
%0 Journal Article
%A Maroco, Jo&atilde;o P. 
%A Rodrigues, M. Luc&iacute;lia 
%A Lopes, Carlos 
%A Chaves, M. Manuela 
%T Limitations to leaf photosynthesis in field-grown grapevine under drought &#8212; metabolic and modelling approaches
%J Functional Plant Biology
%D 2002/04/19
%V 29
%N 4
%P 451-459
%K drought, enzymes of carbon metabolism, gas-exchange, modelling, photosynthesis,Vitis vinifera.
%R https://doi.org/10.1071/PP01040
%U https://www.publish.csiro.au/paper/PP01040 
%X The effects of a slowly-imposed drought stress on gas-exchange, chlorophyll a fluorescence, biochemical and physiological parameters of Vitis vinifera L. leaves (cv. Aragonez, syn. Tempranillo) growing in a commercial vineyard (South Portugal) were evaluated. Relative to well-watered plants (predawn water potential, &Psi;PD = &#8211;0.13 &#177; 0.01 MPa), drought-stressed plants (&Psi;PD = &#8211;0.97 &#177; 0.01 MPa) had lower photosynthetic rates (ca 70%), stomatal conductance, and PSII activity (associated with a higher reduction of the quinone A pool and lower efficiency of PSII open centres). Stomatal limitation to photosynthesis was increased in drought-stressed plants relative to well-watered plants by ca 44%. Modelled responses of net photosynthesis to internal CO2 indicated that drought-stressed plants had significant reductions in maximum Rubisco carboxylation activity (ca 32%), ribulose-1,5-bisphosphate regeneration (ca 27%), and triose phosphate (triose-P) utilization rates (ca 37%) relative to well-watered plants. There was good agreement between the effects of drought on modelled biochemical parameters, and in vitro activities of key enzymes of carbon metabolism, namely Rubisco, glyceraldehyde-3-phosphate dehydrogenase, ribulose-5-phosphate kinase and fructose-1,6-bisphosphate phosphatase. Quantum yields measured under both ambient (35 Pa) and saturating CO2 (100 Pa) for drought-stressed plants were decreased relative to well-watered plants, as well as maximum photosynthetic rates measured at light and CO2 saturating conditions (three times ambient CO2 levels). Although stomatal closure was a strong limitation to CO2 assimilation under drought, comparable reductions in electron transport, CO2 carboxylation, and utilization of triose-P capacities were also adaptations of the photosynthetic machinery to dehydration that slowly developed under field conditions. Results presented in this study confirm that modelling photosynthetic responses based on gas-exchange data can be successfully used to predict metabolic limitations to photosynthesis. 
