Shift In Allocation Research Articles

Variation in Growth, Wood Density, and Stem Taper Along the Stem in Self-Thinning Stands of Sassafras tzumu.

Silvicultural practices greatly improve the economic value of wood products from forests. Stem dimensions, wood density, and stem form are closely linked to end-product performance. This research aimed to examine the effects of stand density and stem height on variables that reflect ring growth and wood properties of Sassafras tzumu stands during the self-thinning phase. Between the ages of 10 and 40 years, the number of stems per hectare has declined from 1,068 to 964 due to density-dependent mortality. As the relative stand density decreased, there were significant reductions in the average tree ring width (5.07–3.51 mm) and increases in latewood proportions (49.88–53.49%) and the density of the annual growth ring (165.60–708.58 kg/m3). Therefore, ring density, earlywood density, and latewood density increased with decreasing relative stand density after self-thinning occurred. Ring width, earlywood width, and latewood width significantly increased from the base to the apex of the stem. Stand density and stem height had additive effects on S. tzumu wood properties during the self-thinning phase. A shift in the growth allocation along the longitudinal stem in response to self-thinning resulted in decreasing radial growth, increasing wood density, and improved stem form. In summary, we found a significant influence of stand density on tree ring growth, wood quality, and stem form of S. tzumu trees during the self-thinning phase.

Dynamic character displacement among a pair of bacterial phyllosphere commensals in situ

Differences between species promote stable coexistence in a resource-limited environment. These differences can result from interspecies competition leading to character shifts, a process referred to as character displacement. While character displacement is often interpreted as a consequence of genetically fixed trait differences between species, it can also be mediated by phenotypic plasticity in response to the presence of another species. Here, we test whether phenotypic plasticity leads to a shift in proteome allocation during co-occurrence of two bacterial species from the abundant, leaf-colonizing families Sphingomonadaceae and Rhizobiaceae in their natural habitat. Upon mono-colonizing of the phyllosphere, both species exhibit specific and shared protein functions indicating a niche overlap. During co-colonization, quantitative differences in the protein repertoire of both bacterial populations occur as a result of bacterial coexistence in planta. Specifically, the Sphingomonas strain produces enzymes for the metabolization of xylan, while the Rhizobium strain reprograms its metabolism to beta-oxidation of fatty acids fueled via the glyoxylate cycle and adapts its biotin acquisition. We demonstrate the conditional relevance of cross-species facilitation by mutagenesis leading to loss of fitness in competition in planta. Our results show that dynamic character displacement and niche facilitation mediated by phenotypic plasticity can contribute to species coexistence.

Effects of Population Age on the Annual Net Primary Productivity and Seed Yield of Artificial Grasslands on the Eastern Qinghai-Tibetan Plateau

The forage yield and quality of artificial grasslands typically decline rapidly over time after planting. Moreover, the reason for this decline of artificial grassland remains unclear. Here, we evaluated the relationship between years since planting and annual net primary productivity (ANPP), seed yield, and reproductive allocation (ie., the ratio of seed yield to annual net primary productivity) for eight common gramineous species separately planted in monoculture artificial grasslands in the Qinghai-Tibetan Plateau. We utilized T50 values (the time when ANPP or seed yield drop to 50% of their maximum values) to quantify the decline rates of eight artificial grasslands respectively, and additionally evaluated the influence of evolutionary history and other plant attributes on T50 (ANPP) and T50 (seed yield). We found that both ANPP and seed yield decreased linearly over time following planting for all species. ANPP generally declined more rapidly than did seed yield. The reproductive allocation of Deschampsia cespitosa, Festuca kirilowii, Festuca kryloviana, and Festuca sinensis increased significantly over time after planting. We did not observe any association of evolutionary history, seed mass, plant height, reproductive allocation, ANPP (second year), seed yield (second year) with T50 (ANPP) and T50 (seed yield). In addition, clonal propagation mode may influence declines of artificial grassland, and evolutionary history may shape shifts in reproductive allocation with plant population aging. This study was the first to utilize T50 values for the study of artificial grassland declines. Our research framework thus has the potential to guide future quantitative studies of artificial grassland declines.

