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Reforestation is one of our most promising natural climate solutions, and one that addresses the looming biodiversity crisis. Tree planting can catalyse forest community reassembly in degraded landscapes where natural regeneration is slow, however, tree survival rates vary remarkably across projects. Building a trait-based framework for tree survival could streamline species selection in a way that generalizes across ecosystems, thereby increasing the effectiveness of the global restoration movement. We investigated how traits mediated seedling survival in a tropical dry forest restoration, and how traits were coordinated across plant structures. We examined growth and survival of 14 species for 2 years and measured six below-ground and 22 above-ground traits. Species-level survival ranged widely from 7.8% to 90.1%, and a model including growth rate, below-ground traits and their interaction explained more than 73% of this variation. A strong interaction between below-ground traits and growth rate indicated that selecting species with fast growth rates can promote establishment, but this effect was most apparent for species that invest in thick fine roots and deep root structures. Overall, results emphasize the prominent role of below-ground traits in determining early restoration outcomes, and highlight little above- and below-ground trait coordination, providing a path forward for tropical dry forest restoration efforts. [ABSTRACT FROM AUTHOR]

To clarify the changes of root traits, soil biological characteristics and yield after applying fertilizers for 39 years, a long-term located fertilization experiment (1981-) was conducted. Compared to NPK (inorganic fertilizer) and M (organic fertilizer), 0.8NPKM (80% of NPK plus 80% of M) and 0.5NPKM (50% of NPK plus 50% of M) obviously improved root traits. The number of bacteria, fungi, actinomycetes in 0.8NPKM and 0.5NPKM were significantly higher than that in NPK, M and CT (no fertilizer). Compared to NPK, M increased soil microbial quantity. Soil microbial biomass carbon and nitrogen, organic carbon and total N in M were higher than that in NPK. The activities of phosphatase, dehydrogenase and urease in M were significantly higher than that in NPK. Compared to NPK and M, 0.8NPKM and 0.5NPKM enhanced above-mentioned soil enzymes activities. The differences in wheat and maize yields between 0.5NPKM and 0.8NPKM were insignificant, and the harvest index in 0.5NPKM was the highest. Soil microbial quantity, microbial biomass carbon and nitrogen were positively correlated with enzymes activities and root traits. Thus, appropriate combined application amount of organic and inorganic fertilizer might be an effective way to improve root traits, rhizosphere soil micro-biological environment and crop yield.AbbreviationsCT No fertilizer addedNPK Inorganic fertilizer onlyM Organic fertilizer only0.5NPKM Organic fertilizer plus inorganic fertilizer (50% of NPK plus 50% of M)0.8NPKM High application ratio of inorganic and organic fertilizers (80% of NPK plus 80% of M) [ABSTRACT FROM AUTHOR]

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Basmati rice is inherently sensitive to various environmental stresses. Abrupt changes in climatic patterns and freshwater scarcity are escalating the issues associated with premium-quality rice production. However, few screening studies have selected Basmati rice genotypes suitable for drought-prone areas. This study investigated 19 physio-morphological and growth responses of 15 Super Basmati (SB) introgressed recombinants (SBIRs) and their parents (SB and IR554190-04) under drought stress to elucidate drought-tolerance traits and identify promising lines. After two weeks of drought stress, several physiological and growth performance traits significantly varied between the SBIRs (p ≤ 0.05) and were less affected in the SBIRs and the donor (SB and IR554190-04) than SB. The total drought response indices (TDRI) identified three superior lines (SBIR-153-146-13, SBIR-127-105-12, SBIR-62-79-8) and three on par with the donor and drought-tolerant check (SBIR-17-21-3, SBIR-31-43-4, SBIR-103-98-10) in adapting to drought conditions. Another three lines (SBIR-48-56-5, SBIR-52-60-6, SBIR-58-60-7) had moderate drought tolerance, while six lines (SBIR-7-18-1, SBIR-16-21-2, SBIR-76-83-9, SBIR-118-104-11, SBIR-170-258-14, SBIR-175-369-15) had low drought tolerance. Furthermore, the tolerant lines exhibited mechanisms associated with improved shoot biomass maintenance under drought by adjusting resource allocation to roots and shoots. Hence, the identified tolerant lines could be used as potential donors in drought-tolerant rice breeding programs, administered for subsequent varietal development, and studied to identify the genes underlying drought tolerance. Moreover, this study improved our understanding of the physiological basis of drought tolerance in SBIRs.

Aim of study: To characterize the colonization of Pinus herrerae roots in trunks of dead standing trees and to evaluate the composition of roots and decomposing tissues of standing dead trees. Area of study. Jaguariaíva, Paraná state, Southern Brazil. Material and methods: This study evaluated root attributes in the soil, litter, and trunks of dead standing trees and the composition of wood and bark of trees. Root traits (length, mass mycorrhizal colonization, and mean nutrient concentrations), soil and organic layers, and mean nutrient concentrations of wood and bark for were analyzed by non-parametric test. Main results: Approximately 2 to 3.5 years after tree death, roots of adjacent trees in F and H horizon litter migrate into the wood/bark interface. Eight and a half years after tree death, roots of adjacent trees reached up to 3.3 m above the litter surface. At the wood/bark interface, a root mantle formed (length greater than 1 km m-2) with ~5% ectomycorrhizal colonization. Root presence in the wood/bark interface reduced P, K, and Fe concentration of dead wood and Zn concentration in bark. Research highlights: Our results indicate that roots of P. herrerae are capable of colonizing dead tree trunks as a nutrient resource pool. This nutrient acquisition mechanism may function as a shortcut in the biogeochemical cycling of nutrients in forest systems.

In soils, high aggregate stability often represents higher quality and anti-erosion ability; however, few studies have systematically analyzed how different forest stands affect soil aggregate stability. We selected five typical mixed forest stands on Jinyun Mountain in Chongqing, China, as research sites to evaluate soil aggregate stability. Within these sites, we analyzed the factors influencing soil aggregate stability in different stands by measuring soil characteristics and root traits. Soil aggregation stability, plant root traits, and soil properties varied among the mixed forest stands. The broadleaf tree mixed forest improved soil aggregate stability by 57%–103% over that of the Pinus massoniana mixed forest. The soil organic carbon, cation exchange capacity, Fe-Al oxides, and fine root proportion were positively correlated with soil aggregate stability. The specific root length and very fine root proportion were negatively correlated with soil aggregate stability, whereas the fine root proportion was positively correlated with this property. Specifically, we found that arbuscular mycorrhizal fungi did not affect soil aggregate stability in acid rain areas. Structural equation modeling indicated that soil aggregate stability was closely related to soil physicochemical properties and plant root characteristics. Predictive factors accounted for 69% of the variation in mean weight diameter, and plant root traits influenced soil aggregate stability by affecting soil organic matter, texture, and Fe-Al oxides. This study elucidated the impact of soil physicochemical properties and plant root characteristics on soil aggregate stability in different forest stand types, which has crucial implications for optimizing the management of various forest types.

Nitrogen fertilizer input is the main determinant of wheat yield, and heavy nitrogen fertilizer application causes serious environmental pollution. It is important to understand the genetic response mechanism of wheat to nitrogen and select wheat germplasm with high nitrogen efficiency. In this study, 204 wheat species were used to conduct genome-wide association analysis. Nine phenotypic characteristics were obtained at the seedling stage in hydroponic cultures under low-, normal, and high-nitrogen conditions. A total of 765 significant loci were detected, including 438, 261, and 408 single nucleotide polymorphisms (SNPs) associated with high-, normal, and low-nitrogen conditions, respectively. Among these, 14 SNPs were identified under three conditions, for example, AX-10887638 and AX-94875830, which control shoot length and root–shoot ratio on chromosomes 6A and 6D, respectively. Additionally, 39 SNPs were pleiotropic for multiple traits. Further functional analysis of the genes near the 39 SNPs shows that some candidate genes play key roles in encoding proteins/enzymes, such as transporters, hydrolases, peroxidases, glycosyltransferases, oxidoreductases, acyltransferases, disease-resistant proteins, ubiquitin ligases, and sucrose synthetases. Our results can potentially be used to develop low-nitrogen-tolerant species using marker-assisted selection and provide a theoretical basis for breeding efficient nitrogen-using wheat species.

