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Seagrass seed‐based restoration has been developed in several places worldwide, but disturbance at the vulnerable initial stages of seedling recruitment has proved to be a major bottleneck to successful restoration. A detailed investigation of seagrass seedling survival and growth at the earliest stages of seedling development is an important contribution to developing techniques to improve seedling establishment and survival. Here, we investigated the early seedling development of Posidonia australis and P. sinuosa as well as quantifying the variation in seedling survival and development under different seed‐based restoration methods. Early seedling development was documented in indoor aquaria during the first month after fruit dehiscence. In the second ex situ experiment, we determined the effects of three different restoration methods (surface sowing, seedling planting, and planting inside a hessian bag) on seedling survival and development over the first 2 months of life. In the first experiment, a primary root with the first root hairs developed after 7 days. After 1 month, roots were 20–60 mm in length, firmly establishing the seedling into the sediment. Compared to surface sowing, seedling planting and hessian bag restoration treatments did not significantly affect survival for P. australis but increased seedling mortality in P. sinuosa, although growth was greater (shoot and root lengths were approximately 50 and 40% longer, respectively). These aquarium‐scale experiments suggest that planting methods would enhance seedling establishment at larger scales in some species, promoting restoration of damaged seagrass habitats. [ABSTRACT FROM AUTHOR]

Background and aims: Rhizosheath, a mixture of soil and mucilage that remains attached to the root system after being removed from the soil and shaken, plays a prominent role in the resistance of plants to drought stress. This study aims to investigate the effect of silicon (Si) on rhizosheath formation and mitigate the effects of drought stress in wheat. It was hypothesized that Si positively enhances root hair formation and rhizosheath formation under soil drying conditions, improving plant access to water under soil drying conditions. Methods: Wheat seeds were grown under different levels of Si (control, 150 and 300 mg kg−1 monosilicic acid, and 150 and 300 mg kg−1 nano-silicon) and irrigation (0.4 field capacity (FC) and 0.8 FC) under greenhouse conditions. Results: Under drought stress, the application of Si significantly increased root hair length, density, rhizosheath formation, and transpiration rate. Applying Si increased the length of root hairs by 45–107% and their density by 25–78%. Under drought stress, application of 150 and 300 mg kg−1 of monosilicic acid and nano-silicon increased rhizosheath formation by 40.3, 48.2, 16.8, and 17.5%, and transpiration rate by 17.8, 36.4, 11.4, and 29.1%, respectively. Si also increased superoxide dismutase and catalase activity, while decreasing malondialdehyde and hydrogen peroxide content. Conclusion: Silicon application in drought-stricken wheat improved water uptake, leading to improved plant water relations and other morpho-physiological and biochemical responses. This was achieved by modifying root system traits, particularly increasing root hair length and density, which facilitated the formation of rhizosheath. [ABSTRACT FROM AUTHOR]

Background And Aims: Root hair emergence is affected by heterogeneities in water availability in the growth medium. Root hairs preferentially emerge into air, whereas their emergence into water is inhibited. Yet, these results were based either on destructive methods or on roots grown on an agar-air interface. Additionally, there is a lack of knowledge about the spatial distribution of root hairs as hairs elongate radially across the rhizosphere. Therefore, root hair growth in soils remains largely unexplored. Methods: Maize (Zea Mays L.) plants were grown in microcosms which were scanned with a synchrotron-based X-ray μ CT. The distribution of root hairs along the root epidermis and radially across the rhizosphere (i.e. as function of distance from the root epidermis) was analysed using spatial point pattern analysis. Results: While hairs emerged randomly in air-filled pores, their emergence was inhibited where the root was in contact with the soil matrix. As hairs elongated radially into the soil, they were preferentially located in the close proximity of soil particles. In maize, we rarely observed root hairs penetrating into soil aggregates. Conclusion: We conclude that in maize, root hairs grow in air-filled pores at the root-soil interface, where the flow of nutrients and water is impeded. Across the rhizosphere, hairs establish contact to the soil by growing in the proximity to soil particles. The effect of hairs on uptake processes, plant anchorage and rhizosheath formation might be limited (in maize) as they hardly penetrate into soil aggregates. [ABSTRACT FROM AUTHOR]

AbstractUltrastructural changes and visual symptoms resulting from nutritional disorders involving boron, manganese, iron, zinc, copper, molybdenum, and nickel depend on the species of the plant, and are unknown in passion fruit plants (Passiflora edulis Sims). A hydroponic experiment evaluated the symptoms of nickel addition and micronutrient deficiency in passion fruit seedlings “BRS Gigante Amarelo” and determined the micronutrient contents in leaf and root tissue, root development, ultrastructural changes (leaf tissue deformations) and dry matter accumulation when visual symptoms were observed. Results showed that the order of manifestation of deficiencies was Fe > Mn > Zn > Cu > Mo > B. Nickel toxicity appeared 40 days after the experiment was started, presenting chlorosis in the new leaves followed by general yellowing and some white parts. Boron omission of resulted in deformations in the leaf limbus and loss of apical dominance, showing deformation of the growth points. Mn omission caused reduction of growth and generalized chlorosis of young leaves with a thick reticulum. Iron omission of resulted in internerval chlorosis with a fine lattice appearance. Omission of zinc and copper resulted in deformation and elongation of the leaves, reducing height and root development. Molybdenum omission caused chlorosis in the older leaves, which was observed to spread over time. Iron was the nutrient that most reflected symptoms of deficiency by the formation of root hairs. The findings of this research suggest that the knowledgement of plant micronutrients status permits an understanding of the physiological responses of passion fruit plants to crop fertilization. [ABSTRACT FROM AUTHOR]

Abstract Arabidopsis root is a classic model system in plant cell and molecular biology. The sensitivity of plant roots to local environmental perturbation challenges data reproducibility and incentivizes further optimization of imaging and phenotyping tools. Here we present RoPod, an easy-to-use toolkit for low-stress live time-lapse imaging of Arabidopsis roots. RoPod comprises a dedicated protocol for plant cultivation and a customizable 3D-printed vessel with integrated microscopy-grade glass that serves simultaneously as a growth and imaging chamber. RoPod reduces impact of sample handling, preserves live samples for prolonged imaging sessions, and facilitates application of treatments during image acquisition. We describe a protocol for RoPods fabrication and provide illustrative application pipelines for monitoring root hair growth and autophagic activity. Furthermore, we showcase how the use of RoPods advanced our understanding of plant autophagy, a major catabolic pathway and a key player in plant fitness. Specifically, we obtained fine time resolution for autophagy response to commonly used chemical modulators of the pathway and revealed previously overlooked cell type-specific changes in the autophagy response. These results will aid a deeper understanding of the physiological role of autophagy and provide valuable guidelines for choosing sampling time during end-point assays currently employed in plant autophagy research.

