Biogenic Volatile Organic Compounds (BVOCs) exchanges over Sorghum bicolor L. during a whole growing season in the Southern Europe

Biogenic volatile organic compounds (BVOCs) might affect air quality and regional climate and their emissions strongly depend from plants. BVOCs exchanges are related to plant species and environmental factors, as temperature, radiation and water availability. Since Sorghum bicolor L. is becoming an increasingly valid alternative to maize in Southern Europe as well as in any non-irrigated region with limited precipitation, is important understand its potential BVOCs exchanges pattern. Up to now, only few studies have focused on BVOCs exchanges at ecosystem scale over an entire growing season, and no one investigated sorghum or other crops in the Mediterranean area. For the first time in this paper, BVOCs fluxes in a sorghum field at ecosystem scale over a whole growing season in Southern Italy are presented. Using online PTR-TOF BVOCs detection and eddy covariance technique, we continuously followed BVOCs exchanges for about 3 months. Methanol was the main emitted compound with a total average emission of 0.1 nmol m-2 s-1, followed by acetaldehyde, with a total average emission of 0.04 nmol m-2 s-1. Their fluxes were correlated with developing and cutting, following the plant growth and the escaping routes from intracellular storage. Other oxygenated compounds (OVOCs) like formaldehyde acetone, acetic acid, formic acid, MVK/MAC, were also exchanged. Monoterpenes were mainly taken up, with a total average uptake of -0.015 nmol m-2 s-1. Net emissions of green leaves volatiles (GLVs) during the stages where lodging and cutting occurred, are related to mechanical stress. These results show variable dynamics for the investigated BVOCs. The exchanges match with those observed on other croplands (mainly maize) for some compounds, meanwhile for other compounds they seem to be different, revealing a variability related to species and world region. Finally, is to be considered that not only weather and seasonality determine BVOCs exchanges patterns, but also phenology, crop management and stress. Therefore, BVOCs can be used to predict changes in phenology or the onset of stress, helping to determine the health state of crops in a climate changes scenarios.