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Interventions aimed at preventing chronic pain after acute traumatic injury have significant potential to reduce healthcare expenditures and improve quality of life for millions of individuals. Given recent development of such interventions, limited research has examined mechanisms of change using repeated measures (e.g., session-by-session assessments). This study examines within-person relationships between pain catastrophizing and intensity during and after a four-session mind-body intervention for individuals with acute traumatic orthopedic injury (N = 76, T = 445). Random intercept cross-lagged panel models were used to examine within-person autoregressive, contemporaneous, and cross-lagged effects between pain catastrophizing and pain intensity, after accounting for stable between-person differences. Our primary hypothesis that improvements in catastrophizing would be associated with subsequent reductions in pain intensity was partially supported by a significant within-person cross-lagged effect between catastrophizing at post-test and pain with activity reported at three-month follow-up (β = 0.421, SE = 0.099, p < .001). Improvement in catastrophizing was also associated with same-session improvement in pain intensity midway through the intervention. Importantly, bidirectional within-person analyses allowed us to rule out the possibility that improvements in pain were responsible for subsequent improvements in catastrophizing, but not vice versa. Together, these findings suggest improvements in catastrophizing during psychosocial intervention may prevent transition from acute to chronic pain after injury. Future research with larger between-person sample sizes, more frequent within-person assessment, and comparable control group data is necessary to facilitate greater understanding of psychosocial mechanisms for preventing chronic pain after injury. PERSPECTIVE: This study examines within-person relationships between pain catastrophizing and intensity during and after a four-session mind-body intervention to prevent persistent pain after acute traumatic orthopedic injury. Improved catastrophizing at post-test was associated with reduced pain with activity at three-month follow-up. Within-person analyses enhance understanding of psychosocial mechanisms for preventing chronic pain after injury., Competing Interests: Declaration of Competing Interest None., (Copyright © 2024. Published by Elsevier Inc.)

Chronic musculoskeletal pain (CMP) is highly prevalent, frequently associated with negative health outcomes, and disproportionately impacts Black Americans. Perceived racial and ethnic discrimination has emerged as a factor that may influence the experience of chronic pain in this population. Identifying modifiable psychosocial factors that influence the link between perceived discrimination and pain and that can be directly targeted in treatment is vital to reducing the disproportionate burden of CMP among Black individuals. The present study examines the moderating role of five risk factors (i.e., pain avoidance, pain fusion, experiential avoidance, pain catastrophizing, and pain anxiety) on the relationship between perceived discrimination and pain outcomes (i.e., pain intensity and interference) in a sample of 401 Black adults with CMP. We recruited 401 Black individuals (M age = 35.98, 51.9% female) with self-reported CMP and assessed their self-reported perceived discrimination, pain intensity, pain interference, and pain-related psychosocial risk factors. Results indicated that higher scores on each of the psychosocial risk factors (i.e., pain avoidance, pain fusion, experiential avoidance, pain catastrophizing, and pain anxiety) were significantly associated with greater pain intensity and pain interference (all ps < 0.01). Further, pain avoidance (B = 0.12, p = .006), pain fusion (B = 0.13, p = .002), and pain anxiety (B = 0.13, p = .002) each significantly moderated the relation between perceived discrimination and pain intensity. Greater perceived discrimination was associated with greater pain intensity at higher levels of avoidance and fusion, and was associated with less pain intensity at lower levels of avoidance and pain anxiety. In interaction models predicting pain interference, both pain fusion (B = 0.14, p = .001) and pain anxiety (B = 0.10, p = .01) significantly moderated the relation between perceived discrimination and pain interference. Perceived discrimination was associated with greater pain interference at higher levels of pain fusion and pain anxiety, and was not associated with pain interference at lower levels of pain fusion and pain anxiety. The present findings provide important insights into psychosocial risk factors that moderate the link between perceived discrimination and pain outcomes, providing important clinical implications for the treatment of Black adults with chronic musculoskeletal pain., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Objective: Chronic musculoskeletal pain (CMP) is prevalent, burdensome, and associated with an increased risk for opioid use disorder. Evidence suggests that perceived racial/ethnic discrimination is associated with problematic substance use among Black individuals, but studies have not focused on problematic opioid use among Black individuals with CMP specifically or explored the contribution of perceived discrimination, pain intensity, and pain-relevant psychological factors to this association., Method: We recruited 401 Black individuals ( M age = 35.98, 51.9% female) with self-reported CMP and prescription opioid use. We tested whether perceived discrimination (a) was associated with self-reported problematic opioid use and (b) explained unique variance in this outcome after accounting for pain intensity, demographic factors, and psychological factors previously implicated in problematic opioid/substance use (distress tolerance and pain avoidance)., Results: Hierarchical linear regression analysis revealed that our model as a whole explained significant variance in problematic opioid use, R ² = .30, F (6, 394) = 28.66, p < .001. Perceived discrimination specifically was associated with more problematic opioid use (β = .39, SE = .05, p < .001) and explained unique variance in this outcome even after accounting for pain intensity (β = .06, SE = .04, p = .20), distress tolerance (β = -.10, SE = .05, p = .04), pain avoidance (β = .12, SE = .05, p = .02), age (β = -.10, SE = .05, p < .05), and employment status (β = .13, SE = .11, p < .01)., Conclusions: Systemic efforts to combat racism along with individualized therapeutic approaches to process and cope with perceived racial discrimination may be particularly important to prevent and reduce problematic opioid use among Black individuals with CMP. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Background: Chronic pain is associated with substantial impairment in physical function, which has been identified as a top concern among persons with pain. GetActive-Fitbit, a mind-body activity program, is feasible, acceptable, and associated with improvement in physical function among primarily White, sedentary individuals with pain. In preparation for a multisite efficacy trial, we must examine feasibility across multiple sites with diverse patient populations. Here we describe the protocol of a multisite, feasibility RCT comparing GetActive-Fitbit with a time- and attention-matched educational comparison (Healthy Living for Pain). We aim to 1) test multisite fidelity of clinician training; 2) evaluate multisite feasibility benchmarks, including recruitment of chronic pain patients taking <5000 steps/day and racial and ethnic minorities; and 3) optimize fidelity and study protocol in preparation for a future multisite efficacy trial., Methods: Clinician training fidelity was assessed via roleplays and mock group sessions. Feasibility (i.e., recruitment, acceptability, credibility, adherence, satisfaction), multimodal physical function (e.g., self-report, 6-Minute Walk Test, step-count), and other psychosocial outcomes are assessed at baseline, posttest, and 6 months. Protocol optimization will be assessed using exit interviews and cross-site meetings., Results: The trial is ongoing. Clinician training is complete. 87 participants have been recruited. 54 completed baseline assessments and randomization, 44 are mid-intervention, and 9 have completed the intervention and posttest., Conclusions: This study addresses the critical need for feasible, acceptable mind-body-activity interventions for chronic pain that follow evidence-based guidelines and improve all aspects of physical function across diverse populations. Results will inform a future fully-powered multisite efficacy trial., Clinical Trial Registration: NCT05700383., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background: Chronic musculoskeletal pain is prevalent and disabling among older adults in underserved communities. Psychosocial pain management is more effective than pharmacological treatment in older adults. However, underserved community clinics often lack psychosocial treatments, in part because of a lack of trained providers. Shared medical appointments, in which patients undergo brief medical evaluation, monitoring, counseling, and group support, are an efficacious and cost-effective method for chronic disease management in underserved clinics, reducing the need for specialized providers. However, shared medical visits are often ineffective for chronic pain, possibly owing to lack of inclusion of skills most relevant for older adults (eg, pacing to increase engagement in daily activities)., Objective: We have described the protocol for the development and initial pilot effectiveness testing of the GetActive+ mind-body activity intervention for older adults with chronic pain. GetActive+ was adapted from GetActive, an evidence-based intervention that improved pain outcomes among mostly affluent White adults. We aim to establish the initial feasibility, acceptability, fidelity, and effectiveness of GetActive+ when delivered as part of shared medical appointments in a community clinic., Methods: We conducted qualitative focus groups and individual interviews with providers (n=25) and English-speaking older adults (aged ≥55 y; n=18) with chronic pain to understand the pain experience in this population, perceptions about intervention content, and barriers to and facilitators of intervention participation and implementation in this setting. Qualitative interviews with Spanish-speaking older adults are in progress and will inform a future open pilot of the intervention in Spanish. We are currently conducting an open pilot study with exit interviews in English (n=30 individuals in total). Primary outcomes are feasibility (≥75% of patients who are approached agree to participate), acceptability (≥75% of patients who enrolled complete 8 out of 10 sessions; qualitative), and fidelity (≥75% of session components are delivered as