Root hairs have become an important model system for studying plant growth, and in particular how plants modulate their growth in response to cell-intrinsic and environmental stimuli. In this review, we discuss recent advances in our understanding of the molecular mechanisms underlying the growth of Arabidopsis root hairs in the interface between responses to environmental cues (e.g. nutrients such as nitrates and phosphate, and microorganisms) and hormonal stimuli (e.g. auxin). Growth of root hairs is under the control of several transcription factors that are also under strong regulation at different levels. We highlight recent new discoveries along these transcriptional pathways that might have the potential to increase our capacity to enhance nutrient uptake by the roots in the context of abiotic stresses. We use the text-mining capacities of the PlantConnectome database to generate an up-to-date view of root hairs growth within these complex biological contexts. [ABSTRACT FROM AUTHOR]

Pearl millet is a key food security grain crop in the world's drylands due to its tolerance to abiotic stresses. However, its yield remains low and is negatively impacted by climate change. Root phenes are potential targets to improve crop productivity and resilience to environmental stress. However, the sheer number of combinations resulting from interactions of multiple phenes is a challenge for empirical research. In silico approaches are a plausible alternative to assess the utility of different phene combinations in varying states over diverse environmental contexts. Here, we developed an implementation of the functional-structural plant/soil model – OpenSimRoot, for pearl millet in typical sub-Sahelian soil and environmental conditions. Root architectural, anatomical, and physiological parameters were measured using a popular pearl millet variety (Souna 3) and implemented in the model. The above-ground biomass and root length density predicted by the model were similar to data from field trials. The utility of different root phenes was then evaluated for improved phosphorus uptake and plant growth in P deficient soils. Doubled root hair length and density, shallower root angle (−15°) and doubled long lateral root density were found to improve plant growth by 76 ​%, 33 ​% and 33 ​% respectively under low P conditions. Moreover, these phenes showed synergism when combined in silico and led to optimal biomass production in low P supply conditions that resulted in a 75 ​% loss of biomass in the reference variety. Our study suggests that these phenotypes could be targeted to improve biomass production in pearl millet and consequently its yield in low-P availability conditions.

Drought is a major threat to food security worldwide. Recently, the root–soil interface has emerged as a major site of hydraulic resistance during water stress. Here, we review the impact of soil drying on whole-plant hydraulics and discuss mechanisms by which plants can adapt by modifying the properties of the rhizosphere either directly or through interactions with the soil microbiome. [ABSTRACT FROM AUTHOR]

Summary: The effect of root hairs on water uptake remains controversial. In particular, the key root hair and soil parameters that determine their importance have been elusive.We grew maize plants (Zea mays) in microcosms and scanned them using synchrotron‐based X‐ray computed microtomography. By means of image‐based modelling, we investigated the parameters determining the effectiveness of root hairs in root water uptake. We explicitly accounted for rhizosphere features (e.g. root–soil contact and pore structure) and took root hair shrinkage of dehydrated root hairs into consideration.Our model suggests that > 85% of the variance in root water uptake is explained by the hair‐induced increase in root–soil contact. In dry soil conditions, root hair shrinkage reduces the impact of hairs substantially.We conclude that the effectiveness of root hairs on root water uptake is determined by the hair‐induced increase in root–soil contact and root hair shrinkage. Although the latter clearly reduces the effect of hairs on water uptake, our model still indicated facilitation of water uptake by root hairs at soil matric potentials from −1 to −0.1 MPa. Our findings provide new avenues towards a mechanistic understanding of the role of root hairs on water uptake. See also the Commentary on this article by Boursiac & Bauget 240: 2173–2175. [ABSTRACT FROM AUTHOR]

Background Aims Methods Results Conclusions Boron (B) is an essential micronutrient for plants. Dicot plants respond to insufficient B supply by altering root architecture and root hair growth. How root systems of rather low‐B demanding monocot species such as maize (Zea mays L.) respond to B deficiency in terra has not been experimentally resolved, yet.The study aims to investigate root responses and their physiological consequences under B deficiency during the vegetative growth of maize.B73 wild‐type (WT) maize and its root hairless rth3 mutant were grown under varying B supply conditions in soil columns and in an automated root phenotyping facility. Biomass data, root system architecture traits, the mineral elemental composition and molecular B‐deficiency responses were quantified.Though having very low leaf B concentrations, no major growth deficit, apart from chlorotic stripes on leaves, was recorded on maize root and shoot development, with or without root hairs, on B‐deficient conditions. Although leaf B concentration of the rth3 mutant is significantly lower under B‐deficient and under B‐surplus conditions compared to the WT, the rth3 mutant neither developed a larger total root length, more fine roots nor displayed a higher expression of B uptake transporters as compensatory adaptations.Strikingly, maize plants did neither react with an inhibited root growth nor by a compensatory root foraging behaviour to severe B‐deficient in terra growth conditions. This is rather atypical for plants. The performance and altered leaf B concentrations of rth3 mutants may be biased by secondary effects, such as an overall reduced root growth. [ABSTRACT FROM AUTHOR]

This article is a Commentary on Duddek et al. (2023), 240: 2484–2497. [ABSTRACT FROM AUTHOR]

Summary: Plants impact the development of their rhizosphere microbial communities. It is yet unclear to what extent the root cap and specific root zones contribute to microbial community assembly.To test the roles of root caps and root hairs in the establishment of microbiomes along maize roots (Zea mays), we compared the composition of prokaryote (archaea and bacteria) and protist (Cercozoa and Endomyxa) microbiomes of intact or decapped primary roots of maize inbred line B73 with its isogenic root hairless (rth3) mutant. In addition, we tracked gene expression along the root axis to identify molecular control points for an active microbiome assembly by roots.Absence of root caps had stronger effects on microbiome composition than the absence of root hairs and affected microbial community composition also at older root zones and at higher trophic levels (protists). Specific bacterial and cercozoan taxa correlated with root genes involved in immune response.Our results indicate a central role of root caps in microbiome assembly with ripple‐on effects affecting higher trophic levels and microbiome composition on older root zones. [ABSTRACT FROM AUTHOR]

