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eaf water potential (psi(leaf)), typically measured using the pressure chamber, is the most important metric of plant water status, providing high theoretical value and information content for multiple applications in quantifying critical physiological processes including drought responses. Pressure chamber measurements of psi(leaf) (psi(leafPC)) are most typical, yet, the practical complexity of the technique and of the underlying theory has led to ambiguous understanding of the conditions to optimize measurements. Consequently, specific techniques and precautions diversified across the global research community, raising questions of reliability and repeatability. Here, we surveyed specific methods of psi(leafPC) from multiple laboratories, and synthesized experiments testing common assumptions and practices in psi(leafPC) for diverse species: (i) the need for equilibration of previously transpiring leaves; (ii) leaf storage before measurement; (iii) the equilibration of psi(leaf) for leaves on bagged branches of a range of dehydration; (iv) the equilibration of psi(leaf) across the lamina for bagged leaves, and the accuracy of measuring leaves with artificially 'elongated petioles'; (v) the need in psi(leaf) measurements for bagging leaves and high humidity within the chamber; (vi) the need to avoid liquid water on leaf surfaces; (vii) the use of 'pulse' pressurization versus gradual pressurization; and (viii) variation among experimenters in psi(leafPC) determination. Based on our findings we provide a best practice protocol to maximise accuracy, and provide recommendations for ongoing species-specific tests of important assumptions in future studies.

Hydraulic failure of the plant vascular system is a principal cause of forest die-off under drought. Accurate quantification of this process is essential to our understanding of the physiological mechanisms underpinning plant mortality. Imaging techniques increasingly are applied to estimate xylem cavitation resistance. These techniques allow forin situmeasurement of embolism formation in real time, although the benefits and trade-offs associated with different techniques have not been evaluated in detail. Here we compare two imaging methods, microcomputed tomography (microCT) and optical vulnerability (OV), to standard hydraulic methods for measurement of cavitation resistance in seven woody species representing a diversity of major phylogenetic and xylem anatomical groups. Across the seven species, there was strong agreement between cavitation resistance values (P-50) estimated from visualization techniques (microCT and OV) and between visual techniques and hydraulic techniques. The results indicate that visual techniques provide accurate estimates of cavitation resistance and the degree to which xylem hydraulic function is impacted by embolism. Results are discussed in the context of trade-offs associated with each technique and possible causes of discrepancy between estimates of cavitation resistance provided by visual and hydraulic techniques.

Drought stress can result in significant impairment of the plant hydraulic system via blockage of xylem conduits by gas emboli. Recovery after drought stress is an essential component of plant survival but is still a poorly understood process. In this study, we examined the capacity of woody species from two genera (Eucalyptus and Quercus) to refill embolized xylem vessels during a cycle of drought and recovery. Observations were made on intact plants of Eucalyptus calmudulensis, E. grandis, E. saligna and Quercus palustris using X-ray microtomography. We found no evidence of an effective xylem refilling mechanism in any of the plant species. Despite rehydration and recovery of plant water potential to near pre-drought levels, embolized vessels were not refilled up to 72 h after rewatering. In E. saligna, water droplets accumulated in previously air-filled vessels for a very small percentage of vessels. However, no instances of complete refilling that would restore embolized vessels to hydraulic function were observed. Our observations suggest that rapid refilling of embolized vessels after drought may not be a wide spread mechanism in woody plants and that embolism formed during drought represents long term cost to the plant hydraulic system.

Drought stress can result in significant impairment of the plant hydraulic system via blockage of xylem conduits by gas emboli. Recovery after drought stress is an essential component of plant survival but is still a poorly understood process. In this study, we examined the capacity of woody species from two genera (Eucalyptus and Quercus) to refill embolized xylem vessels during a cycle of drought and recovery. Observations were made on intact plants of Eucalyptus calmudulensis, E. grandis, E. saligna and Quercus palustris using X-ray microtomography. We found no evidence of an effective xylem refilling mechanism in any of the plant species. Despite rehydration and recovery of plant water potential to near pre-drought levels, embolized vessels were not refilled up to 72 h after rewatering. In E. saligna, water droplets accumulated in previously air-filled vessels for a very small percentage of vessels. However, no instances of complete refilling that would restore embolized vessels to hydraulic function were observed. Our observations suggest that rapid refilling of embolized vessels after drought may not be a wide spread mechanism in woody plants and that embolism formed during drought represents long term cost to the plant hydraulic system.