We aimed to study the effects of mycorrhizal and extraradical hyphae on soil physical and chemical properties and enzyme activity characteristics in a subtropical plantation and to explore its indicative effect on the effectiveness of soil nutrients. In this study, three native afforestation tree species, Cunninghamia lanceolata, Schima superba, and Liquidambar formosana, with different biological characteristics, root functional traits, and nutrient acquisition strategies in subtropical regions were selected as the research objects. Based on the method of in-growth soil cores, the nylon mesh with different pore sizes was used to limited the root system and hypha into the soil column. The soil physical and chemical properties of five kinds of hydrolase related to the carbon (C), nitrogen (N), and phosphorus (P) cycles were determined in this study. The correlation of different tree species, roots, and mycelia with soil physicochemical properties, enzyme activity, and stoichiometric ratios was analyzed. The results revealed that mycorrhizal treatment significantly affected the soil total carbon (TC) and pH but had no significant effect on hydrolase activity and its stoichiometric ratio. Tree species significantly affected soil physical and chemical properties, soil β-1,4-N-acetylglucosaminidase (NAG), β-1,4-glucosidase (βG), and cellobiohydrolase (CB) activities and soil enzyme stoichiometric ratios. The soil enzyme activity and stoichiometric ratio of the Chinese fir forest had higher values than in monoculture broad-leaved stands of both Schima superba and Liquidambar formosana. There was no significant interaction effect of mycorrhizal treatments and tree species on all soil properties, enzyme activities, and stoichiometric ratios. In addition, the soil enzyme activity and stoichiometric characteristics were mainly affected by the pH. In this study, the soil enzyme activity ratios In(BG + CB):In(AP) and In(NAG + LAP):In(AP) were lower values than the global scale, while the ratios of In(βG + CB):In(NAG + LAP) were higher than the average, indicating that the soil microorganisms in this area were limited by C and P. Moreover, the soil enzyme activity and chemical metrology characteristics were mainly affected by the pH change. In conclusion, differences in litter quality and root functional traits of tree species affected the soil enzyme activity and its stoichiometric characteristics through the shaping of the forest environment by organic matter input, and the influence of pH was the main regulating factor.

Abstract Background Among phosphate (P) fertilizers, polyphosphates (PolyPs) have shown promising results in terms of crop yield and plant P nutrition. However, compared to conventional P inputs, very little is known on the impact of PolyPs fertilizers on below- and above-ground plant functional traits involved in P acquisition. This study aims to evaluate agro-physiological responses of durum wheat variety ´Karim´ under different PolyPs applications. Three PolyPs fertilizers (PolyA, PolyB, and PolyC) versus one orthophosphate (OrthoP) were applied at three doses; 30 (D30), 60 (D60), and 90 (D90) kg P/ha under controlled conditions. The PolyPs (especially PolyB and PolyC) application at D60 significantly increased morphophysiological root traits (e.g., RL: 42 and 130%; RSA:40 and 60%), shoot inorganic P (Pi) content (159 and 88%), and root P acquisition efficiency (471 and 296%) under PolyB and PolyC, respectively compared to unfertilized plants. Above-ground physiological parameters, mainly nutrient acquisition, chlorophyll content and chlorophyll fluorescence parameters were also improved under PolyB and PolyA application at D60. A significant and positive correlation between shoot Pi content and rhizosphere soil acid phosphatase activity was observed, which reveal the key role of these enzymes in PolyPs (A and B) use efficiency. Furthermore, increased P uptake/RL ratio along with shoot Pi indicates more efficient P allocation to shoots with less investment in root biomass production under PolyPs (especially A and B). Conclusions Under our experimental conditions, these findings report positive impacts of PolyPs on wheat growth performance, particularly on photosynthesis and nutrient acquisition at D60, along with modulation of root morpho-physiological traits likely responsible of P acquisition efficiency.

Root growth patterns respond to small-scale resource heterogeneity and the presence of roots of neighboring plants, but how a plant integrates its responses to these cues is not well understood. In the presence of neighbors, plants may shift allocation to roots as a consequence of plant size and root:shoot allometry, as a response to resource depletion by neighbors, or through a direct response to neighbor presence. The same response pathways also have the potential to alter proliferation in resource-rich patches in soil.Four species of grassland plants were grown in the greenhouse as single plants, monocultures, and mixtures. Root length allocation as a function of shoot mass was examined for background soil and fertilized patches. Plants grown with same-species neighbors followed the same allometric trajectory as single plants for root length in background soil, so any change in root allocation was due only to reduced plant size. Root proliferation in patches declined with neighbors, consistent with a response to resource depletion. Mixtures overproduced roots in both background soil and in patches, relative to plants of the same size in monocultures.

Challenges of soil degradation and changing climate pose major threats to food security in many parts of the world, and new approaches are required to close yield and nutrition gaps through enhanced agronomic efficiency. Combined use of mineral fertilizers, organic inputs, improved germplasm and adaptation of these practices to local contexts through improved agronomy can promote efficiency whilst building stocks of soil organic matter (SOM). Within this framework, recent attention has turned to the nature of plant-soil interactions to increase response to mineral fertilizer inputs through utilisation of nutrients from SOM that are replenished through management. This utilisation has been shown in barley and maize to vary with genotype and to be related to root physiological traits associated with rhizodeposition. The identification of candidate genes associated with rhizodeposition takes this a step closer towards the possibility of breeding for sustainability. Here we discuss this potential and feasibility in the context of maize cropping systems, and explore the potential for a combined approach that optimises utilisation of SOM nutrients together with enhanced biological nitrification inhibition to further improve agronomic efficiency.

Nitrogen and phosphorus are important nutrient elements for plants and underground organisms. The nematode is an important part of the soil food web. Although many studies have explored the effects of fertilization on soil nematode community structure, little is known about the response mechanism of the nematode community to fertilization. In this study, we investigated the diversity and functional diversity of soil nematode communities, as well as soil physicochemical properties, root functional traits, and plant richness. We explored the response mechanism of soil nematode communities to nitrogen and phosphorus fertilizer. Nitrogen fertilizer increased the abundance and richness of bacterivorous nematodes, while phosphorus fertilizer decreased the total abundance of bacterivorous nematodes. Meanwhile, the diversity of the nematode community was significantly affected by soil physicochemical properties and plant root functional traits. Therefore, our study revealed the effects of nitrogen and phosphorus fertilizer on soil nematode community diversity and functional diversity. Exploring the response mechanism of soil nematode communities to fertilization interference provides further evidence for the role of nematodes in maintaining the function of subsurface ecosystems.

Abstract Plant functional traits offer ecologists quantifiable characteristics that may be used to determine the underlying mechanisms and drivers of processes at scales ranging from individual plants to entire ecosystems. While research on belowground functional traits has increased in recent years, most of this work has not fully considered the traits of mycorrhizal fungi, key symbionts responsible for much nutrient uptake and soil exploration in trees. We argue that, because of the important role of mycorrhizae in resource uptake, the measurement of belowground plant traits without the inclusion of mycorrhizal fungal traits potentially misses key mechanistic factors affecting plant performance, which has implications across ecological scales. In doing so, we provide a synopsis of current and past work on plant root traits and mycorrhizal fungal traits. Finally, we suggest potential key fungal traits to be measured and possible methods for measurement as ways to address the current gaps in our knowledge.

Phosphorus (P) is one of the essential macronutrients for plant growth and development, and it is an integral part of the major organic components, including nucleic acids, proteins and phospholipids. Although total P is abundant in most soils, a large amount of P is not easily absorbed by plants. Inorganic phosphate (Pi) is the plant-available P, which is generally immobile and of low availability in soils. Hence, Pi starvation is a major constraint limiting plant growth and productivity. Enhancing plant P efficiency can be achieved by improving P acquisition efficiency (PAE) through modification of morpho-physiological and biochemical alteration in root traits that enable greater acquisition of external Pi from soils. Major advances have been made to dissect the mechanisms underlying plant adaptation to P deficiency, especially for legumes, which are considered important dietary sources for humans and livestock. This review aims to describe how legume root growth responds to Pi starvation, such as changes in the growth of primary root, lateral roots, root hairs and cluster roots. In particular, it summarizes the various strategies of legumes to confront P deficiency by regulating root traits that contribute towards improving PAE. Within these complex responses, a large number of Pi starvation-induced (PSI) genes and regulators involved in the developmental and biochemical alteration of root traits are highlighted. The involvement of key functional genes and regulators in remodeling root traits provides new opportunities for developing legume varieties with maximum PAE needed for regenerative agriculture.