intended). Secondary outcomes include physical function-self-reported, performance based (6-minute walk test), and objective (step count)-and emotional function (depression and anxiety). Other assessments include putative mechanisms (eg, mindfulness and pain catastrophizing)., Results: We began enrolling participants for the qualitative phase in November 2022 and the open pilot phase in May 2023. We completed the qualitative phase with providers and English-speaking patients, and the results are being analyzed using a hybrid, inductive-deductive approach. We conducted rapid analysis of these data to develop GetActive+ before the open pilot in English, including increasing readability and clarity of language, reducing the number of skills taught to increase time for individual check-ins and group participation, and increasing experiential exercises for skill uptake., Conclusions: We provide a blueprint for the refinement of a mind-body activity intervention for older adults with chronic pain in underserved community clinics and for incorporation within shared medical visits. It will inform a future, fully powered, effectiveness-implementation trial of GetActive+ to help address the chronic pain epidemic among older adults., Trial Registration: ClinicalTrials.gov NCT05782231; https://clinicaltrials.gov/study/NCT05782231., International Registered Report Identifier (irrid): DERR1-10.2196/52117., (©Katherine McDermott, Nadine Levey, Julie Brewer, Madison Ehmann, Julia E Hooker, Roger Pasinski, Neda Yousif, Vidya Raju, Milton Gholston, Jonathan Greenberg, Christine S Ritchie, Ana-Maria Vranceanu. Originally published in JMIR Research Protocols (https://www.researchprotocols.org), 29.12.2023.)

Background: Chronic pain and early cognitive decline, which are costly to treat and highly prevalent among older adults, commonly co-occur, exacerbate one another over time, and can accelerate the development and progression of Alzheimer disease and related dementias. We developed the first mind-body activity program (Active Brains [AB]) tailored to the needs of older adults with chronic pain and early cognitive decline. Results from our previous study strongly supported the feasibility of conducting AB remotely and provided evidence for improvements in outcomes., Objective: We are conducting a single-blinded, National Institutes of Health stage-2, randomized clinical trial to establish the efficacy of AB versus a time-matched and dose-matched education control (Health Enhancement Program [HEP]) in improving self-reported and objective outcomes of physical, cognitive, and emotional functions in 260 participants. The methodology described in this paper was informed by the lessons learned from the first year of the trial., Methods: Participants are identified and recruited through multidisciplinary clinician-referred individuals (eg, pain psychologists and geriatricians), the Rally Research platform, social media, and community partnerships. Interested participants complete eligibility screening and electronic informed consent. Baseline assessments include self-report, performance-based measures (eg, 6-min walk test) and objective measures (eg, Repeatable Battery for the Assessment of Neuropsychological Status). Participants are mailed a wrist-worn ActiGraph device (ActiGraph LLC) to passively monitor objective function (eg, steps) during the week between the baseline assessment and the beginning of the programs, which they continue to wear throughout the programs. After baseline assessments, participants are randomized to either AB or HEP and complete 8 weekly, remote, group sessions with a Massachusetts General Hospital psychologist. The AB group receives a Fitbit (Fitbit Inc) to help reinforce increased activity. Assessments are repeated after the intervention and at the 6-month follow-up. Coprimary outcomes include multimodal physical function (self-report, performance based, and objective). Secondary outcomes are cognitive function (self-report and objective), emotional function, and pain., Results: We began recruitment in July 2022 and recruited 37 participants across 4 cohorts. Of them, all (n=37, 100%) have completed the baseline assessment, 26 (70%) have completed the posttest assessment, and 9 (24%) are actively enrolled in the intervention (total dropout: n=2, 5%). In the three cohorts (26/37, 70%) that have completed the AB or HEP, 26 (100%) participants completed all 8 group sessions (including minimal makeups), and watch adherence (1937/2072, 93.48%, average across ActiGraph and Fitbit devices) has been excellent. The fourth cohort is ongoing (9/37, 24%), and we plan to complete enrollment by March 2026., Conclusions: We aim to establish the efficacy of the AB program over a time-matched and dose-matched control in a live video-based trial and test the mechanisms through theoretically driven mediators and moderators. Findings will inform the development of a future multisite effectiveness-implementation trial., Trial Registration: ClinicalTrials.gov NCT05373745; https://classic.clinicaltrials.gov/ct2/show/NCT05373745., International Registered Report Identifier (irrid): DERR1-10.2196/47319., (©Ana-Maria Vranceanu, Nathaniel R Choukas, Elizabeth A Rochon, Brooke Duarte, Malvina O Pietrzykowski, Katherine McDermott, Julia E Hooker, Ronald Kulich, Yakeel T Quiroz, Robert A Parker, Eric A Macklin, Christine Ritchie, The Active Brains Project, Ryan A Mace. Originally published in JMIR Research Protocols (https://www.researchprotocols.org), 28.09.2023.)

