The effects of seed mix and management on the abundance of desirable and pernicious unsown species in arable buffer strip communities

Buffer strips are refuges for a variety of plants providing resources, such as pollen, nectar and seeds, for higher trophic levels, including invertebrates, mammals and birds. Margins can also harbour plant species that are potentially injurious to the adjacent arable crop (undesirable species). Sowing perennial species in non-cropped buffer strips can reduce weed incidence, but limits the abundance of annuals with the potential to support wider biodiversity (desirable species). We investigated the responses of unsown plant species present in buffer strips established with three different seed mixes managed annually with three contrasting management regimes (cutting, sward scarification and selective graminicide). Sward scarification had the strongest influence on the unsown desirable (e.g. Sonchus spp.) and unsown pernicious (e.g. Elytrigia repens) species, and was generally associated with higher cover values of these species. However, abundances of several desirable weed species, in particular Poa annua, were not promoted by scarification. The treatments of cutting and graminicide tended to have negative impacts on the unsown species, except for Cirsium vulgare, which increased with graminicide application. Differences in unsown species cover between seed mixes were minimal, although the grass-only mix was more susceptible to establishment by C. vulgare and Galium aparine than the two grass and forb mixes. Annual scarification can enable desirable annuals and sown perennials to co-exist, however, this practice can also promote pernicious species, and so is unlikely to be widely adopted as a management tool in its current form.

Effects of seed mixture and management on beetle assemblages of arable field margins

Beetle assemblages and their response to plant community composition and architectural structure were monitored from 2002 to 2006 within arable field margins. Field margins were sown with either tussock grass and forbs, fine grass and forbs or grass only seed mixtures. After an establishment year, field margins were managed using standard sward cuts, scarification, or graminicide application. For predatory beetles, overall density was greatest where tussock grasses were included within the seed mixtures, while the densities of phytophagous beetles were greatest where forbs were present. Unexpectedly, species rarefaction curves suggested that phytophagous beetle species richness was greatest where field margins were established using a grass only seed mixture. The structure of the beetle assemblages, i.e., the relative abundances of individual species, was largely dependent on seed mixture, although margin management also played an important role. The results suggest that field margins established using seed mixtures containing tussock grasses and forbs would be expected to provide the greatest resources for beetles, at least at local scales. However, the use of a single standardised seed mixture for margin establishment would result in a homogenisation of beetle assemblages at a regional scale. (C) 2008 Elsevier B.V. All rights reserved.

Do seed lists have a future?

In the 1960s Taxon published articles aimed at improving botanical Seed Lists. We compared suggestions made then with the situation in 2007. Sadly the majority of problems raised in the original manuscripts were still evident today. Botanic gardens must improve if this practice is to survive.

The influence of winter oilseed rape (Brassica napus ssp oleifera var. biennis) canopy size on grass weed growth and grass weed seed return

Four experiments conducted over three seasons (2002-05) at the Crops Research Unit, University of Reading, investigated effects of canopy management of autumn sown oilseed rape (Brassica napus L. ssp. oleifera var. biennis (DC.) Metzg.) on competition with grass weeds. Emphasis was placed on the effect of the crop on the weeds. Rape canopy size was manipulated using sowing date, seed rate and the application of autumn fertilizer. Lolium multiflorum Lam., L. x boucheanum Kunth and Alopecurus myosuroides Huds. were sown as indicative grass weeds. The effects of sowing date, seed rate and autumn nitrogen on crop competitive ability were correlated with rape biomass and fractional interception of photosynthetically active radiation (PAR) by the rape floral layer, to the extent that by spring there was good evidence of crop: weed replacement. An increase in seed rate up to the highest plant densities tested increased both rape biomass and competitiveness, e.g. in 2002/3, L. multiflorum head density was reduced from 539 to 245 heads/m(2) and spikelet density from 13 170 to 5960 spikelets/m(2) when rape plant density was increased from 16 to 81 plants/m(2). Spikelets/head of Lolium spp. was little affected by rape seed rate, but the length of heads of A. myosuroides was reduced by 9 % when plant density was increased from 29-51 plants/m(2). Autumn nitrogen increased rape biomass and reduced L. multiflorum head density (415 and 336 heads/m(2) without and with autumn nitrogen, respectively) and spikelet density (9990 and 8220 spikelets/m(2) without and with autumn nitrogen, respectively). The number of spikelets/head was not significantly affected by autumn nitrogen. Early sowing could increase biomass and competitiveness, but poor crop establishment sometimes overrode the effect. Where crop and weed establishment was similar for both sowing dates, a 2-week delay (i.e. early September to mid-September) increased L. multiflorum head density from 226 to 633 heads/m(2) and spikelet density from 5780 to 15 060 spikelets/m(2).

