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A two-year research was carried out in 2004-2005 in order to evaluate the effects of biodegradable green mulch on melon (Cucumis melo L. var. reticulatus Naud.) yield and quality. The loss of quality due to the presence of spot caused by the residues of biodegradable plastics was also investigated. The research was conducted over two years, in open field, at S. Piero a Grado, Pisa, Italy, (lat. 43.67498, long. 10.34737), from the beginning of May to the end of July of each year. The films tested in the first year experiment were two biodegradable ones with different colours (black and green) compared with a low-density polyethylene (LDPE) film, while in 2005 three biodegradable films, (two green and one black) were compared with a traditional LDPE film. The two green biodegradable films had different properties related to the biodegradation rate, faster in film Cv205, because of a different degree of Mater Bi polymer inside the film. In each year a randomized block design with four replications was followed. Green biodegradable films allowed obtaining a higher yield than LDPE films maybe because of the higher soil temperatures reached, and excellent fruit quality, especially for the soluble solids content and the ripening process. At the same time, the presence of residues on the fruit skin was rather low because of the degradation of films occurred at the ripening time. In the first year, the percentage of spotted fruits was low for every kind of film, while in the second one the green film showed a higher presence of residues on skin compared with the black one. The biodegradable materials covered the soil for the whole crop cycle with a good mulching effect, and the successive degradation allowed to avoid the removal and disposal of plastic film, with a certain economic advantage

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The photosynthetic response was studied in two clones (Populus deltoides x maxi-mowiczii Eridano and Populus x euramericana I-214), known for their differential response to ozone (O-3) in terms of visible symptoms, when exposed to O-3 (60 nl l(-1) 5 h day(-1), 7 and 15 days). The photosynthetic ability was tested using gas exchange and chlorophyll fluorescence analysis. O-3 caused a decrease in the CO2 assimilation rate at light saturation level in mature leaves of both clones. Alterations of Chi fluorescence parameters, in particular the F-v/F-m ratio and non-photochemical quenching were also observed. The effects were similar for both clones and it could not be concluded that differential effects on electron transport capacity were responsible for the observed reduction in photosynthesis. The reduction of photosynthetic rate in Eridano was due mainly to a reduced mesophyll activity, as evidenced by the increase in intercellular CO2 concentration and the minimal changes in stomatal conductance. In contrast, in I-214. stomatal effects were primarily responsible, although effects on the mesophyll cannot be excluded. Data obtained indicate that the effects observed at the mesophyll level may be attributed to indirect effects caused by membrane disorders