Co-use of alcohol and prescription opioid medication increases risk for harmful and potentially fatal health effects (e.g., overdose). Behavioral intentions (i.e., the immediate antecedent of corresponding behavior according to the Theory of Planned Behavior) are important in prediction of substance use, and a valid measure assessing intentions to co-use alcohol and opioids is needed to identify individuals at-risk for harmful substance use. The goal of the current study was to develop and conduct the psychometric validation of a six-item Intentions to Co-Use Alcohol and Opioids (ICAO) scale. Participants included 261 ( M age  = 38; 64% male) past-month drinkers with a current opioid prescription and chronic musculoskeletal pain who completed a targeted online survey. Confirmatory factor analysis indicated that a single-factor structure provided good model fit (Bollen-Stine bootstrap p = .121). Moreover, the ICAO demonstrated high internal consistency (α = .96) and was correlated with measures of alcohol and opioid use/co-use. These findings provide support for the single-factor structure, reliability, and concurrent/convergent validity of the ICAO among individuals who endorse alcohol use, opioid use, and chronic musculoskeletal pain. The ICAO may offer clinical utility as a tool to identify individuals at greater risk of potentially fatal co-use of alcohol and opioid medications.

Purpose: To test the effects of the Relaxation Response Resiliency Program - Neurofibromatosis (3RP-NF), a mind-body resilience program for people with NF, on resilience factors from baseline to post-treatment and 6- and 12-month follow-up., Methods: This is a secondary analysis of a fully powered randomized clinical trial (RCT) of 3RP-NF and health education control (HEP-NF). We recruited adults with NF1, NF2, or schwannomatosis who reported stress or difficulty coping with NF symptoms. Both conditions received 8 weekly 90-minute group sessions; 3RP-NF focused on building resilience skills. We measured resilience factors via the Measure of Current Status-A (adaptive coping), Cognitive and Affective Mindfulness Scale-Revised (mindfulness), Gratitude Questionnaire-6 (gratitude), Life Orientation Test Optimism Scale (optimism), and Medical Outcomes Study Social Support Survey (perceived social support) at baseline, post-intervention, and 6- and 12-month follow-up. We used linear mixed models with completely unstructured covariance across up to four repeated measurements (baseline, post-treatment, and 6- and 12-month follow-up) to investigate treatment effects on resilience factors., Results: We enrolled 228 individuals (M age =42.7, SD = 14.6; 74.5% female; 87.7% White; 72.8% NF1, 14.0% NF2, 13.2% schwannomatosis). Within groups, both 3RP-NF and HEP-NF showed statistically significant improvements in all outcomes across timepoints. 3RP-NF showed significantly greater improvement in adaptive coping compared to HEP-NF from baseline to post-intervention and baseline to 6 months (M difference = 0.29; 95% CI 0.13-0.46; p < 0.001; M difference = 0.25; 95% CI 0.07-0.33; p = 0.005); there were no other between-group differences amongst the remaining resilience factors., Conclusion: 3RP-NF showed promise in sustainably improving coping abilities amongst people with NF., Trial Registration Information: ClinicalTrials.gov Identifier: NCT03406208. Registration submitted December 6, 2017, first patient enrolled October 2017., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Objective: Clinical trials of cannabinoids for chronic pain have mixed and often inconclusive results. In contrast, many prospective observational studies show the analgesic effects of cannabinoids. This survey study aimed to examine the experiences/attitudes of individuals with chronic pain who are currently taking, have previously taken, or never taken cannabinoids for chronic pain to inform future research., Methods: This study is based on a cross-sectional, web-based survey of individuals with self-reported chronic pain. Participants were invited to participate through an email that was distributed to the listservs of patient advocacy groups and foundations that engage individuals with chronic pain., Results: Of the 969 respondents, 444 (46%) respondents reported currently taking, 213 (22%) previously taken, and 312 (32%) never taken cannabinoids for pain. Participants reported using cannabinoids to treat a wide variety of chronic pain conditions. Those currently taking cannabinoids (vs previously) more frequently reported: (1) large