Cadmium (Cd) is a persistent heavy metal that poses environmental and public health concerns. This study aimed to identify the potential biomarkers responsible for Cd tolerance and accumulation by investigating the response of the content of essential metal elements, transporter gene expression, and root exudates to Cd stress in broomcorn millet (Panicum miliaceum). A hydroponics experiment was conducted using two broomcorn millet cultivars with distinct Cd tolerance levels and accumulation phenotypes (Cd-tolerant and Cd-sensitive cultivars). Cd stress inhibited lateral root growth, especially in the Cd-sensitive cultivar. Furthermore, Cd accumulation was significantly greater in the Cd-tolerant cultivar than in the Cd-sensitive cultivar. Cd stress significantly inhibited the absorption of essential metal elements and significantly increased the calcium concentration. Differentially expressed genes involved in metal ion transport were identified via transcriptome analysis. Cd stress altered the composition of root exudates, thus increasing lipid species and decreasing alkaloid, lignan, sugar, and alcohol species. Moreover, Cd stress significantly reduced most alkaloid, organic acid, and phenolic acid exudates in the Cd-tolerant cultivar, while it increased most lipid and phenolic acid exudates in the Cd-sensitive cultivar. Some significantly changed root exudates (ferulic acid, O-coumaric acid, and spermine) are involved in the phenylalanine biosynthesis, and arginine and proline metabolic pathways, thus, may be potential biomarkers of Cd stress response. Overall, metal ion absorption and root exudates are critical for Cd tolerance and accumulation in broomcorn millet. These findings provide valuable insights into improving Cd phytoremediation by applying mineral elements or metabolites.

Background and Aims Our understanding of plant responses to biotic and abiotic drivers is largely based on above-ground plant traits, with little focus on below-ground traits despite their key role in water and nutrient uptake. Here, we aimed to understand the extent to which above- and below-ground traits are co-ordinated, and how these traits respond to soil moisture gradients and plant intraspecific competition. Methods We chose seedlings of five tropical tree species and grew them in a greenhouse for 16 weeks under a soil moisture gradient [low (drought), medium and high (well-watered) moisture levels] with and without intraspecific competition. At harvest, we measured nine above- and five below-ground traits of all seedlings based on standard protocols. Key Results In response to the soil moisture gradient, above-ground traits are found to be consistent with the leaf economics spectrum, whereas below-ground traits are inconsistent with the root economics spectrum. We found high specific leaf area and total leaf area in well-watered conditions, while high leaf dry matter content, leaf thickness and stem dry matter content were observed in drought conditions. However, below-ground traits showed contrasting patterns, with high specific root length but low root branching index in the low water treatment. The correlations between above- and below-ground traits across the soil moisture gradient were variable, i.e. specific leaf area was positively correlated with specific root length, while it was negatively correlated with root average diameter across moisture levels. However, leaf dry matter content was unexpectedly positively correlated with both specific root length and root branching index. Intraspecific competition has influenced both above- and below-ground traits, but interacted with soil moisture to affect only below-ground traits. Consistent with functional equilibrium theory, more biomass was allocated to roots under drought conditions, and to leaves under sufficient soil moisture conditions. Conclusions Our results indicate that the response of below-ground traits to plant intraspecific competition and soil moisture conditions may not be inferred using above-ground traits, suggesting that multiple resource use axes are needed to understand plant ecological strategies. Lack of consistent leaf–root trait correlations across the soil moisture gradient highlight the multidimensionality of plant trait relationships which needs more exploration. [ABSTRACT FROM AUTHOR]

Vegetation has been proven to be an effective measure to mitigate soil erosion in most regions and climates. However, it is not clear how some herbaceous plants affect the ability of soil to resist slope flow erosion in the Mollisol region of Northeast China. In this study, four herbaceous plant plots of 50 m × 4.5 m, including Zea mays L., Sorghum bicolor × Sudanense, Avena sativa L. and Lolium multiflorum Lam., were established in a sloping land with an abandoned land as the control to detect the effect of herbaceous plants on soil anti-scourability (ANS). A hydraulic flume experiment was carried out to determine the soil ANS, and the root traits and soil properties were also measured at different slope positions. The results showed that the mean soil ANS ranged from 17.55 to 94.77 L g−1 among different herbaceous plants, of which the Lolium multiflorum Lam. showed the strongest controlling effect on soil ANS (259.87%), followed by Sorghum bicolor × Sudanense (66.87%) and Avena sativa L. (18.12%), while the soil ANS of Zea mays L. decreased by 33.37% compared with the control. Soil ANS varied with slope position, and the mean soil ANS at the upslope was 116.50–134.21% higher than that of the middle slope and downslope. Additionally, soil ANS was positively related to root mass density (RMD), root length density (RLD), root surface area density (RSAD), soil total porosity and field capacity but was negatively related to soil bulk density (p < 0.05). Furthermore, the Lolium multiflorum Lam. exhibited better root distribution (i.e., high RSAD, RLD, RMD, and low root diameter) and soil physical structure (i.e., high soil porosity structure, water-holding capacity and low bulk density) than other plant species. Thus, the Lolium multiflorum Lam. is beneficial for enhancing soil erosion resistance to overland flow, especially at the up and middle slopes, and it could be preferred to control sloped soil erosion in Northeast China. [ABSTRACT FROM AUTHOR]

Dioecious species may be particularly vulnerable to climate change because they often exhibit skewed sex ratios that are reinforced by the physiological and biological specialization of each sex to specific microhabitats. Yet, it is unclear how differences in functional traits between female and male plants lead to sex‐specific responses to drought and whether these responses are associated with phosphorus (P) acquisition diverge or converge.Here, we measured the morphological and physiological traits of roots, and the functional micro‐organisms related to P acquisition in Populus euphratica females and males in the rhizosphere under different water availability.The specific root length of females was greater than that of males, regardless of soil water availability. Therefore, the P concentration of females was significantly higher than that of males under well‐watered conditions. In contrast, the physiological adjustment to drought showed distinct sexual patterns: males significantly increased the foliar manganese concentration and maintained higher acid phosphatase activities in the rhizosphere. Moreover, the arbuscular mycorrhizal hyphal biomass reduced less in males than in females under water deficiency. Soil water shortage also decreased the α diversity of phosphate solubilizing bacteria (PSB) and changed the co‐occurrence network in the rhizosphere of females, but it had little effect on males. Consequently, the favourable physiological processes and effective maintenance of functional microbial homoeostasis in the rhizosphere were the reasons that enabled males to reduce P loss in leaves under water deficiency.Our study indicated that, within P. euphratica populations, covariations and trade‐offs simultaneously occurred among the three groups (root morphology, physiology and functional micro‐organisms) of functional traits evaluated. More generally, the assessment of variations in sex‐specific P acquisition strategies may help to understand the causes of sex ratio bias and how P. euphratica males and females mitigate resource shortage. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Nitrogen deposition will alleviate the nitrogen limitation in terrestrial ecosystems and greatly affect vegetation growth, thereby soil erosion. It is important to clarify the effects of nitrogen addition to the plant roots and soil properties on the soil erosion process. A nitrogen addition experiment was conducted in the grassland dominated by Bothriochloa ischaemum (Linn.) Keng (BI), which has received 0, 2.5, 5, and 10 g N m−2 yr−1 (N0, N2.5, N5 and N10, respectively) for three consecutive years. Then, a total of 150 undisturbed soil samples were collected (including bare soil control) and subjected to flowing water to test their soil detachment capacities under six shear stress levels (10.2 Pa to 29.9 Pa). Three-year nitrogen addition increased the soil bulk density, soil cohesion and nitrate nitrogen while decreasing the saturated hydraulic conductivity, soil water-stable aggregates, soil organic carbon, total nitrogen and ammonium nitrogen. The root mass density and root diameter decreased with nitrogen addition. And the root length, surface area and volume density of the N0 and N5 treatments were larger than those of the other treatments, while the plant roots were significantly inhibited by N10. Additionally, the soil detachment capacity (Dc) and rill erodibility (Kr) of the N0 and N5 treatments were significantly less than those of the N2.5 and N10 treatments, of which the Dc (0.020 kg m−2 s−1) of the N0 treatment was 69.0%, 24.3% and 66.8% less than that of the N2.5, N5 and N10 treatments, respectively. The Kr of the N0 treatment was 0.0012 s m−1, which was 72.1%, 25.0% and 70.0% less than that of the others. This study implies that an increase in nitrogen addition likely exacerbates soil erosion in the early (approximately 2.5 g N m−2 yr−1) and late phases (more than 10 g N m−2 yr−1). However, when the nitrogen addition rate is approximately 5 g m−2 yr−1, soil erosion may be inhibited because of the responses of the plant roots and soil to nitrogen addition. [ABSTRACT FROM AUTHOR]

