Plants are permanently facing challenges imposed by the environment which, in the context of the current scenario of global climate change, implies a constant process of adaptation to survive and even, in the case of crops, at least maintain yield. O₂ deficiency at the rhizosphere level, i.e., root hypoxia, is one of the factors with the greatest impact at whole-plant level. At cellular level, this O₂ deficiency provokes a disturbance in the energy metabolism which has notable consequences on the yield of plant crops. In this sense, although several physiological studies describe processes involved in plant adaptation to root hypoxia in woody fruit trees, with emphasis on the negative impacts on photosynthetic rate, there are very few studies that include -omics strategies for specifically understanding these processes in the roots of such species. Through a de novo assembly approach, a comparative transcriptome study of waterlogged Prunus spp. genotypes contrasting in their tolerance to root hypoxia was revisited in order to gain a deeper insight into the reconfiguration of pivotal pathways involved in energy metabolism. This re-analysis describes the classically altered pathways seen in the roots of woody fruit trees under hypoxia, but also routes that link them to pathways involved with nitrogen assimilation and the maintenance of cytoplasmic pH and glycolytic flow. In addition, the effects of root hypoxia on the transcription of genes related to the mitochondrial oxidative phosphorylation system, responsible for providing adenosine triphosphate (ATP) to the cell, are discussed in terms of their roles in the energy balance, reactive oxygen species (ROS) metabolism and aerenchyma formation. This review compiles key findings that help to explain the trait of tolerance to root hypoxia in woody fruit species, giving special attention to their strategies for managing the energy crisis. Finally, research challenges addressing less-explored topics in recovery and stress memory in woody fruit trees are pointed out.

Mediterranean viticulture is highly dependent on soil water availability. Moreover, global warming is likely to increase average temperatures and the frequency of heat waves, thus leading to greater water scarcity. To cope with this situation, much research focused on the selection of genotypes with higher water use efficiency (WUE). Several previous studies indicated that WUE varies between genotypes of the Tempranillo cultivar with some showing interesting improvement in the leaf WUE. Here, we assessed the associations between the leaf WUE and physiological parameters in six selected Tempranillo clones. The plants were cultivated in pots and two water conditions were applied sequentially: a well-watered period followed by a moderate water stress and recovery phase. Growth parameters and intrinsic WUE were monitored during both periods. Pressure–volume and A_N/C_i curves were measured after the plants were re-watered. At the end of the season, biomass accumulation and total irrigation water were used to calculate whole plant WUE (WUE_WP). A_N/C_i curves revealed significant differences in several photosynthetic parameters, including mesophyll conductance (g_m), maximum velocity of carboxylation (V_cmax) and leaf respiration (R). Clones RJ51 and 1048 both exhibited high WUE, but presented distinct physiological traits: RJ51 had the highest gm, while genotype 1048, had the lowest R. This study confirms that physiological traits generally explain the intracultivar diversity in WUE observed in previous studies.

Disease severity and drought due to climate change present significant challenges to orchard productivity. This study examines the effects of spring inoculation with Pseudomonas syringae pv. syringae (Pss) on sweet cherry plants, cvs. Bing and Santina with varying defense responses, assessing plant growth, physiological variables (water potential, gas exchange, and plant hydraulic conductance), and the levels of abscisic acid (ABA) and salicylic acid (SA) under two summer irrigation levels. Pss inoculation elicited a more pronounced response in ‘Santina’ compared to ‘Bing’ at 14 days post-inoculation (dpi), and those plants inoculated with Pss exhibited a slower leaf growth and reduced transpiration compared to control plants during 60 dpi. During differential irrigations, leaf area was reduced 14% and 44% in Pss inoculated plants of ‘Bing’ and ‘Santina’ respectively, under well-watered (WW) conditions, without changes in plant water status or gas exchange. Conversely, water-deficit (WD) conditions led to gas exchange limitations and a 43% decrease in plant biomass compared to that under WW conditions, with no differences between inoculation treatments. ABA levels were lower under WW than under WD at 90 dpi, while SA levels were significantly higher in Pss-inoculated plants under WW conditions. These findings underscore the influence on plant growth during summer in sweet cherry cultivars that showed a differential response to Pss inoculations and how the relationship between ABA and SA changes in plant drought level responses.

Water scarcity increasingly threatens viticulture, yet the drought-response strategy of patrimonial cultivars such as País remains poorly characterized. This study evaluated intra-cultivar variation in the drought response of three País provenances from northern Chile (Arica, Huasco, and Limarí), using Cabernet Franc as a reference cultivar. The experiment was conducted under semi-controlled pot conditions at the Limarí Campus of the University of La Serena, Ovalle, Chile, using a completely randomized design (n = 5). Plants were subjected to a four-week dry-down followed by rewatering. Relative pot water content, stem water potential, and stomatal conductance were monitored, and stomatal thresholds (Pg12, Pg50, and Pg88) were estimated from nonlinear vulnerability curves. Water deficit reduced plant water status and stomatal conductance. Cabernet Franc maintained the highest maximum stomatal conductance, whereas País showed a more conservative stomatal pattern. Within País, Pg50 differences were weakly supported and model-dependent: Huasco tended to reach 50% stomatal reduction at more negative stem water potentials than Arica and Limarí, while Pg12 and Pg88 largely overlapped. After rewatering, stem water potential recovered faster than stomatal conductance, particularly in Arica and Limarí. These results indicate that drought-response variation in País reflects provenance-specific stomatal regulation and recovery rather than source-site aridity alone.

Accurate, continuous monitoring of plant water status is critical for precision irrigation, yet the standard method — the Scholander pressure chamber — provides only discrete, labour-intensive measurements of stem water potential (Ψstem). Here we validate optical dendrometry — a camera-based, non-destructive technique that tracks organ width as a continuous proxy for Ψstem — in almond, grapevine, and olive subjected to progressive water deficit and subsequent rewatering under field-like conditions. Optical dendrometers (CaviCam) were deployed on petioles (almond, grapevine) and branchlets (olive) of potted plants and calibrated against simultaneous pressure-chamber Ψstem. Calibrations were robust within each species (R2=0.79–0.97). Leave-one-out cross-validation across 90 paired observations spanning a Ψstem range of -0.58 to -10.12 MPa yielded pooled R2=0.84, root-mean-square error of 1.20 MPa, and mean bias of -0.33 MPa. Systematic biases were predictable and quantifiable (+0.73, +0.16, and -1.25 MPa for almond, grapevine, and olive, respectively) and propagated linearly into the Ψstem at 50% stomatal closure (Ψgsw50) derived from sigmoidal stomatal conductance–Ψstem relationships (R2=0.72–0.89), shifting species-specific baselines that already differed markedly: grapevine closed stomata earliest (Ψgsw50 = -1.00 MPa), followed by olive (-1.93 MPa) and almond (-2.13 MPa), reflecting contrasting drought-response strategies. Continuous 30-min records resolved diurnal Ψstem oscillations and stress dynamics revealing species differences in post-rewatering hydraulic recovery rate (olive: 0.35 > grapevine: 0.07 > almond: 0.04 MPa h-1). These results establish optical dendrometry as a practical, automatable tool for real-time plant water status monitoring, provided per-species bias is accounted for when estimating physiological thresholds.