improvements from cannabinoids in all pain types, including particularly difficult-to-treat chronic overlapping pain conditions (eg, pelvic pain), (2) improvements in comorbid symptoms (eg, sleep), and (3) lower interference from side effects. Those currently taking cannabinoids reported more frequent and satisfactory communication with clinicians regarding cannabinoid use. Those never taken cannabinoids reported a lack of suggestion/approval of a clinician (40%), illegality (25%), and lack of FDA regulation (19%) as reasons for never trying cannabinoids., Conclusion: These findings underscore the importance of conducting high-quality clinical trials that include diverse pain populations and clinically relevant outcomes that if successful, could support FDA approval of cannabinoid products. Clinicians could then prescribe and monitor these treatments similarly to other chronic pain medications., Competing Interests: GW Pharmaceuticals (Cambridgeshire, UK) provided funds to support the conduct of the survey, including consulting fees too. The analyses and writing of this manuscript were supported by NIH (Bethesda, MD) grant K24NS126861. R.F., J.S.G., K.P.H., R.R.E., and A.D.W. received consulting fees from GW to design the survey. B.L.F. has obtained funding from Pfizer Inc. (GRAND Awards, including salary support) for investigator-initiated projects; Indivior for a clinical trial sponsored by Indivior. B.L.F. has in-kind donations of cannabis products from Aurora Cannabis Enterprises Inc. and study medication donations from Pfizer Inc. (varenicline for smoking cessation) and Bioprojet Pharma. He was also provided a coil for a Transcranial magnetic stimulation (TMS) study from Brainsway. B.L.F. has obtained industry funding from Canopy Growth Corporation (through research grants handled by the Centre for Addiction and Mental Health and the University of Toronto), Bioprojet Pharma, Alcohol Countermeasure Systems (ACS), Alkermes and Universal Ibogaine. He has participated in a session of a National Advisory Board Meeting (Emerging Trends BUP-XR) for Indivior Canada and has been consultant for Shinogi. He is supported by CAMH, Waypoint Centre for Mental Health Care, a clinician-scientist award from the department of Family and Community Medicine of the University of Toronto, and a Chair in Addiction Psychiatry from the department of Psychiatry of University of Toronto. The remaining authors declare no conflict of interest., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Benzodiazepines (BZDs), a class of sedative-hypnotic medications, generated concern as their popularity grew, with particular alarm regarding elevated rates of BZD use among chronic pain populations. Consistent with negative reinforcement/motivational models of substance use, desire for pain alleviation may motivate BZD use. Yet, little is known about relations between pain and addiction-relevant BZD use processes. This cross-sectional survey study aimed to: a) test associations between pain intensity and clinically relevant BZD use patterns, and b) examine the role of pain catastrophizing in hypothesized pain-BZD relations. Participants included 306 adults with chronic musculoskeletal pain and a current BZD prescription who completed an online survey study (M age  = 38.7, 38.9% female). Results indicated that pain intensity was positively associated with past-month BZD use frequency, BZD dependence severity, and likelihood of endorsing BZD misuse behaviors (ps < .05). Pain catastrophizing was positively associated with BZD dependence/likelihood of BZD misuse, covarying for pain intensity (P < .05). These findings build upon an emerging literature by highlighting positive covariation of pain intensity and pain catastrophizing with addiction-relevant BZD use behaviors. Results underscore the need to further investigate high-risk BZD use among individuals with chronic pain, with and without concurrent opioid use, to inform prevention/intervention efforts. PERSPECTIVE: This article presents findings on cross-sectional associations of pain intensity and pain catastrophizing with clinically relevant benzodiazepine (BZD) use outcomes, including dependence and misuse, among individuals with chronic pain. Findings help elucidate the higher burden of BZD misuse/dependence in chronic pain populations and suggest that pain relief may be a common, yet under recognized, self-reported motivation for taking BZDs., (Copyright © 2022 United States Association for the Study of Pain, Inc. Published by Elsevier Inc. All rights reserved.)

Objective: Chronic pain and hazardous alcohol use (i.e., a pattern of alcohol consumption that increases risk for harmful consequences) are prevalent and frequently comorbid conditions that have been posited to interact in a bidirectional manner, leading to greater pain and heavier drinking. Despite evidence that emotion dysregulation (i.e., difficulty modulating emotional responses when experiencing negative emotions) is independently associated with both greater pain and greater alcohol consumption, we are not aware of any previous research examining relations between emotion dysregulation, pain intensity, and hazardous alcohol use among individuals with chronic pain., Method: Participants included 125 past-month alcohol users with chronic musculoskeletal pain (38.4% female; mean age = 32.97 years; mean drinks/day = 1.62) who were recruited for an online survey study of pain and substance use., Results: As expected, emotion dysregulation was positively associated with increased odds of hazardous alcohol use. We also observed a significant indirect association, such that higher levels of emotion dysregulation were associated with greater pain intensity, which in turn was associated with a greater likelihood of scoring above the Alcohol Use Disorders Identification Test cutoff for hazardous alcohol use., Conclusions: These findings suggest that emotion dysregulation may contribute to hazardous drinking among individuals with chronic pain, perhaps indirectly via pain amplification. Emotion dysregulation warrants consideration as a potential transdiagnostic vulnerability factor in comorbid chronic pain and hazardous drinking. Future prospective research is needed to examine causal pathways and establish temporal precedence.

Background: Cognitive behavioral therapy (CBT) is effective in the treatment of major depressive disorder (MDD). Transcranial Direct Current Stimulation (tDCS) has demonstrated preliminary antidepressant effects and beneficial effects on cognitive function., Objective: We investigated the feasibility and acceptability of using tDCS to enhance the effects of computer-based CBT for treatment of MDD., Materials and Methods: In a randomized, double-blind, sham-controlled study, 14 patients with MDD on stable or no pharmacotherapy received active or sham bifrontal tDCS for four weeks with concurrent CBT., Results: Ten participants completed the protocol. Three withdrew from the study because of lack of efficacy or dislike of the eCBT program. One was discontinued from the protocol by the investigators. Treatment was well tolerated, and most side-effects were mild and consistent with prior tDCS research. Pooled data from both groups showed significant baseline to endpoint improvement in depression (p = 0.008). Overall percent change on the HAMD-21 was 28.98%. The study was underpowered to detect differences in tDCS treatment groups., Conclusions: Combining tDCS with computer-based CBT is feasible for MDD. Further work is needed to evaluate potential synergistic effects of combined tDCS and CBT., (© 2018 International Neuromodulation Society.)

