A/Ci curves in response to water limitation in Glera cultivar: Preliminary results

¹ Department of Agronomy, Food, Natural resources, Animals and Environment—DAFNAE, University of Padova, Agripolis, Viale dell’università 16, Legnaro, 35020 Padova, Italy
² Interdepartmental Research Centre for Viticulture and Enology—CIRVE, University of Padova, Via XXVIII Aprile 14, Conegliano, 31015 Treviso, Italy

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

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 (V_cmax) and maximum electron transport (J_max) 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 V_cmax and J_max 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.