Effects of Different Planting Densities on Photosynthetic Characteristics, Yield and Quality of Centella asiatica(L.) Urban

Abstract

【Objective】The study was carried out to investigate the effects of different planting densities on the photosynthetic characteristics, yield and quality of Centella asiatica(L.) Urban, which will provide a theoretical basis for the improvement of yield and quality during artificial cultivation.【Method】Five different planting densities, including 30 000, 60 000, 120 000, 160 000, and 250 000 plants/hm2, were set in greenhouse by using single factor randomized block design.The Li-6400 portable photosynthesis measure system was used to determine the photosynthetic characteristics in leaves and the content of asiaticoside and madecassoside in herbs was determined by HPLC.【Result】The planting density had no significant effects on branching number, dry weight per plant, stem diameter, leaf thickness, petiole length, leaf length and width of C asiatica(L.) Urban seedlings among in five different densities. The chlorophyll content, net photosynthetic rate(Pn), stomatal conductance(Gs), intercellular CO2 concentration(Ci), and transpiration rate(Tr) increased gradually and then decreased with the increase of density. Although the highest Pn [(15.241 μmol CO2/(m2·s) ﹞ was appeared at the density of 120 000plants/hm2, there was no significant difference between 60 000 and 120 000 plants/hm2. The highest chlorophyll a, chlorophyll b, chlorophyll total content, Gs, Ci, and Tr were all appeared under the 60 000 plants/hm2, which was significantly higher than those of other treatments. With the increase of density, the fresh yield, the dry yield, and the drying rate showed a trend of first increasing and then decreasing, which were the highest(21.437 t/hm2, 4.196 t/hm2, and 19.599%, respectively) when the density was 60 000 plants/hm2. At the density of 60 000 plants/hm2, all the fresh yield, the dry yield, and the drying rate were significantly higher than those of other treatments. The total contents of asiaticoside and madecassoside ranged from 1.95%to 2.78% among different densities, which were exceeded the requirement of Chinese Pharmacopoeia Version 2020(0.8%).The contents of asiaticoside and madecassoside also showed a trend of first increasing and then decreasing as the increase of density, and the total contents of asiaticoside and madecassoside were the highest(2.73%) when the density was 60 000 plants/hm2. Correlation analysis results showed that there was a significantly positive correlation between fresh yield and Tr, and a significantly positive correlation were also appeared among dry yield and Tr, Gs as well as total chlorophyll.【Conclusion】Planting density of 60 000 plants/hm2 was the most appropriate for C. asiatica in greenhouse. Reasonably dense planting could effectively increase the photosynthetic characteristics, increase photosynthetic efficiency, and improve the yield and quality of medicinal plants.

Keywords

• centella asiatica
• planting density
• photosynthetic characteristics
• chlorophyll content
• asiaticoside
• madecassoside