As the only endemic member in New Zealand of the ancient conifer family, Araucariaceae, Agathis australis is an ideal species to study putatively long-evolved mycorrhizal symbioses. However, little is known about A. australis root and nodular arbuscular mycorrhizal fungi (AMF), and how mycorrhizal colonisation occurs. We used light, scanning and transmission electron microscopy to characterise colonisation, and 454-sequencing to identify the AMF associated with A. australis roots and nodules. We interpreted the results in terms of the edaphic characteristics of the A. australis-influenced ecosystem. Representatives of five families of Glomeromycota were identified via high-throughput pyrosequencing. Imaging studies showed that there is abundant, but not ubiquitous, colonisation of nodules, which suggests that nodules are mostly colonised by horizontal transmission. Roots were also found to harbour AMF. This study is the first to demonstrate the multiple Glomeromycota lineages associated with A. australis including some that may not have been previously detected., (Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Alnus glutinosa is an important pioneer species that forms effective symbioses with Frankia and ecto and arbuscular mycorrhizal fungi (AMF). There is evidence that Frankia and AMF interact and the focus of this study was to investigate how interactions affected root system and root hair development. A. glutinosa seedlings were grown in pots in soil pre-inoculated with the AMF Gigaspora rosea. Seedlings were inoculated with Frankia either immediately on transfer to AMF-inoculated pots (day 0) on day 15 or on day 30 following AMF inoculation so the effect of timing of inoculation on interactions could be determined. Seedlings were harvested in batches at intervals of 10, 15, 20, 25 and 30 days after the commencement of each treatment. Both G. rosea and Frankia increased root branching and effects were greater when both were present. By contrast, both G. rosea and Frankia decreased root hair numbers markedly. Effects on root hair development were not a consequence of phosphorous, as P levels were not changed significantly in seedlings colonised by G. rosea or nodulated by Frankia. Effects are not due to differences in root system size but conceivably could offset some of the carbon costs incurred by the symbioses.

Flavonoids are a diverse class of polyphenolic compounds that are produced as a result of plant secondary metabolism. They are known to play a multifunctional role in rhizospheric plant-microbe and plant-plant communication. Most familiar is their function as a signal in initiation of the legume-rhizobia symbiosis, but, flavonoids may also be signals in the establishment of arbuscular mycorrhizal symbiosis and are known agents in plant defence and in allelopathic interactions. Flavonoid perception by, and impact on, their microbial targets (e.g. rhizobia, plant pathogens) is relatively well characterized. However, potential impacts on 'non-target' rhizosphere inhabitants ('non-target' is used to distinguish those microorganisms not conventionally known as targets) have not been thoroughly investigated. Thus, this review first summarizes the conventional roles of flavonoids as nod gene inducers, phytoalexins and allelochemicals before exploring questions concerning 'non-target' impacts. We hypothesize that flavonoids act to shape rhizosphere microbial community structure because they represent a potential source of carbon and toxicity and that they impact on rhizosphere function, for example, by accelerating the biodegradation of xenobiotics. We also examine the reverse question, 'how do rhizosphere microbial communities impact on flavonoid signals?' The presence of microorganisms undoubtedly influences the quality and quantity of flavonoids present in the rhizosphere, both through modification of root exudation patterns and microbial catabolism of exudates. Microbial alteration and attenuation of flavonoid signals may have ecological consequences for below-ground plant-microbe and plant-plant interaction. We have a lack of knowledge concerning the composition, concentration and bioavailability of flavonoids actually experienced by microbes in an intact rhizosphere, but this may be addressed through advances in microspectroscopic and biosensor techniques. Through the use of plant mutants defective in flavonoid biosynthesis, we may also start to address the question of the significance of flavonoids in shaping rhizosphere community structure and function.

The effect of interactions between Casuarina species, Frankia strains and AMF on nitrogen isotope fractionation within the plant were determined under conditions where changes in source nitrogen were minimized by growing plants in mineral nitrogen-deficient conditions and without added organic N. Casuarina cunninghamiana, C. equisetifolia, C. glauca, and C. junghuniana were inoculated singly with three Frankia strains or were dual inoculated with Frankia and Glomus fasciculatum. The %N and delta 15N of separated parts of plants inoculated with the three Frankia strains or with Frankia + Glomus were not significantly different within Casuarina species. However, the slow-growing C. junghuniana differed in several variables from the other three species. There was a highly significant, linear relationship between the natural logarithms of cladode N content and delta 15N of plants of the four Casuarina species when inoculated with Frankia or with Frankia + Glomus, showing that nitrogen supply and the correlated variable, plant growth rate, were major determinants of delta 15N. Provision of small quantities of (NH4)2SO4 or KNO3 increased several-fold the growth of three of the Casuarina species when inoculated with Frankia alone or with Frankia + Glomus. Within species, mycorrhizal and non-mycorrhizal plants receiving supplementary soluble phosphate were of similar dry weights at harvest. delta 15N values for cladodes of C. cunninghamiana, C. equisetifolia and C. glauca were similar, but values for the poor growing C. junghuniana were more variable and, with the exception of plants receiving KNO3, were lower than those of the other three species. Reduced growth due to suboptimal availability of N or P had a major influence on delta 15N and, in these conditions where plants could not access significant amounts of organic N, outweighed any effects on cladode delta 15N of colonization by Glomus. delta 15N values of nodules were higher than other parts of Frankia or Frankia + Glomus inoculated Casuarinas, conceivably due to retention in nodules of fixed N, with delta 15N close to zero.