Plants have evolved a water transport system that relies on water sustaining a tensile force. Counter intuitively, this means water moves through the plant as a liquid under negative absolute pressures. This mechanism is made possible by the intricate plumbing system that constitutes the xylem tissue of plants. However, water under tension is prone to cavitation, which results in the formation of a gas bubble (embolism). Embolism reduces the capacity of the xylem tissue to deliver water to the canopy, eventually causing dieback and whole plant mortality. Xylem embolism is exacerbated by environmental stresses and is now considered one of the leading causes of plant mortality resulting from drought stress.Non-invasive imaging techniques offer the potential to make direct observations on intact plants at high resolution and in real time. In this presentation, I discuss recent exciting developments in the application of non-invasive imaging technologies such as X-ray Micro Computed Tomography (microCT) and optical imaging to studies of plant vascular function. This includes visualisation of xylem networks during drought stress and recovery in leaves, stems and roots. MicroCT imaging of stems and roots indicated that significant embolism formation occurs at similar time points and levels of water stress in dehydrating plants. This result was observed in herbaceous and woody species, and is surprising given previous hydraulic measurements indicating that, within a plant, roots were more vulnerable to drought-induced embolism than stems. A newly developed optical technique indicates that leaf vasculature is also similar in vulnerability to stems and roots. The overlap in vulnerability suggests that induction of embolism occurs at the same time in different organs or is propagated rapidly through the plant. In examining recovery from drought stress, we saw little evidence of embolism refilling in the xylem of woody plants, except in cases where substantial root pressure is

The capacity of plant species to resist xylem cavitation is an important determinant of resistance to drought, mortality thresholds, geographic distribution and productivity. Unravelling the role of xylem cavitation vulnerability in plant evolution and adaptation requires a clear understanding of how this key trait varies between the tissues of individuals and between individuals of species. Here, we examine questions of variation within individuals by measuring how cavitation moves between organs of individual plants. Using multiple cameras placed simultaneously on roots, stems and leaves, we were able to record systemic xylem cavitation during drying of individual olive plants. Unlike previous studies, we found a consistent pattern of root > stem > leaf in terms of xylem resistance to cavitation. The substantial variation in vulnerability to cavitation, evident among individuals, within individuals and within tissues of olive seedlings, was coordinated such that plants with more resistant roots also had more resistant leaves. Preservation of root integrity means that roots can continue to supply water for the regeneration of drought-damaged aerial tissues after post-drought rain. Furthermore, coordinated variation in vulnerability between leaf, stem and root in olive plants suggests a strong selective pressure to maintain a fixed order of cavitation during drought.

When students have a strong sense of belonging to their university or institution, they may experience gains in outcomes such as higher achievement and retention levels, but predominantly white institutions (PWIs) have traditionally had hostile environments for underrepresented student populations such as low-income students and students of color. We used an interview-based method to examine the sense of belonging amongst 21st Century Scholars students at Indiana University in Bloomington (IUB). The interview questions were constructed using four indicators within Museus’ CECE Model, and responses were analyzed using these same indicators to create a picture of the students' experiences at IUB and within the 21st Century Scholars Program. The results of the interview analysis formulated findings for future research and implications for the 21st Century Scholars program itself.

When students have a strong sense of belonging to their university or institution, they may experience gains in outcomes such as higher achievement and retention levels, but predominantly white institutions (PWIs) have traditionally had hostile environments for underrepresented student populations such as low-income students and students of color. We used an interview-based method to examine the sense of belonging amongst 21st Century Scholars students at Indiana University in Bloomington (IUB). The interview questions were constructed using four indicators within Museus’ CECE Model, and responses were analyzed using these same indicators to create a picture of the students' experiences at IUB and within the 21st Century Scholars Program. The results of the interview analysis formulated findings for future research and implications for the 21st Century Scholars program itself.

When students have a strong sense of belonging to their university or institution, they may experience gains in outcomes such as higher achievement and retention levels, but predominantly white institutions (PWIs) have traditionally had hostile environments for underrepresented student populations such as low-income students and students of color. We used an interview-based method to examine the sense of belonging amongst 21st Century Scholars students at Indiana University in Bloomington (IUB). The interview questions were constructed using four indicators within Museus’ CECE Model, and responses were analyzed using these same indicators to create a picture of the students' experiences at IUB and within the 21st Century Scholars Program. The results of the interview analysis formulated findings for future research and implications for the 21st Century Scholars program itself.