Fungal volatile organic compounds and their effects on seed germination and plant growth in arabidopsis thaliana

The biological effects of volatile organic compounds (VOCs) have been studied in depth in many organisms. Known volatile interactions include insect–insect or insect–plant interactions, effects of industrial volatiles on humans, plant–plant interactions, plant–bacterial interactions as well as others. Both plant and fungal volatiles have been heavily researched, however, very little research has been conducted to determine the effects of fungal VOCs on plant growth and health. In order to test these effects in a controlled and reproducible manner, I designed a novel exposure system to assess plant sensitivity to fungal VOCs. This system is designed to expose plants to any microbial or anthropogenic volatile source. In addition, it is scalable to conduct larger experiments and/or expose larger plants to VOCs. With this exposure system, I have determined that Trichoderma viride VOCs induce increased growth in the plant model system Arabidopsis thaliana (45% greater freshweight and 58% greater chlorophyll concentration after four weeks). To determine the volatile or group of volatiles responsible for inducing growth promotion, gas chromatography and mass spectroscopy were conducted, identifying 56 unique compounds. After a literature review of volatiles commonly produced by fungi, 23 compounds were selected to test. A. thaliana plants were exposed to these compounds individually at 1ppm for 3 days. Various effects on the plants were observed ranging from complete inhibition of seedling formation by 1-octen-3-one to increased fresh weight (4.2%) and chlorophyll concentration (3.7%) in plants exposed to (-)limonene. No single compound tested induced the growth promotion observed in the T. viride exposure experiment indicating that a different compound or a mixture of compounds is possibly responsible for T. viride VOC induced growth promotion. These results show that naturally occurring fungal VOCs have the ability to induce positive or negative changes in plant growth and health. As pressure on agricultural production for fiber, food, and fuel increases for the ever growing human population, volatile gasses will be an important factor to consider as phytostimulants and phytotoxins. The application of stimulatory volatiles for growth enhancement could be used to increase crop yield.Ph. D.Includes bibliographical referencesby Richard Hun