Post dispersal weed seed predation by avian and non-avian predators

Seed predation by avian and non-avian predators was quantified in the boundaries and cropped areas of cereal fields by presenting known quantities of seed with and without exclusion cages. Predator encounter-rates with the dishes exceeded 99%. Birds removed on average 6.7% seed from the dishes during the seven-day trials compared to 51% by non-avian predators. A comparison was made of the causal factors responsible for predation of Avena fatua, Chenopodium album and Cirsium arvense seeds. A. fatua seeds were preyed most heavily by both avian and non-avian predators. Seed removal by birds was greater in the cropped area than in the field boundary, non-avian predators being generally more active in the field boundary. Seed predation by birds was greater in spring than in any other season, whilst losses to other animals were greater during autumn and winter. Although, birds were not the main seed predators in cereal fields, they may contribute to weed seed depletion, of relevance to reduced-input farming systems where herbicides use is restricted.

Post-dispersal seed predation of non-target weeds in arable crops

Field experiments were conducted to quantify the natural levels of post-dispersal seed predation of arable weed species in spring barley and to identify the main groups of seed predators. Four arable weed species were investigated that were of high biodiversity value, yet of low to moderate competitive ability with the crop. These were Chenopodium album, Sinapis arvensis, Stellaria media and Polygonum aviculare. Exclusion treatments were used to allow selective access to dishes of seeds by different predator groups. Seed predation was highest early in the season, followed by a gradual decline in predation over the summer for all species. All species were taken by invertebrates. The activity of two phytophagous carabid genera showed significant correlations with seed predation levels. However, in general carabid activity was not related to seed predation and this is discussed in terms of the mainly polyphagous nature of many Carabid species that utilized the seed resource early in the season, but then switched to carnivory as prey populations increased. The potential relevance of post-dispersal seed predation to the development of weed management systems that maximize biological control through conservation and optimize herbicide use, is discussed.

The assessment of enriched apoplastic extracts using proteomic approaches

In plant tissues the extracellular environment or apoplast, incorporating the cell wall, is a highly dynamic compartment with a role in many important plant processes including defence, development, signalling and assimilate partitioning. Soluble apoplast proteins from Arabidopsis thaliana, Triticum aestivum and Oryza sativa were separated by two-dimensional electrophoresis. The molecular weights and isoelectric points for the dominant proteins were established prior to excision, sequencing and identification by matrix-assisted laser-desorption ionisation time of flight mass spectrometry (MALDI - TOF MS). From the selected spots, 23 proteins from O. sativa and 25 proteins from A. thaliana were sequenced, of which nine identifications were made in O. sativa (39%) and 14 in A. thaliana (56%). This analysis revealed that: (i) patterns of proteins revealed by two-dimensional electrophoresis were different for each species indicating that speciation could occur at the level of the apoplast, (ii) of the proteins characterised many belonged to diverse families reflecting the multiple functions of the apoplast and (iii), a large number of the apoplast proteins could not be identified indicating that the majority of extracellular proteins are yet to be assigned. The principal proteins identified in the aqueous matrix of the apoplast were involved in defence, i.e. germin-like proteins or glucanases, and cell expansion, i.e. β-D-glucan glucohydrolases. This study has demonstrated that proteomic analysis can be used to resolve the apoplastic protein complement and to identify adaptive changes induced by environmental effectors.

Mutant alleles at the rugosus loci in pea affect seed moisture sorption isotherms and the relations between seed longevity and moisture content

Pea (Pisum sativum L.) mutant near-isogenic lines (RRrbrb, rrRbRb, rrrbrb) with lower starch but higher lipid contents, brought about by lesions in the starch biosynthetic pathway, had seed moisture sorption isotherms displaced below that of the wild type (RRRbRb). The negative logarithmic relationship between seed longevity and seed storage moisture content (%, f.wt basis), determined in hermetic storage at 65 °C, also differed: longevity in the mutant near-isogenic lines was poorer and less sensitive to moisture content than in the wild type (i.e. CW was lower). The low-moisture-content limit (mc) to this relation also differed, being lower in the mutant near-isogenic lines (5.4–5.9%) than in the wild type (6.1%). In contrast, all four near-isogenic lines showed no difference (P >0.25) in the negative semi-logarithmic relationship between equilibrium relative humidity (ERH) and seed longevity. It is concluded that the effect of these alleles at the r and rb loci on seed longevity was largely indirect; a consequence of their effect on seed composition and hence on moisture sorption isotherms. However, this explanation could not be invoked at moisture contents below mc where differences in longevity remained substantial (RRRbRb double that of rrrbrb). Hence, these mutant alleles affected seed longevity directly at very low moisture contents.

Extraction and determination of ellagic acid content in chestnut bark and fruit

Chestnuts are an important economic resource in the chestnut growing regions, not only for the fruit, but also for the wood. The content of ellagic acid (EA), a naturally occurring inhibitor of carcinogenesis, was determined in chestnut fruits and bark. EA was extracted with methanol and free ellagic acid was determined by HPLC with UV detection, both in the crude extract and after hydrolysis. The concentration of EA was generally increased after hydrolysis due to the presence of ellagitannins in the crude extract. The concentration varied between 0.71 and 21.6 ing g(-1) (d.w.) in un-hydrolyzed samples, and between 2.83 and 18.4 mg g(-1) (d.w.) ill hydrolyzed samples. In chestnut fruits, traces of EA were present in the seed, with higher concentrations in the pellicle and pericarp. However, all fruit tissues had lower concentrations of EA than had the bark. The concentration of EA in the hydrolyzed samples showed a non-linear correlation with the concentration in the unhydrolyzed extracts. (C) 2008 Elsevier Ltd. All rights reserved.

High temperature reduction of metmyoglobin in aqueous muscle extracts

Oxymyoglobin in aqueous extracts of fresh beef longissimus dorsi muscles was initially oxidised to metmyoglobin during heat treatments at temperatures in the range 50-70 degreesC. The metmyoglobin then underwent reduction to a red pigment that was shown spectrally to be identical to oxymyoglobin. The formation of oxymyoglobin involved a heat induced precipitate that when removed from the solution, allowed oxidation to metmyoglobin to occur. However, on re-addition of the precipitate further reduction to oxymyoglobin took place. Dialysis of the muscle extract prior to heating markedly inhibited the reduction but addition of NADH to the dialysate permitted further reduction. The precipitate plus NADH caused oxymyoglobin formation in the presence of metmyoglobin but neither the precipitate nor NADH alone induced this formation. It is concluded that the initial conversion of oxymyoglobin to metmyoglobin on heating fresh beef muscle extracts was reversible and that the reverse reaction depended on the presence of both NADH and a muscle protein.

Characterization of the phytochemicals and antioxidant properties of extracts from Teaw (Cratoxylum formosum Dyer)

The leaves of the Thai vegetable, Teaw (Cratoxylum formosum Dyer) were extracted with ethanol to provide an extract that had antioxidant properties. The composition of the extract was studied by high-performance liquid chromatography with a diode array detector, and by electrospray ionization mass spectrometry. The main antioxidant component (peak 1) was chlorogenic acid, which was present at 60% of the extract. Three minor components were present at 7%, 3% and 2%, and other components that were present at lower concentrations were also observed. Treatment of the Teaw extract with 2,2-diphenyl-1-picrylhydrazyl radical (DPPH center dot) caused a similar reduction in peak area of 55.2-58.1% for chlorogenic acid and the three minor components, indicating that these components had common structural features. Component 2 was identified as dicaffeoylquinic acid, and compounds 3 and 4 were identified as ferulic acid derivatives. The radical-scavenging activity of the Teaw extract was compared with alpha-tocopherol, BHT and chlorogenic acid, using the DPPH center dot and 2,2'-azinobis (3-ethylbenzothialozinesulfonic acid) radical cation (ABTS(center dot+)) assays. The Teaw extract scavenged both free radicals more strongly than did a-tocopherol and BHT, and the activity of the extract was consistent with the concentration of chlorogenic acid that was present, confirming that this component is a major contributor to the antioxidant activity. The acute toxicity of the Teaw leaf extract was investigated in mice, and it was found that the LD50 of the extract was > 32 g/kg. Consequently, this plant is a promising source of a natural food antioxidant. (c) 2006 Elsevier Ltd. All rights reserved.