Provider and community stakeholder perspectives of expanding Medicaid coverage of abortion in Illinois

BackgroundMany people seeking abortion encounter financial difficulties that delay or prevent them from accessing care. Although some patients qualify for Medicaid (a public program that can help cover health care costs), laws in some states restrict the use of Medicaid for abortion care. In 2017, Illinois passed House Bill 40 (HB-40), which allowed patients with Medicaid to receive coverage for their abortion. This study aimed to understand how HB-40 affected abortion affordability from the perspectives of individuals that work directly or indirectly with abortion patients or facilities providing abortion care.MethodsWe conducted interviews with clinicians and administrators from facilities that provided abortion services; staff from organizations that provided resources to abortion providers or patients; and individuals at organizations involved in the passage and/or implementation of HB-40. Interviews were audio-recorded and transcribed. We created codes based on the interview guides, coded each transcript using the web application Dedoose, and summarized findings by code.ResultsInterviews were conducted with 38 participants. Participants reflected that HB-40 seemed to remove a significant financial barrier for Medicaid recipients and improve the experience for patients seeking abortion care. Participants also described how the law led to a shift in resource allocation, allowing financial support to be directed towards uninsured patients. Some participants thought HB-40 might contribute to a reduction in abortion stigma. Despite the perceived positive impacts of the law, participants noted a lack of public knowledge about HB-40, as well as confusing or cumbersome insurance-related processes, could diminish the law’s impact. Participants also highlighted persisting barriers to abortion utilization for minors, recent and undocumented immigrants, and people residing in rural areas, even after the passage of HB-40.ConclusionsHB-40 was perceived to improve the affordability of abortion. However, participants identified additional obstacles to abortion care in Illinois that weakened the impact of HB-40 for patients and required further action, Findings suggest that policymakers must also consider how insurance coverage can be disrupted by other legal barriers for historically excluded populations and ensure clear information on Medicaid enrollment and abortion coverage is widely disseminated.

Modeling resurgence with an evolutionary theory of behavior dynamics

McDowell’s (2004) Evolutionary Theory of Behavior Dynamics (ETBD) is a computational theory that has reproduced a wide variety of behavioral phenomena observed in material reality. Here, we extended the generality of the ETBD by successfully replicating laboratory studies of resurgence with live animals using artificial organisms (AOs) animated by the theory. We ran AOs on concurrent random-interval random-interval (conc RI RI) schedules of reinforcement wherein one alternative (i.e., a target behavior) was reinforced while the other alternative (i.e., an alternative behavior) was not reinforced. Then, we placed the target behavior on extinction and reinforced the alternative response, producing a shift in allocation of responding from the target behavior to the alternative response. Finally, schedule thinning of the alternative response (i.e., downshifts) resulted in resurgence of target behavior. Our findings indicated that resurgence increased as a function of the relative downshift in reinforcement rate and magnitude, replicating findings from previous studies with live animals. These results further illustrate the utility of the ETBD for generating dynamic behavioral data and serve as a proof-of-concept for a novel computational approach for studying and understanding resurgence in future studies.

Soil enzymes in response to climate warming: Mechanisms and feedbacks

Abstract Soil enzymes are central to ecosystem processes because they mediate numerous reactions that are essential in biogeochemical cycles. However, how soil enzyme activities will respond to global warming is uncertain. We reviewed the literature on mechanisms linking temperature effects on soil enzymes and microbial communities, and outlined a conceptual overview on how these changes may influence soil carbon fluxes in terrestrial ecosystems. At the enzyme scale, although temperature can have a positive effect on enzymatic catalytic power in the short term (i.e. via the instantaneous response of activity), this effect can be countered over time by enzyme inactivation and reduced substrate affinity. At the microbial scale, short‐term warming can increase enzymatic catalytic power via accelerated synthesis and microbial turnover, but shifts in microbial community composition and growth efficiency may mediate the effect of warming in the long term. Although increasing enzyme activities may accelerate labile carbon decomposition over months to years, our literature review highlights that this initial stage can be followed by the following phases: (a) a reduction in soil carbon loss, due to changing carbon use efficiency among communities or substrate depletion, which together can decrease microbial biomass and enzyme activity and (b) an acceleration of soil carbon loss, due to shifts in microbial community structure and greater allocation to oxidative enzymes for recalcitrant carbon degradation. Studies that bridge scales in time and space are required to assess whether there will be an attenuation or acceleration of soil carbon loss through changes in enzyme activities in the very long term. We conclude that soil enzymes determine the sensitivity of soil carbon to warming, but that the microbial community and enzymatic traits that mediate this effect change over time. Improving representation of enzymes in soil carbon models requires long‐term studies that characterize the response of wide‐ranging hydrolytic and oxidative enzymatic traits—catalytic power, kinetics, inactivation—and the microbial community responses that govern enzyme synthesis. Read the free Plain Language Summary for this article on the Journal blog.

