The Impact Of Exogenous Potassium Levels On Growth And Alkaloid Accumulation In Catharanthus

Potassium nutrition plays an important role in plant growth and development. The present work was to explore the changes of biomass, ROS level and antioxidant enzyme activities, photosynthetic characteristics, alkaloids content and expression level of genes in the synthesis pathway under different levels of exogenous potassium. Our results will provide potential approaches to promote the growth and alkaloid accumulation in Catharanthus roseus, the main conclusions including:1. Exogenous potassium nutrition supplied at an appropriate dose was beneficial for plant growth regarding plant height, root length, total biomass of C.roseus seedlings. It was found that the potassium concentration supplemented at10mM and15mM significantly facilitated growth and biomass accumulation in this species.2. Exogenous potassium nutrition significantly reduced the ROS level in root tip. The most significant effect was at the10mM concentration. The activity of antioxidant enzymes was enhanced under the condition with increased potassium nutrition. Especially, the activities of POD and CAT were significant increase at15mM concentration, whereas SOD and APX were in the case of10mM concentration.3. The photosynthetic characteristics, such as photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), water use efficiency (Wue), displayed a consistent changing trend and they reached a maximum level under the10mM concentration. Changes in chlorophyll content shared a similar property with that of Pn.4. Exogenous potassium nutrition in an appropriate level could significantly increase C.roseus indole alkaloid contents. The content of catharanthine was increased with the increase of the potassium nutrition concentration. The contents of vindoline and vinblastine were showed to be elevated to the maximum levels under the15mM condition. In summary, excess dose of potassium external supplied not only resulted in damages to plant growth but also inhibited alkaloid accumulations.5. The supplement with15mM potassium increased the expression level of Str, Dat and Prx1genes encoding vinblastine synthesis and this provided evidence at the molecular level that potassium had the ability to promote the synthesis of alkaloids.