The effect of protective covers on pollinator health and pollination service delivery

Protective covers (i.e., glasshouses, netting enclosures, and polytunnels) are increasingly used in crop production to enhance crop quality, yield, and production efficiency. However, many protected crops require insect pollinators to achieve optimal pollination and there is no consensus about how best to manage pollinators and crop pollination in these environments. We conducted a systematic literature review to synthesise knowledge about the effect of protective covers on pollinator health and pollination services and identified 290 relevant studies. Bees were the dominant taxon used in protected systems (90%), represented by eusocial bees (e.g., bumble bees (Bombus spp.), honey bees (Apis spp.), stingless bees (Apidae: Meliponini)) and solitary bees (e.g., Amegilla spp., Megachile spp., and Osmia spp.). Flies represented 9% of taxa and included Calliphoridae, Muscidae, and Syrphidae. The remaining 1% of taxa was represented by Lepidoptera and Coleoptera. Of the studies that assessed pollination services, 96% indicate that pollinators were active on the crop and/or their visits resulted in improved fruit production compared with flowers not visited by insects (i.e., insect visits prevented, or flowers were self- or mechanically pollinated). Only 20% of studies evaluated pollinator health. Some taxa, such as mason or leafcutter bees, and bumble bees can function well in covered environments, but the effect of covers on pollinator health was negative in over 50% of the studies in which health was assessed. Negative effects included decreased reproduction, adult mortality, reduced forager activity, and increased disease prevalence. These effects may have occurred as a result of changes in temperature/humidity, light quality/quantity, pesticide exposure, and/or reduced access to food resources. Strategies reported to successfully enhance pollinator health and efficiency in covered systems include: careful selection of bee hive location to reduce heat stress and improve dispersal through the crop; increased floral diversity; deploying appropriate numbers of pollinators; and manipulation of flower physiology to increase attractiveness to pollinating insects. To improve and safeguard crop yields in pollinator dependent protected cropping systems, practitioners need to ensure that delivery of crop pollination services is compatible with suitable conditions for pollinator health

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Evidence of mechanical tissue strain in the development of hollow stem in broccoli

The underlying cause of hollow stem in commercially grown broccoli and cauliflower crops has been debated as arising from boron deficiency or high plant growth rates. This study recorded the development of hollow stem in plants grown in the field at standard commercial density (CD; 33,000plantsm-2) compared with high density (HD; 150,000plantsm-2). Hollow stem did not develop in plants grown at HD which had relatively tall, slender stems in comparison with plants grown at CD which had relatively short, wide stems. Hollow stem developed in all plants grown at CD just after inflorescence initiation, a time when stems began to rapidly enlarge and starch content in the pith decreased. Cavities first appeared in the upper sections of the stem as a fine fracture either at the edge of or traversing the pith cylinder. Many symptoms associated with a boron deficiency in broccoli and cauliflower were not observed and environmental scanning electron microscopy micrographs of the newly formed cavity revealed cell fracture consistent with mechanical strain. Furthermore, the elliptical shape of stems with hollow stem was consistent with the release of mechanical strain and this may provide a non-destructive method for determining hollow stem occurrence and severity

AN ALTERNATIVE VIEW OF RAIN-INDUCED CRACKING OF SWEET CHERRIES (PRUNUS AVIUM L.)

Fruit cracking in sweet cherries is unpredictable and is an economically significant problem for growers world-wide. The need for adequate management strategies based on informed risk assessment is clearly evident. Recent resultss from a University of Tasmania project have broadened the understanding of this fruit cracking phenomenon through a number of novel findings. It was discovered that two water uptake pathways result in cherry fruit cracking, and that each pathway results in particular crack types. Current management strategies for fruit cracking focus on water uptake across the fruit skin. Results from this study show that the development of apical and stem end cracks are induced by skin surface wetting, while deep cracks on the side of the fruit are induced by water moving via the vascular system. This new knowledge provides the basis for developing more effective management strategies. The project has further identified that the extent and type of fruit cracking are impacted by variety, season, and crop load. Nine varieties were monitored over four years and it was established that each variety had a particular tendency for crack type. Crop load was negatively correlated with fruit cracking. In addition, the amount or distribution of rainfall in the weeks prior to harvest did not significantly affect cracking incidence, yet season was highly influential, suggesting more than a direct rainfall effect. There are also strong indications that diurnal rhythms, and ambient environmental conditions, play a role in the development of cracking. These findings are important for the development of future cherry fruit cracking management strategies, which may need to be variety specific and encompass whole tree water relations based on the different mechanisms of cracking