Sorghum is an essential crop for resilient and adaptive responses to climate change. The root systems of crop plants significantly contribute to the tolerance of abiotic stresses. There is little information on sorghum genotypes' root systems and plasticity to external P supply. In this paper, we investigated the variations in root systems, as well as the responses, trait relationships, and plasticity of two sorghum genotypes (Naga Red and Naga White), popularly grown in Ghana, to five external P concentrations ([P]ext): 0, 100, 200, 300, and 400 mg P kg−1 soil. Sorghum plants were grown in greenhouse pots and harvested for root trait measurements at the five‐leaf and growing point differentiation (GPD) developmental stages. The plants were responsive to [P]ext and formed rhizosheaths. The two genotypes showed similar characteristics for most of the traits measured but differed significantly in total and lateral root lengths in favor of the red genotype. For example, at the five‐leaf growth stage, the lateral root length of the red and white genotypes was 22.8 and 16.2 cm, respectively, but 124 and 88.9 cm, at the GPD stage. The responses and plasticity of the root system traits, including rhizosheath, to [P]ext were more prominent, positive, and linear at the five‐leaf stage than at the GPD growth stage. At the five‐leaf growth stage, total root length increased by about 2.5‐fold with increasing [P]ext compared to the unamended soil. At the GPD stage, however, total root length decreased by about 1.83‐fold as [P]ext increased compared to the unamended soil. Specific rhizosheath weight correlated with RHD, albeit weakly, and together explained up to 59% of the variation in tissue P. Root hair density was more responsive to P supply than root hair length and showed a similar total and lateral root length pattern. Most desirable responses to P occurred at a rate of 200–300 mg P kg−1 soil. It is concluded that sorghum would form rhizosheath, and [P]ext could be critical for the early vigorous growth of sorghum's responsive root and shoot traits. Beyond the early days of development, additional P application might be necessary to sustain the responses and plasticity observed during the early growth period, but this requires further investigation, potentially under field conditions. [ABSTRACT FROM AUTHOR]

Leguminous plants have established mutualistic endosymbiotic interactions with nitrogen-fixing rhizobia to secure nitrogen sources in root nodules. Before nodule formation, the development of early symbiotic structures is essential for rhizobia docking, internalization, targeted delivery, and intracellular accommodation. We recently reported that overexpression of stress-induced mitogen-activated protein kinase (SIMK) in alfalfa affects root hair, nodule, and shoot formation, raising the question of how SIMK modulates these processes. In particular, detailed subcellular spatial distribution, activation, and developmental relocation of SIMK during early stages of alfalfa nodulation remain unclear. Here, we characterized SIMK distribution in Ensifer meliloti -infected root hairs using live-cell imaging and immunolocalization, employing alfalfa stable transgenic lines with genetically manipulated SIMK abundance and kinase activity. In the SIMKK-RNAi line, showing down-regulation of SIMKK and SIMK , we found considerably decreased accumulation of phosphorylated SIMK around infection pockets and infection threads. However, this was strongly increased in the GFP-SIMK line, constitutively overexpressing green fluorescent protein (GFP)-tagged SIMK. Thus, genetically manipulated SIMK modulates root hair capacity to form infection pockets and infection threads. Advanced light-sheet fluorescence microscopy on intact plants allowed non-invasive imaging of spatiotemporal interactions between root hairs and symbiotic E. meliloti , while immunofluorescence detection confirmed that SIMK was activated in these locations. Our results shed new light on SIMK spatiotemporal participation in early interactions between alfalfa and E. meliloti , and its internalization into root hairs, showing that local accumulation of active SIMK modulates early nodulation in alfalfa. [ABSTRACT FROM AUTHOR]

Abstract Background Genome wide association (GWA) studies demonstrate linkages between genetic variants and traits of interest. Here, we tested associations between single nucleotide polymorphisms (SNPs) in rice (Oryza sativa) and two root hair traits, root hair length (RHL) and root hair density (RHD). Root hairs are outgrowths of single cells on the root epidermis that aid in nutrient and water acquisition and have also served as a model system to study cell differentiation and tip growth. Using lines from the Rice Diversity Panel-1, we explored the diversity of root hair length and density across four subpopulations of rice (aus, indica, temperate japonica, and tropical japonica). GWA analysis was completed using the high-density rice array (HDRA) and the rice reference panel (RICE-RP) SNP sets. Results We identified 18 genomic regions related to root hair traits, 14 of which related to RHD and four to RHL. No genomic regions were significantly associated with both traits. Two regions overlapped with previously identified quantitative trait loci (QTL) associated with root hair density in rice. We identified candidate genes in these regions and present those with previously published expression data relevant to root hair development. We re-phenotyped a subset of lines with extreme RHD phenotypes and found that the variation in RHD was due to differences in cell differentiation, not cell size, indicating genes in an associated genomic region may influence root hair cell fate. The candidate genes that we identified showed little overlap with previously characterized genes in rice and Arabidopsis. Conclusions Root hair length and density are quantitative traits with complex and independent genetic control in rice. The genomic regions described here could be used as the basis for QTL development and further analysis of the genetic control of root hair length and density. We present a list of candidate genes involved in root hair formation and growth in rice, many of which have not been previously identified as having a relation to root hair growth. Since little is known about root hair growth in grasses, these provide a guide for further research and crop improvement.

Summary: Root hairs (RH) are excellent model systems for studying cell size and polarity since they elongate several hundred‐fold their original size. Their tip growth is determined both by intrinsic and environmental signals. Although nutrient availability and temperature are key factors for a sustained plant growth, the molecular mechanisms underlying their sensing and downstream signaling pathways remain unclear.We use genetics to address the roles of the cell surface receptor kinase FERONIA (FER) and the nutrient sensing TOR Complex 1 (TORC) in RH growth.We identified that low temperature (10°C) triggers a strong RH elongation response in Arabidopsis thaliana involving FER and TORC. We found that FER is required to perceive limited nutrient availability caused by low temperature. FERONIA interacts with and activates TORC‐downstream components to trigger RH growth. In addition, the small GTPase Rho of plants 2 (ROP2) is also involved in this RH growth response linking FER and TOR. We also found that limited nitrogen nutrient availability can mimic the RH growth response at 10°C in a NRT1.1‐dependent manner.These results uncover a molecular mechanism by which a central hub composed by FER‐ROP2‐TORC is involved in the control of RH elongation under low temperature and nitrogen deficiency. [ABSTRACT FROM AUTHOR]

