Abstract
Our objective was to investigate the effect of water and nitrogen (N) availability on the carbon isotope composition of leaf blades, canes and ripe berry must (juice) in field grown grapevines.In two consecutive years, the combination of two irrigation treatments [Irrigation (I): 70 % of crop evapotranspiration (ETc) and no irrigation (NI)] and three rates of ammonium nitrate [0 (N0), 60 (N60) and 120 (N120) kg/ha N] were applied to two separate vineyards planted with cv. Xinomavro and cv. Cabernet-Sauvignon respectively in a randomised complete block design. Carbon isotope composition (δ13C) of leaf blades, stem water potential (Ψs), and leaf gas exchange were measured at berry set, bunch closure, veraison and maturity during each growing season. δ13C of bulk berry must at maturity and of dormant canes was also measured.Leaf δ13C and cane δ13C decreased with water supply, but increased with N fertilisation. Must δ13C was lower in the irrigated N0 and N60 vines, whereas irrigation treatments did not differ under the N120 rate. The relative weight of irrigation and fertilisation effect on leaf δ13C varied across samplings: N application accounted for a higher proportion of leaf δ13C variance during the early stages of berry growth, whereas irrigation induced higher variance of leaf δ13C after veraison. The weight of the irrigation effect on cane δ13C was higher from that of fertilisation.Discrimination mechanisms against 13C in grapevine could be mediated by both N fertilisation and irrigation. The well-documented explanation of δ13C variation based on isotopic effects during CO2 diffusion through leaf stomata and carboxylation driven by water conditions may not apply to all cases, since additional discriminating processes against 13C associated with CO2 transfer from the intercellular spaces to the carboxylation sites may be affected by nitrogen supply.The study provides evidence for the first time that carbon isotope composition of leaf blades, canes and berry must is modulated by nitrogen supply. Interpretations of carbon isotope natural abundance in field grown grapevine tissues should therefore consider both water and nitrogen availability.
Highlights
Chemical elements like carbon, nitrogen, oxygen, sulfur, and hydrogen, which form part of most of the structural elements of living organisms, have more than one stable - nonradioactive - isotopes
This relationship was evident only on data pooled from two vineyards that were planted with a winegrape (CabernetSauvignon) and a table grape variety (Crimson Seedless), whereas there was no significant relationship between leaf N and berry must δ13C within each of the vineyards
Considering that both nitrogen and water availability may influence the carbon isotope composition of plants and the knowledge gap that exists on any possible effects of N availability in grapevines under varying water supply, our study aimed to investigate the responses of δ13C measured in the bulk dry matter of main leaf blades and canes, and in the bulk berry must, to N fertilisation and water application
Summary
This study was conducted during the growing seasons of 2009 and 2010 in two 18-year-old vineyards located in the Goumenissa region of north Greece (40°52’ N, 22°29’ S). The vineyards were planted with the red winegrape varieties Cabernet-Sauvignon (CS) and Xinomavro (XM), both Vitis vinifera L. cultivars, and grafted onto the 1103 Paulsen rootstock Both vineyards had the same vine spacing (2.2 m and 1.3 m between and within row respectively) and a north to south row orientation. Drip irrigation started at berry set (growth stage E-L 27, according to the modified EichhornLorenz system) in both seasons and was continued at weekly intervals, according to the estimates obtained from the potential evapotranspiration measured by an automated weather station located in the XM vineyard. Carbon isotope composition (δ13C) and total nitrogen content were measured in the bulk dry matter (BDM) of leaf blades, sampled at four time points (BS, BC, VE and MT, corresponding to the growth stages of berry set, bunch closure, veraison and maturity respectively) during each growing season. The measurements were taken at solar noon (between 12:30 and 13:00) under clear sky conditions
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