Effects of lifelong [CO2] enrichment on carboxylation and light utilization of Quercus pubescens Willd. examined with gas exchange, biochemistry and optical techniques
Cd. Stylinski et al., Effects of lifelong [CO2] enrichment on carboxylation and light utilization of Quercus pubescens Willd. examined with gas exchange, biochemistry and optical techniques, PL CELL ENV, 23(12), 2000, pp. 1353-1362
Lifelong exposure to elevated concentrations of atmospheric CO2 may enhance
carbon assimilation of trees with unlimited rooting volume and consequentl
y may reduce requirements for photoprotective pigments. In early summer the
effects of elevated [CO2] on carboxylation and light utilization of mature
Quercus pubescens trees growing under chronic [CO2] enrichment at two CO2
springs and control sites in Italy were examined. Net photosynthesis was en
hanced by 36 to 77%. There was no evidence of photosynthetic downregulation
early in the growing season when sink demand presumably was greatest. Spec
ifically, maximum assimilation at saturating [CO2], electron transport capa
city, and Rubisco content, activity and carboxylation capacity were not sig
nificantly different in trees growing at the CO2 springs and their respecti
ve control sites. Foliar biochemical content, leaf reflectance index of chl
orophyll pigments (NDVI), and photochemical efficiency of PSII (DeltaF/F-m'
) also were not significantly affected by [CO2] enrichment except that star
ch content and DeltaF/F-m' tended to be higher at one spring (42 and 15%, r
espectively). Contrary to expectation, prolonged elevation of [CO2] did not
reduce xanthophyll cycle pigment pools or alter mid-day values of leaf ref
lectance index of xanthophyll cycle pigments (PRI), despite the enhancement
of carbon assimilation. However, both these pigments and PRI were well cor
related with electron transport capacity.