Root traits are often used to predict the ecological adaptations of plants. Water and nutrient availability together with fragment size are likely to affect the adaptative capacity of Stipa breviflora and help plants spread and explore new sites, while the effects of water, nutrients and fragment size on S. breviflora's root traits have rarely been studied in combination. Here, a standard Taguchi L8(27) array design was conducted with four single factors, water (W), nitrogen (N), phosphorus (P) and fragment size (C), and three interactions (N × P, N × W and P × W). Each of the four factors had two levels (1 = low level and 2 = high level). This study found that water was the most important contributor influencing S. breviflora root growth, followed by N and P, respectively. W2 and P2 additions both promoted root growth, whereas N2 addition significantly inhibited root growth. Though C2 had higher values of total root length, surface area, volume, number of tips and biomass than C1, its root growth rate was lower than C1, and its small size fragment had a higher capacity of root growth under low N addition. These findings suggest that clonal fragmentation may enhance the adaptation of S. breviflora in low nitrogen habitats, and that nitrogen is one of the limiting factors influencing their growth and distribution. [ABSTRACT FROM AUTHOR]

To minimize unused nitrogen (N) fertilizer in the soil, improving the nitrogen use efficiency of the cropping system is of utmost importance. Plants mainly absorb N from the soil through roots. The study was, therefore, carried out to know the inheritance pattern of root traits responsible for N uptake. Extreme six spring wheat lines selected from 175 genotypes screened for root dry weight under hydroponic condition were crossed in half diallel to generate 15 F1s. These F1s along with their parents were evaluated under hydroponic condition for rooting depth (RD), root surface area (RSA), root volume (RV), total root length (TRL) and numbers of root tips (N tips) under N-limiting and N-non-limiting environment. Combining ability analysis revealed significant contribution due to both general combining ability and specific combining ability for all root traits indicating the importance of both additive and non-additive gene actions under both N environments. However, the relative importance of each was different in the two environments, indicating, therefore, separate breeding strategies for the two environments. Early generation selection for the root traits like RD, TRL, RSA, RV and N tips under N non-limiting can be effectively integrated into the breeding programme as indicated by preponderance of additive gene effects in the study. The distribution pattern of the various roots traits in the F2 generation of a specific cross indicates the involvement of multiple genes with minor effects for the most of root traits and therefore confirms our earlier observations that selection for the root traits can be effective; however, the stage of selection (early vs. late generation) depends upon the N environment. [ABSTRACT FROM AUTHOR]

Roots are the major organs for water and nutrient acquisition and substantially affect plant growth, development and reproduction. Improvements to root system architecture are highly important for the increased yield potential of bread wheat. QMrl-7B, a major stable quantitative trait locus (QTL) that controls maximum root length (MRL), essentially contributes to an improved root system in wheat. To further analyze the biological functions of QMrl-7B in root development, two sets of Triticum aestivum near-isogenic lines (NILs), one with superior QMrl-7B alleles from cultivar Kenong 9204 (KN9204) named NILKN9204 and another with inferior QMrl-7B alleles from cultivar Jing 411 (J411) named NILJ411, were subjected to transcriptomic analysis. Among all the mapped genes analyzed, 4871 genes were identified as being differentially expressed between the pairwise NILs under different nitrogen (N) conditions, with 3543 genes expressed under normal-nitrogen (NN) condition and 2689 genes expressed under low-nitrogen (LN) condition. These genes encode proteins that mainly include NO3- transporters, phytohormone signaling components and transcription factors (TFs), indicating the presence of a complex regulatory network involved in root determination. In addition, among the 13524 LN-induced differentially expressed genes (DEGs) detected in this study, 4308 and 2463 were specifically expressed in the NILKN9204 and NILJ411, respectively. These DEGs reflect different responses of the two sets of NILs to varying N supplies, which likely involve LN-induced root growth. These results explain the better-developed root system and increased root vitality conferred by the superior alleles of QMrl-7B and provide a deeper understanding of the genetic underpinnings of root traits, pointing to a valuable locus suitable for future breeding efforts for sustainable agriculture. [ABSTRACT FROM AUTHOR]

Summary: Improving nitrogen (N) use efficiency (NUE) to reduce the application of N fertilisers in a way that benefits the environment and reduces farmers' costs is an ongoing objective for sustainable wheat production. However, whether and how arbuscular mycorrhizal fungi (AMF) affect NUE in wheat is still not well explored.Three independent but complementary experiments were conducted to decipher the contribution of roots and AMF to the N uptake and utilisation efficiency in wheat.We show a temporal complementarity pattern between roots and AMF in shaping NUE of wheat. Pre‐anthesis N uptake efficiency mainly depends on root functional traits, but the efficiency to utilise the N taken up during pre‐anthesis for producing grains (EN,g) is strongly affected by AMF, which might increase the uptake of phosphorus and thereby improve photosynthetic carbon assimilation. Root association with AMF reduced the N remobilisation efficiency in varieties with high EN,g; whilst the overall grain N concentration increased, due to a large improvement in post‐anthesis N uptake supported by AMF and/or other microbes.The findings provide evidence for the importance of managing AMF in agroecosystems, and an opportunity to tackle the contradiction between maximising grain yield and protein concentration in wheat breeding. [ABSTRACT FROM AUTHOR]

Context: In recent years, direct-seeded rice (DSR) cultivation methods have been widely adopted in Asia. Aims: The objective of this study was to evaluate the grain yield, nitrogen use efficiency and associated plant traits of DSR in northeastern China. Methods: A 2-year field experiment was conducted using two varieties under three cultivation methods (1) conventional transplanted rice (CTR); (2) wet direct-seeded rice (WDSR); and (3) dry direct-seeded rice (DDSR). Key results: The grain yield of CTR and DSR ranged from 10.16 to 9.39 t ha−1 and from 8.85 to 6.90 t ha−1, respectively, accross varieties and years. The wide difference was attributed to the differences in spikelet number per panicle and biomass. Compared with the CTR, the DSR decreased the spikelet number per panicle, which resulted in lower spikelet number per m2. Meanwhile, a significant positive correlation was observed between spikelet number per m2 and nitrogen uptake. The nitrogen uptake of CTR and DSR ranged from 151 to 153 kg ha−1 and from 96 to 132 kg ha−1, respectively. The root biomass, root length and zeatin + zeatin riboside contents in roots were higher in CTR than DSR, which contributed to the higher nitrogen uptake. Conclusions: These results suggest that DSR reduced nitrogen uptake, thereby resulting in decreased number of spikelets per panicle, and hence lower rice grain yield. Implications: These findings have highlighted the deficiencies in direct seeded rice system, and further research is required to overcome these deficiencies. In recent years, alternative rice cultivation methods have been widely developed in Asia. Realising the yield potential and raising the ceiling of yield potential even further have been the production priorities of direct-seeded rice cultivation. To establish cultivation methods for direct-seeded rice and to develop breeding targets for further increases in yield, an evaluation of their yield potential and growth characteristics is essential. [ABSTRACT FROM AUTHOR]

Our research demonstrates that plant material can be produced in the nursery with asymmetrical root systems, which may have utility for reforestation of difficult planting sites characterized by steep slopes and/or windy conditions. Such a root system can be generated using chemical root pruning by applying cupric carbonate (Cu) that can arrest the development of, or cause mortality to, root apical meristems resulting in the formation of new lateral roots with an overall increase in the biomass, length, and volume of the root system. Our objective was to investigate the effect of chemical root pruning on the morphological and architectural traits of adventitious roots produced by poplar cuttings (Populus nigra L.) grown in containers coated with Cu in various symmetrical (Side, Bottom, Side + Bottom) and asymmetrical (half side + half bottom) patterns. After six weeks, roots of the cuttings were extracted from different container depths (Top, Middle, and Bottom) and portions (non-coated, Cu-coated), and analyzed. The root systems reacted to all coating patterns by increasing length, biomass, volume, and average diameters, but magnitude of increase was further affected by depth. In particular, root growth was unaffected at the Top of the container, and length was the highest at the Bottom depth. The Middle depth had a significant increment in both biomass and volume. Also, the root population increased in diameter as a possible response to Cu exposure. Interestingly, in the asymmetrically coated containers this depth response in the non-coated portions was of higher magnitude than in the Cu-coated portions. [ABSTRACT FROM AUTHOR]

