C4 Grasses Research Articles

Optimal coordination and reorganization of photosynthetic properties in C4 grasses.

Each of >20 independent evolutions of C4 photosynthesis in grasses required reorganization of the Calvin-Benson-cycle (CB-cycle)within the leaf, along with coordination of C4 -cycle enzymes with the CB-cycle to maximize CO2 assimilation. Considering the vast amount of time over which C4 evolved, we hypothesized (i) trait divergences exist within and across lineages with both C4 and closely related C3 grasses, (ii) trends in traits after C4 evolution yield the optimization of C4 through time, and (iii) the presence/absence of trends in coordination between the CB-cycle and C4 -cycle provides information on the strength of selection. To address these hypotheses, we used a combination of optimality modelling, physiological measurements and phylogenetic-comparative-analysis. Photosynthesis was optimized after the evolution of C4 causing diversification in maximal assimilation, electron transport, Rubisco carboxylation, phosphoenolpyruvate carboxylase and chlorophyll within C4 lineages. Both theory and measurements indicated a higher light-reaction to CB-cycle ratio (Jatpmax /Vcmax ) in C4 than C3 . There were no evolutionary trends with photosynthetic coordination between the CB-cycle, light reactions and the C4 -cycle, suggesting strong initial selection for coordination. The coordination of CB-C4 -cycles (Vpmax /Vcmax ) was optimal for CO2 of 200 ppm, not to current conditions. Our model indicated that a higher than optimal Vpmax /Vcmax affects assimilation minimally, thus lessening recent selection to decrease Vpmax /Vcmax .

Genetic control of morphological traits useful for improving sorghum.

Global climate change and global warming, coupled with the growing population, have raised concerns about sustainable food supply and bioenergy demand. Sorghum [Sorghum bicolor (L.) Moench] ranks fifth among cereals produced worldwide; it is a C4 crop with a higher stress tolerance than other major cereals and has a wide range of uses, such as grains, forage, and biomass. Therefore, sorghum has attracted attention as a promising crop for achieving sustainable development goals (SDGs). In addition, sorghum is a suitable genetic model for C4 grasses because of its high morphological diversity and relatively small genome size compared to other C4 grasses. Although sorghum breeding and genetic studies have lagged compared to other crops such as rice and maize, recent advances in research have identified several genes and many quantitative trait loci (QTLs) that control important agronomic traits in sorghum. This review outlines traits and genetic information with a focus on morphogenetic aspects that may be useful in sorghum breeding for grain and biomass utilization.

The benefits of publishing in society‐owned scientific journals

The benefits of publishing in society‐owned scientific journals

Diet composition and selection of Père David's deer in Hubei Shishou Milu National Nature Reserve, China.

Hubei Shishou Milu National Nature Reserve is an ideal place to restore the wild population of Père David's deer (Elaphurus davidianus). Understanding foraging ecology and diet composition is essential for assessing population development or establishing long-term effective conservation measures for endangered species. However, little is known about the diet composition of Père David's deer and its diet selection mechanism. In this study, we used stable isotope technology to investigate the diet composition of Père David's deer according to various tissues (i.e., fur, muscle, liver, heart, and feces) and seasons, and evaluated the correlation between the nutrient composition of plants and diet composition. Bayesian isotope analysis showed that the autumn and winter diet estimated by fur and fecal samples indicated a diet dominated by C3 grasses (42.7%-57.2%, mean), while the summer diet estimated by muscle and liver samples was dominated by C3 forbs (30.9%-41.6%, mean). The Pearson correlation test indicated that the contribution of winter diet composition reflected by fur and fecal samples was associated with correlations with crude protein (r=.666, p < .01) and soluble sugars (r=.695, p <.01). The results indicated that crude protein and soluble sugars were important factors influencing the winter diet selection of Père David's deer. In the context of the current reintroduction facing many challenges, such as habitat fragmentation, wetland degradation, and human disturbance, comprehensively evaluating the diet selection mechanism of Père David's deer under different resource specificities and temporal changes should be considered in the future.

