Author(s)

Meseret C. Egigu, Mohamed A. Ibrahim, Johanna Riikonen, Asha Yahya, Toini Holopainen, Riitta Julkunen-Tiitto, Jarmo K. Holopainen

Department of Biology, Haramaya University, Dire Dawa, Ethiopia.
Department of Biology, University of Eastern Finland, Joen-suu, Finland.
Department of Crop Production Ecology, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden.
Department of Environmental Science, University of Eastern Finland, Kuopio Campus, Kuopio, Finland.
The Finnish Forest Research Institute, Suonenjoki, Finland.

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 rise 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 appeared to help plants to sustain abiotic stresses, arid/semi-arid species might 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.

Cordeauxia edulis; Climatic Warming; Elevated Temperature; Gas Exchange; Isoprenoids; Phenolics

Egigu, M. , Ibrahim, M. , Riikonen, J. , Yahya, A. , Holopainen, T. , Julkunen-Tiitto, R. and Holopainen, J. (2014) Effects of Rising Temperature on Secondary Compounds of Yeheb (Cordeauxia edulis Hemsley). American Journal of Plant Sciences, 5, 517-527. doi: 10.4236/ajps.2014.55066.