We revisited a Pinus ponderosa planting 32 years after it was established with one-year-old seedlings grown in copper-treated containers that modified their root systems. This technique was intended to promote more root egress after outplanting from the entire length of the root plug with a goal of providing greater stem stability. After excavating and digitizing the root systems of five treated and five non-treated plants, we observed that regardless of treatment, all trees initiated more roots and accumulated more root volume in apparent response to mechanical stresses invoked by wind and slope, with more roots occurring windward and downslope. Few differences were noted between treatments for root length and volume for either the cage or the entire root system. Trees treated with copper were taller (8%) with stouter taproots (less taper) and less root volume in the lower soil profile than control trees. Although the copper treatment may have induced short-term changes to root system architecture, the long-term, plastic response of this species to mechanical stresses, and the time duration involved, was more critical to the observed expression of traits. [ABSTRACT FROM AUTHOR]

The rhizosphere is a nexus for plant–microbe interactions and, as a host-structured environment, a location of high activity for distinct microbes and plant species. Although our insights into this habitat have exploded in recent years, we are still limited in our ability to answer key questions about the specificity of these root-microbial relationships. In particular, it can be difficult to confirm or reject microbiome heritability in many plant systems and to pinpoint which microbial taxa are key to plant functioning. Like other host-structured environments, the rhizosphere is structurally, chemically, and biologically complex, driven largely by differences in root anatomy, location, and function. In this Correspondence, we describe a review of 377 "rhizosphere microbiome" research papers and demonstrate how matching a sampling method to the biological question can advance our understanding of host-microbe interactions in a functionally heterogeneous environment. We found that the vast majority of studies (92%) pool all roots from a root system during sampling, ignoring variation in microbial composition between roots of different function and limiting insight into key root-microbial relationships. Furthermore, approaches for removing root-associated microbes are highly variable and non-standard, complicating multi-study analyses. Our understanding of the strength and nature of host-microbe relationships in heterogenous host-microbiome environments can be clarified by targeting sampling to locations of high interaction. While the high complexity of the rhizosphere creates logistical challenges, we suggest that unambiguous language and refined approaches will improve our ability to match methods to research questions and advance our understanding of the specificity of plant-microbial interactions. [ABSTRACT FROM AUTHOR]

Root traits have an important impact on plant growth, which reflects the adaptation of plants to nutrients. This paper describes the focus and progress of root traits research and provides references for future research. Based on the Web of Science online database, articles related to root traits from 2000–2021 were evaluated using bibliometric methods. The results showed that the study of root traits has been growing steadily in the last two decades. Wang Yan is the author with the highest number of published papers, the most citations and the highest H-index. The top three published countries are the USA, China and India. The top three institutions are the University of Western Australia, China Agricultural University and Nanjing Agricultural University. Plant and Soil, Frontiers in Plant Science and PLoS One have the highest number of published articles. In terms of co-occurrence of keyword analysis, growth, soil and plant diversity are highly correlated with root traits. It was found that cooperation between authors, institutions and countries are not close enough and that z global network of cooperation has not yet been formed. Therefore, worldwide cooperation should be strengthened to promote resource sharing and the openness of relevant mechanisms. [ABSTRACT FROM AUTHOR]

Intercropping is especially relevant for low-income farmers when crop production is developed in soils under the new scenario produced by climatic change, mainly water shortage and low availability of nutrients especially P. An example of this would happen in volcanic soils of Southern Chile with high P fixing capacity and where most cereals are cropped. The aim of this study was to compare the benefits obtained on soil biochemical properties and on wheat (Triticum aestivum L.) growth when sowed under monoculture or intercropped with non-mycorrhizal plants such as quinoa (Chenopodium quinoa Willd.), buckwheat (Fagopyrum esculentum Moench), canola (Brassica napus L.) and white lupin (Lupinus albus L.) Wheat plants parameters such as shoot growth and morphological root traits together with some soil biological and chemical characteristics were measured after 30 and 44 d of plant growing in pots under controlled conditions. Results showed nonsignificant differences on growth parameters (i.e., height and shoot/root biomass) and P acquisition between monocrop and intercropped wheat. Conversely, wheat root morphological traits namely total length, root area, and forks were greatly reduced (around 50%) regardless of plant species. Intercropping tended to increase P availability and significantly reduced rhizosphere soil pH, with the lowest levels observed for wheat-canola combination (from 7.5 to 5.6). Intercropping produced a slight reduction in mycorrhizal colonization but increased over 100% viable spores' number and exerted a variable effect on the microbial C-biomass, with greater values observed in wheat-canola combination (1.49 mg g-1). These results encourage us to deepen the use of some new plant combinations in family farming carried out in volcanic soils. [ABSTRACT FROM AUTHOR]

Abstract Background Potato (Solanum tuberosum L.), the world’s third most important crop, is frequently thought to be sensitive to moderately sensitive to drought, and yield has fallen considerably over consecutive stress periods. Drought produces a wide range of responses in potato, from physiological alterations to variations in growth rates and yield. Knowledge about these responses is essential for getting a full understanding of drought-tolerance mechanism in potato plants which will help in the identification of drought-tolerant cultivars. Results A set of 21 commercial potato cultivars representing the genetic diversity in the Middle East countries market were screened for drought tolerance by measuring morpho-physiological traits and tuber production under in vitro and field trials. Cultivars were exposed to drought stress ranging from no drought to 0.1, 0.2 and 0.3 mol L−1 sorbitol in in vitro-based screening and 60, 40 and 20% soil moisture content in field-based screening. Drought stress adversely affected plant growth, yield and cultivars differed for their responses. Shoots and roots fresh weights, root length, surface area of root, no. of roots, no. of leaves, leaf area, plant water content %, K+ content, under in vitro drought treatments and shoots fresh and dry weights, no. of tubers and tuber yield under field drought treatments were examined and all decreased due to drought. The stress tolerance index decreased with increasing drought in examined cultivars; nevertheless, it revealed a degree of tolerance in some of them. Grouping cultivars by cluster analysis for response to drought resulted in: (i) a tolerant group of five cultivars, (ii) a moderately tolerant group of 11 cultivars, and (iii) a sensitive group of five cultivars. Furthermore, stress-related genes, i.e., DRO, ERECTA, ERF, DREB and StMYB were up-regulated in the five cultivars of the tolerant group. Likewise, the stomatal conductance and transpiration explained high correlation with the tuber yield in this group of cultivars. Conclusion The diversity in germplasm indicated that potato cultivars can be developed for production under certain degrees of drought. Some cultivars are good candidates to be included in drought-tolerant breeding programs and recommended for cultivation in drought-stricken regions. Graphical Abstract

Abstract Background The incorporation of root traits into elite germplasm is typically a slow process. Thus, innovative approaches are required to accelerate research and pre-breeding programs targeting root traits to improve yield stability in different environments and soil types. Marker-assisted selection (MAS) can help to speed up the process by selecting key genes or quantitative trait loci (QTL) associated with root traits. However, this approach is limited due to the complex genetic control of root traits and the limited number of well-characterised large effect QTL. Coupling MAS with phenotyping could increase the reliability of selection. Here we present a useful framework to rapidly modify root traits in elite germplasm. In this wheat exemplar, a single plant selection (SPS) approach combined three main elements: phenotypic selection (in this case for seminal root angle); MAS using KASP markers (targeting a root biomass QTL); and speed breeding to accelerate each cycle. Results To develop a SPS approach that integrates non-destructive screening for seminal root angle and root biomass, two initial experiments were conducted. Firstly, we demonstrated that transplanting wheat seedlings from clear pots (for seminal root angle assessment) into sand pots (for root biomass assessment) did not impact the ability to differentiate genotypes with high and low root biomass. Secondly, we demonstrated that visual scores for root biomass were correlated with root dry weight (r = 0.72), indicating that single plants could be evaluated for root biomass in a non-destructive manner. To highlight the potential of the approach, we applied SPS in a backcrossing program which integrated MAS and speed breeding for the purpose of rapidly modifying the root system of elite bread wheat line Borlaug100. Bi-directional selection for root angle in segregating generations successfully shifted the mean root angle by 30° in the subsequent generation (P ≤ 0.05). Within 18 months, BC2F4:F5 introgression lines were developed that displayed a full range of root configurations, while retaining similar above-ground traits to the recurrent parent. Notably, the seminal root angle displayed by introgression lines varied more than 30° compared to the recurrent parent, resulting in lines with both narrow and wide root angles, and high and low root biomass phenotypes. Conclusion The SPS approach enables researchers and plant breeders to rapidly manipulate root traits of future crop varieties, which could help improve productivity in the face of increasing environmental fluctuations. The newly developed elite wheat lines with modified root traits provide valuable materials to study the value of different root systems to support yield in different environments and soil types.