A 6-yr evaluation of prescribed-fire timing on yearling cattle growth performance and plant community dynamics on native tallgrass prairie in the Kansas Flint Hills

Abstract A 6-yr experiment was conducted to determine the effects of prescribed-fire season on stocker cattle growth performance and rangeland plant community characteristics in the Kansas Flint Hills. Eighteen pastures were grouped by watershed and each watershed was randomly assigned to 1 of 3 prescribed-fire treatments: spring (11 April ± 5.7 d), summer (25 August ± 6.2 d), or autumn (2 October ± 9.0 d). All burns were applied prior to grazing in years 1, 2, 3, and 5; however, no burns were applied in year 4 because of unfavorable burn conditions. Over 5 consecutive grazing seasons, 1,939 yearling stocker calves (initial BW = 281 ± 58.9 kg) were grazed from May to August at a targeted stocking density of 280 kg live-weight + ha−1. Beginning in June of 2018 (pretreatment), a permanent 100-m transect was established in each pasture and was used to determine plant-species composition using a modified step-point method. Forage biomass accumulation and root carbohydrate concentrations of 4 native tallgrass plant species were also measured. All data were analyzed as a completely randomized design using a mixed model. Average daily gain (ADG) was 0.05 to 0.07 kg greater (P = 0.02) for calves grazing spring-burned pastures compared with calves grazing summer- or autumn-burned pastures; however, ADG did not differ (P ≥ 0.55) between calves assigned to the summer or autumn prescribed-fire treatments. Basal cover of all graminoids and all forbs did not differ (P ≥ 0.30) among prescribed-fire treatments; however, basal cover of C3 grasses tended (P = 0.06) to be greater while basal cover of C4 grasses tended (P = 0.08) to be less in autumn-burned pastures compared with spring-burned pastures. Forage biomass accumulation did not differ (P = 0.58) among treatments. In addition, root starch or root water-soluble carbohydrate concentrations in big bluestem (Andropogon gerardii), little bluestem (Schizachyrium scoparium), Indiangrass (Sorghastrum nutans), or purple prairieclover (Dalea purpurea) did not differ (P ≥ 0.26) among prescribed-fire treatments. Overall, we interpreted these data to suggest that prescribed-fire timing had small influences on yearling stocker cattle growth performance and rangeland plant composition but did not influence forage biomass accumulation or root carbohydrate concentrations of key native tallgrass plant species in the Kansas Flint Hills.

Implications of plant N/P stoichiometry influenced by arbuscular mycorrhizal fungi for stability of plant species and community in response to nutrient limitation

Arbuscular mycorrhizal fungi (AMF) influence plant nitrogen/phosphorus (N/P) by modifying plant N and P uptake, which further affects plant stoichiometric N/P homeostasis. Plant species and community stoichiometric N/P homeostasis can impact plant species and community stability, respectively, in response to variations of soil N and P availabilities. We investigated interspecific plant interactions via AMF in regard to plant and soil microbial N/P stoichiometry across different soil N and P availabilities induced by N and P addition (0 mg N kg−1, 25 mg N kg−1, 50 mg N kg−1, 30 mg P kg−1 and 100 mg P kg−1). We selected one dominant (Bothriochloa ischaemum; C4 grass) and one subordinate (Lespedeza davurica; legume) species in a natural grassland climax community. We examined how AMF influences stoichiometric N/P homeostasis in monoculture and mixed culture systems, and the resulting consequences for temporal stability of plant species and community in response to variations in soil N and P availability.The AMF mitigated the P limitation of soil microbial communities and decreased the degree of stoichiometric N/P homeostasis of host plants in monoculture. Through their resource‐scavenging and soil organic matter mineralisation functions, AMF enhances plant ‘luxury consumption', promoting species stability in monoculture in response to soil N and P availability variations. Compared with plants in monoculture, the interaction between B. ischaemum and L. davurica via AMF increased shoot N/P under soil N‐poor conditions, leading to an enhanced degree of stoichiometric N/P homeostasis in both plant species, especially the legume.Our results suggest that interspecific plant interaction between C4 grass and legume mediated by AMF confers an advantage in complementarity in plant N acquisition under N‐poor conditions, leading to increased stability of plant communities and better maintenance of subordinate species (legume) in response to soil N deficiency.

