Annual estimations of ecophysiological parameters and biogenic volatile compounds (BVOCs) emissions in Citrus sinensis (L.) Osbeck

Chemical and physical interactions among trace gases (CH4, N2O, VOCs) contribute towards greenhouse effects. This paper by using a original simulation model analyses the annual trends of net photosynthesis, transpiration, and water use efficiency, the total primary production and finally the emission of monoterpenes from orange groves located in the Burriana plain (Spain). The net photosynthetic rate showed a bell-shaped trend with maximum average values of 3.5 mu molCO(2) m(-2) s(-1) calculated for the months of June and July. The canopy transpiration rate reached maximum values of approximately 2.5 mmolH(2)O m(-2) s(-1). Monoterpene emissions displayed a relevant increase during spring time reaching the highest values ol approximately 70 ng monoterpene m(-2) s(-1) during the summer period and a progressive decrease during the successive months. The loss of carbon by monoterpene emissions for the different plant organs is evaluated at approximately 0.404% of the total carbon fixed by photosynthesis (559.77 gC m(-2) y(-1)). On a fractionated basis the contribution of the leaves is 0.083% those of the fruits is 0.243% (for a period lasting from July to December), and only for the May period 0.079% for the flowers.