Assessment of the influence of bamboo expansion on Si pools and fluxes in a disturbed subtropical evergreen broadleaved forest

Silicon (Si) pools and fluxes are affected by plant community shifts in forest ecosystems. Moso bamboo (Phyllostachys pubescens) is a Si accumulating plant, and its expansion exerts various ecological effects in colonized forest ecosystems. However, it is unclear how bamboo expansion might alter the biogeochemical Si cycle. To estimate the consequences of bamboo expansion on Si availability and biochemical cycling in subtropical areas, we selected bamboo-pure forest (BPF), bamboo-broadleaved mixed forest (BMF), and adjacent secondary evergreen broadleaved forest (EBF) stands in an area of bamboo expansion and compared Si pools and fluxes of plants in each forest type. We found that the content of the soluble and exchangeable Si in soils of BPF was lower than EBF (0.18 g kg−1 versus 0.25 g kg−1), that is, bamboo expansion decreased the soluble and exchangeable Si fraction, whereas there was no significant difference among BPF, BMF and EBF. In addition, the plant Si pool in BPF (285 g Si m−2) was 32.6 % lower than EBF (428 g Si m−2), and there was a shift in Si allocation from aboveground to belowground with conversion from EBF to BPF, largely attributed to abundant roots in BPF. We found that bamboo expansion accelerated the biogeochemical Si cycle to some extent, with higher production of phytoliths and quicker turnover of fine roots in BPF than EBF. We also highlight that bamboo expansion accelerated the uptake and return of Si, and promoted the release and dissolution of phytoliths. These results have implications for assessing the impacts of vegetation shifts on the biogeochemical Si cycle.

Elevated atmospheric CO2 changes defence allocation in wheat but herbivore resistance persists.

Predicting how plants allocate to different anti-herbivore defences in response to elevated carbon dioxide (CO2) concentrations is important for understanding future patterns of crop susceptibility to herbivory. Theories of defence allocation, especially in the context of environmental change, largely overlook the role of silicon (Si), despite it being the major anti-herbivore defence in the Poaceae. We demonstrated that elevated levels of atmospheric CO2 (e[CO2]) promoted plant growth by 33% and caused wheat (Triticum aestivum) to switch from Si (-19%) to phenolic (+44%) defences. Despite the lower levels of Si under e[CO2], resistance to the global pest Helicoverpa armigera persisted; relative growth rates (RGRs) were reduced by at least 33% on Si-supplied plants, irrespective of CO2 levels. RGR was negatively correlated with leaf Si concentrations. Mandible wear was c. 30% higher when feeding on Si-supplemented plants compared to those feeding on plants with no Si supply. We conclude that higher carbon availability under e[CO2] reduces silicification and causes wheat to increase concentrations of phenolics. However, Si supply, at all levels, suppressed the growth of H. armigera under both CO2 regimes, suggesting that shifts in defence allocation under future climate change may not compromise herbivore resistance in wheat.

Energy allocation shifts from sperm production to self-maintenance at low temperatures in male bats

The ability of animals to produce endogenous heat provides a buffer against environmental changes but also incurs high energetic costs. Especially small endothermic mammals have high energy demands. Some temperate-zone species (heterotherms) regularly use torpor, which slows down their entire metabolism but also potentially delays reproduction, to compensate for this. We used a unique experimental approach to test the consequences of extended low and high ambient temperatures on the trade-off in energy allocation to body mass maintenance, thermoregulation effort and seasonal sexual maturation in temperate zone male bats. We showed that long exposure to low ambient temperature shifts energy allocation away from sexual maturation to self-maintenance and results in a delay of sperm maturation by as much as an entire month. This effect was partially buffered by higher body mass. Heavier bats were able to afford more intensive thermoregulation and consequently speed up maturation. Interestingly, bats at constant high temperatures avoided deep torpor and matured faster than those at low temperatures, but sperm production was also slower than under natural conditions. Our results show that not only low, but also constant high ambient temperatures are detrimental during seasonal sexual maturation and the trade-off between investing into self-maintenance and fitness is a finely tuned compromise.

Endometriosis and Cannabis Consumption During the COVID-19 Pandemic: An International Cross-Sectional Survey.