Divergent climate impacts on C3 versus C4 grasses imply widespread 21st century shifts in grassland functional composition

AbstractAimGrasslands cover a third of Earth's landmass and provide critical ecosystem services. Anticipating how perennial C3 (cool‐season) and C4 (warm‐season) grasses respond to climate change will be key to predicting future composition and functioning of grasslands. Here, we evaluate environmental drivers of C3 and C4 perennial distributions and assess how C3 and C4 grass distributions shift in response to future climate change.LocationWestern United States.MethodsWe developed integrated species distribution models to identify climate and soil drivers of relative abundance of C3 and C4 perennial grasses. We then created projections of species abundances under future climate and evaluated when and where projected shifts in relative abundance were robust across climate models.ResultsHistorically, C3 grasses occupied areas with lower temperature and more variable precipitation regimes, while C4 grasses occupied areas of higher temperature, greater temperature variability and greater warm‐season precipitation. C4 species also occupied narrower soil texture niches. In response to future climate change, C3 grass abundance declined across 74% of areas, while C4 abundance increased across 66% of areas. C3 grasses expanded in mid‐ to higher‐latitude areas with increasing temperature and decreasing seasonality of precipitation. In contrast, C4 grasses increased in higher‐latitude regions, but declined in lower‐latitude, dryer regions. Results were surprisingly robust across climate scenarios, suggesting high confidence in the direction of these future changes.Main ConclusionsFindings imply C3 and C4 perennial grasses will have highly divergent responses to climate change that may result in grassland functional compositional changes. Increasing temperatures and precipitation variability may favour some C4 grasses, but C4 habitat expansion may be constrained by soil conditions in western USA. Results provide actionable insights for anticipating the impacts of climate change on grass‐dominated and co‐dominated ecosystems and improving large‐scale conservation and restoration efforts.

Linking resource- and disturbance-based models to explain tree-grass coexistence in savannas.

Savannas cover a significant fraction of the Earth's land surface. In these ecosystems, C3 trees and C4 grasses coexist persistently, but the mechanisms explaining coexistence remain subject to debate. Different quantitative models have been proposed to explain coexistence, but these models make widely contrasting assumptions about which mechanisms are responsible for savanna persistence. Here, we show that no single existing model fully captures all key elements required to explain tree-grass coexistence across savanna rainfall gradients, but many models make important contributions. We show that recent empirical work allows us to combine many existing elements with new ideas to arrive at a synthesis that combines elements of two dominant frameworks: Walter's two-layer model and demographic bottlenecks. We propose that functional rooting separation is necessary for coexistence and is the crux of the coexistence problem. It is both well-supported empirically and necessary for tree persistence, given the comprehensive grass superiority for soil moisture acquisition. We argue that eventual tree dominance through shading is precluded by ecohydrological constraints in dry savannas and by fire and herbivores in wet savannas. Strong asymmetric grass-tree competition for soil moisture limits tree growth, exposing trees to persistent demographic bottlenecks.