Nutrition and Irrigation:Towards a practical solution for cherry picking

Fruit cracking in sweet cherries is an economically significant problem for growers world-wide and is associated with late season rainfall. Building resilience into fruit from an early stage in order to withstand rapid excess water entry without cracking, is important.This trial assessed calcium (Ca) levels and fruit characteristics of sweet cherry fruit produced under three different irrigation volumes, following on previous research suggesting low irrigation increased cracking susceptibility. In the present study, higher irrigation volumes also resulted in reduced cracking levels at harvest.Given the structural role of Ca in plant cells and that Ca is xylem mobile, it was hypothesised that higher irrigation volumes may favour the uptake and incorpo-ration of Ca into fruit cells. While Ca concentration increased with increased irriga-tion levels at harvest (when cracking occurs) Ca concentration was not significantly different between treatments. Both the high and low irrigation treatments resulted in fruit with increased firmness and skin puncture force compared to the medium (commercial orchard practice) irrigation level. This provided information about building resilience to cracking in sweet cherry fruit, highlighted the importance of both nutrition and irrigation in managing risk and applies the knowledge to provide solutions to a very real dilemma.The findings will be important for the development of future cherry fruit cracking management strategies, which may need to be considered early, rather than later during fruit growth

An alternative view on rain-induced cracking of sweet cherries (Prunus avium L.)

Fruit cracking in sweet cherries is unpredictable and is an economically significant problem for growers world-wide. The need for adequate management strategies based on informed risk assessment is clearly evident. Recent resultss from a University of Tasmania project have broadened the understanding of this fruit cracking phenomenon through a number of novel findings. It was discovered that two water uptake pathways result in cherry fruit cracking, and that each pathway results in particular crack types. Current management strategies for fruit cracking focus on water uptake across the fruit skin. Results from this study show that the development of apical and stem end cracks are induced by skin surface wetting, while deep cracks on the side of the fruit are induced by water moving via the vascular system. This new knowledge provides the basis for developing more effective management strategies. The project has further identified that the extent and type of fruit cracking are impacted by variety, season, and crop load. Nine varieties were monitored over four years and it was established that each variety had a particular tendency for crack type. Crop load was negatively correlated with fruit cracking. In addition, the amount or distribution of rainfall in the weeks prior to harvest did not significantly affect cracking incidence, yet season was highly influential, suggesting more than a direct rainfall effect. There are also strong indications that diurnal rhythms, and ambient environmental conditions, play a role in the development of cracking. These findings are important for the development of future cherry fruit cracking management strategies, which may need to be variety specific and encompass whole tree water relations based on the different mechanisms of cracking

Tree water relations: Flow and fruit

This study explores vascular influx of water in sweet cherry (Prunus avium L.) fruit because water is a key component of fruit quality and has been implicated in cherry fruit cracking. Flow to fruit is influenced by changing water potential of the fruit, and of potential gradients between the fruit and the spur. Water potential was influenced by vapour pressure deficit. In all seasons of this study, the most negative fruit water potential occurred in mid-afternoon when the magnitude of fruit water potential (ΨF) was greater than leaf water potential (ΨL) and analysis showed that there was a significant difference in this potential gradient between days with and without rainfall. Frequency analysis of days monitored over seasons further showed a significant association between the incidence of natural or simulated rainfall and the direction of sap flow to the fruit. This implies that manipulation of the driving forces within sweet cherry trees could be a viable management strategy for the prevention of cracking in cherry fruit. Furthermore, it suggests a role for orchard irrigation, in avoiding development of water potential gradients of fruit that favour rapid vascular influx of water following rainfall