Secondary metabolite regulation and UV-B tolerance mechanisms in Ocimum basilicum Var. Genovese

Our idea was to investigate whether there is a link between secondary metabolite regulation and UV-B tolerance exploiting the natural variation among the accessions-ecotypes of Ocinum basilicum coming from different country. To answer to this question: 1) Set-up a rapid screening growing methods under laboratory condition to easily compare plants from different geographic area. 2) Identify the dose of UV-B that primer and trigger the plants to UV-B response allow the elucidation of adaptative strategy. 3) Identify Ocinum basilicum genotypes with differential sensitivity to UV-B. 4) Define the relation between secondary metabolites and signaling molecules in the defence mechanism to stress. For doing this experiment we tested different methods of in-vitro cultivation, but finally decided to use Falcon Tubes. As well we tested acute, sub-acute and sub-chronic experiments and different UV-B doses. Finally with regard to fluorimeter parameters like the maximum yield of photosystem and phenolic content we decided to focus on these two doses, 8.5 as a low dose that cause acclimation response and 68 kJ as a high dose that induce programmed cell death. We focused on acute experiment that UV-B doses were given once continuously in a single day. According to our observation the exposure to UVB radiation caused an increase in the UV absorbing compounds. Anthocyanin concentrations increased in response to high UVB dose. By exposure plants to low UVB radiation we observed a fast increase in minutes in ABA and ET content, furthermore improve photosynthetic machinery modifying the level of photosynthetic pigments like Chlorophyll a, b, violaxanthin, zeaxanthin, lutein and beta-carotene. Low UVB dose activate acclimation response in plants. On the other hand, under high UVB doses we observed a biphasic increase in phytohormones like SA, ABA. Also chlorophyll fluorescence measurements were carried out for evaluating the effects of high UVB dose on different O. basilicum ecotypes at the end of UVB exposure (0 time) and during the recovery phases (24 and 48 h). According to the maximum quantum efficiency of PSII photochemistry, Fv/Fm, the ecotype160 from Cuba was the less affected by UVB stress.