Effect of Environmental Factors on Essential Oil Biosynthesis, Chemical Stability, and Yields

Essential oils are major secondary metabolites of aromatic plants and composed of complex mixture of terpenoids and phenylpropanoids components. Complex metabolic cross talk between mevalonic acid, methylerythritol, malonic acid, and DOXP pathways are involved for synthesis of essential oils. The biosynthesis and yield of essential oils are regulated by various environmental factors like light, temperature, drought, salinity, heavy metals, seasonal variations, and mineral concentrations. These environmental factors also have significant impact on chemical nature and stability of essential oil components. The essential oil ingredients are converted into structurally related components by oxidation, reduction, polymerization, dehydrogenation, and cyclization. However, in changing environmental conditions plants develop various mechanisms related to the production of secondary messengers, and signal transduction through mitogen-activated protein kinase and calcium-dependent protein kinases for activation or repression of different transcription factors. The upstream and downstream regulation of genes regulates the metabolic responses of aromatic plants which ultimately serve a crucial role in essential oil biosynthesis. Based on the above background, the article comprises biosynthesis of essential oils through different pathways, cross talk of metabolic reactions, and effect of various environmental factors, namely, light, temperature, oxygen availability, seasonal variation, salinity, and toxic contaminants on chemical stability of essential oils.