Introduction: Endometriosis affects 1 in 10 women worldwide, with most experiencing difficulties achieving adequate symptom control. These difficulties have been compounded by the onset of the COVID-19 pandemic due to worldwide shifts in health care resource allocation. As cannabis is a relatively common form of self-management in endometriosis, this study aims to explore the impact of the COVID-19 pandemic on cannabis consumption in those with endometriosis. Methods: An anonymous, cross-sectional online international survey was developed and promoted by endometriosis advocacy/support organizations worldwide. Respondents needed to have a diagnosis of endometriosis and be aged between 18 and 55. Results: A total of 1634 responses were received from 46 different countries. The average age of respondents was 30, with a mean diagnosis age of 25. Eight hundred forty-six respondents (51%) reported consuming cannabis in the past 3 months, with 55% of these reporting use for symptom management only. One in five respondents (20%) reported having consumed cannabis previously, the most common reason for discontinuation (65%) was access difficulties during COVID. Those who had legal access were more likely to consume cannabis than those without (p<0.0001) and were more likely to disclose usage to health care professionals (p<0.0001). The most common reasons for consuming cannabis during COVID was increased stress/anxiety (59%) and lack of access to normal medical care (48%). Pre-pandemic, cannabis was mostly consumed at least once a day (61%) and in inhaled forms (51.6%). Consumption increased for most people (57%) during the pandemic. During the pandemic just under a quarter (23%) of respondents changed their mode of consumption, with a reduction in inhaled forms (39.5%) and an increase in consumption of edibles (40%) or oil (25.2%). Conclusions: Cannabis consumption, especially for symptom relief, was relatively common among those with endometriosis, with some people starting their consumption of cannabis due to health care restrictions that occurred due to the COVID-19 pandemic. Difficulties accessing cannabis and unpleasant/unwanted side effects were the most common reasons for lack of current cannabis consumption in those who had previously consumed it. Cannabis consumption may form an important part of endometriosis management especially when access to routine medical care is restricted.

Determinants of Large Shifts in Official Development Aid Allocation by Major Countries

This study provides a comparative analysis of the main determinants of large shifts in aid allocation by major donors, namely China, France, the United Kingdom, and the United States. In contrast to continuing assistance, significant year-over-year variation of allocated aid to a given recipient is considered a new and deliberate decision by the donors. Using a version of quantile regression to account for heterogeneity in the characteristics of aid recipients, we show that significant differences exist in the aid allocation strategies of the major donors. There is no conditionality attached to Chinese aid, while self-economic interests and corruption levels at home and in the recipient countries determine aid allocated by France and the U.K. to their former colonies. In addition, recipient needs affect aid from France, the U.K., and the U.S. Over the 2000-2014 period, there is no significant change in the determinants of aid allocation by China in response to various criticisms of its approach. Confronted with the growing influence of emerging donors such as China, the three major traditional donors seem to adjust their aid allocation policy towards their own economic interests.

Ectomycorrhizal fungus supports endogenous rhythmic growth and corresponding resource allocation in oak during various below- and aboveground biotic interactions

Endogenous rhythmic growth (ERG) is displayed by many tropical and some major temperate tree species and characterized by alternating root and shoot flushes (RF and SF). These flushes occur parallel to changes in biomass partitioning and in allocation of recently assimilated carbon and nitrogen. To address how biotic interactions interplay with ERG, we cross-compared the RF/SF shifts in oak microcuttings in the presence of pathogens, consumers and a mycorrhiza helper bacterium, without and with an ectomycorrhizal fungus (EMF), and present a synthesis of the observations. The typical increase in carbon allocation to sink leaves during SF did not occur in the presence of root or leaf pathogens, and the increase in nitrogen allocation to lateral roots during RF did not occur with the pathogens. The RF/SF shifts in resource allocation were mostly restored upon additional interaction with the EMF. Its presence led to increased resource allocation to principal roots during RF, also when the oaks were inoculated additionally with other interactors. The interactors affected the alternating, rhythmic growth and resource allocation shifts between shoots and roots. The restoring role of the EMF on RF/SF changes in parallel to the corresponding enhanced carbon and nitrogen allocation to sink tissues suggests that the EMF is supporting plants in maintaining the ERG.

Crop yield convergence across districts in India’s poorest state

Bihar, India’s poorest state, witnessed impressive yield growth in its three principal crops during the last decade or so. This paper examines whether a reduction in regional yield disparities accompanied these state-level productivity gains. The convergence test allows the district-specific element of productivity to vary with time, thus permitting divergence in interim phases. District rice yields converged towards a common growth path. The results for wheat and maize are not as conclusive. However, there is strong evidence of divergence for each crop in recent years. This divergence, nonetheless, happens in the presence of club convergence. The club classification transcends agro-climatic boundaries, indicating a role for policy to aid growth in the lagging districts. The shifts in credit allocation over the years do not appear to be driving the yield divergence, highlighting the limitations of a macro credit-driven policy.