Abstract Sorghum is an essential crop for resilient and adaptive responses to climate change. The root systems of crop plants significantly contribute to the tolerance of abiotic stresses. There is little information on sorghum genotypes' root systems and plasticity to external P supply. In this paper, we investigated the variations in root systems, as well as the responses, trait relationships, and plasticity of two sorghum genotypes (Naga Red and Naga White), popularly grown in Ghana, to five external P concentrations ([P]ext): 0, 100, 200, 300, and 400 mg P kg−1 soil. Sorghum plants were grown in greenhouse pots and harvested for root trait measurements at the five‐leaf and growing point differentiation (GPD) developmental stages. The plants were responsive to [P]ext and formed rhizosheaths. The two genotypes showed similar characteristics for most of the traits measured but differed significantly in total and lateral root lengths in favor of the red genotype. For example, at the five‐leaf growth stage, the lateral root length of the red and white genotypes was 22.8 and 16.2 cm, respectively, but 124 and 88.9 cm, at the GPD stage. The responses and plasticity of the root system traits, including rhizosheath, to [P]ext were more prominent, positive, and linear at the five‐leaf stage than at the GPD growth stage. At the five‐leaf growth stage, total root length increased by about 2.5‐fold with increasing [P]ext compared to the unamended soil. At the GPD stage, however, total root length decreased by about 1.83‐fold as [P]ext increased compared to the unamended soil. Specific rhizosheath weight correlated with RHD, albeit weakly, and together explained up to 59% of the variation in tissue P. Root hair density was more responsive to P supply than root hair length and showed a similar total and lateral root length pattern. Most desirable responses to P occurred at a rate of 200–300 mg P kg−1 soil. It is concluded that sorghum would form rhizosheath, and [P]ext could be critical for the early vigorous growth of sorghum's responsive root and shoot traits. Beyond the early days of development, additional P application might be necessary to sustain the responses and plasticity observed during the early growth period, but this requires further investigation, potentially under field conditions.

Introduction: VPS45 belongs to the Sec1/Munc18 family of proteins, which interact with and regulate Qa-SNARE function during membrane fusion. We have shown previously that Arabidopsis thaliana VPS45 interacts with the SYP61/SYP41/VTI12 SNARE complex, which locates on the trans-Golgi network (TGN). It is required for SYP41 stability, and it functions in cargo trafficking to the vacuole and in cell expansion. It is also required for correct auxin distribution during gravitropism and lateral root growth. Results: As vps45 knockout mutation is lethal in Arabidopsis, we identified a mutant, vps45-3, with a point mutation in the VPS45 gene causing a serine 284- to-phenylalanine substitution. The VPS45-3 protein is stable and maintains interaction with SYP61 and SYP41. However, vps45-3 plants display severe growth defects with significantly reduced organ and cell size, similar to vps45 RNAi transgenic lines that have reduced VPS45 protein levels. Root hair and pollen tube elongation, both processes of tip growth, are highly compromised in vps45-3. Mutant root hairs are shorter and thicker than those of wild-type plants, and are wavy. These root hairs have vacuolar defects, containing many small vacuoles, compared with WT root hairs with a single large vacuole occupying much of the cell volume. Pollen tubes were also significantly shorter in vps45-3 compared to WT. Discussion: We thus show that VPS45 is essential for proper tip growth and propose that the observed vacuolar defects lead to loss of the turgor pressure needed for tip growth. [ABSTRACT FROM AUTHOR]

Summary: Root hairs and soil water content are crucial in controlling the release and diffusion of root exudates and shaping profiles of biochemical properties in the rhizosphere. But whether root hairs can offset the negative impacts of drought on microbial activity remains unknown.Soil zymography, 14C imaging and neutron radiography were combined to identify how root hairs and soil moisture affect rhizosphere biochemical properties. To achieve this, we cultivated two maize genotypes (wild‐type and root‐hair‐defective rth3 mutant) under ambient and drought conditions.Root hairs and optimal soil moisture increased hotspot area, rhizosphere extent and kinetic parameters (Vmax and Km) of β‐glucosidase activities. Drought enlarged the rhizosphere extent of root exudates and water content. Colocalization analysis showed that enzymatic hotspots were more colocalized with root exudate hotspots under optimal moisture, whereas they showed higher dependency on water hotspots when soil water and carbon were scarce.We conclude that root hairs are essential in adapting rhizosphere properties under drought to maintain plant nutrition when a continuous mass flow of water transporting nutrients to the root is interrupted. In the rhizosphere, soil water was more important than root exudates for hydrolytic enzyme activities under water and carbon colimitation. See also the Commentary on this article by Zhang et al., 237: 707–709. [ABSTRACT FROM AUTHOR]

Background: Genome wide association (GWA) studies demonstrate linkages between genetic variants and traits of interest. Here, we tested associations between single nucleotide polymorphisms (SNPs) in rice (Oryza sativa) and two root hair traits, root hair length (RHL) and root hair density (RHD). Root hairs are outgrowths of single cells on the root epidermis that aid in nutrient and water acquisition and have also served as a model system to study cell differentiation and tip growth. Using lines from the Rice Diversity Panel-1, we explored the diversity of root hair length and density across four subpopulations of rice (aus, indica, temperate japonica, and tropical japonica). GWA analysis was completed using the high-density rice array (HDRA) and the rice reference panel (RICE-RP) SNP sets. Results: We identified 18 genomic regions related to root hair traits, 14 of which related to RHD and four to RHL. No genomic regions were significantly associated with both traits. Two regions overlapped with previously identified quantitative trait loci (QTL) associated with root hair density in rice. We identified candidate genes in these regions and present those with previously published expression data relevant to root hair development. We re-phenotyped a subset of lines with extreme RHD phenotypes and found that the variation in RHD was due to differences in cell differentiation, not cell size, indicating genes in an associated genomic region may influence root hair cell fate. The candidate genes that we identified showed little overlap with previously characterized genes in rice and Arabidopsis. Conclusions: Root hair length and density are quantitative traits with complex and independent genetic control in rice. The genomic regions described here could be used as the basis for QTL development and further analysis of the genetic control of root hair length and density. We present a list of candidate genes involved in root hair formation and growth in rice, many of which have not been previously identified as having a relation to root hair growth. Since little is known about root hair growth in grasses, these provide a guide for further research and crop improvement. [ABSTRACT FROM AUTHOR]

Recent investigations in Arabidopsis thaliana suggest that SUPPRESSOR of MORE AXILLARY GROWTH 2 1 (SMAX1) and SMAX1-LIKE2 (SMXL2) are negative regulators of karrikin (KAR) and strigolactone (SL) signaling during plant growth and development, but their functions in drought resistance and related mechanisms of action remain unclear. To understand the roles and mechanisms of SMAX1 and SMXL2 in drought resistance, we investigated the drought-resistance phenotypes and transcriptome profiles of smax1 smxl2 (s1,2) double-mutant plants in response to drought stress. The s1,2 mutant plants showed enhanced drought-resistance and lower leaf water loss when compared with wild-type (WT) plants. Transcriptome comparison of rosette leaves from the s1,2 mutant and the WT under normal and dehydration conditions suggested that the mechanism related to cuticle formation was involved in drought resistance. This possibility was supported by enhanced cuticle formation in the rosette leaves of the s1,2 mutant. We also found that the s1,2 mutant plants were more sensitive to abscisic acid in assays of stomatal closure, cotyledon opening, chlorophyll degradation and growth inhibition, and they showed a higher reactive oxygen species detoxification capacity than WT plants. In addition, the s1,2 mutant plants had longer root hairs and a higher root-to-shoot ratio than the WT plants, suggesting that the mutant had a greater capacity for water absorption than the WT. Taken together, our results indicate that SMAX1 and SMXL2 negatively regulate drought resistance, and disruption of these KAR- and SL-signaling-related genes may therefore provide a novel means for improving crop drought resistance. [ABSTRACT FROM AUTHOR]

IntroductionVPS45 belongs to the Sec1/Munc18 family of proteins, which interact with and regulate Qa-SNARE function during membrane fusion. We have shown previously that Arabidopsis thaliana VPS45 interacts with the SYP61/SYP41/VTI12 SNARE complex, which locates on the trans-Golgi network (TGN). It is required for SYP41 stability, and it functions in cargo trafficking to the vacuole and in cell expansion. It is also required for correct auxin distribution during gravitropism and lateral root growth.ResultsAs vps45 knockout mutation is lethal in Arabidopsis, we identified a mutant, vps45-3, with a point mutation in the VPS45 gene causing a serine 284-to-phenylalanine substitution. The VPS45-3 protein is stable and maintains interaction with SYP61 and SYP41. However, vps45-3 plants display severe growth defects with significantly reduced organ and cell size, similar to vps45 RNAi transgenic lines that have reduced VPS45 protein levels. Root hair and pollen tube elongation, both processes of tip growth, are highly compromised in vps45-3. Mutant root hairs are shorter and thicker than those of wild-type plants, and are wavy. These root hairs have vacuolar defects, containing many small vacuoles, compared with WT root hairs with a single large vacuole occupying much of the cell volume. Pollen tubes were also significantly shorter in vps45-3 compared to WT.DiscussionWe thus show that VPS45 is essential for proper tip growth and propose that the observed vacuolar defects lead to loss of the turgor pressure needed for tip growth.

Nuclear migration during growth and development is a conserved phenomenon among many eukaryotic species. In Arabidopsis, movement of the nucleus is important for root hair growth, but the detailed mechanism behind this movement is not well known. Previous studies in different cell types have reported that the myosin XI-I motor protein is responsible for this nuclear movement by attaching to the nuclear transmembrane protein complex WIT1/WIT2. Here, we analyzed nuclear movement in growing root hairs of wild-type, myosin xi-i , and wit1 wit2 Arabidopsis lines in the presence of actin and microtubule-disrupting inhibitors to determine the individual effects of actin filaments and microtubules on nuclear movement. We discovered that forward nuclear movement during root hair growth can occur in the absence of myosin XI-I, suggesting the presence of an alternative actin-based mechanism that mediates rapid nuclear displacements. By quantifying nuclear movements with high temporal resolution during the initial phase of inhibitor treatment, we determined that microtubules work to dampen erratic nuclear movements during root hair growth. We also observed microtubule-dependent backwards nuclear movement when actin filaments were impaired in the absence of myosin XI-I, indicating the presence of complex interactions between the cytoskeletal arrays during nuclear movements in growing root hairs. [ABSTRACT FROM AUTHOR]

Background and aims: Impact of drought on crop growth depends on soil and root hydraulic properties that determine the access of plant roots to soil water. Root hairs may increase the accessible water pool but their effect depends on soil hydraulic properties and adaptions of root systems to drought. These adaptions are difficult to investigate in pot experiments that focus on juvenile plants. Methods: A wild-type and its root hairless mutant maize (Zea mays) were grown in the field in loam and sand substrates during two growing seasons with a large precipitation deficit. A comprehensive dataset of soil and plant properties and monitored variables were collected and interpreted using simulations with a mechanistic root water uptake model. Results: Total crop water use was similar in both soils and for both genotypes whereas shoot biomass was larger for the wild type than for the hairless mutant and did not differ between soils. Total final root length was larger in sand than in loam but did not differ between genotypes. Simulations showed that root systems of both genotypes and in both soils extracted all plant available soil water, which was similar for sand and loam, at a potential rate. Leaf water potentials were overestimated by the model, especially for the hairless mutant in sand substrate because the water potential drop in the rhizosphere was not considered. Conclusions: A direct effect of root hairs on water uptake was not observed but root hairs might influence leaf water potential dependent growth. [ABSTRACT FROM AUTHOR]

Aims: Root hairs and lateral growth are root traits among many which enable plants to adapt to environmental conditions. How different traits are coordinated under local heterogeneity, especially when two or more environmental factors vary in space, is currently poorly understood. We investigated the effect of heterogeneity on root system architecture of maize in response to the presence of loamy macroaggregates, which come along with both, increased penetration resistance and nutrient availability, i.e., two important environmental factors shaping root system architecture. The comparison between a mutant with defective root hairs and the corresponding wild type made it possible to investigate the importance of root hairs in the adaptation strategies of plant roots to these factors. Methods: Changes in root growth and root distribution with respect to macroaggregates were investigated using X-ray computed tomography. The wild-type of Zea mays L. was compared with the root hair defective mutant (rth3) to investigate the importance of root hairs in addition to adaption of root architecture. Results: The presence of aggregates lead to increased root length and branch densities around aggregates, while only a few roots were able to grow into them. Thereby, wildtype and rth3 were influenced in the same way. Aboveground biomass, however, was not affected by the presence of macroaggregates, as compared to controls with homogenously distributed loam. Conclusions: Macroaggregation of loam in sandy soil shows little influence on maize growth, due to local adaptations of root architecture to the heterogeneity in nutrient availability and penetration resistance caused by the aggregates. [ABSTRACT FROM AUTHOR]

Root systems are uniquely adapted to fluctuations in external nutrient availability. In response to suboptimal nitrogen conditions, plants adopt a root foraging strategy that favors a deeper and more branched root architecture, enabling them to explore and acquire soil resources. This response is gradually suppressed as nitrogen conditions improve. However, the root hairless mutant buzz in Brachypodium distachyon shows a constitutive nitrogen-foraging phenotype with increased root growth and root branching under nitrate-rich conditions. To investigate how this unique root structure and root hair morphology in the buzz mutant affects nitrate metabolism, we measured the expression of nitrate-responsive genes, nitrate uptake and accumulation, nitrate reductase activity, and nitrogen use efficiency. We found that nitrate responses were upregulated by low nitrate conditions in buzz relative to wild type and correlated with increased expression of nitrate transport genes. In addition, buzz mutants showed increased nitrate uptake and a higher accumulation of nitrate in shoots. The buzz mutant also showed increased nitrate reductase activity in the shoots under low nitrate conditions. However, developmentally mature wild-type and buzz plants grown under low nitrate had similar nitrogen use efficiencies. These findings suggest that BUZZ influences nitrate signaling and that enhanced responsiveness to nitrate is required in buzz seedlings to compensate for the lack of root hairs. These data question the importance of root hairs in enhancing nitrate uptake and expand our understanding of how root hairs in grasses affect physiological responses to low nitrate availability., (© 2024 The Author(s). The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.)

In Arabidopsis (Arabidopsis thaliana (L.) Heynh), exposure to volatile compounds (VCs) emitted by Penicillium aurantiogriseum promotes root hair (RH) proliferation and hyper-elongation through mechanisms involving ethylene, auxin and photosynthesis signaling. In addition, this treatment enhances the levels of the small signalling peptide RAPID ALKALINIZATION FACTOR 22 (RALF22). Here we used genetics to address the role of RALF22 in fungal VC-promoted RH growth and to identify the bioactive fungal VC. We found that RHs of ralf22 and feronia (fer-4) plants impaired in the expression of RALF22 and its receptor FERONIA, respectively, responded weakly to fungal VCs. Unlike in WT roots, fungal VC exposure did not enhance RALF22 transcript levels in roots of fer-4 and ethylene- and auxin- insensitive mutants. In ralf22 and fer-4 roots, this treatment did not enhance the levels of ERS2 transcripts encoding one member of the ethylene receptor family and those of some RH-related genes. RHs of ers2-1 and the rsl2rsl4 double mutants impaired in the expression of ERS2 and the ethylene- and auxin-responsive ROOT HAIR DEFECTIVE 6-LIKE 2 and 4 transcription factors, respectively, weakly responded to fungal VCs. Moreover, roots of plants defective in photosynthetic responsiveness to VCs exhibited weak RALF22 expression and RH growth responses to fungal VCs. VCs of ΔefeA strains of P. aurantiogriseum cultures impaired in ethylene synthesis weakly promoted RH proliferation and elongation in exposed plants. We conclude that RALF22 simultaneously functions as a transcriptionally regulated signaling molecule that participates in the ethylene, auxin and photosynthesis signaling-mediated RH growth response to fungal ethylene emissions and regulation of ethylene perception in RHs., (© The Author(s) 2024. Published by Oxford University Press on behalf of American Society of Plant Biologists. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Respiratory Burst Oxidase Homologues (RBOHs) are involved in plant growth, development, and stress adaptation. How OsRBOHs affect root hair formation and consequently nutrient acquisition and drought resistance in rice is not well understood. We knocked out six OsRBOH genes in rice that were expressed in roots and identified OsRBOHE as the only one affecting root hair formation. OsRBOHE was strongly expressed in the root epidermis, root hairs and tiller buds. OsRBOHE is localised at the plasma membrane. Knockout of OsRBOHE decreased reactive oxygen species generation in the root hairs and tiller buds, downregulated genes involved in cell wall biogenesis, and decreased root hair length and tillering by 90% and 30%, respectively. Knockout of OsRBOHE decreased phosphorus acquisition only in low available P soil under aerobic conditions, but not in high P soil or under flooded conditions when P was likely not limited by diffusion. Knockout of OsRBOHE markedly decreased drought resistance of rice plants through the effect on root hair formation and the associated rhizosheath. Taken together, OsRBOHE is crucial for root hair formation and tillering and consequently on drought resistance in rice. The contribution of root hairs to P acquisition in rice is limited to aerobic soil., (© 2024 John Wiley & Sons Ltd.)

Summary: Root hair growth is tuned in response to the environment surrounding plants. While most previous studies focused on the enhancement of root hair growth during nutrient starvation, few studies investigated the root hair response in the presence of excess nutrients.We report that the post‐embryonic growth of wild‐type Arabidopsis plants is strongly suppressed with increasing nutrient availability, particularly in the case of root hair growth. We further used gene expression profiling to analyze how excess nutrient availability affects root hair growth, and found that RHD6 subfamily genes, which are positive regulators of root hair growth, are downregulated in this condition.However, defects in GTL1 and DF1, which are negative regulators of root hair growth, cause frail and swollen root hairs to form when excess nutrients are supplied. Additionally, we observed that the RHD6 subfamily genes are mis‐expressed in gtl1‐1 df1‐1. Furthermore, overexpression of RSL4, an RHD6 subfamily gene, induces swollen root hairs in the face of a nutrient overload, while mutation of RSL4 in gtl1‐1 df1‐1 restore root hair swelling phenotype.In conclusion, our data suggest that GTL1 and DF1 prevent unnecessary root hair formation by repressing RSL4 under excess nutrient conditions. [ABSTRACT FROM AUTHOR]

Root hair initiation is a highly regulated aspect of root development. The plant hormone ethylene and its precursor, 1-amino-cyclopropane-1-carboxylic acid, induce formation and elongation of root hairs. Using confocal microscopy paired with redox biosensors and dyes, we demonstrated that treatments that elevate ethylene levels lead to increased hydrogen peroxide accumulation in hair cells prior to root hair formation. In the ethylene-insensitive receptor mutant, etr1-3, and the signaling double mutant, ein3eil1, the increase in root hair number or reactive oxygen species (ROS) accumulation after ACC and ethylene treatment was lost. Conversely, etr1-7, a constitutive ethylene signaling receptor mutant, has increased root hair formation and ROS accumulation, similar to ethylene-treated Col-0 seedlings. The caprice and werewolf transcription factor mutants have decreased and elevated ROS levels, respectively, which are correlated with levels of root hair initiation. The rhd2-6 mutant, with a defect in the gene encoding the ROS-synthesizing RESPIRATORY BURST OXIDASE HOMOLOG C (RBOHC), and the prx44-2 mutant, which is defective in a class III peroxidase, showed impaired ethylene-dependent ROS synthesis and root hair formation via EIN3EIL1-dependent transcriptional regulation. Together, these results indicate that ethylene increases ROS accumulation through RBOHC and PRX44 to drive root hair formation. [ABSTRACT FROM AUTHOR]

