Responses Of VOCs Emission To Light And Mechanical Damage In Two Species Of Cinnamomum Camphora And Cinnamomum Japonicum

Cinnamomum camphora and Cinnamomum japonicum play an important role in urban landscaping.C.camphora and C.japonicum emitted large amounts of VOCs.C.camphora emitted mainly terpenes,and C.japonicum emitted mainly isoprene.The energy and carbon substrates required for the synthesis of these VOCs come from photosynthesis.In order to explore the photosynthetic energy and substrate supply of plants,biosynthesis and release of VOCs control,this experiment adopts two different release the abundance and type of plants,C.camphora and C.japonicum as experimental material,the use of PTR-MS and GC-MS,the photosynthetic characteristics and VOCs emission characteristics of intact and damaged leaves of the two plants were studied under light and different dark conditions,and the main conclusions were as follows:（1）Under normal condition,the net photosynthetic rate and stomatal conductance of C.camphora were significantly higher than C.japonicum.VOCs emissions of C.camphora and C.japonicum leaves were affected by light,and VOCs emissions decreased under dark condition.Compared with light,VOCs emission in C.camphora decreased 61.0%,58.8%and 83.1%under light darkening,interrupted light 3 h and natural dark 3 h,respectively,·total VOCs emissions in C.japonicum decreased by 87.2%,58.6%and94.0%,respectively.（2）Under light conditions,the net photosynthetic rate and stomatal conductance of C.camphora decreased,and the VOCs emission of C.camphora increased by 15.5%,170%and 300%,respectively,after 3 h of light,dark and natural darkness.Under light condition,C.camphora leaves had the highest VOCs emission(23.81 nmol·m^-2·s^-1).When C.camphora leaves were damaged in light or dark,the emission of monoterpene and green leaf volatiles（GLVs）increased immediately and decreased to a stable value within 30 min.After leaves of C.japonicum was damaged,photosynthetic parameters of C.camphora under light condition were consistent with those of C.japonicum.The total VOCs emission of C.camphora decreased by 1.9%under light condition,and the VOCs emission of C.camphora increased by 28%and 760%during 3 h and 3 h,respectively.The transient changes of monoterpenes and GLVs were consistent with C.camphora.（3）In C.camphora,the release ofβ-ocimene is affected by light,and in C.japonicum,isoprene is affected by light.After the light turns dark,the isoprene emission decreases immediately,then rises,and finally falls to the base level.In the damaged leaves,both C.camphora and C.japonicum releaseα-pinene,D-limonene,phellandrene and p-cymene.The difference is that C.camphora mainly releases monoterpenes,while C.japonicum mainly releases isoprene.C.japonicum only releases non-oxygenated monoterpenes,while C.camphora releases both non-oxygenated monoterpenes and oxygenated monoterpenes,and the oxygenated monoterpenes released by C.camphora are mainly eucalyptol and camphor.In conclusion,C.camphora and C.japonicum mainly release terpenes,among which C.camphora mainly release monoterpenes and C.japonicum mainly release isoprene,but the overall release is affected by light,which is related to the energy and carbon substrate provided by photosynthesis in the daytime.The VOCs release amount and types of C.camphora and C.japonicum in daytime light were more than those in dark condition.After mechanical injury,the photosynthesis of C.camphora and C.japonicum was partially impaired,and the monoterpene and GLVs release increased instantly,which might be related to the initiation of stress and defense response of plants.The data from this study revealed that VOCs release of two lauraceae plants was affected by light conditions and also related to leaf state,which could provide accurate estimation of VOCs release from plants in regional environment.