UV-B Physiological Changes Under Conditions of Distress and Eustress in Sweet Basil.

UV-B radiation has been previously reported to induce protective or deleterious effects on plants depending on the UV-B irradiation doses. To elucidate how these contrasting events are physiologically coordinated, we exposed sweet basil plants to two UV-B doses: low (8.5 kJ m-2 day-1, 30 min exposure) and high (68 kJ m-2 day-1, 4 h exposure), with the plants given both doses once continuously in a single day. Physiological tests during and after both UV-B exposures were performed by comparing the stress-induced damage and adverse effects on photosynthetic activity, the concentration and composition of photosynthetic and non-photosynthetic pigments, and stress-related hormones biosynthesis in basil plants. Our results showed that upon receiving a high UV-B dose, a severe inactivation of oxygen evolving complex (OEC) activity at the PSII donor side and irreversible PSII photodamage caused primarily by limitation of the acceptor side occurred, which overloaded protective mechanisms and finally led to the death of the plants. In contrast, low UV-B levels did not induce any signs of UV-B stress injuries. The OEC partial limitation and the inactivation of the electron transport chain allowed the activation of photoprotective mechanisms, avoiding irreversible damage to PSII. Overall results indicate the importance of a specific response mechanisms regulating photoprotection vs irreversible photoinhibition in basil that were modulated depending on the UV-B doses.

Plant tissue culture--an opportunity for the production of nutraceuticals.

This chapter provides a short discussion about the opportunity to cultivate in vitro plant tissue of species which synthesize secondary metabolites of nutraceutical interest. The introduction of species of particular interest in cultivation and domestication, can be an alternative to the harvest of wild species. In vitro culture techniques are a useful tool to improve production and marketing nutraceutical species which allows to make a rapid clonal propagation of plants selected for their active principles. The techniques of tissue culture are described in detail. In particular, it is underlined the necessity to clone selected plants and produce true-type plants when standardized plant products are the main goal. This can be reached by conventional micropropagation protocols culturing plants in vitro through the five culture phases. Another approach consists in applying unconventional systems in the last phase of in vitro culture which permit to develop autotrophy of the explants. Autotrophic growth improves the quality of the multiplied shoots and facilitates the acclimatization of the plantlets.