Aims: Recent laboratory studies revealed that root hairs may alter soil physical behaviour, influencing soil porosity and water retention on the small scale. However, the results are not consistent, and it is not known if structural changes at the small-scale have impacts at larger scales. Therefore, we evaluated the potential effects of root hairs on soil hydro-mechanical properties in the field using rhizosphere-scale physical measurements. Methods: Changes in soil water retention properties as well as mechanical and hydraulic characteristics were monitored in both silt loam and sandy loam soils. Measurements were taken from plant establishment to harvesting in field trials, comparing three barley genotypes representing distinct phenotypic categories in relation to root hair length. Soil hardness and elasticity were measured using a 3-mm-diameter spherical indenter, while water sorptivity and repellency were measured using a miniaturized infiltrometer with a 0.4-mm tip radius. Results: Over the growing season, plants induced changes in the soil water retention properties, with the plant available water increasing by 21%. Both soil hardness (P = 0.031) and elasticity (P = 0.048) decreased significantly in the presence of root hairs in silt loam soil, by 50% and 36%, respectively. Root hairs also led to significantly smaller water repellency (P = 0.007) in sandy loam soil vegetated with the hairy genotype (-49%) compared to the hairless mutant. Conclusions: Breeding of cash crops for improved soil conditions could be achieved by selecting root phenotypes that ameliorate soil physical properties and therefore contribute to increased soil health. [ABSTRACT FROM AUTHOR]

The role of root phenes in nitrogen (N) acquisition and biomass production was evaluated in 10 contrasting natural accessions of Arabidopsis thaliana L. Seedlings were grown on vertical agar plates with two different nitrate supplies. The low N treatment increased the root to shoot biomass ratio and promoted the proliferation of lateral roots and root hairs. The cost of a larger root system did not impact shoot biomass. Greater biomass production could be achieved through increased root length or through specific root hair characteristics. A greater number of root hairs may provide a low-resistance pathway under elevated N conditions, while root hair length may enhance root zone exploration under low N conditions. The variability of N uptake and the expression levels of genes encoding nitrate transporters were measured. A positive correlation was found between root system size and high-affinity nitrate uptake, emphasizing the benefits of an exploratory root organ in N acquisition. The expression levels of NRT1.2 / NPF4.6 , NRT2.2 , and NRT1.5 / NPF7.3 negatively correlated with some root morphological traits. Such basic knowledge in Arabidopsis demonstrates the importance of root phenes to improve N acquisition and paves the way to design eudicot ideotypes. [ABSTRACT FROM AUTHOR]

RLRHRoot hair-forming root length: the length of root segments on which root hairs are formed One measure of the distribution of root hair initiation. That method is applicable to images with suboptimal optical or digital resolution, and can be used to quantify root hair-forming root length, root hair density, mean root hair length, and total root hair area on a whole root organ scale. ARHRoot hair area: total projected two-dimensional area of root hairs Summary of total root hair formation, possibly a measure of total soil solution contact of root hairs. Keywords: Natural variation; nitrogen nutrition; root hairs; phenotyping EN Natural variation nitrogen nutrition root hairs phenotyping 3304 3307 4 06/08/22 20220602 NES 220602 Although root hairs are recognized as a major component of root function, difficulties in quantification limit the study of root hairs on a sufficient scale for ecological and agronomic relevance. [Extracted from the article]

Abstract—We tested a hypothesis about the different abilities of alien and native plants to form arbuscular mycorrhizae. The studies were carried out in the Belarusian Polesia (Eastern Europe) in the zone of mixed coniferous–deciduous forests with a temperate continental climate. The intensity of formation of various structures of arbuscular mycorrhizae (arbuscule, vesicles, and hyphae), as well as root hairs, was determined microscopically in 19 alien and 25 native plant species collected in six different habitats. In each habitat, both alien and native plants were collected. In mycorrhizal alien plants, arbuscules were formed less frequently (28 ± 6%) than in native plants (48 ± 6%). Root hairs in alien species were laid more often (43 ± 6%) than in native species (32 ± 4%). In both native and alien plants, the mycorrhiza was more actively formed in disturbed habitats, but the interaction between the factors "degree of naturalization" and "degree of habitat disturbance" has not been established. Thus, arbuscular mycorrhizae function less effectively in alien plants of the Belarusian Polesia than in native plants. [ABSTRACT FROM AUTHOR]

Premise: For vascular epiphytes, secure attachment to their hosts is vital for survival. Yet studies detailing the adhesion mechanism of epiphytes to their substrate are scarce. Examination of the root hair–substrate interface is essential to understand the attachment mechanism of epiphytes to their substrate. This study also investigated how substrate microroughness relates to the root–substrate attachment strength and the underlying mechanism(s). Methods: Seeds of Anthurium obtusum were germinated, and seedlings were transferred onto substrates made of epoxy resin with different defined roughness. After 2 months of growth, roots that adhered to the resin tiles were subjected to anchorage tests, and root hair morphology at different roughness levels was analyzed using light and cryo scanning electron microscopy. Results: The highest maximum peeling force was recorded on the smooth surface (glass replica, 0 µm). Maximum peeling force was significantly higher on fine roughness (0, 0.3, 12 µm) than on coarse (162 µm). Root hair morphology varied according to the roughness of the substrate. On smoother surfaces, root hairs were flattened to achieve large surface contact with the substrate. Attachment was mainly by adhesion with the presence of a glue‐like substance. On coarser surfaces, root hairs were tubular and conformed to spaces between the asperities on the surface. Attachment was mainly via mechanical interlocking of root hairs and substrate. Conclusions: This study demonstrates for the first time that the attachment mechanism of epiphytes varies depending on substrate microtopography, which is important for understanding epiphyte attachment on natural substrates varying in roughness. [ABSTRACT FROM AUTHOR]

