Friend or foe : exotic flora and ecosystem function

Exotic flora, particularly weeds, are renowned for out-competing and displacing native flora, consequently affecting native fauna and pollinator relationships. Nonetheless, it stands to reason that weeds must provide some compensatory ecological value. This study assessed whether weeds are friend or foe to ecosystem function by considering the quality and quantity of pollen offered by widespread weeds in Australian ecosystems. Using the Honeybee Apis mellifera as a case study, and information derived from highly experienced commercial apiarists, we determined that 32 exotic plants are important pollen sources. Most species offered high to very high quality pollen. Pollen quality varied temporally, spatially and infraspecifically. Fifteen species were considered more beneficial to A. mellifera than others; only seven species were considered less beneficial. Thus, exotic flora contribute pollen resources that are valuable to maintain ecosystem function, particularly at times when flowering native species are few.

Major grass pollen allergen Lol p 1 binds to diesel exhaust particles : implications for asthma and air pollution

Background Grass pollen allergens are known to be present in the atmosphere in a range of particle sizes from whole pollen grains (approx. 20 to 55 μim in diameter) to smaller size fractions < 2.5 μ (fine particles, PM2.5). These latter particles are within the respirable range and include allergen-containing starch granules released from within the grains into the atmosphere when grass pollen ruptures in rainfall and are associated with epidemics of thunderstorm asthma during the grass pollen season. The question arises whether grass pollen allergens can interact with other sources of fine particles, particularly those present during episodes of air pollution.

Objective We propose the hypothesis that free grass pollen allergen molecules, derived from dead or burst grains and dispersed in microdroplets of water in aerosols, can bind to fine particles in polluted air.

Methods We used diesel exhaust carbon particles (DECP) derived from the exhaust of a stationary diesel engine, natural highly purified Lol p 1, immunogold labelling with specific monoclonal antibodies and a high voltage transmission electron -microscopic imaging technique

Results DECP are visualized as small carbon spheres, each 30–60 nm in diameter, forming fractal aggregates about 1–2μ in diameter. Here we test our hypothesis and show by in vitro experiments that the major grass pollen allergen, Lol p I. binds to one defined class of fine particles, DECP.

Conclusion DECP are in the respirable size range, can bind to the major grass pollen allergen Lol p I under in vitro conditions and represent a possible mechanism by which allergens can become concentrated in polluted air and thus trigger attacks of asthma.