Changes in key volatile organic components associated with leaf quality of Pandanus amaryllifolius alongside the growth duration
Description
The leaves of Pandan (Pandanus amaryllifolius Roxb.) are one of the traditional food materials in Southeast Asian countries. The color and aroma have been considered as the main traits to judge the quality of pandan for a long time. However, the volatile aroma components of leaves at different growth stages have great differences. In order to determine the best harvesting time of pandan, a field experiments were established in this study. The volatile organic compounds (VOCs) were identified and analyzed using gas chromatography-mass spectrometry (GC-MS) from different leaf positions of Pandan. Photosynthetic physiology and agronomic traits such as photosynthesis, transporition, stomatal conductivity, leaf relative water content, chlorophyll content, dry matter mass, and leaf area were determined. Subsequently, the differences in VOCs and agronomic traits of leaves at different leaf positions were analyzed, and the correlation between VOCs and agronomic traits was explored. The results showed that, as the new leaves (L1-L3) at the top of Pandan had high transporition and water content, whlie had low photosnthesis, dry matter mass, chlorophyll content, and small leaf area; The components of VOCs in L1-L3 are less, and different from other leaf positions, but the content of pyrroles and furanones is relatively high. The dry matter accumulation reached a steady state in Pandan leaves below L4, photosynthesis, chlorophyll content and the total VOCs content also begins to reach a high level, which is suitable for harvesting. Among them, the content of squalene, neophytadiene, and phytol gradually increases with the growth of the leaves, except for the decrease of neophytadiene in aging leaves, meanwhilem the 2-Acetyl-1-pyrroline (2AP) content begins to slowly decrease and is significantly lower than that of new leaves. The synergistic effect between physiological activity and VOCs synthesis of Pandan are significantly higher than the antagonistic effect, although there is a complex interaction between photosynthetic indicators, agronomic traits, and volatile organic compound content. In summary, this study provide data support for the scientific judgement of the harvesting site and timing of Pandan that harvesting the L4-L8 position leaves of Pandan for obtaining 2AP, leaves below L11 position for obtaining squalene, and leaves at L7-L20 position for obtaining neophytadiene. The result of this study will also provide theoretical basis for the cultivation management and quality control of Pandan.