Dun-Xian Tan, M.D., Ph.D., Department of C&S Biology, The University of Texas Health Science Center, San Antonin. He has published 250 articles with 27,000 citations and h-index 92.
Melatonin, a derivative of tryptophan was clarified as a unique animal neurohormone for decades. Subsequently, melatonin has been found to be a phylogenic old molecule present in all organisms tested. Its origin can be traced to primitive bacteria and other unicellular organisms. It has been found that considerably high levels of melatonin are present in green plants. It appears that this molecule involves many aspects of plant physiology including seed germination, biomass growth, flowering, fruit repining and resistance to abiotic and biotic stressors. The mechanisms of melatonin on plant physiology are not fully uncovered. However; melatonin as an endogenously occurring potent free radical scavenger and antioxidant modifies the redox status of plants under unfavorable environmental conditions and this builds a corner stone for melatonin’s beneficial effects on plants. Melatonin preserves the photo capturing-molecules, chlorophylls, carotenoids and other pigments, improves photosynthetic efficiency and increases the biomass weight. We hypothesize that melatonin application in agriculture will significantly increase the crop production especially under the unfavorable environmental conditions including drought, cold and high salinity field conditions.
Shelley Jones earned her B.S. in Biology in 1989 from Old Dominion University in Norfolk, Va. She has worked at the UF Citrus Research and Education Center for almost 15 years, gaining experience in many areas of research including post-harvest quality, citrus flavors and byproduct chemistry, food technology and engineering, and most recently in the vector-pathogen-host interactions lab of Dr. Nabil Killiny. In addition to leaf volatile analysis, she specializes in metabolomics and using GC-MS for analysis of complex biological samples including plant phloem sap, insect hemolymph and honeydew.
Citrus species are considered the most widely grown fruit crop worldwide. Volatile organic compounds (VOCs), which are hydrocarbons with high vapor pressures, such as D-limonene and other terpenes, readily enter the air at room temperature. Citrus VOCs have been extensively studied in relation to citrus peel oils, which are commonly used as flavors and fragrances. Citrus volatiles mainly consist of alcohols, aldehydes, monoterpenes, oxygenated monoterpenes, sesquiterpenes and esters. Leaf volatiles function as plant signaling phytohormones, attractants for insect pollinators, and many are released in response to biostresses (such as herbivory or pathogen attack). The roles of specific released volatiles in response to leaf maturation are not well understood. In this study we detected changes in profiles of VOCs from young, intermediate and mature leaf clusters collected from Citrus macrophylla by in vivo headspace-SPME- GC-MS. Using an apparatus that isolates intact leaf clusters, we collected the released volatiles from living citrus plants without interference from those released when plants are sampled in a destructive manner. We detected more than 40 biogenic volatile compounds released from maturing citrus leaves. VOCs which increased with maturity included z-citral, citronellal, geranyl acetate and z-farnesol. Compounds which decreased with maturity included α-pinene, Δ-carene, β-ocimene and one unknown volatile. Determining the volatile profiles of citrus varieties at different stages of development will help elucidate the roles of specific volatiles in leaf maturation and developmental physiology without interference of those released as a response to biostress.