Some insights into composition and monoterpene emission rates from selected dominant tropical tree species of Central India: Plant-specific seasonal variations

In this article, we discuss about the seasonal variations in the monoterpene emission rates and chemical composition of monoterpenes from selected tropical tree species of Central India. The highest normalized total average monoterpene emission rates (normalized at 30 degrees C) from all the plant species were found in summer followed by rainy and winter seasons, respectively. The composition of individual monoterpene compounds emitted from all the tropical plant species showed significant seasonal variations. Nine monoterpene compounds were determined across three seasons from these selected plants: alpha-pinene, beta-pinene, and limonene represented up to 72.6% of the total monoterpene emission. Although the main compounds emitted were alpha-pinene, beta-pinene, and limonene, the other minor compounds were also found at varying emission rates. alpha-Terpinene and carene were not observed in Eucalyptus globulus and Pongamia pinnata during winter and rainy seasons. Sabinene was only recorded from Azadirachta indica. We have thus observed clearly that the seasonal as well as monthly variations in chemical composition of monoterpene emission rate are species specific. Furthermore, the effect of environmental variables such as temperature (TEM), photosynthetically active radiation (PAR), relative humidity, and carbon dioxide from plant species in distinct seasons revealed that the monoterpene emissions were mainly temperature (TEM) and PAR dependent.