Optimized Production of Second-Generation Bioethanol from a Spent C4 Grass: Vetiver (Chrysopogon zizanioides)

Vetiver grass (Chrysopogon zizanioides) is well-known for its contaminant phytoextraction potential and its capacity to reduce soil erosion, owing to its massive, dense root system. However, the shoots are not major contributors to either of these processes, and are either not utilized at all or they become part of the waste stream. It is well-recognized that lignocellulosic biomass can serve as a source of raw material to produce second-generation bioethanol. This study investigated the simultaneous saccharification and fermentation (SSF) of acid–alkali pretreated vetiver (VG) shoots by Saccharomyces cerevisiae. Vetiver shoots were obtained from three sources: (1) shoots from VG grown in clean potting soil, (2) shoots from VG used for antibiotics phytoextraction from a constructed wetland setup, and (3) shoots from VG used for lead phytoextraction during soil remediation. Bioethanol yield from the shoots from clean soil was the highest (19.58 g/L), followed by the one used for lead phytoextraction (19.50 g/L) and the one used for antibiotics phytoextraction (19.17 g/L). Bioethanol yield and quality obtained from these three VG shoots was superior or similar to other C4 grasses used for bioethanol generation. This study successfully demonstrated that spent vetiver biomass after phytoextraction applications can be repurposed to generate high-quality bioethanol.

Edaphic controls of soil organic carbon in tropical agricultural landscapes

Predicting soil organic carbon (SOC) is problematic in tropical soils because mechanisms of SOC (de)stabilization are not resolved. We aimed to identify such storage mechanisms in a tropical soil landscape constrained by 100 years of similar soil inputs and agricultural disturbance under the production of sugarcane, a C4 grass and bioenergy feedstock. We measured soil physicochemical parameters, SOC concentration, and SOC dynamics by soil horizon to one meter to identify soil parameters that can predict SOC outcomes. Applying correlative analyses, linear mixed model (LMM) regression, model selection by AICc, and hierarchical clustering we found that slow moving SOC was related to many soil parameters, while the fastest moving SOC was only related to soil surface charge. Our models explained 78–79%, 51–57%, 7–8% of variance in SOC concentration, slow pool decay, and fast pool decay, respectively. Top SOC predictors were roots, the ratio of organo-complexed iron (Fe) to aluminum (Al), water stable aggregates (WSagg), and cation exchange capacity (CEC). Using hierarchical clustering we also assessed SOC predictors across gradients of depth and rainfall with strong reductions in Roots, SOC, and slow pool decay associated with increasing depth, while increased rainfall was associated with increased Clay and WSagg and reduced CEC in surface soils. Increased negative surface charge, water stable aggregation, organo-Fe complexation, and root inputs were key SOC protection mechanisms despite high soil disturbance. Further development of these relationships is expected to improve understanding of SOC storage mechanisms and outcomes in similar tropical agricultural soils globally.

Comprehensive expression analyses of the ABCG subfamily reveal SvABCG17 as a potential transporter of lignin monomers in the model C4 grass Setaria viridis

Although several aspects of lignin metabolism have been extensively characterized, the mechanism(s) by which lignin monomers are transported across the plasma membrane remains largely unknown. Biochemical, proteomic, expression and co-expression analyses from several plant species support the involvement of active transporters, mainly those belonging to the ABC superfamily. Here, we report on the genome-wide characterization of the ABCG gene subfamily in the model C4 grass Setaria viridis and further identification of the members potentially involved in monolignol transport. A total of 48 genes encoding SvABCGs were found in the S. viridis genome, from which 21 SvABCGs were classified as full-size transporters and 27 as half-size transporters. Comprehensive analysis of the ABCG subfamily in S. viridis based on expression and co-expression analyses support a role for SvABCG17 in monolignol transport: (i) SvABCG17 is orthologous to AtABCG29, a monolignol transporter in Arabidopsis thaliana; (ii) SvABCG17 displays a similar expression profile to that of lignin biosynthetic genes in a set of different S. viridis tissues and along the elongating internode; (iii) SvABCG17 is highly co-expressed with lignin-related genes in a public transcriptomic database; (iv) SvABCG17displays particularly high expression in the top of the S. viridis elongating internode, a tissue undergoing active lignification; (v) SvABCG17 mRNA localization coincides with the histochemical pattern of lignin deposition; and (vi) the promoter of SvABCG17 is activated by secondary cell wall-associated transcription factors, especially by lignin-specific activators of the MYB family. Further studies might reveal further aspects of this potential monolignol transporter, including its real substrate specificity and whether it works redundantly with other ABC members during S. viridis lignification.

