Life-long growth of Quercus ilex L. at natural CO

The aim of the present study was to analyse whether offspring of mature Quercus ilex trees grown under life-long elevated p CO 2 show alterations in the physiological response to elevated p CO 2 in comparison with those originating from mature trees grown at current ambient p CO 2 . To investigate changes in C(for changes in photosynthesis, biomass and lignin see Polle, McKee & Blaschke Plant, Cell and Environment 24, 1075–1083, 2001), N-, and Smetabolism soluble sugar, soluble non-proteinogenic nitrogen compounds (TSNN), nitrate reductase (NR), thiols, adenosine 5 ¢ -phosphosulphate (APS) reductase, and anions were analysed. For this purpose Q. ilex seedlings were grown from acorns of mother tree stands at a natural spring site (elevated p CO 2 ) and a control site (ambient p CO 2 ) of the Laiatico spring, Central Italy. Short-term elevated p CO 2 exposure of the offspring of control oaks lead to higher sugar contents in stem tissues, to a reduced TSNN content in leaves, and basipetal stem tissues, to diminished thiol contents in all tissues analysed, and to reduced APS reductase activity in both, leaves and roots. Most of the components of C-, Nand S-metabolism including APS reductase activity which were reduced due to short-term elevated p CO 2 exposure were recovered by life-long growth under elevated p CO 2 in the offspring of spring oaks. Still TSNN contents in phloem exudates increased, nitrate contents in lateral roots and glutathione in leaves and phloem exudates remained reduced in these plants. The present results demonstrated that metabolic adaptations of Q. ilex mother trees to elevated p CO 2 can be passed to the next generation. Shortand long-term effects on source-to-sink relation and physiological and genetic acclimation to elevated p CO 2 are discussed. Key-words : amino compounds; cysteine; ecotypic differentiation; elevated p CO 2 ; glutathione; oak; phloem transport; sugar. Abbreviations : CHES, 2-(cyclohexylamino)-ethansulfonacid; DTNB, 5,5 ¢ -dithiobis(2-nitrobenzolacid); DTE, dithioerythritol; g -EC, g -glutamylcysteine; mBBr, monobromobimane; NR, nitrate reductase; PVPP, polyvinypolypyrrolidone; TSNN, total soluble non-proteinogenic nitrogen.