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BackgroundPeople with HIV experiencing homelessness have low rates of viral suppression, driven by sociostructural barriers and traditional care system limitations. Informed by the capability-opportunity-motivation-behavior (COM-B) model and patient preference research, we developed POP-UP, an integrated drop-in (nonappointment-based) HIV clinic with wrap-around services for persons with housing instability and viral nonsuppression in San Francisco.MethodsWe report HIV viral suppression (VS;

The resistance of xylem conduits to embolism is a major factor defining drought tolerance and can set the distributional limits of species across rainfall gradients. Recent work suggests that the proximity of vessels to neighbors increases the vulnerability of a conduit. We therefore investigated whether the relative vessel area of xylem correlates with intra- and inter-generic variation in xylem embolism resistance in species pairs or triplets from the genera Acer , Cinnamomum , Ilex , Quercus and Persea , adapted to environments differing in aridity. We used the optical vulnerability method to assess embolism resistance in stems and conducted anatomical measurements on the xylem in which embolism resistance was quantified. Vessel lumen fraction (VLF) correlated with xylem embolism resistance across and within genera. A low VLF likely increases the resistance to gas movement between conduits, by diffusion or advection, whereas a high VLF enhances gas transport thorough increased conduit-to-conduit connectivity and reduced distances between conduits and therefore the likelihood of embolism propagation. We suggest that the rate of gas movement due to local pressure differences and xylem network connectivity is a central driver of embolism propagation in angiosperm vessels. [ABSTRACT FROM AUTHOR]

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Xylem embolism resistance varies across species influencing drought tolerance, yet little is known about the determinants of the embolism resistance of an individual conduit. Here we conducted an experiment using the optical vulnerability method to test whether individual conduits have a specific water potential threshold for embolism formation and whether pre‐existing embolism in neighbouring conduits alters this threshold. Observations were made on a diverse sample of angiosperm and conifer species through a cycle of dehydration, rehydration and subsequent dehydration to death. Upon rehydration after the formation of embolism, no refilling was observed. When little pre‐existing embolism was present, xylem conduits had a conserved, individual embolism‐resistance threshold that varied across the population of conduits. The consequence of a variable conduit‐specific embolism threshold is that a small degree of pre‐existing embolism in the xylem results in apparently more resistant xylem in subsequent dehydrations, particularly in angiosperms with vessels. While our results suggest that pit membranes separating xylem conduits are critical for maintaining a conserved individual conduit threshold for embolism when little pre‐existing embolism is present, as the percentage of embolized conduits increases, gas movement, local pressure differences and connectivity between conduits increasingly contribute to embolism spread. Summary statement: We find that pit membranes are able to prevent embolism spreading between gas and water‐filled conduits until there is a considerable number of embolized conduits. Consequently, conduits appear to have specific thresholds of embolism resistance, and that a small degree of pre‐existing embolism in the xylem may make the remaining xylem apparently more resistant. [ABSTRACT FROM AUTHOR]

Xylem resistance to embolism is a key metric determining plant survival during drought. Yet, we have a limited understanding of the degree of plasticity in vulnerability to embolism. Here, we tested whether light availability influences embolism resistance in leaves and stems. The optical vulnerability method was used to assess stem and leaf resistance to embolism in Phellodendron amurense and Ilex verticillata acclimated to sun and shade microenvironments within the same canopy. In both species, we found considerable segmentation in xylem resistance to embolism between leaves and stems, but only minor acclimation in response to light availability. With the addition of a third species, Betula pubescens, which shows no vulnerability segmentation, we sought to investigate xylem anatomical traits that might correlate with strong vulnerability segmentation. We found a correlation between the area fraction of vessels in the xylem and embolism resistance across species and tissue types. Our results suggest that minimal acclimation of embolism resistance occurs in response to light environment in the same individual and that the degree of vulnerability segmentation between leaves and stems might be determined by the vessel lumen fraction of the xylem. [ABSTRACT FROM AUTHOR]

Despite being evolved in shaded environments, most coffee (Coffea arabica L.) is cultivated worldwide under sparse shade or at full sunlight. Coffee is ranked as greatly responsive to climate change (CC), and shading has been considered an important management strategy for mitigating the harmful CC outcomes on the crop. However, there is no information on the effects of enhanced [CO 2 (e C a) on coffee performance in response to light availability. Here, we examined how carbon assimilation and use are affected by e C a in combination with contrasting light levels. For that, greenhouse-grown plants were submitted to varying light levels (16 or 7.5 mol photons m−2 day−1) and [CO 2 (ca. 380 or 740 μmol mol−1 air) over six months. We demonstrated that both high light and e C a improved growth and photosynthetic performance, independently. Despite marginal alterations in biomass partitioning, some allometric changes, such as higher root biomass-to-total leaf area and lower leaf area ratio under the combination of e C a and high light were found. Stimulation of photosynthetic rates by e C a occurred with no direct effect on stomatal and mesophyll conductances, and no signs of photosynthetic down-regulation were found irrespective of treatments. Particularly at high light, e C a led to decreases in both photorespiration rates and oxidative pressure. Overall, our novel findings suggest that e C a could tandemly act with shading to mitigate the harmful CC effects on coffee sustainability. • High light and elevated [CO 2 improved coffee growth and photosynthetic performance, independently. • Elevated [CO 2 decreased photorespiration rates and oxidative pressure, especially at high light. • No signs of photosynthetic down-regulation were found irrespective of light and CO 2 supplies. • Elevated [CO 2 could tandemly act with shading to mitigate the harmful climate change effects on coffee sustainability. [ABSTRACT FROM AUTHOR]