How do policy instruments generate new ones? Analysing policy instruments feedback and interaction in educational research in England, 1986-2014

The study of research funding arrangements and the production of scientific knowledge has been marked by a lack of understanding about how research funding instruments interact and how these instruments shape policy-making and research fields. To fill this research gap, this study is theoretically supported by policy feedback and policy instruments’ interaction studies. It investigates the effects of the UK's research assessment exercise in the creation of the most emblematic national thematic research program for the field of educational research in the country – the Teaching and Learning Research Programme (TLRP). Based on qualitative analysis of policy documents and semi-structured interviews with policy-makers and boundary-spanners, this paper shows how the research assessment exercise contributed to the creation of the TLRP and how the interaction between the two policy instruments shaped the field of educational research in England. In particular, the results show a) how the institutionalisation of the research assessment led to frame a “quality problem” in educational research that legitimated several policy initiatives, including the creation of the national thematic research programme (interpretative effects) and a shift in resources allocation (resource/incentive effects); and b) how the interaction between the two policy instruments contributed to methodological and epistemic drifts in the field of educational research.

Attitudinal Effects of Stimulus Co-occurrence and Stimulus Relations: Paradoxical Effects of Cognitive Load.

Research suggests that evaluations of an object can be jointly influenced by (a) the mere co-occurrence of the object with a pleasant or unpleasant stimulus (e.g., mere co-occurrence of object A and negative event B) and (b) the object's specific relation to the co-occurring stimulus (e.g., object A starts vs. stops negative event B). Three experiments investigated the impact of cognitive load during learning on the effects of stimulus co-occurrence and stimulus relations. Counter to the shared prediction of competing theories suggesting that effects of stimulus relations should be reduced by cognitive load during learning, effects of stimulus relations were greater (rather than smaller) under high-load compared with low-load conditions. Effects of stimulus co-occurrence were not significantly affected by cognitive load. The results are discussed in terms of theories suggesting that cognitive load can influence behavioral outcomes via strategic shifts in resource allocation in response to task-specific affordances.

Phenotypic plasticity in plant defense across life stages: Inducibility, transgenerational induction, and transgenerational priming in wild radish

As they develop, many plants deploy shifts in antiherbivore defense allocation due to changing costs and benefits of their defensive traits. Plant defenses are known to be primed or directly induced by herbivore damage within generations and across generations by long-lasting epigenetic mechanisms. However, little is known about the differences between life stages of epigenetically inducible defensive traits across generations. To help fill this knowledge gap, we conducted a multigenerational experiment to determine whether defense induction in wild radish plants was reflected in chromatin modifications (DNA methylation); we then examined differences between seedlings and reproductive plants in current and transgenerational plasticity in chemical (glucosinolates) and physical (trichomes) defenses in this species. Herbivory triggered genome methylation both in targeted plants and their offspring. Within one generation, both defenses were highly inducible at the seedling stage, but only chemical defenses were inducible in reproductive plants. Across generations, herbivory experienced by mother plants caused strong direct induction of physical defenses in their progeny, with effects lasting from seedling to reproductive stages. For chemical defenses, however, this transgenerational induction was evident only in adults. Transgenerational priming was observed in physical and chemical defenses, particularly in adult plants. Our results show that transgenerational plasticity in plant defenses in response to herbivore offense differs for physical and chemical defense and changes across plant life stages.

Seedling survival after simulating grazing and drought for two species from the Pamirs, northwestern China

