Variation in stem xylem anatomy among almond cultivars was associated with differences in hydraulic vulnerability, indicating that anatomical traits contributed more strongly than stomatal behavior to cultivar-level drought responses. Understanding the mechanisms underlying isohydric and anisohydric behavior in woody species is critical for predicting their performance under increasing drought stress. We combined hydraulic, anatomical, and gas exchange measurements during progressive soil drought and re-watering in three Prunus dulcis cultivars (Avijor, Isabelona, and Soleta) to evaluate how coordinated traits explain drought responses and recovery. Hydroscape analysis confirmed the isohydric–anisohydric ranking previously reported, with Avijor being the most isohydric and Soleta the most anisohydric. Across cultivars, a common sequence of responses was observed: early decline in leaf hydraulic conductivity (Kleaf), followed by turgor loss point (ΨTLP), stomatal closure, and onset of embolism. Despite this shared pattern, cultivars differed in key drought thresholds. The more anisohydric cultivars showed more negative ΨTLP, and Soleta exhibited greater stem embolism resistance than Avijor. Cultivar differentiation was also clearer in stem xylem anatomy than in leaf traits, with variation in vessel-related traits being consistent with differences in stem vulnerability. By contrast, leaf vulnerability thresholds showed no clear differences among cultivars. Relative Kleaf recovery differed among cultivars, with higher recovery in Soleta than in Avijor, while Isabelona was intermediate. This pattern may reflect that Soleta and Isabelona did not reach water potentials lower than their stem P50 during drought, unlike Avijor. The separation between leaf and stem vulnerability thresholds also varied between cultivars and was greatest in Soleta, suggesting possible inter-cultivar variability in hydraulic vulnerability segmentation. Overall, cultivar-level drought responses in almond were explained by differences in stem embolism resistance, ΨTLP, and stem xylem analysis than by stomatal behavior alone.
At the northern edge of Abies alba’s range, populations differ in budburst and growth, key for conservation planning and assisted migration, while photosynthetic capacity is mainly shaped by shading. Shade tolerance and phenotypic plasticity are critical for the survival and growth of Abies alba seedlings, particularly at the northern edge of its range. Seedlings from six provenances of different origins were grown under high light and low light to assess phenological, growth, and photosynthetic responses. We show that, under low light (36
Exogenous sucrose is frequently used to explore carbon–signalling interactions during secondary growth, but its direct effects on conifer stems remain poorly resolved. This study involved the application of sucrose at concentrations of 0
The genus Lobostemon (Boraginaceae) comprises 28 shrubby species endemic to the Cape Floristic Region of South Africa. We investigated mature wood structure in 11 species and examined correlations between wood traits, plant stature, and climate to clarify the adaptive roles of living fibre-tracheids, vessel dimorphism, and related features. Vestured intervessel pits proved characteristic of Lobostemon. Contrary to the view that fibre-tracheids with living protoplasts are juvenile (Frankiewicz et al., 2024), we found that the ground tissue of mature wood is largely composed of these elements. Their bordered pits may facilitate the release of stored water into the transpiration stream, thereby enhancing hydraulic capacitance. Grouping of wider vessels increased with aridity and continentality, suggesting a role in sustaining water transport during seasonal drought by forming subsidiary pathways around embolized vessels. By contrast, the percentage of solitary narrow vessels positively associated with milder hot seasons, suggesting their function in capillary water storage and lateral transfer between vessels and fibre-tracheids, also supporting hydraulic capacitance. Increased plant stature in drier habitats likely reflects the need for greater stem storage capacity, consistent with an avoidance strategy that allows Lobostemon species to withstand seasonal drought.
Although leaf turgor loss point reflects osmotic potential variation in Eucalyptus, the osmometer method alone does not reliably rank drought tolerance among genotypes in breeding-oriented common-garden trials. Increasing droughts driven by climate change highlight the need to identify traits associated with drought tolerance in tree breeding programs. However, finding operationalizable traits that effectively distinguish drought tolerance among genotypes of the same species remains challenging. Here, we assessed 21 commercial Eucalyptus genotypes grown in a common garden in southern Brazil to evaluate the potential of leaf water relation traits for drought tolerance phenotyping. These traits were derived from pressure-volume curves. We also tested the utility of the osmometer method as a rapid estimator of the leaf water potential at turgor loss (Ψtlp), using osmotic potential at full hydration (π0). Among all leaf traits studied, only Ψtlp and π0 showed some association with expected drought tolerance. Both traits exhibited significant seasonal plasticity, but were unrelated to a field-based with drought tolerance index. Variation in Ψtlp across genotypes was limited, likely due to prior selection forproductivity, which may have narrowed trait variability. Although Ψtlp was strongly influenced by π0, the osmometer method failed to reliably rank genotypes by drought tolerance. Our findings indicate that, while leaf water relation traits—particularly Ψtlp and π0—have some potential for phenotyping, their current application in fast, operational screening for drought tolerance in Eucalyptus breeding programs remains limited. Further research is needed to validate and improve the practical use of these traits and methods.
