs.