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Honey is a highly valued product due to its nutritional value, pro-health and healing properties. Pollutants from the environment penetrate into nectar, honeydew, pollen and next into bee products and can cause human exposure after ingestion. Mercury (Hg) is a toxic metal to living organisms. This is why it was important to determine the level of Hg in consumed honey.The aim of this manuscript is to analyse mercury concentration in honeys collected on the territory of Poland. A total of 108 samples of honey purchased in regional apiaries and hypermarkets were tested. The concentration of Hg was analysed in various types of honey (multifloral, honeydew, linden, goldenrod, acacia, buckwheat, rapeseed, sunflower, heather, dandelion, phacelia). The values of the Estimated Daily Intake (EDI), Estimated Weekly Intake (EWI) and % Provisional Tolerable Weekly Intake (% PTWI) were calculated. This allowed estimating the amount of Hg taken during consumption of the tested honeys.The concentration of Hg ranged from 0.01 to 1.71 µg/kg and was 0.43 µg/kg on average. A higher concentration of Hg, which was statistically significant, was recorded in honeydew honey, then in compound honeys. Honeys produced from one raw material had the lowest concentration of Hg. There were no significant differences in the concentration of Hg depending on the origin of honey. The calculations have shown that consumption of a portion (19 g) of the tested honey per week is safe for both adults and children according to the applicable standards.

It is unclear whether the frequently observed increase in non-structural carbohydrates (NSC) in plants exposed to low temperatures or drought reflects a higher sensitivity of growth than photosynthesis in such conditions (i.e. sink limitation), or a prioritization of carbon (C) allocation to storage. Alpine areas in Mediterranean-type climate regions are characterized by precipitation increases and temperature decreases with elevation. Thus, alpine plants with wide elevational ranges in Mediterranean regions may be good models to examine these alternative hypotheses. We evaluated storage and growth during experimental darkness and re-illumination in individuals of the alpine plant Phacelia secunda from three elevations in the Andes of central Chile. We hypothesized that storage is prioritized regarding growth in plants of both low- and high elevations where drought and cold stress are greatest, respectively. We expected that decreases in NSC concentrations during darkness should be minimal and, more importantly, increases in NSC after re-illumination should be higher than increases in biomass. We found that darkness caused a significant decrease in NSC concentrations of both low- and high-elevation plants, but the magnitude of the decrease was lower in the latter. Re-illumination caused higher increase in NSC concentration than in biomass in both low- and high-elevation plants (1.5- and 1.9-fold, respectively). Our study shows that C allocation in Phacelia secunda reflects ecotypic differences among elevation provenances and suggests that low temperature, but not drought, favours C allocation to storage over growth after severe C limitation.

Eleven samples of Polish Phacelia tanacetifolia Benth., three Brassica napus and one Salix spp. honeys were characterized by melissopalynology and analysis of the compositions of their volatile fractions. Headspace solid-phase microextraction coupled with gas chromatography mass spectrometry (HS-SPME/GC–MS) using PDMS/CAR/DVB fiber was used for the isolation of low-molecular weight compounds which create a volatile fraction. To differentiate and indicate the most representative unifloral samples, chemometric techniques such as principal component analysis (PCA) and hierarchical-tree clustering (HTC) were applied to the dataset of the chromatographic fingerprints. Based on the obtained results, a unique chemical fingerprint of phacelia honey was generated. This study allows us to discriminate the botanical origin of the phacelia honeys based on the GC–MS and HPTLC analysis. In case of the GC–MS analysis trans-linalool oxide, hotrienol, cis-linalool oxide and cis-epoxylinalool were identified as a predominant compound. Additionally lipophilic fractions obtained by ultrasound-assisted extraction (UAE) and solid-phase extraction (SPE) were subjected to the HPTLC analysis. It allowed the construction of a barcode-type identifier that could be used to differentiate the honey samples even without identifying the individual components of the obtained fraction.

The central Chilean Andes are located in a Mediterranean-type climate zone, characterized by dry summers and high irradiance. This creates a contrasting elevational gradient because higher elevations get more solid precipitation and lower temperatures, resulting in higher soil humidity along the growing season compared with severe drought at lower elevations. Therefore, species with wide elevational distributions, such as Phacelia secunda, must have developed specific adaptations to cope with contrasting severity of drought stress-induced photoinhibition at different elevations. We hypothesize that P. secunda from lower elevation, is more tolerant to drought stress-induced photo-damage than plants from high elevation. This higher tolerance will be associated to a higher diversity of photoprotective strategies in plants that naturally suffers severe drought every growing season. To test this hypothesis, plants from 2700 and 3600 m in the central Chilean Andes were grown under the common garden and then subjected to water restriction. We measured stress indicators, photochemistry of PSII and PSI and estimate alternative electron sinks. Drought affected P. secunda photosynthetic performance differentially depending on the elevation of provenance. Plants from lower elevation exhibited higher drought tolerance than higher elevation ones. This was related to higher levels of heat dissipation and alternative electron sinks exhibited by plants from lower elevation under drought stress. We concluded that plants naturally subjected to recurrent drought are better adapted to respond to drought stress using additional photochemical photoprotective mechanisms and confirm the role of alternative electron sinks ameliorating photodamage.

Aims: \ud We studied the effects of Phacelia tanacetifolia, increasingly used as a cover-crop species in arable agricultural systems, upon soil structural properties in the context of two contrasting soil textures. We hypothesised there would be differential effects of the plants upon soil structure contingent on the texture.\ud \ud Methods: \ud A sandy-loam and a clay soil were destructured by passing through 2 mm sieves, and planted with Phacelia in a replicated pot experiment, with associated unplanted controls. X-ray Computed Tomography was used to visualise and quantify the soil pore networks in 3D.\ud \ud Results: \ud For the sandy-loam soil, there was no impact of plants upon aggregate size distribution porosity, pore connectivity, and pore surface density decreased in the presence of plants, whereas for the clay, there was a significant increase of aggregates

Intensive agriculture, which is associated with heavy inputs of synthetic insecticides, has serious ecological impacts, leading to loss of vital ecosystem services including insect-mediated pest suppression. In recent years, efforts have been made towards obtaining safer options to chemical insecticides for sustainable pest management. Habitat manipulation is a part of conservation biological control which aims at providing floral resources, alternative prey and shelter to predators and parasitoids to enhance and sustain natural pest suppression. The use of plant extracts as botanical insecticides is also an important provisioning ecosystem service. Selection of plant species for habitat manipulation has focused mainly on plants with suitable floral qualities to support natural enemies. To increase the benefits, habitat manipulation plants that can provide multiple ecosystem services in addition to floral resources would be an ideal. In this review, we focus on the potential of achieving the dual ecosystem services of bioinsecticidal source plants in addition to the provision of floral resources from selected plant species. Our literature search found 283 plants species from 44 plant families that have been involved in habitat manipulation studies. Fifteen of these plant families have species that have been exploited for their insecticidal properties. Three families, Apiaceae, Asteraceae and Lamiaceae, have the largest number of species that have been used for both habitat manipulation and botanical insecticides. Of the four most popular habitat manipulation plants, alyssum Lobularia maritime (L.) Desv. (Brassicaceae), buck wheat Fagopyrum esculentum Moench (Polygonaceae), coriander Coriandrum sativum L. (Apiaceae) and phacelia Phacelia tanacetifolia Benth. (Boraginaceae), buckwheat and coriander have been used for insecticidal purposes whilst no records exist of phacelia and alyssum as botanical insecticide species. There is great potential for identifying plant species that can support natural enemies as well as providing potent plant extracts as botanical insecticides by selecting species from the Apiaceae, Asteraceae and Lamiaceae families.

Climate change will not only alter mean conditions, but increase the frequency and intensity of extreme events such as severe droughts. Yet the consequences of extreme drought for plant demography are poorly understood. We compared phenology, demographic rates and effects of competition with exotic grasses for the California annual forb Phacelia distans between a year with slightly below average precipitation (2011–2012) and one in extreme drought (2012–2013). We also contrasted these demographic responses with changes in seedling emergence rates and cover in the annual plant community. Early Phacelia mortality actually fell in the extreme drought year, as low October rainfall shifted germination to cooler conditions in November. Survival from mid December to flowering did not change between years. In contrast to expectations, competition with early-emerging exotic annual grasses did not reduce Phacelia spring survival in 2012–2013. A shorter window for fall germination that reduced priority effects may explain this result. Yet the 2012–2013 growing season ended a month earlier than in 2011–2012, significantly reducing Phacelia size at flowering and inflorescence production. Community seedling emergence and cover changed only weakly between the 2 years. Our results demonstrate the importance of within season precipitation patterns in determining whether a climatically extreme year will lead to extreme ecological outcomes. This work also illustrates how annual plant drought responses depend critically on germination behavior and phenology. An important future question is whether seed banks can sustain native forb population persistence through an extended drought with multiple years of low or failed reproduction.

Competitive suppression of native species has long been considered among the most important mechanisms allowing exotic plants to dominate some communities, but recent work has focused attention on the potential role of native seed limitation. We tested effects of competition from exotic annual grasses and seed limitation on the abundances of four native annual plants in invaded southern California grassland for two different years. Both initial responses and effects still present 1–3 years later were measured. In the wetter year of 2006, all four native species (Amsinckia menziesii var. intermedia, Phacelia distans, Camissonia bistorta and Clarkia purpurea ssp. quadrivulnera) increased in abundance with exotic grass removal, and two (Clarkia and Camissonia) responded significantly to seed addition. We observed limited treatment effects during the much drier growing season of 2007. By 2008–2009, any initial effects of exotic grass removal had disappeared. However, for both the 2006 and 2007 experiments seeding significantly increased native cover in 2009, independent of initial grass removal. Abundances of both Amsinckia and Phacelia, but not Camissonia or Clarkia, were significantly higher in seeded plots during 2008–2009. These delayed responses may have resulted from seed dormancy. Our results support the importance of both competition with exotics and seed limitation in determining native annual community composition of California grasslands. An interesting future question is whether traits related to resource use or germination phenology may predict differences in native species interactions with exotic grasses.

The possible effects and implications of climate change on plant growth have not yet been studied in the central Chilean Andes, where a dry growing season differentiates this area from other mountainous areas around the world. At lower elevations, plants exposed to high temperatures and dry soil may experience severe water limitations, causing lower photosynthetic performance. At higher elevations, where water is not a limiting factor but air temperature is lower, an increase in temperature could have a positive effect on photosynthesis. We assessed whether experimental warming affects the photosynthetic performance and photoprotective mechanisms as photorespiration, Mehler reaction and cyclic electron flow in Phacelia secunda plants growing at 1600, 2800 and 3600 m elevation. Plants were exposed to a passive increase in the air temperature using open top chambers (OTC). Xylematic leaf water potential increased with elevation, and the OTC’s decreased xylematic water potential at the lower elevations but not at 3600 m. While warming was associated with a decrease in the maximal carbon gain assimilation at lower elevations, it was associate with an increase at 3600 m. Photorespiration differed among elevations and was increased by warming only at 1600 m. The Mehler reaction was higher at 1600, but not affected by warming. Warming increased the cyclic electron flow only in plants at 1600 m. Plants growing inside OTCs at all three elevations exhibited lower xanthophyll pools than control plants, but similar de-epoxidation states (DEPS). Our results show that alpine plant responses to warming will most likely depend on elevation, soil moisture availability and the combination of these two factors in relation to climate change.

Positive interactions between cushion plant and associated plants species in the high Andes of central Chile should also include the effects of fungal root symbionts. We hypothesized that higher colonization by arbuscular mycorrhizal (AM) fungi exists in cushion-associated (nursling) plants compared with conspecific individuals growing on bare ground. We assessed the AM status of Andean plants at two sites at different altitudes (3,200 and 3,600 m a.s.l.) in 23 species, particularly in cushions of Azorella madreporica and five associated plants; additionally, AM fungal spores were retrieved from soil outside and beneath cushions. 18 of the 23 examined plant species presented diagnostic structures of arbuscular mycorrhiza; most of them were also colonized by dark-septate endophytes. Mycorrhization of A. madreporica cushions showed differences between both sites (68% and 32%, respectively). In the native species Hordeum comosum, Nastanthus agglomeratus, and Phacelia secunda associated to A. madreporica, mycorrhization was six times higher than in the same species growing dispersed on bare ground at 3,600 m a.s.l., but mycorrhiza development was less cushion dependent in the alien plants Cerastium arvense and Taraxacum officinale at both sites. The ratio of AM fungal spores beneath versus outside cushions was also 6:1. The common and abundant presence of AM in cushion communities at high altitudes emphasizes the importance of the fungal root symbionts in such situations where plant species benefit from the microclimatic conditions generated by the cushion and also from well-developed mycorrhizal networks.

Cover crops are plants that are integrated in the crop rotation between two cash crops. The main objectives of cover cropping are organic matter input, mitigation of nitrate leaching and reduction of soil erosion. These benefits will only be achieved efficiently if the selected cover crop species are adapted to local environmental conditions and appropriate for the defined agro-ecological target. Therefore, a main limitation in cover cropping is the lack of a comprehensive species description. An improved cover crop characterization could be achieved with quantitative parameters derived from growth functions. Here, we show the use of this approach to assess plant traits relevant for erosion control by cover cropping. An experiment with four cover crop species (phacelia, vetch, rye and mustard) was performed over two years at a semi-arid site in Eastern Austria. Canopy cover was measured four times over the vegetation period. Root length density measurements were made to 40 cm soil depth before winter. Canopy dynamics were characterized by parameters from the asymptotic Gompertz function and from an extended logistic model that includes a parameter for decay after maximum coverage. Our results show that vetch had the lowest early vigor after dry conditions at sowing, with +45% longer time to attain maximum growth rate (parameter tmax) than the other species. Drought during the later autumn growing period led to the highest reduction in maximum canopy cover (parameter ymax) for phacelia (-41%). The rooting pattern was assessed by parameters from the exponential distribution function of Gerwitz and Page. The most intense rooting near the soil surface (parameter L0) was found for phacelia (9.7 cm cm −3 ). Vetch had the lowest L0 (4.6 cm cm −3 ) but highest root allocation to deeper soil layers. Mustard combined high average values in ymax (76%) and L0 (6.3 cm cm −3 ) with a stable growth over both years. The potential strengths of phacelia and vetch were more dependent on the particular year. Rye showed a stably high L0 (8.6 cm cm −3 ), but had only a low average value of ymax (55.1%). The quantitative parameter sets we derived for plant traits required for erosion control improved cover crop comparison and analysis of their local adaptation. Based on this extended species description our approach allows a better evaluation of cover crops and can be used for the optimization of management and decision support. cover crops / growth functions / species description / rooting pattern / rainfall distribution

Heavy metal phytoextraction is a soil remediation technique, which makes use of plants in removing contamination from soil. The plants must thus be tolerant to heavy metals, adaptable to soil and climate characteristics, and able to take up large amounts of heavy metals. Most of the high biomass productive plants such as, maize, oat and sunflower are plants, which do not grow in cold climates or need intensive care. In this study three “weed” plants, Borago officinalis; Sinapis alba L. and Phacelia boratus were investigated for their ability to tolerate and accumulate high amounts of Cd and Pb. Pot experiments were performed with soil containing Cd and Pb at concentrations of up to 180 mg kg−1 and 2,400 mg kg−1 respectively. All three plants showed high levels of tolerance. Borago officinalis; and Sinapis alba L. accumulated 109 mg kg−1 and 123 mg kg−1 Cd, respectively at the highest Cd spiked soil concentration. Phacelia boratus reached a Cd concentration of 42 mg kg−1 at a Cd soil concentration of 100 mg kg−1. In the case of Pb, B. officinalis and S. alba L. displayed Pb concentrations of 25 mg kg−1 and 29 mg kg−1, respectively at the highest Pb spiked soil concentration. Although the Pb uptake in P. boratus reached up to 57 mg kg−1 at a Pb spiked soil concentration of 1,200 mg kg−1, it is not suitable for phytoextraction because of its too low biomass.

Introduction During green manure application the relatively fast growing and huge yielding biomass providing plants are produced so as to get the green parts applied back into the soil by rotation (plowing) or by shallow mixing (e.g. by disc harrow or cultivator). Westsik (1965) studied green manure application of different pulses. Nevertheless there are numerous other plants involved in production for the above purpose, for example mustard, oil radish, phacelia, buckwheat, purple clover, forage radish, sweet clover, and different ration of mixture of the above plants. Production of these plants can be as a mainor as a secondary crop. The main seeding is not widely applied either in Hungary or abroad (Kahnt 1986), in Hungary there are backgrounds existing for the production of the second seeded green manure plants (Gyarfas, 1953). The green parts applied into the soil improve the physical and biological conditions and the nutrient state of the soil, contribute to increase of organic matter, protect the surface from windand water erosion. Due to the intense root development they also have a biological loosening effect in the soil decreasing this way the chance for formation of a compacted layer. Being produced the above plants as a secondary crop they reduce leaching of nutrients, mainly in very wet years. Primarily they take up nitrogen in huge amount, this way it can be utilized by the following plant directly (Birkas et al. 2002; Hansen and Djurhuus, 1997; Jamriska 2002; Sainju and Singh 1997). Some green manure plants can also be utilized to create a more diverse animal feeding. In this case specific parts of the green manure plants are chopped and fed by animals in fresh condition or as silage.

Allelopathic performance of the bark and seed of Tamarindus indica L. tree was evaluated through bioassay-guided studies using seven common agronomic crops (asparagus, cucumber, lettuce, radish, sesame, tomato and welsh onion) and seven weed species (barnyard grass, Chinese milk vetch, perennial ryegrass, phacelia, timothy grass, white clover and wild ginger) under laboratory conditions. As demonstrated by a sandwich method, the bark of the tamarind tree caused strong growth inhibition (compared to the corresponding controls) in both radicles and hypocotyls of the species tested, and the inhibitory effect was highest in barnyard grass (52–65%) and lowest in welsh onion (19–13%). The crude-water soluble extracts of bark at different concentrations (1, 5 and 10%) (w/v) exhibited a strong growth inhibition in all the plant species tested, and a proportional increase in the percentage of growth inhibition was observed with an increase in the concentrations of the extracts. The magnitude of inhibition in weed species was higher (5–60%) than those of agronomic crop species (3–40%). The growth of all the weed species tested was strongly inhibited (17–56%), while the agronomic crop species showed both inhibited (5–21%) and stimulated (5–27%) growth due to the effect of crude-water soluble exudates of tamarind seed. Among the agronomic crop species tested, lettuce (22–27%) followed by radish (20–25%) and sesame (5–8%) showed stimulatory growth with the crude-water soluble exudates of seed. In the pot culture experiments using four agronomic crops (lettuce, radish, tomato and cucumber) and two weed species (barnyard grass and white clover), spraying of crude-water soluble extracts of tamarind seed-coat at three different concentrations (1, 5 and 10%) (w/v) showed that the growth of lettuce (35–62%) and radish (32–56%) was stimulated, while all other species tested showed growth inhibition (29–61%). When the spraying of crude extracts of seed-coat was turned off, the growth of both lettuce and radish continued to be stimulated (4–7%) and all other previously inhibited species recovered well, the recovery percentage ranging between 78 and 82%. However, when spraying of crude extracts of seed-coat was continued, growth increased (10–14%) in lettuce and radish, and reduced (37–76%) in four other species tested. The inhibitory or stimulatory effects of the crude extracts on agronomic crop and weed species were higher in the radicle than the hypocotyl and reached a peak with 10% (w/v) concentrations. These results clearly demonstrated the differential allelopathic effects (inhibitory and excitatory) of bark and seed of tamarind tree in the species tested. Thus, it is evident that these two organs contain certain biologically active true growth regulator(s) and are either additively or synergistically involved in the plant-specific expression, particularly by the seed-coat.

The management of field margin strips for the enhancement of biodiversity of plant-insect communities and natural-enemy populations was studied on experimental farms near Göttingen (Germany). Young and old, sown and naturally developed field margin strips were compared and differences to large fallows established. The five types of field margin strips (around cereal fields) were: (1, 2) 1- or 6-year-old naturally developed strips, (3) strips sown with a Phacelia mixture, (4) strips sown with a mixture of 19 wild flower species, and (5) strips sown with winter wheat or oat as a control. The naturally developed vegetation of the field margin strips was dominated by aggressive weeds, presumably due to the intensive farming practices and the fertile soils. Cirsium arvense populations decreased, while Elymus repens populations increased with age of habitat. Sowings were suitable to suppress these aggressive weeds. Potted plants of mugwort (Artemisia vulgaris) and red clover (Trifolium pratense) were exposed in the field margin strips to study arthropod colonization of these experimentally standardized plant patches. Arthropod species richness did not differ between field margin types, reflecting the overall similarity in floristic diversity, but sprayed and strip-free edges of cereal fields had a reduced diversity. Dispersal of insect populations of red clover into the cereal fields decreased with increasing distance, but benefited from adjacent field margin strips. Populations of predators (mainly spiders) as well as predator-prey ratios were significantly larger in 6-year-old than in 1-year-old strips emphasizing the importance of habitat age for natural enemies and possible biological control. Predator-prey ratios were also higher on old than young fallows. Large fallows had greater predator-prey ratios than small field margin strips emphasizing the trophic-level hypothesis of island biogeography in that the relative importance of natural enemies increased with habitat area. Insect species richness was only marginally influenced by area and not by age. As species richness of predators did not increase with area and age, species diversity and the possible biological-control function did not covary.

Intensification of agriculture in recent decades has impoverished farmland for insect pollinators by removing their food plants. Arable farmland can be enhanced as a habitat for these insects by growing annual nectar- and pollen-producing herbaceous plants for them in non-cropped areas such as set-aside and field margins. In 1996 and 1997, observations were made in Hertfordshire, UK, on the flowering phenology and flower-attractiveness to visiting Hymenoptera, Diptera and Lepidoptera of plots sown to mixtures of six annual flowering plant species: borage (Borago officinalis), buckwheat (Fagopyrum esculentum), cornflower (Centaurea cyanus), mallow (Malva sylvestris), marigold (Calendula officinalis) and phacelia (Phacelia tanacetifolia) in different proportions. The mixtures had good agronomic and biological properties. They established and flowered well from a range of seed rates and sowing-dates. They attracted a diversity of flower-visiting insects, including the honey bee and eightspecies of bumble bee amongst 16 species of aculeate Hymenoptera, 17 species of Diptera, mostly syrphids, and six species of Lepidoptera. Sequential sowings provided nectar and pollen from early summer to late autumn during the period after arable crops had finished flowering and food for pollinators was scarce. Different insect species were favoured by different sowing-dates and plant species

The ability to germinate under a variety of environmental conditions is essential for plant species inhabiting a wide range of altitudes and latitudes. Phacelia secunda J. F. Gmel. (Hydrophyllaceae) is a perennial herb with wide latitudinal and altitudinal distributional ranges. In the central Chilean Andes (33 °S) P. secunda can be found from 1600 m sealevel up to the vegetation limit at 3400 m. It has been suggested that seeds from populations encountering long periods with snow cover and adverse winter conditions would require longer periods of cold stratification for germination than those from populations exposed to milder winters. Given that the snow-free period decreases with elevation, seeds from high elevation populations could require longer period of cold stratification to germinate. Moreover, it has been shown that seeds from arctic and higher elevations environments are adapted to germinate better under high temperature conditions. Germination response with increasing periods of cold stratification (0–6 mo.) and under two contrasting thermoperiods (20 °/1O °C; 10 °/5 °C; 12 h day/night), were studied for 4 populations of P. secunda located at 1600, 2100, 2900 and 3400 m a.s.l. Initiation of germination required increasingly longer periods of stratification with elevation, and proportionately fewer seeds germinated for any one stratification treatment at the higher elevations. Seeds from higher elevations germinated to a higher percentage under the high than the low temperature thermoperiods. These results illustrates a significant variation in germination characteristics over a spatially short environmental gradient.

We measured newly-produced seeds entering the soil (Potential Seed Bank) to assess the timing and spatial patterning of Phase I dispersal in the central Monte desert, Argentina. Rates of forb- (6.13 mg m-2 d-1) and shrub-seed input (48.9 mg m-2 d-1) were maximum in early summer. The rate of grass-seed input, instead, was similar in early and late summer (7 to 8 mg m-2 d-1). About 90% of forb- and shrub-seed mass entered the habitat through protected (i.e., under canopy) areas, whereas 70% of grass-seed mass did so through exposed areas. Adult plant location and the uneven impact of wind on shrub, forb and grass seeds may explain such patterns. We also compared the Potential Seed Bank with the soil seed bank in the following spring (Realized Seed Bank). Seeds that form transient banks in other ecosystems (e.g., shrub seeds of the genus Larrea, or perennial grass seeds like those of Pappophorum and Trichloris) prevailed in the Potential Seed Bank. Some annual forb seeds, instead, appeared to form a more persistent seed bank, and prevailed in the Realized Seed Bank (e.g., Chenopodium). Horizontal redistribution did not affect the spatial patterning of forb and shrub seeds, but produced a more homogeneous distribution of grass seeds in the habitat. The impact of wind could explain the redistribution pattern of grass seeds. Finally, we found almost 80% of total seeds in the top 2 cm of soil. The smallest grass and forb seeds (Sporobolus and Descurainia) as well as some medium-sized and large forb seeds (e.g., Glandularia, Sphaeralcea, Phacelia) were able to reach deeper soil layers in the central Monte desert.

A preliminary study was conducted using the stable isotope 13C to pulse label the cover crop phacelia (Phacelia tanacetifolia) to examine its decomposition in soil, under field conditions. Plants were grown, in pots, in the greenhouse and after four weeks of growth were labelled with 13CO2 six times, at 1–2 week intervals. A single chamber was placed over the pots, and 13CO2 was generated, inside the chamber, by injecting lactic acid into sodium carbonate (99 atom % 13C). For calculating the quantity of Na2CO3 required, a target enrichment of 5 atom% 13C within the shoots of plants, assuming no respiration losses, was used. When harvested, at flowering, the mean enrichment of the shoot material was 3.0466 atom% 13C, or 1.9654 atom% excess 13C. To assess uniformity of labelling within plants, the shoot of a single plant was divided into leaves and stem from three sections of equal length. Ninety-three percent of this plant's dry matter had a 13C enrichment within 20 % of the weighted mean. At a field site with sandy soil, 13C labelled shoot and root material were combined and mixed with soil (0–15 cm). The soil was sampled 16 and 179 days later to determine the recovery of the added excess 13C in soil total C. The recoveries in soil (0–30 cm) were, respectively, 78 and 40 % at 16 and 179 days; there was appreciable variation associated with the recovery data from day 16, much less so at day 179. Methodological procedures for (i) enhancing the uniformity of labelling with 13C within plants, and (ii) minimising variability in the recovery of 13C from soil are suggested. ei]R Merckx

Three new species ofPhacelia from Nuevo Leon, Mexico are described and illustrated. Two of these,P. hintoniorum andP. potosina, belong to theCrenulata group; the former, with included anthers, relates toP. coerulea; the latter, with exserted anthers, relates toP. alba orP. coulteri. The remaining novelty,P. zaragozana, belongs to the subgenusCosmanthus where its closest relationship is withP. laxa.

Phacelia cookei andP. stebbinsii, thus far found only in California, are described as new. The former is apparently endemic to ashy volcanic sand on Mt. Shasta; the latter is found on metamorphic rock cliffs in Eldorado County.