Plants can affect N 2 O emissions by enhancing nitrogen (N) uptake and other below-ground interactions. However, the specific effect of the root systems of different plant species on the production and accumulation of N 2 O within the soil profile remain largely unknown. The aim of this study was to investigate how plant species from different functional groups, their productivity and root traits affect N 2 O emissions and N 2 O concentrations within the soil profile in a fertilised grassland. We conducted a field experiment with two grasses (Phleum pratense , Lolium perenne), two legumes (Trifolium repens , Trifolium pratense), two forbs (Cichorium intybus , Plantago lanceolata), and the six-species mixture in a fertilised grassland. The effects of these plant communities on N-cycling processes were then assessed through the measurement of above- and below-ground plant traits, plant productivity, soil nutrient availability, N 2 O emissions and its distribution in the soil profile. We found that C. intybus and P. pratense had the lowest N 2 O emissions from the soil, which was mainly related to higher root biomass. The six-species mixture also showed lower N 2 O emissions compared to L. perenne monoculture which was explained by complementary effects between the different plant species. We did not find a relationship between N 2 O emission and its concentration in the soil profile. Higher specific root length and root length density coincided with higher N 2 O concentrations at 10–20 and 20–30 cm soil depths. Since these two traits have been previously linked to reductions in N 2 O emissions emitted from the soil, our results show that the relationships between root traits and N 2 O emissions may not be reflected down in the soil profile. Overall, this study underscores the often-neglected importance of root traits for N-cycling and emphasises the need to better understand how root traits modify N 2 O consumption within the soil profile to design more sustainable grasslands. • C. intybus and P. pratense decreased N 2 O emissions due to higher root biomass. • Mixture lower N 2 O emissions compared to L. perenne due to complementary effects. • There is no relationship between N 2 O emission and its concentration in the soil profile. • Higher root traits coincided with higher N 2 O concentrations in the soil profile. [ABSTRACT FROM AUTHOR]

• Natural grasslands improve soil infiltration capacity in both plant and bare patches. • Patchy mosaic patterns make infiltration heterogeneity and redistribute water on slope scale. • Plant with tap root systems produce more effective macropores as preferential flow paths. • Fine roots have a significantly negative effect on the soil infiltration capacity. Soil infiltration capacity is an important factor affecting soil moisture, and is of great significance to plant growth and groundwater recharge in arid and semiarid areas. Patchiness of grasslands widely exist and have a crucial effect on hydrological processes in water-limited regions. This study investigated soil infiltrability under natural grasslands with patchy mosaic patterns based on a series of in-situ tests. Two dominated natural restoration vegetation communities (Bothriochloa ischaemum (B. ischaemum) with fibrous root systems and Artemisia gmelinii (A. gmelinii) with tap root systems) and abandoned land (as control) were selected in the loess hilly and gully region of the Loess Plateau, China. The results showed that natural restoration grasslands significantly improved soil infiltrability in both plant and bare patches, and the emergence of patchy mosaic patterns can result in infiltration heterogeneity to redistribute water on a hillslope scale. Compared to B. ischaemum , A. gmelinii are more likely to facilitate the formation of preferential flow, contributing to the increased soil infiltration rates. The initial, steady and average infiltration rates (IIR , SIR , and AIR , respectively) and soil infiltration capacity index (SIC) were all negatively correlated with both root length density (RLD) and root surface area density (RSAD) of fine roots (diameter < 2 mm) but positively correlated with those of coarse roots (diameter ≥ 2 mm). The main factors influencing the infiltration capacity were the mean weight diameter in the 10−20 cm layer and the RSAD of the fine roots in the 0−20 cm layer, which can explain 98.6 %, 81.7 %, 63.9 %, and 91.3 % of the total variance of IIR , SIR , AIR , and SIC , respectively. This work highlights the important roles of patchy mosaic patterns in affecting soil water redistribution and the stabilization of ecological systems, providing a scientific basis for vegetation selection in the process of vegetation restoration in water-limited regions. [ABSTRACT FROM AUTHOR]

Soil erodibility by wind is not only affected by the basic physical and chemical properties of the soil but also the functional traits of plant roots. However, the roles played by the morphological and architectural traits of plant roots on wind-based soil erodibility in the Bashang region of China are still unclear. Therefore, two typical tree shelterbelts and two shrub shelterbelts in the Bashang region were selected to assess and determine how the root traits affected soil erodibility, especially characteristics such as dry aggregate, soil organic matter, and shearing resistance. The results showed that the soil dry aggregates of the two shrubs (Lycium barbarum and Caragana korshinskii) had higher geometric mean diameters (0.40 ± 0.03 mm) and mean weight diameters (0.82 ± 0.08 mm) but a lower erodible fraction (81.81% ± 1.62%) compared to the two trees (Populus simonii and Ulmus pumila). The mean weight diameter (MWDd) and geometric mean diameter (GMDd) of dry soil aggregates were negatively correlated with the soil erodible fraction (EFd), but these parameters were positively correlated with shearing resistances. The specific root length (SRL) and surface area (SSA) of plant roots were positively correlated with the GMDd of the soils, though these two parameters negatively correlated with the soil erodible fraction. The root branching intensity (BI) was negatively correlated with the MWDd and GMDd of dry soil aggregates. The total carbon or nitrogen of the soil displayed significantly positive and negative correlations to the geometric mean diameters and erodible fractions of the soils, respectively. The findings showed that plant roots with higher SRLs, as well as lower root diameters and BIs, played positive key roles in soil stability. The same applied to soils with higher nitrogen, carbon, and water content. The results from this study suggest that L. barbarum is superior to the other three species based on root traits and wind erosion resistance. These findings provide critical information for selecting plants for the sustainable management of windbreak and sand fixation.

Rapid apple decline is a phenomenon characterized by a weakening of young apple trees in high density orchards, often followed by their quick collapse. The nature of this phenomenon remains unclear. In this work, we investigated the root system architecture (RSA) of declining and non-declining apple trees in two orchards in New York State. High-density orchard A consisted of 4-year-old ‘Honeycrisp’ on ‘Malling 9 Nic29’, and conventional orchard B consisted of 8-year-old ‘Fuji’ on ‘Budagovsky 9’. In both orchards, a negative correlation (−0.4–−0.6) was observed between RSA traits and decline symptoms, suggesting that declining trees have weaker root systems. Scion trunk diameter at the graft union, total root length, and the length of fine and coarse roots were significantly (p < 0.05) reduced in declining trees in both orchards. Additionally, internal trunk necrosis at, above, and below the graft union was observed in declining trees in orchard A but not in orchard B. Finally, latent viruses were not associated with decline, as their occurrence was documented in declining and non-declining trees in orchard A, but not in orchard B. Together, these results showed weakened root systems of declining trees, suggesting that these trees may experience deficiencies in water and nutrient uptake, although distinct RSA and trunk health traits between the two orchards were noticeable.

