Effects Of Calcium Reagents On Photosynthesis Characteristics Of Enhanced UV-B Radiation Stressed And Non-stressed Catharanthus Roseus

We studied the influence of plasmalemma calcium channel blocker (LaCl3), intracellular IP3 channel blocker (Heparin) and intracellular CaM activity inhibitor (TFP) and co-effect of these calcium reagents with enhanced UV-B radiation on intracellular Ca2+ concentration and photosynthetic characteristics of Catharanthus roseus. Our research shows that:1. After the addition of Heparin, LaCl3 and TFP, intracellular Ca2+ concentration of Catharanthus roseus leaves decreased. On the contrary, intracellular Ca2+ concentration increased under the UV-B radiation. These Catharanthus roseus leaves which exposed to enhanced UV-B radiation after the addition of Heparin, LaCl3 and TFP also showed the increase of intracellular Ca2+ concentration, while the range of increase was different with these leaves which had only been treated with UV-B radiation. It suggests that calcium involves in the signal transduction of UV-B radiation stressed Catharanthus roseus.2. These Heparin, LaCl3 and TFP treatments on Catharanthus roseus resulted in decrease of net photosynthesis rate (Pn), maximal PSII quantum (Fv/Fm), PSII quantum yield (Yield), relative electron transport rate (ETR) and photochemical quenching (qP), while non-photochemical quenching (qN), chlorophyll a concentration, chlorophyll b concentration increased. We can conclude that calcium channel blocker can affect the photosynthesis of Catharanthus roseus significantly. Notably, Heparin caused the biggest photosynthesis parameter variation range of Catharanthus roseus, which means the calcium released by intracellular calcium pool through IP3 channel play an active role in the photosynthesis of Catharanthus roseus.3. Compare to UV-B stressed Catharanthus roseu, these Catharanthus roseu which first treated by calcium channel blocker Heparin, LaCl3 and TFP then exposed to enhanced UV-B radiation showed decrease of net photosynthesis rate (Pn), maximal PSII quantum (Fv/Fm), PSII quantum yield (Yield), relative electron transport rate (ETR) and photochemical quenching (qP); while increase of non-photochemical quenching (qN). It suggests that calcium channel involves in the signal transduction of UV-B radiation stressed Catharanthus roseus.