Climate Change and Its Impact on Crops: A Comprehensive Investigation for Sustainable Agriculture

Plants are a highly advanced kingdom of living organisms on the earth. They survive under all climatic and weather variabilities, including low and high temperature, rainfall, radiation, less nutrients, and high salinity. Even though they are adapted to various environmental factors, which are variable, the performance of a crop will be compensated under sub/supra optimal conditions. Hence, current and future climate change factors pose a challenge to sustainable agriculture. Photosynthesis is the primary biochemical trait of crops that are affected by abiotic stress and elevated CO2 (eCO2). Under eCO2, the C3 legumes could perform better photosynthesis over C4 grasses. The associated elevated temperature promotes the survival of the C4 crop (maize) over C3 plants. In the American Ginseng, the elevated temperature promotes the accumulation of phytocompounds. Under less water availability, poor transpirational cooling, higher canopy temperatures, and oxidative stress will attenuate the stability of the membrane. Altering the membrane composition to safeguard fluidity is a major tolerance mechanism. For protection and survival under individual or multiple stresses, plants try to undergo high photorespiration and dark respiration, for instance, in wheat and peas. The redox status of plants should be maintained for ROS homeostasis and, thereby, plant survival. The production of antioxidants and secondary metabolites may keep a check on the content of oxidating molecules. Several adaptations, such as deeper rooting, epicuticular wax formation such as peas, and utilization of non-structural carbohydrates, i.e., wheat, help in survival. In addition to yield, quality is a major attribute abridged or augmented by climate change. The nutrient content of cereals, pulses, and vegetables is reduced by eCO2; in aniseed and Valeriana sp., the essential oil content is increased. Thus, climate change has perplexing effects in a species-dependent manner, posing hurdles in sustainable crop production. The review covers various scientific issues interlinked with challenges of food/nutritional security and the resilience of plants to climate variability. This article also glimpses through the research gaps present in the studies about the physiological effects of climate change on various crops.

Soil pollution driven by duration of urbanisation and dwelling quality in urban areas: An example from Auckland, New Zealand

Soil chemistry is driven by environmental conditions, parent material and the rate and type of anthropogenic input. Cities built on soil derived from volcanic rock make up a rare yet important subset of urban areas globally. Here we conducted an urban geochemical baseline survey over Auckland, New Zealand's most populous city, built over several volcanic fields and formations. Soils were analysed by aqua regia digestion and inductively coupled plasma mass spectrometry for 65 elements, and C and N isotopes. Multivariate analysis showed volcanic parent material was a dominant natural source of metals in Auckland soils. C4 grasses significantly influenced the isotope signature in urban soils. Metal contamination was associated with urban soils and is linked to anthropogenic sources including leaded paint, tyre wear and industrialisation, and pesticides and spray residues on land that was formerly horticultural. We compare our results against other urban areas built on volcanic rock and with either a similar duration of urbanisation (Dunedin, New Zealand: c. 180 years) or a much longer period (Naples, Italy: c. 3000 years) and one urban area built on a non-volcanic substrate (Arica, Chile: 500 year-occupation). We found Dunedin soils are elevated in Cd, Pb and Zn relative to Auckland, despite an 11-fold smaller population. We attribute these legacy elements to a high proportion of pre-1970, timber clad dwellings in Dunedin with original leaded paint, relative to Auckland. Both Naples and Arica have elevated As, Pb and Zn in soil, and Naples also has higher Cd and Cu, relative to the New Zealand urban studies. We conclude that duration of urbanisation is a dominant factor in soil pollution, but where cities have similar urbanisation periods, then factors such as the age and quality of housing can be dominant. Cities built over volcanic rock like Auckland and Naples have soils elevated in Cr, Ni, large ion lithophiles, high field strength elements and rare earth elements, relative to cities with non-volcanic substrates, such as Arica.

