Photosynthetic CO2 responses are studied to understand how photosynthesis adapts to changing environmental conditions and to predict plant carbon uptake under future climate scenarios. The aim of the present work was to gain understanding photosynthesis response to drought stress and plant water status in grapevines. The open field experiment focused on Vitis vinifera cv. ‘Glera’ and applied two treatments: irrigated and not irrigated. A/Ci curves were measured using a Li-6400XT portable photosynthesis system. Measurements were conducted at 30°C and 400 ppm CO2, followed by 300, 200, 100, 50, 400, 600, and 800 ppm CO2 under 1500 µmol m2 s-1 of photosynthetic photon flux density (PPFD). The Farquhar, von Caemmerer, and Berry photosynthesis model (‘FvCB model’) was used to estimate the maximum carboxylation (Vcmax) and maximum electron transport (Jmax) rates. Plant water status was assessed by stem and leaf water potential (Ψleaf, MPa). A parallel measure of leaf dark respiration was done at different temperatures. Despite regular precipitation during fruit growth, some differences in photosynthetic capacity highlighted variations between irrigated and not irrigated plants. For irrigated plants, A/Ci curves were grouped together compared to not irrigated ones and presented higher photosynthetic rates. Leaf water potential showed similarity between treatments, differing for some specific days but not causing excessive stress to the plants. Irrigated plants exhibited higher correlation between Vcmax and Jmax rates. Leaf dark respiration increased linearly with rising temperatures. The study revealed the resilience of grapevines to challenging weather conditions and highlighted the positive impact of irrigation on physiological processes, photosynthesis, and water status.
Canton et al. (Wed,) studied this question.