Root hair cells are important sensors of soil conditions. They grow towards and absorb water-soluble nutrients. This fast and oscillatory growth is mediated by continuous remodeling of the cell wall. Root hair cell walls contain polysaccharides and hydroxyproline-rich glycoproteins, including extensins (EXTs). Class-III peroxidases (PRXs) are secreted into the apoplastic space and are thought to trigger either cell wall loosening or polymerization of cell wall components, such as Tyr-mediated assembly of EXT networks (EXT-PRXs). The precise role of these EXT-PRXs is unknown. Using genetic, biochemical, and modeling approaches, we identified and characterized three root-hair-specific putative EXT-PRXs, PRX01, PRX44, and PRX73. prx01,44,73 triple mutation and PRX44 and PRX73 overexpression had opposite effects on root hair growth, peroxidase activity, and ROS production, with a clear impact on cell wall thickness. We use an EXT fluorescent reporter with contrasting levels of cell wall insolubilization in prx01,44,73 and PRX44-overexpressing background plants. In this study, we propose that PRX01, PRX44, and PRX73 control EXT-mediated cell wall properties during polar expansion of root hair cells. [ABSTRACT FROM AUTHOR]

Six cycles of recurrent selection for early shoot vigour in wheat resulted in significant increases in leaf width and shoot biomass. Here, in replicated controlled-environment studies, the effect of early shoot vigour on root biomass, rhizosheath size, root hair length, and cell size in the roots and leaves was examined across different cycles of selection. Increased shoot vigour was associated with greater root biomass, larger rhizosheath size, and longer root hairs. Our findings demonstrate that rhizosheath size was a reliable surrogate for root hair length in this germplasm. Examination of the root epidermis revealed that the 'cell body' of the trichoblasts (hair-forming cells) and the atrichoblasts (non-hair-forming cells) decreased in size as shoot vigour increased. Therefore, in higher vigour germplasm, longer root hairs emerged from smaller trichoblasts so that total trichoblast volume (root hair plus cell body) was generally similar regardless of shoot vigour. Similarly, the sizes of the four main cell types on the leaf epidermis became progressively smaller as shoot vigour increased, which also increased stomatal density. The relationship between shoot vigour and root traits is considered, and the potential contribution of below-ground root traits to performance and competitiveness of high vigour germplasm is discussed. [ABSTRACT FROM AUTHOR]

Root hairs absorb soil nutrients and water, and anchor the plant in the soil. Treatment of tobacco (Nicotiana tabacum) roots with glycine (Gly) amino acid, and glycilglycine (GlyGly) and glycilaspartic acid (GlyAsp) dipeptides (10−7 M concentration) significantly increased the development of root hairs. In the root, peptide accumulation was tissue-specific, with predominant localization to the root cap, meristem, elongation zone, and absorption zone. Peptides penetrated the epidermal and cortical cell and showed greater localization to the nucleus than to the cytoplasm. Compared with the control, tobacco plants grown in the presence of Gly, GlyGly, and GlyAsp exhibited the activation of WER, CPC, bHLH54, and bHLH66 genes and suppression of GTL1 and GL2 genes during root hair lengthening. Although Gly, GlyGly, and GlyAsp have a similar structure, the mechanism of regulation of root hair growth in each case were different, and these differences are most likely due to the fact that neutral Gly and GlyGly and negatively charged GlyAsp bind to different motives of functionally important proteins. Short peptides site-specifically interact with DNA, and histones. The molecular mechanisms underlying the effect of exogenous peptides on cellular processes remain unclear. Since these compounds acted at low concentrations, gene expression regulation by short peptides is most likely of epigenetic nature. [ABSTRACT FROM AUTHOR]

Soil drying is a limiting factor for crop production worldwide. Yet, it is not clear how soil drying impacts water uptake across different soils, species, and root phenotypes. Here we ask (1) what root phenotypes improve the water use from drying soils? and (2) what root hydraulic properties impact water flow across the soil–plant continuum? The main objective is to propose a hydraulic framework to investigate the interplay between soil and root hydraulic properties on water uptake. We collected highly resolved data on transpiration, leaf and soil water potential across 11 crops and 10 contrasting soil textures. In drying soils, the drop in water potential at the soil–root interface resulted in a rapid decrease in soil hydraulic conductance, especially at higher transpiration rates. The analysis reveals that water uptake was limited by soil within a wide range of soil water potential (−6 to −1000 kPa), depending on both soil textures and root hydraulic phenotypes. We propose that a root phenotype with low root hydraulic conductance, long roots and/or long and dense root hairs postpones soil limitation in drying soils. The consequence of these root phenotypes on crop water use is discussed. Summary statement: During soil drying, the drop in soil–plant hydraulic conductance causes a decline in root water uptake, which is impacted by soil and root hydraulic phenotypes. Lower root conductance, longer root length and longer root hairs would allow plants to maintain water uptake at lower soil matric potential. [ABSTRACT FROM AUTHOR]

Symbioses between plants and fungi are important in both promoting plant fitness and maintaining soil structure. The ways in which these relationships change across an urban gradient is subject to debate. Here we measured root colonisation including the presence of arbuscular mycorrhizal fungi, non-mycorrhizal fungi, and root hair presence. We found no evidence of changes in levels of arbuscular mycorrhizal fungal colonisation across an urban gradient, colonisation levels being driven instead by plant community. However, we did observe an increase in non-mycorrhizal fungal colonisation in association with increasing urbanity. Additionally, we observed an urban-related increase in root hair presence. Using principal component analysis we were able to provide strong evidence for these patterns being driven by an “urban syndrome”, rather than soil chemistry. Our findings have important implications for the wider understanding of abiotic stresses on fungal endophyte presence and shed light on the impacts of urbanity upon plant roots.

Key message: Eucalypt seedlings differently modulate root morphology in response to phosphorus availability, with changes in the length or density of root hairs being more common that changes in root length. Phosphorus (P) is an essential nutrient for plant growth and development and thus can restrict biomass accumulation when it is at low levels in the soil. Eucalypts cover large areas of planted forests in the world, including regions with naturally low P availability. This study was conducted to evaluate the morphological changes in the roots of seedlings of five eucalypt species: Eucalyptus acmenoides, E. globulus, E. grandis, E. tereticornis and Corymbia maculata in response to low P concentration. Seedlings were grown in pots with vermiculite and received a nutrient solution of low (25 μM), and sufficient concentration (500 μM) of P. Root hair length and density were evaluated in secondary root segments, and the production of plant biomass and P concentration in the shoots were determined. The species modulated root morphology differently in response to P limitation. E. tereticornis showed the lowest plasticity of these morphological traits in response to P concentration. The total root length increased in some species, but changes in the length and/or density of root hairs were the commonest response to low P concentration. P concentrations in the shoots and biomass production were not related to increase of root length or root hair density and length. [ABSTRACT FROM AUTHOR]