And proper erogenous supplement of PGR-S-Y decreased the endogenous synthesis of PGR-S-Y in the leaves, and
made the joint biosynthesis precursor (Geranylgeranyl Pyrophosphate GGPP) of S-Y, chlorophyll and stevioside more [14-15], so it could improve the content of chlorophyll, provide more essential condition for photosynthesis. At the same time, it could promote the synthesis of the stevioside, increase the content of stevioside in the plant.