Time vs drought: leaf age rather than drought drives osmotic adjustment in V. vinifera cv. Pinot Noir
Global warming and increased frequency and/or severity of drought events are among the most threatening consequences of climate change for agricultural crops. In response to drought, grapevine (as many other plants) exhibits osmotic adjustment through active accumulation of osmolytes which in turn shift the leaf turgor loss point (TLP) to more negative values, allowing to maintain stomata opened at lower water potentials1. We investigated the capacity of Pinot noir leaves to modulate their osmotic potential as a function of: (i) time (seasonal osmoregulation), (ii) growing temperatures, and (iii) drought events, to enhance comprehension of the resilience of grapevines in drought conditions. We performed trails under semi-controlled field conditions, and in two different greenhouse chambers (20/15 °C vs 25/20 °C day/night). For two consecutive vegetative seasons, grafted potted grapevines (Pinot noir/SO4) were subjected to two different water regimes for at least 30 days: well-watered (WW) and water deficit (WD). Via pressure-volume (PV) curves and osmometer measurements we derived the leaf osmotic adjustment capability and TLP, while monitoring the plant gas exchange and water potential. Surprisingly, lower water potentials in WD vines throughout the season and in all situations (field and greenhouse) did not trigger osmoregulation, changes in TLP nor a modification of the modulus of elasticity. PV curves provided clear evidence that both temperature and water availability do not stimulate active osmotic adjustment in Vitis vinifera cv. Pinot Noir. Conversely, there is a clear impact of seasonal osmoregulation throughout the growing season2, decreasing the osmotic potential at full turgor by an average of 0.46 MPa in 90 days. Lack of osmotic adjustment in response to drought observed in this cultivar suggests Vitis genotypes have a broad spectrum of responses to drought and the strategy adopted to cope with it is highly dependent on the cultivar under analysis.
The work was financially supported by the Austrian Science Fund (FWF): I 4848 “PlasticGrape”.
1) Bartlett, M. K., Scoffoni, C., & Sack, L. (2012). The determinants of leaf turgor loss point and prediction of drought tolerance of species and biomes: a global meta‐analysis. Ecology letters, 15(5), 393-405.
2) Herrera, J. C., Calderan, A., Gambetta, G. A., Peterlunger, E., Forneck, A., Sivilotti, P., … & Hochberg, U. (2022). Stomatal responses in grapevine become increasingly more tolerant to low water potentials throughout the growing season. The Plant Journal, 109(4), 804-815.
Issue: ICGWS 2023
1University of Natural Resources and Life Sciences, Vienna, Department of Crop Sciences, Institute of Viticulture and Pomology, 3430 Tulln an der Donau, Austria
2University of Natural Resources and Life Sciences, Vienna, Department of Crop Sciences, Institute of agronomy, 3430 Tulln an der Donau, Austria
3University of Nova Gorica, School for Viticulture and Enology, Dvorec Lanthieri/Lanthieri Mansion Glavni trg 8, 5271 Vipava, Slovenia