Studies On The Effect Of Different Light Intensity On The Photosynthesis And Secondary Metabolit Of Catharanthus Roseus

Light intensity is an essential factor on plants' growth and morphogenesis. It has been reported that the influence of light intensity on the metabolic process of plant physiology. Catharanthus roseus has attracted many people's attention in biopharmacy; it was make certain the mode plant in study the pathway of secondary metabolites, for the cause of it is applied efficiency in anti-tumour at present.In this paper, physiological metabolism dynamics of Catharanthus roseus under different light intensity (100%,42.5% and 12.5% full light) were determined by measured some index such as of photosynthesis indexes and the content of some metabolite and the activities of related enzymes. The result is followed:1. Catharanthus roseus was lower in Specific leaf area (SLA) , Mean leaf area (MLA) and Leaf area ratio (LAR) at high light levers. With a decrease in lightintensity, Leaf mass ratio (LMR) and leaf mass fraction (LMF) increased while Root mass ratio (RMR) , supporting organs biomass ratio (SBR ) and root mass/Crown mass (R/C) decreased.2. With the decrease of growth light intensity LMA, Chla/Chlb, Car/Chl, maximum net photosynthetic rate (Pmax ) , light saturation point and light compensation point decreased, Fo, Fm, Fv, Fv/Fm, Fv/Fo, Fm/Fo, qP andφPS II were decreased, chloroplast granas enlarged and grana lamella were bad-developed, while chlorophyll concentration increased.3. With the decrease of growth light intensity the content of starch and soluble sugar dropped obviously while the content of soluble protein,free amino acid and nitrate increased. The difference of activities of enzymes involved in carbon and nitrogen metabolism is clear. The activities of amylase, sucrose phosphate synthase(SPS), nitrate reductase (NR ) and glutamine synthase (GS) decreased while sucrose synthase (SS) increased with the decrease of growth light intensity4. Weak light did not favour the accumulation of flavoniod. With the light intensity decreased, VIN and CAT content increased while VLB and VCR content firstly increased and then decreased. VLB and VCR have the highest accumulation under 42.5% full light. With the light intensity decreased, the activities of PAL and POD decreased but the activities of TDC had not significant difference.The results indicates that suitable shading (passing throgh light rate is 42.5%) is the most suitable illumination environment for growth of Catharanthus roseus and the accumulation of alkaloids. So, monolayer shading is the best model to culture Catharanthus roseus.