Identification, characterization and domestication of new sorghum (Sorghum bicolor L.) genotypes to saline environments of the Aral sea regions

Assessment of crop genetic resources is an efficient tool to generate new stress-tolerant varieties with high yield characteristics for harsh environments such as in the Aral Sea regions. Sorghum is a C4 grass capable of both high biomass and grain yields in semiarid and drier parts of the world. In this study, sixteen sorghum genotypes were assessed in terms of grain and biomass production under the saline aquifer of the Aral Sea region during the 2019-2021 growing seasons. The tested sorghum genotypes were planted as a split-plot design with three replicates in the experimental field. The highest plant height was found in SSV-84 (288 cm) and Kulzha (272 cm), indicating good adaptation features under the saline environment (moderately saline serosems soil; EC 8-10 dS m-1). A considerable difference was observed in the grain and biomass yield of the tested sorghum genotypes. The highest grain yield was produced by Kazakhstanskoe-16 (6970 kg ha-1) while the highest biomass yield was achieved by Orange-160 (57770 kg ha-1). The correlation analysis showed a weak interaction (r=0.524) between the grain yield and vegetation period parameters, implying a genetic specificity has an advantage of the agronomic performance. Lab experiments also confirmed the superiority of the selected genotypes over the local genotype in regards of seed germination and seedling growth. Based on the field and lab experiments, Kazakhstanskoe-16 and Orange-160 were found to be salt tolerant sorghum genotypes with high yield traits and recommended for further assessment to the State Varietal Commission of Agricultural Crops for large-scale use in salt-affected arid areas.

Can spatial food web subsidies associated with river hydrology and lateral connectivity be detected using stable isotopes?

During and following lateral connections, aquatic organisms residing in the river channel may assimilate material from sources imported from oxbows, and oxbow residents may consume and assimilate material imported from the channel. Hydrology, lateral connectivity, and stable isotope ratios of fishes and mussels were analyzed for evidence of spatial food web subsidies between the active channel and oxbow lakes in the floodplain of the Guadalupe River, Texas. During surveys conducted between March 2016 and April 2017, fish, mussel, periphyton, seston, and riparian plant samples were collected in and around two oxbows and adjacent channel sites for analysis of stable isotope ratios. Biplots of δ13C and δ15N were graphed for basal sources and specimens of six common fish species, four sunfish species (Lepomis spp. combined), and two mussel species (Unionidae combined) captured from oxbows and the channel. Within each graph, polygons were drawn to indicate the space occupied by animals that could have assimilated feasible combinations of source materials originating from either oxbows or the river channel. Based on positions of animals within source polygons, riparian C4 grasses were not an important source of organic matter supporting biomass of fishes and mussels within the channel or oxbows. Overall, 84% of organisms had isotopic signatures consistent with assimilation of in situ sources, but also 76% of all organisms were inconclusive with regards to cross-habitat exchanges. Outliers that may have assimilated ex situ source material were observed for only 4% of 313 organisms from oxbows and 9% of 232 organisms from the channel, and some but not all of these cases followed high flow pulses that connected oxbows for extended periods. Several issues that compromise inferences from stable isotope analysis were identified, and estimation of spatial food web subsidies in fluvial systems could be enhanced by analyzing additional biomarkers, such as isotopic ratios of other elements and compound-specific stable isotopes, as well as additional sources, time-specific biotracers, and experimental approaches that directly track movement of sources and organisms in spatially structured food webs.