Grafting a scion onto a rootstock results in physical and physiological changes in plant growth and development, which can affect tree vigor, productivity, and tolerance to stress and disease. Huanglongbing (HLB) is one of the most destructive citrus diseases and has become endemic in Florida since its introduction in 2005. It is associated with the phloem-limited bacteria Candidatus Liberibacter asiaticus (CLas), which cause severe metabolic disruptions in affected plants. Although most scion cultivars are highly susceptible, some rootstock cultivars are tolerant and allow the grafted tree to cope better with the disease. The objectives of this study were to identify rootstock traits that can be used to assess cultivars under controlled greenhouse conditions in advance of longer-term field trials. We used 10 commercially important rootstocks with different genetic backgrounds and known field performance in graft combination with ‘Valencia’ sweet orange scion. Trees were graft-inoculated with CLas and compared against mock-inoculated trees. Tree health and CLas populations were assessed regularly, and root growth was monitored using a minirhizotron imaging system. Plants were excavated and destructively sampled 21 months after inoculation to assess biomass distributions and other CLas-induced effects. We found significant differences between healthy and infected trees for most variables measured, regardless of the rootstock. In contrast to leaf CLas titers, root titers were significantly influenced by the rootstock, and highest levels were measured for ‘Ridge’ sweet orange and sour orange. Root growth and root biomasses were reduced upon infection but differences among rootstocks did not always agree with reported field performances. Despite severe biomass reductions plants maintained their relative distribution of biomass among different components of the root system, and no dead roots were observed. Root respiration was reduced by CLas infection and was overall higher in tolerant cultivars suggesting its potential as a physiological marker. This study improves our knowledge about the strengths and weaknesses of assessing rootstock traits of grafted trees in a controlled greenhouse setting. Results from the study suggest that in addition to HLB tolerance, other rootstock traits will ultimately have major contributions to field survival and productivity of the grafted trees in an HLB endemic production environment.

Vegetable grafting is increasingly recognized as an effective and sustainable plant production alternative. Grafted plants usually show increased uptake of water and minerals compared with self-rooted plants, mostly thought a consequence of the vigorous rootstocks selected. However, while studies frequently addressed the effects of rootstocks on the performance of scions, knowledge on the influences of scions on biomass allocation, morphology, and metabolic activity of roots is rare. In particular, the plasticity of root traits affecting resource acquisition and its efficiency remains poorly understood. Two different rootstock species, Cucurbita maxima x Cucurbita moschata and Lagenaria siceraria, were grafted in combination with melon (Cucumis melo) and watermelon (Citrullus lanatus). Self-grafted rootstocks were used as control. Plant biomass and root traits were determined after destructive harvesting 30 and/or 60 days after grafting. Traits included biomass allocation, leaf and root morphology, potential activities of four extracellular enzymes on root tips and basal root segments, and root respiration. Successfully grafted scions increase the ratio of root to whole plant dry matter (RMF), and increased ratios of root length to whole plant dry matter (RLR) and to plant leaf area (RL : LA). In contrast, morphological root traits such as diameter, tissue density, and specific root length remain surprisingly stable, and thus scion-induced changes of those traits may only play a minor role for the beneficial effects of grafting in Cucurbitaceae. Incompatibility in melon/L. siceraria grafts, however, was likely responsible for the reduced root growth in combination with clear changes in root morphological traits. Reduced root respiration rates seem to be the effects of a non-compatible rootstock--scion combination rather than an active, C-efficiency increasing acclimation. In contrast, heterografts with melon and watermelon frequently resulted in root-stock-specific, often enhanced potential enzymatic activities of acid phosphatase, b-glucosidase, leucine-amino-peptidase, and N-acetylglucosaminidase both at root tips and basal parts of lateral roots--presenting a potential and complementary mechanism of grafted plants to enhance nutrient foraging. The studied melon and watermelon scions may thus increase the nutrient foraging capacity of grafted plants by fostering the relative allocation of C to the root system, and enhancing the extracellular enzymatic activities governed by roots or their rhizobiome. [ABSTRACT FROM AUTHOR]

The adoption of a holistic approach to root research, that is, one that takes into account all categories of root traits, from anatomy to root morphology, physiology and architecture, as well as interactions with the rhizosphere microbiota, was emphasised as a crucial step in facing the challenges posed by global change. Keywords: Ambassador Program; ISRR11; rhizosphere; root phenotyping; root traits; Rooting2021; roots EN Ambassador Program ISRR11 rhizosphere root phenotyping root traits Rooting2021 roots 2149 2154 6 08/22/22 20220915 NES 220915 Emerging frontiers: root and rhizosphere research in the context of global environmental chan... Natural ecosystems and agricultural production have been threatened by multifaceted global environmental changes. ISRR11, rhizosphere, root traits, Ambassador Program, root phenotyping, Rooting2021, roots Root biology never sleeps: 11th Symposium of the International Society of Root Research (ISRR11) and the 9th International Symposium on Root Development (Rooting2021), 24-28 May 2021. [Extracted from the article]

To fully explore the effects of N on enhancing photosynthesis, grain quality, and yield of wheat (Ningmai 13), experiments with four nitrogen levels 0 (N0), 120 (N1), 180 (N2), and 240 (N3) kg N ha−1 and four ratios of basal to topdressing R0 (0:0), R1 (7:3), R2 (6:4), and R3 (5:5) were conducted. The basal N was applied to soil before sowing and the topdressing N was applied at jointing stage. The effect of N topdressing ratio on improving leaf area of photosynthetic efficiency was insignificant under the same N level. The effect of N fertilization level on increasing chlorophyll content was more significant than that of N topdressing ratio. Within the same N level, the canopy photosynthetically active radiation in R2 was higher than that in R1 and R3, and increasing N by 60 kg ha−1 significantly enhanced canopy photosynthetically active radiation. The effect of N topdressing ratio on photosynthetic rate, stomatal conductance, and transpiration rate were consistently R2 > R3 > R1; compared to N1, N3 could significantly increase photosynthetic rate. Increasing 120 kg N ha−1 significantly enhanced grain protein content, wet gluten, and sedimentation value, while the effect of N topdressing ratio was insignificant. Increasing N dose from 120 kg ha−1 to 180 kg ha−1 significantly enhanced yield, and the yields and harvest indexes in 2019, 2020, and 2021 were consistently R2 > R3 > R1. The findings suggested that the effect of increasing N dose (60 kg ha−1) was more considerable than that of N topdressing ratio, N3R2 (within the range of N application in this experiment) was more conducive to improving canopy photosynthesis, yield, and harvest index, and R3 was more conducive to increasing grain protein content, wet gluten, and sedimentation value. [ABSTRACT FROM AUTHOR]

Climate change mainly alters the plant phyllosphere and rhizosphere resource allocations. Compared with shoot parameters, there is less information about how roots, especially root system architecture (RSA) and their interactions with others, may respond to elevated temperature changes. These responses could greatly influence different species acquisition of resources and their competition with their neighbours. The main aim of this experiment was to evaluate the effects of ambient temperature (T1) and elevated temperature (+4°C) (T2) in Open-top chamber (OTC) on root traits and microbial interaction changes in cotton (Gossypium hirsutum L.). A pot experiment was conducted at the Department of Crop Physiology, Tamil Nadu Agricultural University, Coimbatore, during 2020-2021 to investigate the root traits and microbial interactions. Cotton varieties, namely KC3, SVPR6, TSH325, TSH357 and TSH375 were screened at the seedling level for cellular thermo tolerance and further, at the root level, these selected varieties were studied against the elevated temperature condition for 10 days in OTC during the stage of flowering to boll development period along with control temperature condition. Root interactions' intensity and direction may fluctuate as a result of variations in RSA responses between species. Negative root interactions could become more intense under high temperature circumstances and species with bigger roots and greater early root growth had stronger competitive advantages. The present findings showed that elevated temperatures promote various microbial growths in the geothermal regions, enhancing the root angle and root length of cotton species. Among the genotypes, KC3 and SVPR6 performed better under elevated temperatures. [ABSTRACT FROM AUTHOR]

Background and Aims Plant performance is enhanced by balancing above- and below-ground resource uptake through the intraspecific adjustment of leaf and root traits. It is assumed that these organ adjustments are at least partly coordinated, so that analogous leaf and root traits broadly covary. Understanding the extent of such intraspecific leaf–root trait covariation would strongly contribute to our understanding of how plants match above- and below-ground resource use strategies as their environment changes, but comprehensive studies are lacking. Methods We measured analogous leaf and root traits from 11 species, as well as climate, soil and vegetation properties along a 1000-m elevation gradient in the French Alps. We determined how traits varied along the gradient, to what extent this variation was determined by the way different traits respond to environmental cues acting at different spatial scales (i.e. within and between elevations), and whether trait pairs covaried within species. Key Results Leaf and root trait patterns strongly diverged: across the 11 species along the gradient, intraspecific leaf trait patterns were largely consistent, whereas root trait patterns were highly idiosyncratic. We also observed that, when compared with leaves, intraspecific variation was greater in root traits, due to the strong effects of the local environment (i.e. at the same elevation), while landscape-level effects (i.e. at different elevations) were minor. Overall, intraspecific trait correlations between analogous leaf and root traits were nearly absent. Conclusions Our study suggests that environmental gradients at the landscape level, as well as local heterogeneity in soil properties, are the drivers of a strong decoupling between analogous leaf and root traits within species. This decoupling of plant resource acquisition strategies highlights how plants can exhibit diverse whole-plant acclimation strategies to modify above- and below-ground resource uptake, improving their resilience to environmental change. [ABSTRACT FROM AUTHOR]