For plant populations to persist, seedling recruitment is essential, requiring seed germination, seedling survival and growth. Drought and grazing potentially reduce seedling recruitment via increased mortality and reduced growth. We studied these seed–related processes for two species indigenous to the Pamir Mountains of Xinjiang in northwestern China: Saussurea glacialis and Plantago lessingii. Seeds collected from Taxkorgan, Xinjiang, had a viability rate of 15.8% for S. glacialis but 100% for P. lessingii. Of the viable seeds, the highest germination rates were 62.9% for S. glacialis and 45.6% for P. lessingii. In a greenhouse experiment, we imposed a series of stressful conditions, involving a combination of simulated grazing and drought events. These had the most severe impact on younger seedlings. Modelling showed that 89% of S. glacialis mortality was due to early simulated grazing, whereas 80% of P. lessingii mortality was due to early simulated drought. Physiological differences could contribute to their differing resilience. S. glacialis may rely on water storage in leaves to survive drought events, but showed no shifts in biomass allocation that would improve grazing tolerance. P. lessingii appears more reliant on its root system to survive grazing, but the root reserves of younger plants could be insufficient to grow deeper in response to drought. After applying all mortality factors, 17.7 seedlings/parent of P. lessingii survived, while only <0.1 seedlings/parent of S. glacialis survived, raising concerns for its capacity to persist in the Pamirs. Inherent genetic differences may underlie the two species’ contrasting grazing and drought responses. Thus, differing conservation strategies are required for their utilization and protection.

Life-history trade-offs and the genetic basis of fitness in Arabidopsisthaliana.

Resources allocated to survival cannot be used to increase fecundity, but the extent to which this trade-off constrains adaptation depends on overall resource status. Adaptation to local environmental conditions may therefore entail the evolution of traits that increase the amount of resources available to individuals (their resource status or 'condition'). We examined the relative contribution of trade-offs and increased condition to adaptive evolution in a recombinant inbred line population of Arabidopsis thaliana planted at the native sites of the parental ecotypes in Italy and Sweden in 2years. We estimated genetic correlations among fitness components based on genotypic means and explored their causes with QTL mapping. The local ecotype produced more seeds per fruit than did the non-local ecotype, reflected in stronger adaptive differentiation than was previously shown based on survival and fruit number only. Genetic correlations between survival and overall fecundity, and between number of fruits and number of seeds per fruit, were positive, and there was little evidence of a trade-off between seed size and number. Quantitative trait loci for these traits tended to map to the same regions of the genome and showed positive pleiotropic effects. The results indicate that adaptive differentiation between the two focal populations largely reflects the evolution of increased ability to acquire resources in the local environment, rather than shifts in the relative allocation to different life-history traits. Differentiation both in phenology and in tolerance to cold is likely to contribute to the advantage of the local genotype at the two sites.

Seasonal changes in temperate woody plant phloem anatomy and physiology: implications for long-distance transport.

Seasonal changes in climate are accompanied by shifts in carbon allocation and phenological changes in woody angiosperms, the timing of which can have broad implications for species distributions, interactions and ecosystem processes. During critical transitions from autumn to winter and winter to spring, physiological and anatomical changes within the phloem could impose a physical limit on the ability of woody angiosperms to transport carbon and signals. There is a paucity of the literature that addresses tree (floral or foliar) phenology, seasonal phloem anatomy and seasonal phloem physiology together, so our knowledge of how carbon transport could fluctuate seasonally, especially in temperate climates is limited. We review phloem phenology focussing on how sieve element anatomy and phloem sap flow could affect carbon availability throughout the year with a focus on winter. To investigate whether flow is possible in the winter, we construct a simple model of phloem sap flow and investigate how changes to the sap concentration, pressure gradient and sieve plate pores could influence flow during the winter. Our model suggests that phloem transport in some species could occur year-round, even in winter, but current methods for measuring all the parameters surrounding phloem sap flow make it difficult to test this hypothesis. We highlight outstanding questions that remain about phloem functionality in the winter and emphasize the need for new methods to address gaps in our knowledge about phloem function.

Reproductive resilience but not root architecture underpins yield improvement under drought in maize.

Because plants capture water and nutrients through roots, it was proposed that changes in root systems architecture (RSA) might underpin the 3-fold increase in maize (Zea mays L.) grain yield over the last century. Here we show that both RSA and yield have changed with decades of maize breeding, but not the crop water uptake. Results from X-ray phenotyping in controlled environments showed that single cross (SX) hybrids have smaller root systems than double cross (DX) hybrids for root diameters between 2465 µm and 181µm (P<0.05). Soil water extraction measured under field conditions ranged between 2.6 mm d–1 and 2.9 mm d–1 but were not significantly different between SX and DX hybrids. Yield and yield components were higher for SX than DX hybrids across densities and irrigation (P<0.001). Taken together, the results suggest that changes in RSA were not the cause of increased water uptake but an adaptation to high-density stands used in modern agriculture. This adaptation may have contributed to shift in resource allocation to the ear and indirectly improved reproductive resilience. Advances in root physiology and phenotyping can create opportunities to maintain long-term genetic gain in maize, but a shift from ideotype to crop and production system thinking will be required.