XVI International Botanical Congess
Plants contribute more volatile hydrocarbons to the atmosphere than human activities. Some hydrocarbons are pleasant smelling such as the smell of oranges. Some evoke strong memories, such as the smell of cut grass. However, some hydrocarbons are not readily detected despite their abundance. Most monoterpenes are formed in storage structures and deter herbivory. Isoprene is formed in chloroplasts and is not stored but may provide thermotolerance. Acetone can be emitted, possibly as a by-product of lipid breakdown, methanol may be released during pectin demethylation. Hexenol and related compounds give cut grass its smell and may have antimicrobial activity. However, though one bad apple can spoil the barrel by releasing ethylene, it is unlikely that plants signal their neighbors when under herbivore or pathogen attack by releasing methyl jasmonate or methyl salicylate. Some of the compounds emitted by plants participate in chemical reactions in the atmosphere that lead to ozone.