Effects of two contrasting potting media on the leaf development index, photosynthetic rate, and metabolite profile of camphor (Dryobalanops aromatica) seedlings

Abstract

Camphor (Dryobalanops aromatica C. F. Gaertn.) is a vulnerable tropical tree species that has been exploited for its timber as well as its resin, which is used for medicinal uses. The use of camphor in Indonesia is limited owing to the decreasing size of the species' population in its native habitat. Therefore, replanting programs have been encouraged for this species owing to its adaptability to mineral soils and shallow peatlands. However, experimental evidence of the effect of different growing media on morphology, physiology, and biochemistry is very limited, which is needed to evaluate the replanting program's success. Therefore, this study aimed to determine the responses of camphor (D. aromatica) seedlings grown in two different types of potting media i.e. mineral and peat, for 8 weeks of planting. In particular, the types of bioactive compounds produced in camphor leaves and their levels were assessed by analyzing their metabolite profiles. Leaf growth was evaluated morphologically using the plastochron index, while photosynthetic rates were measured with LI-6800 Portable Photosynthesis System. Metabolites were identified by using liquid chromatography-tandem mass spectrometry. The percentage of LPI of 5 or more was lower in the peat medium at 8% than in the mineral medium at 12%. The photosynthetic rate of camphor seedlings was 1–9 μmol CO2 m⁻2 s⁻1, with a higher rate in the peat medium than in the mineral medium, suggesting that the peat medium was better for growth. Lastly, the metabolomic analysis in the leaf extract revealed the presence of 21 metabolites, which were dominated by flavonoid compounds.