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Rising temperature extremes during critical reproductive periods threaten the yield of major grain and fruit crops. Flowering plant reproduction depends on the ability of pollen grains to generate a pollen tube, which elongates through the pistil to deliver sperm cells to female gametes for double fertilization. We used tomato as amodel fruit croptodeterminehowhigh temperature affects the pollen tube growthphase, takingadvantage of cultivars noted for fruit production in exceptionally hot growing seasons. We found that exposure to high temperature solely during the pollen tube growth phase limits fruit biomass and seed set more significantly in thermosensitive cultivars than in thermotolerant cultivars. Importantly, we found that pollen tubes from the thermotolerantTamaulipas cultivar have enhanced growth in vivo and in vitro under high temperature. Analysis of the pollen tube transcriptome’s response to high temperature allowed us to define two responsemodes (enhanced induction of stress responses and higher basal levels of growth pathways repressed by heat stress) associated with reproductive thermotolerance. Importantly, we define key components of the pollen tube stress response, identifyingenhancedreactive oxygenspecies (ROS)homeostasis andpollen tubecallose synthesis and deposition as important components of reproductive thermotolerance in Tamaulipas. Our work identifies the pollen tube growth phase as a viable target to enhance reproductive thermotolerance and delineates key pathways that are altered in crop varieties capable of fruiting under high-temperature conditions. 

Abstract Groundwater scarcity poses threats to communities across the globe, and effectively managing those challenges requires designing policy that achieves institutional fit. Collective action is well-suited to match rules with local context, and multiple pathways exist for communities to achieve reductions in groundwater use. To better understand how local conditions influence rule design, we examine two groundwater-reliant communities in the Western US that engaged in collective-action to arrive at distinct groundwater management rules. We consider: what drove stakeholders in Northwestern Kansas (NWKS) and San Luis Valley, Colorado (SLV) to adopt local groundwater policies, and why were different management pathways chosen? Further, why is more heterogeneity observed between local management organizations in SLV as compared to NWKS? To investigate these questions, we employ grounded theory to interpret the rules in reference to local hydro-agro-economic statistics and interviews with stakeholders (n= 19) in each region selected by expert sampling. We find that the additional goals of groundwater rules in SLV, partially driven by key contrasts in the resource system compared to NWKS, and higher resource productivity in SLV, creates both the need for and efficacy of a price-centered policy. Furthermore, variation in the resource systems and associated farm characteristics between subdistricts drives higher heterogeneity in rule design between local management districts in SLV compared to NWKS. More generally, we find the local flexibility afforded through the collective-action process as critical, even if it were to arrive at alternative, non-economic based incentives. 

Farmers in humid states of US, traditionally reliant on rainfall, have more than tripled irrigation since 1978. We examine this trend in Illinois where there has been a nearly threefold increase in center pivot irrigation system (CPIS) installations since 1988. Specifically, we analyze where and when CPIS installations occur and their benefits in terms of crop yield, irrigated acreage, crop selection, and changes to drought-related insurance payouts. To do so, we create a novel data set derived from a deep learning model capable of automatically identifying the location of CPIS during drought years. The results indicate CPIS installations are significantly more common over alluvial aquifers after droughts. Some evidence supports CPIS leads to corn appearing more often in the corn-soy crop rotation. Counties with a higher presence of CPIS do not have higher average crop yields. However, in drought years CPIS presence does have a significant positive effect on corn yield and a significant negative effect on indemnity payments for both soybeans and corn. The results provide insights into an emerging trend of irrigation in humid regions, raising potential policy considerations for crop insurance and signaling a potential need to address water rights as demand increases. 

Abstract Global economic development and urbanization during the past two decades have driven the increases in demand of personal and commercial vehicle fleets, especially in developing countries, which has likely resulted in changes in year-to-year vehicle tailpipe emissions associated with aerosols and trace gases. However, long-term trends of impacts of global gasoline and diesel emissions on air quality and human health are not clear. In this study, we employ the Community Earth System Model in conjunction with the newly developed Community Emissions Data System as anthropogenic emission inventory to quantify the long-term trends of impacts of global gasoline and diesel emissions on ambient air quality and human health for the period of 2000–2015. Global gasoline and diesel emissions contributed to regional increases in annual mean surface PM_2.5(particulate matter with aerodynamic diameters ⩽2.5μm) concentrations by up to 17.5 and 13.7µg m⁻³, and surface ozone (O₃) concentrations by up to 7.1 and 7.2 ppbv, respectively, for 2000–2015. However, we also found substantial declines of surface PM_2.5and O₃concentrations over Europe, the US, Canada, and China for the same period, which suggested the co-benefits of air quality and human health from improving gasoline and diesel fuel quality and tightening vehicle emissions standards. Globally, we estimate the mean annual total PM_2.5- and O₃-induced premature deaths are 139 700–170 700 for gasoline and 205 200–309 300 for diesel, with the corresponding years of life lost of 2.74–3.47 and 4.56–6.52 million years, respectively. Diesel and gasoline emissions create health-effect disparities between the developed and developing countries, which are likely to aggravate afterwards.