Studies investigating the effect of aboveground herbivory on plants often use clipping to simulate the effects of herbivores, for practical reasons. However, herbivore movements and transfer of oral secretions during herbivory may cause a different response in plant physiology and morphology compared to clipping. While studies have compared effects of real herbivory vs. clipping on biomass production, plant physiology, and shoot morphology, no study has compared such effects on root morphology. Therefore, we investigated the effect of herbivory by grasshoppers, herbivory simulated by clipping, and no herbivory on root morphological traits of ten grassland plant species. Root morphological traits were differently affected by the two herbivory treatments. Grasshopper herbivory significantly changed root morphology toward thinner roots with increased specific root length and root area, and decreased root tissue density compared to untreated control plants. Clipping had mostly similar, but weaker effects on root morphology than grasshopper herbivory. On the species level, grasshopper herbivory led to strongest changes in root morphology in almost all cases. In contrast, depending on the species, clipping resulted in varying root morphological trait values similar to grasshopper-damaged plants, or in some cases, more closely aligned with control plants. Though clipping was partly able to mimic the effects of herbivory by grasshoppers, results also indicate that, depending on the species, grasshopper herbivory had different but mostly stronger effects. We, therefore, recommend that future studies apply herbivory with real herbivores to better reflect natural responses in plants and related processes that root morphological traits mediate. [ABSTRACT FROM AUTHOR]

Invasive plants, particularly woody ones, cause significant ecological and economic losses. However, many factors that underlie the plant invasion process are not well known. There is evidence that some plant traits can be indicators of the degree of invasiveness in woody plants. However, root characters, such as the quantity and diversity of secondary metabolites, have been poorly studied. Flavonoids are widely distributed metabolites in plants and are involved in important biological interactions that take place in the soil. They have been related to increases in defense against pathogens, communication with mutualistic organisms, particularly with arbuscular mycorrhizal fungi and nitrogen fixing bacteria, and with allelopathic effects on neighboring plants. If flavonoids are costly to produce and/or implicated in novel interactions established by successful woody invaders, we could expect invasive species to produce unique flavonoids compared to non-invasive ones. We assessed the literature to evaluate whether the production of flavonoids in roots vary among woody invasive and non-invasive species. Specifically, we tested the effect of invasive status on flavonoid richness, composition, and abundance in roots. We also assessed for indicator flavonoids whose presence and abundance reflect the invasive status. Invasive woody species had higher flavonoid richness in roots than non-invasive, particularly within the chemical subgroups flavonols and flavones. Our results suggest that root flavonoids play an important role in determining the invasion success of woody plants. [ABSTRACT FROM AUTHOR]

Frost is an abiotic stress factor that threatens plant development and crop productivity not only in cold regions but also in temperate zones. Roots play an important role in plant growth during frost stress. Therefore, variation in root characteristics could be studied to improve frost tolerance in winter faba bean. The present study aimed to identify the genomic regions that control frost tolerance in a winter faba bean population by focusing on root-related traits. A set of 185 genotypes were tested for frost tolerance under artificial frost growth conditions at -16°C, -18°C, and -19°C in a growth chamber. Frost stress reduced the root-related parameters in all genotypes, with a wide variation among genotypes. A genome-wide association study identified nine novel single-nucleotide polymorphisms that are associated with the root-related traits. The most frost-tolerant genotypes were identified; two genotypes, S&lowbar;028 and S&lowbar;220, exhibited remarkable performance under frost stress. Moreover, they harbored all four of the alleles favorable for frost tolerance. Remarkably, two markers showed genetic pleiotropic effects with positive allele effects on root fresh matter and root dry matter. Thus, both genotypes can be implemented in a breeding program to provide the alleles for healthier roots under frost conditions to develop more frost-tolerant varieties, and the two markers can be used to screen large collections to select for frost tolerance. These results may provide novel insights for improving frost tolerance in faba beans and in other legume crops. [ABSTRACT FROM AUTHOR]

Summary: The extent of intraspecific variation in trait–environment relationships is an open question with limited empirical support in crops. In organic agriculture, with high environmental heterogeneity, this knowledge could guide breeding programs to optimize crop attributes. We propose a three‐dimensional framework involving crop performance, crop traits, and environmental axes to uncover the multidimensionality of trait–environment relationships within a crop.We modeled instantaneous photosynthesis (Asat) and water‐use efficiency (WUE) as functions of four phenotypic traits, three soil variables, five carrot (Daucus carota) varieties, and their interactions in a national participatory plant breeding program involving a suite of farms across Canada. We used these interactions to describe the resulting 12 trait–environment relationships across varieties.We found one significant trait–environment relationship for Asat (taproot tissue density–soil phosphorus), which was consistent across varieties. For WUE, we found that three relationships (petiole diameter–soil nitrogen, petiole diameter–soil phosphorus, and leaf area–soil phosphorus) varied significantly across varieties. As a result, WUE was maximized by different combinations of trait values and soil conditions depending on the variety.Our three‐dimensional framework supports the identification of functional traits behind the differential responses of crop varieties to environmental variation and thus guides breeding programs to optimize crop attributes from an eco‐evolutionary perspective. [ABSTRACT FROM AUTHOR]

Purpose: Roots bridge aboveground and belowground systems, and play a pivotal role in structuring root-associated organisms via influencing food resources and habitat conditions. Most studies focused on the relationships between plant identity and root-associated organisms, however, little is known about how root traits affect nematode communities within the rhizosphere. Methods: We investigated the relationships between root traits of four plant species and nematode abundance, community structure and trophic complexity in an ex-arable field. Results: While the relative abundance of herbivores was negatively associated with specific root length (SRL), specific root area (SRA), root length density (RLD) and root C: N ratio, free-living nematodes were positively affected by these traits, implying a multifaceted effect of root traits on root-associated organisms. Importantly, we found that finer root systems promoted the complexity of rhizosphere nematode community, by increasing the relative abundance of high trophic-level nematodes (i.e., omnivores and predators) and enhancing nematode diversity. Conclusions: Our findings suggest that root traits could comprehensively shape soil community structure and interactions, and provide new insights into soil biodiversity conservation and functional maintenance. [ABSTRACT FROM AUTHOR]

Plant species show a broad spectrum of plasticity in their covarying root traits in response to soil water limitation ranging from no change to shifts towards traits that enhance water and nutrient acquisition. Knowledge of root trait correlations and associated trait plasticity under drought is crucial to sustaining grassland production, including rangelands and pastures, under future, drier climates.Here, we investigated below‐ground responses to drought in four C3 and three C4 grasses and whether these explain above‐ground responses during extreme cool‐season drought and post‐drought recovery in a well‐replicated field experiment. We hypothesised that (a) C3 and C4 functional groups differ in their below‐ground trait responses to drought: C3 species shift their traits in line with a drought avoidance strategy and C4 species shift towards drought tolerance strategies; (b) post‐drought recovery is associated with below‐ground carbon reserves in both functional groups.Root traits in the C3 functional group differed from C4 by having higher values for specific root length, nitrogen and soluble sugar concentrations, while C4 root traits were associated with higher mean diameter, tissue density and starch concentrations. Drought‐induced plasticity in root traits in both functional groups was evidenced by increased values for specific root length, soluble sugars and nitrogen concentrations, and reduced values for tissue density, which we interpret as a drought avoidance strategy. Increasing root soluble sugars in C3 and C4 grasses and lower root tissue density in C4 species under drought were associated with greater above‐ground productivity. Above‐ground biomass recovery post‐drought was predicted by root and crown soluble sugar concentrations and root longevity across both plant functional groups.These findings highlight the importance of understanding links between root trait plasticity and plant productivity during and following drought for predicting plant species' responses to changes in a future climate. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]