The environmental impact of greenhouse production in France is poorly documented. Environmental benefits versus drawbacks of greenhouse production are not well known. Assessments that intregrate pesticide toxicology and transfer of mass and energy are scarce. Here, we compared the main types of tomato production, heated, year-round production in plastic houses or glasshouses, and seasonal production under polytunnel. Environmental impacts where assessed by life cycle analysis. Analyses were performed after the construction of a database relating the integrality of matter and energy fluxes, regarding the structure of the system, the inputs for production, and the waste products. Results show that greenhouse heating had the highest environmental impacts, including toxicological impact. For instance, the mean environmental impact of heated crops under plastic or in glasshouses was 4.5 times higher than in tunnels. Furthermore, pesticides in tunnels had a 3-to 6-fold higher impact in terms of terrestrial or aquatic ecotoxicology or human toxicology. Our results were compared with data from other temperate production regions.
The nutritional status of a plant is known to influence its susceptibility to pathogens. In the case of Botrytis cinerea, the role of nitrogen fertilization of various host plants on disease development appears to be variable. This study was carried out to characterize possible variability associated with isolates and inoculum density of B. cinerea in its ability to infect leaf-pruning wounds and to develop stem lesions on tomato plants, as affected by the nitrogen input. Six isolates differing in their aggressiveness to tomato were compared. They all had similar reaction patterns in vitro in response to differential nitrogen levels. In tests on plants grown with contrasted regimes of nitrate fertilization, overall disease severity was lower for all isolates on plants with higher nitrogen inputs, regardless of inoculum concentration. However, differences among isolates were observed in the effect of plant nitrogen nutrition on infection and on lesion expansion. Disease onset was delayed on all plants with higher nitrogen inputs, but the response was greater for isolates with lower aggressiveness on tomato. The highest contrast among isolates was observed with the colonization of stems. The daily rate of stem lesion expansion decreased with increasing nitrogen fertilization levels for the more aggressive isolates, while it increased for the less aggressive isolate. Hypotheses to explain these results are discussed in light of the possible physiological effects of nitrogen fertilization on nutrient availability for the pathogen in the host tissue and of possible production of defence metabolites by the plant.
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