Effects of Rising Temperature on Secondary Compounds of Yeheb (<i>Cordeauxia edulis</i> Hemsley)

Abstract

The effects of temperature on net photosynthesis and stomatal conductance, emission of foliar volatile organic compounds (VOCs), and phenolics were investigated after exposing Cordeauxia edulis seedlings to control ( 27/19 ° C ) and three levels of elevated (32/23, 37/27, or 42/31 ° C) day/night temperature regimes in controlled growth chambers. Emissions of foliar VOC were measured on 7 th and 14 th day (d) of exposures, whereas net photosynthesis and stomatal conductance were measured on the 8 th and 15 th d. Net photosynthesis and stomatal conductance were not significantly affected by elevated temperatures. Emission rate of isoprene increased by 4-fold with 10 ° C r ise from the control on 7 th d of exposure. Emission rates of monoterpenes, sesquiterpenes and total isoprenoids increased to 2 - 5-fold higher than that of control plants with 5 ° C rise. Foliar isoprene emission peaked at daytime maximum of 37 ° C and the mono- and sesquiterpenes at 32 ° C . Few individual foliar phenolics, and total foliar phenolics showed significant concentration differences between treatments. Although high VOC emissions under warming appear ed to help plants to sustain abiotic stresses, arid/semi-arid species m ight substantially release highly reactive compounds that affect atmospheric chemistry. Hence, more studies are required on plant species of arid/semi-arid ecosystems of Africa to estimate the emission patterns and their role in atmospheric chemistry under the predicted future atmospheric warming.