Grasshopper Species Composition Differs Between Prairie Dog Colonies and Undisturbed Sites in a Sagebrush Grassland

Grasshoppers are major consumers of plant biomass in grassland and shrubland ecosystems. While often considered generalists, grasshopper species have differing habitat preferences and interactions with other consumers in grasslands. There are conflicting accounts of how prairie dog colonies and differences in vegetation impact grasshopper abundance and composition. We conducted a landscape-scale survey of grasshopper communities, plant communities, and prairie dogs in a grassland/shrubland ecosystem in eastern Wyoming. Over the study landscape, spurthroat grasshoppers (Melanoplinae) were associated with lower sagebrush cover and lower cover of C3 perennial graminoids, bandwing grasshoppers (Oedipodinae) were associated with low-lying areas with a high cover of C4 grasses and a low cover of cheatgrass, and slantface grasshoppers (Gomphocerinae) were associated with low vegetation height. Prairie dogs, presumably because of their effects on vegetation, had different impacts on different groups of grasshoppers. Melanoplinae grasshoppers, the Wyoming toothpick grasshopper (Paropomala wyomingensis Thomas), and grasshoppers with early-season phenology were associated with prairie dog colonies. However, because some species of grasshoppers were positively and others negatively associated with prairie dogs, the net effect of prairie dogs on total grasshopper biomass was neutral. Thus, to determine the role of grasshoppers in prairie ecosystems, it will be important to determine whether there is functional equivalence of grasshopper species in consuming plant biomass and as food for vertebrates.

Legacies of precipitation influence primary production in Panicum virgatum.

Precipitation is a key driver of primary production worldwide, but primary production does not always track year-to-year variation in precipitation linearly. Instead, plant responses to changes in precipitation may exhibit time lags, or legacies of past precipitation. Legacies can be driven by multiple mechanisms, including persistent changes in plant physiological and morphological traits and changes to the physical environment, such as plant access to soil water. We used three precipitation manipulation experiments in central Texas, USA to evaluate the magnitude, duration, and potential mechanisms driving precipitation legacies on aboveground primary production of the perennial C4 grass, Panicum virgatum. Specifically, we performed a rainout shelter study, where eight genotypes grew under different precipitation regimes; a transplant study, where plants that had previously grown in a rainout shelter under different precipitation regimes were moved to a common environment; and a mesocosm study, where the effect of swapping precipitation regime was examined with a single genotype. Across these experiments, plants previously grown under wet conditions generally performed better than expected when exposed to drought. Panicum virgatum exhibited stronger productivity legacies of past wet years on current-year responses to drought than of past dry years on current-year responses to wet conditions. Additionally, previous year tiller counts, a proxy for meristem availability, were important in determining legacy effects on aboveground production. As climate changes and precipitation extremes-both dry and wet-become more common, these results suggest that populations of P. virgatum may become less resilient.

Phytoremediation potential of hybrid Pennisetum in cadmium-contaminated soil and its physiological responses to cadmium.

Cadmium (Cd) contamination in soil is a global problem. Recently, phytoremediation with plants, possessing high biomass and moderate Cd enrichment ability, has received excessive attention as a cost-effective method for Cd remediation from the soil. In this study, the plant growth, physiological responses, Cd concentration, accumulation, and distribution of the C4 grass hybrid Pennisetum (HP) were studied in different levels of Cd-contaminated soil in a pot experiment. Furthermore, a field trial was also conducted to accurately assess its practical phytoremediation potential in natural Cd-contaminated fallow filed. The results showed that HP possessed effective antioxidant enzymes to scavenge ROS and strong physiological coordination in response to Cd stress. The HP had a considerable Cd enrichment ability, and the maximal Cd uptake of 1.08mg plant-1 was achieved at 60mgkg-1 Cd in the pot. The maximal concentration of Cd in the aboveground parts and roots of HP were 49.33mgkg-1 and 103.33mgkg-1, respectively, when soil Cd was 70mgkg-1 in the pot. The bioconcentration factor (BCF) of Cd in the aboveground parts was less than 1, while the BCF in the root was greater than 1, and the translocation factor (TF) was less than 0.5 in all Cd treatment groups. A total of 46.89-65.46% absorbed Cd stored in the aboveground parts in the pot. The Cd concentration in roots of HP was significantly higher compared to those in leaves and stems, and all BCFs were greater than 1.5 in a lightly Cd-contaminated field (0.35mgkg-1). Furthermore, HP had high aboveground dry biomass up to 54.63 t ha-1 and accumulated 16.13gha-1 Cd in its aboveground parts in the field, which was accounted for about 91.54% of the total Cd extracted by the plant. The soil Cd concentration was reduced by 60.00% after planting HP. Our results suggest that HP is a potential phytoextractor for Cd in lightly Cd-contaminated soil as well as a phytostabilizer under strong Cd stress in the pot.

