Ecophysiological characterization of Citrus sinensis (L.) Osbeck and relationships with type and amount of biogenic emissions

In this paper are shown the results obtained on Citrus sinensis (L.) Osbeck during the sampling campaigns performed in Burriana (Spain) in the frame o f B.E.M.A. project. The daily trends of photosynthesis (A) showed higher va lues at morning and a decrement during the hottest hours of the day; for le af transpiration (E) we observed a slight increment during the day. During different months (May '96, June '97 and July '95) we noted a progressive re duction in gas exchange of the leaves in relation to build-up of summer str ess condition (-49% and -60% for June and July respect to May). In particul ar, net photosynthesis and leaf transpiration measured on Citrus leaves wer e, in general, characterised by low average values (2.7 +/- 0.06 (s.e.) mu mol CO2 m(-2)s(-1) and 0.665 +/- 0.021 (s.e.) mmol H2O m(-2)s(-1) for curre nt leaves, respectively). The relationship between biogenic volatile organi c compound (BVOC) emission rates normalised by assimilation (A) and gas exc hange parameters as E/A ratio is reported. This latter is considered as an useful functional index to determine different vegetation types on a functi onal basis. We also found a good correlation between BVOC normalised emissi ons with air temperature. This behaviour has been reported for other specie s having monoterpene compounds in storage structures as Pinus species. More over, it is evident an uncoupling between BVOC emissions and photosynthesis . (C) 1999 Elsevier Science Ltd. All rights reserved.