Abstract
The environmental factors affecting flavonoid biosynthesis and accumulation from Ginkgo (Ginkgo biloba L.) plants in production plantation settings is investigated to maximize their production. Objectives: To develop an understanding of the environmental factors (temperature and available soil moisture and their inter-relationship) affecting flavonoids biosynthesis and accumulation in Ginkgo leaves for selection, development, and production purposes for commercial production. Methods: A factorial experiment (temperature: 15/5, 25/15 and 35/25°C (day/night) and soil moisture: 55-60, 40-45 and 30-35% of field capacity) using 2-year-old Ginkgo seedlings to estimated flavonoids content and their expression level in leaves sampled 10, 20, 30, 40 and 50days using high performance liquid chromatography and quantitative real-time PCR (qRT-PCR) of seven flavonoid biosynthesis-related genes, respectively. Results: Flavonoid accumulation was significantly higher under lower temperature (15/5°C) and available soil moisture (40-45 and 30-35%) while it was severely suppressed under high temperature. qRT-PCR indicated that flavonoid biosynthesis differed greatly among the studied genes with some genes being up-regulated under lower or higher temperature and/or moisture. Conclusion: Total flavonoid content was greatly affected by temperature and soil moisture content and their biosynthesis varied among the studied genes suggesting the presence of a synergistic effect on the expression of genes within the flavonoid biosynthesis pathway. The results contributed to the understanding of the environmental factors needed for the successful production of flavonoid from Ginkgo leaves harvest plantations.
Highlights
Flavonoids are important secondary plant metabolites with many essential functions such as attractants and antioxidant enhancing pollination and seeds dispersal and plants’ resistance to UV light, drought, cold temperature and wounding [1,2]
A factorial experiment with two main factors, each with three levels (temperature: 15/5°C, 25/15°C and 35/25°C designated as T1, T2 and T3, respectively, and soil moisture content: 55-60%, 40-45% and 30-35% of field capacity designated as W1, W2 and W3, respectively), producing 9 temperature-soil moisture content combinations expressed as W1T1, W2T1, W3T1, W1T2, W2T2, W3T2, W1T3, W2T3 and W3T3 was performed in phytotrons to allow accurate environmental control and the assessment of flavonoid accumulation and their biosynthesis-related genes expression
It should be highlighted that at the same temperature condition, the total flavonoid content produced under different soil moisture contents varied and did not produce any obvious trend and the observed trend for temperature was not duplicated for soil moisture content as the mean flavonoid content across W1, W2, and W3 and duration were 12.25, 12.13, and 13.22mg/g, respectively, suggesting that lower soil moisture content is favorable but the effect is not as pronounced as that of temperature
Summary
Flavonoids are important secondary plant metabolites with many essential functions such as attractants and antioxidant enhancing pollination and seeds dispersal and plants’ resistance to UV light, drought, cold temperature and wounding [1,2]. While some studies have been conducted to determine the role of environmental factors on flavonoid biosynthesis and accumulation in Ginkgo leaves, present knowledge is still incomplete due to the complex and confounding nature of field testing that precluded isolating the role of each environmental effect individually [16,17]. It has not yet been clarified how the genes of flavonoid biosynthesis pathway respond to various combinations of temperature and soil moisture content
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