Grass species with smoke-released seed dormancy: A response to climate and fire regime but not photosynthetic pathway.

Both C3 and C4 photosynthetic pathways and smoke-released seed dormancy occur among grasses. C4 species evolved from C3 species as seasonality and fire frequency increased and might therefore imply that their smoke sensitivity increased. I searched the worldwide literature for reports on germination responses among grasses, whose photosynthetic pathway was known, to treatment by smoke. Data were obtained for 217 species and 126 genera. While subfamilies tended to be C3 (Pooideae), C4 (Chloridoideae) or a mixture (Panicoideae), a beneficial smoke response was independent of their photosynthetic pathway. The only exceptions were Danthonioideae (C3, non-smoke responsive) and Triodia (C4, smoke responsive). One third of both C3 and C4 genera were smoke responsive. Even within genera, 90% of species showed contrasting smoke responses, confirming that smoke sensitivity is rarely taxonomically constrained. Data on photosynthetic pathway, climate, fire regime and vegetation were compiled for 15 regions that formed four distinct groups: 1) In warm climates with aseasonal rainfall, C4 grasses are moderately better represented, with crown fires and limited smoke responses. 2) In cool regions, most species are C3, with surface-crown fires and lack smoke responses. 3) In warm regions with summer rain (savannas), most species are C4, with surface fires and lack smoke responses. 4) In Mediterranean-climate regions with summer drought, most species are C3, with crown fires and smoke-released dormancy. Thus, even though C3 and C4 grasses are equally capable of expressing smoke sensitivity, their response depends on the region's climate and fire regime that also dictate which photosynthetic pathway dominates.

High soil carbon sequestration rates persist several decades in turfgrass systems: A meta-analysis

Managed turfgrass is a common component of urban landscapes that is expanding under current land use trends. Previous studies have reported high rates of soil carbon sequestration in turfgrass, but no systematic review has summarized these rates nor evaluated how they change as turfgrass ages. Here we conducted a meta-analysis of soil carbon sequestration rates from 63 studies globally, comprised mostly of C3 grass species in the U.S., including 24 chronosequence studies that evaluated carbon changes over 75 years or longer. We showed that turfgrass established within the last ten years had a positive mean soil C sequestration rate of 5.3 Mg CO2 ha−1 yr−1 (95% CI = 3.7–6.2), which is higher than rates reported for several soil conservation practices. Areas converted to turfgrass from forests were an exception, sometimes lost soil carbon, and had a cross-study mean sequestration rate that did not differ from 0. In some locations, soil C accumulated linearly with turfgrass age over several decades, but the major trend was for soil C accumulation rates to decline through time, reaching a cross-study mean sequestration rate that was not different from 0 at 50 years. We show that fitting soil C timeseries with a mechanistically derived function rather than purely empirical functions did not alter these conclusions, nor did employing equivalent soil mass versus fixed-depth carbon stock accounting. We conducted a partial greenhouse gas budget that estimated emissions from mowing, N-fertilizer production, and soil N2O emissions. When N fertilizer was applied, average maintenance emissions offset 32% of C sequestration in recently established turfgrass. Potential emission removals by turfgrass can be maximized with reduced-input management. Management decisions that avoid losing accrued soil C—both when turfgrass is first established and when it is eventually replaced with other land-uses—will also help maximize turfgrass C sequestration potential.