UV and PAR regime in vineyards of Tuscany

Solar ultraviolet radiation (UV) has been demonstrated to produce several effects on grapevine (Vitis vinifera). In particular UV stimulates the production of some important compounds that are directly implied in determining yield characteristics and modulates the interaction between plant pathogens and host responses. UV radiation effects seem to be also connected to photosynthetically active radiation (PAR) levels and consequently UV/PAR ratio can be considered a good indicator for light quality. During 2005 some measurements were performed in two vineyards in order to quantify incident radiation on the wall of grapevine rows with different orientation. The analysis of these results confirmed that PAR was muche influenced by row orientation while UV radiation was much less affected. UV-B/PAR rdiation ratio on wall was also strongly influenced by row orientation.