• Both drought-tolerant and sensitive plants were impaired by waterlogging. • Stomatal closure correlated with declines in plant hydraulic conductance. • Plants exhibited low water potentials after waterlogging relief. • Drought-sensitive plants were severely damaged after waterlogging relief. • Many drought-sensitive plants died after waterlogging relief. Soil waterlogging negatively impacts plants due to reduced oxygen availability in the rhizosphere. Here we selected two Coffea canephora clones with contrasting tolerance to drought and oxidative stress to test whether they would also exhibit contrasting tolerance to waterlogging and post-waterlogging reoxygenation. Plants were exposed to six days of waterlogging followed by 40 days of reoxygenation. During waterlogging, both clones exhibited lower leaf gas exchange rate, electron transport rate and photochemical quenching as well as increased non-photochemical quenching; overall, these changes were stronger in the drought tolerant (DT) clones over the drought sentitive (DS) ones. Photosynthetic limitations were essentially linked to diffusional constraints regardless of clone. In both clones, declines in stomatal conductance were not associated with foliar ABA or ethylene levels, however stomatal conductance correlated with the plant hydraulic conductance. After reoxygenation, DT plants mostly recovered leaf function and plant mortality was less than 10%. Conversely, DS plants displayed very low water potentials after reoxygenation, which was accompanied by photosynthetic and membrane damage and 40% plant mortality. Our findings confirmed that the DT clone is less impaired by soil waterlogging and reoxygenation than the DS one. The differences between clones were more evident during the reoxygenation than during waterlogging, likely due to the drought experienced by the DS but not DT plants. Collectively, this information leads us to a common path to find new coffee genotypes with increased tolerance to both drought and waterlogging aiming at increased coffee sustainability under an ongoing climate changing scenario. [ABSTRACT FROM AUTHOR]

• Elevated [CO 2 led to higher transpiration rates under full irrigation, and lower transpiration under drought. • Varying transpiration patterns were unrelated to maximum stomatal conductance or foliar ABA levels. • Transpiration rates in irrigated plants were linked to varying stomatal closure rate. • Aquaporins may have played key roles in altering stomatal function and hydraulic conductance. • Elevated [CO 2 improved plant water status and growth under drought. Rising air CO 2 concentration ([CO 2) is believed to mitigate the negative impacts of global climate changes such as increased air temperatures and drought events on plant growth and survival. Nonetheless, how elevated [CO 2 affects the way coffee (Coffea arabica L.) plants sense and respond to drought remains a critical unknown. In this study, potted coffee plants were cultivated under two air [CO 2 (ca. 400 ppm or 700 ppm) in open top chambers under greenhouse conditions. After a 5-month exposure to [CO 2 treatments, plants were submitted to a progressive, controlled soil water deficit down to 20 % soil field capacity. Under well-watered (100 % field capacity) conditions, 700-plants displayed lower whole-plant transpiration rates (T) than their 400-counterparts. Changes in T were unrelated to stomatal conductances at the leaf scale (as well as stomatal morphology) or foliar ABA levels, but they were rather associated with faster stomata closure rates upon rapid increases in vapor pressure deficit in the 700-plants. During drought, 700-plants were able to maintain higher water potentials and plant hydraulic conductances for longer in parallel to higher T than their 400-counterparts. Under elevated [CO 2 , the faster stomatal closure rates (irrigated conditions) or the maintenance of plant hydraulic conductances (drought conditions) were associated with higher (3 to 40-fold) transcript abundance of most aquaporin genes. Altogether, our results suggest that elevated [CO 2 has marked implications on how coffee plants respond to soil water deficit, ultimately permitting 700-plants to have improved fitness under drought when compared to 400-plants. [ABSTRACT FROM AUTHOR]

• Elevated [CO 2 improved carbon assimilation balance regardless of watering. • Elevated [CO 2 decreased photorespiration rates and oxidative pressure under drought. • Improved growth under elevated [CO 2 was more evident under drought than under full irrigation. • Elevated [CO 2 led to more biomass partitioning towards roots with greater root length under drought. • Growth changes at elevated [CO 2 were unrelated to altered hormonal pools, but rather with shifts on carbon fluxes. Coffee (Coffea arabica L.) is an important global commodity grown in tropical areas where increased drought severity and frequency are believed to become progressively important due to climate changes. Nonetheless, elevated air [CO 2 is thought to be able to mitigate heat and drought stresses. In this study, we tested how carbon assimilation and use are affected by elevated [CO 2 in combination with a progressive drought, and how this could impact shifts on biomass accumulation and partitioning. For that, we cultivated coffee plants in open top chambers under greenhouse conditions. Plants grown in 12-L pots were then submitted to ambient (386 ± 20 ppm) or elevated (723 ± 83 ppm) [CO 2 during approximately seven months, as well as to varying soil water availabilities (100, 50, 37.5, 25 or 20 % of soil field capacity). Our results demonstrate that elevated [CO 2 improved carbon assimilation rates (>60 %) with unaltered stomatal conductance and no signs of photosynthetic downregulation. This was accompanied by increases in water-use efficiency, respiration rates and biomass accumulation regardless of watering, and decreased photorespiration rates and oxidative pressure under drought. Improved growth under elevated [CO 2 was more evident under drought than under full irrigation, and was unlikely to have been associated with global changes on hormonal pools, but rather with shifts on carbon fluxes. Finally, elevated [CO 2 promoted key allometric adjustments linked to drought tolerance, e.g. , more biomass partitioning towards roots with greater root length. Collectively, our results offer novel and timely information on the mitigating ability of elevated [CO 2 on the photosynthetic performance and growth of coffee plants under drought conditions. [ABSTRACT FROM AUTHOR]