The 3-phosphoglycerate kinase (PGK) gene of the arbuscular mycorrhizal fungus Glomus mosseae has been isolated by differential RNA display (DD). Experimentally, the technique of DD was utilized to simultaneously compare the mRNA transcript populations from Lycopersicon esculentum root systems colonized by the arbuscular mycorrhizal fungus G. mosseae and non-mycorrhizal plants. A differentially expressed band was isolated and cloned from mycorrhizal tissue. The isolated DD fragment was screened and sequenced. A reverse transcription-PCR (RT-PCR) technique detected transcripts in germinated spores and G. mosseae-colonized root systems but not in uncolonised root systems. The full-length cDNA was isolated by RACE and corresponded to the 3-phosphoglycerate kinase gene of G. mosseae. The cDNA encodes a polypeptide of 416 amino acids, with a predicted molecular weight of 44 764 Da. The PGK proteins shows high homology to those PGKs of other fungi and the phylogenetic relationship among 14 isolated fungal PGK sequences is illustrated.

Although the importance of root production and mortality to nutrient fluxes in ecosystems is widely recognized, the difficulties associated with root measurements have limited the availability of reliable data. We have used minirhizotrons and image analysis to measure root longevity of Prunus avium L., Picea sitchensis (Bong.) Carrière, Acer pseudoplatanus L. and Populus x canadensis cv. Beaupre directly in cohorts of roots. Major differences in the longevity of roots among species were identified. For example, 40% of Prunus avium roots but only 6% of Picea sitchensis roots survived for more than 14 days. Survival analysis of cohorts of roots of Prunus avium and Populus x canadensis revealed differences in the distribution of longevity among cohorts. Genetic, biotic and abiotic factors that may influence longevity are discussed.

We compared root system morphogenesis of micropropogated transplants of Prunus cerasifera L. inoculated with either of the arbuscular mycorrhizal (AM) fungi Glomus mosseae or Glomus intraradices or with the ericoid mycorrhizal species Hymenoscyphus ericae. All plants were grown in sand culture, irrigated with a nutrient solution that included a soluble source of phosphorus, for 75 days after transplanting. Arbuscular mycorrhizal colonization increased both the survival and growth (by over 100%) of transplants compared with either uninoculated controls or transplants inoculated with H. ericae. Arbuscular mycorrhizal colonization increased root, stem and leaf weights, leaf area, root length and specific leaf area, and it decreased root length/leaf area ratio, root/shoot weight ratio and specific root length. Both uptake of phosphorus and its concentration in leaves were increased by AM infection, although the time course of the relationships between intensity of AM infection and P nutrition were complex and suggested a role for factors other than nutrition. The time course for the development of infection varied. It was most rapid with G. mosseae, but it was ultimately higher with G. intraradices. None of the treatments significantly affected the lengths of adventitious roots or the first-, second- or third-order laterals that developed from them. Arbuscular mycorrhizal colonization increased the intensity of branching in all root orders with the effect being most obvious on first-order lateral roots where the number of branches increased from under 100 to over 300 brances m(-1). As a result, although first-order laterals made up 55% of the root systems of control plants, the comparable value was 36% in AM-infected plants. In contrast, second-order laterals represented 25% of control root systems, but 50% of AM-colonized root systems. Glomus intraradices but not G. mosseae increased root diameter. Anatomical studies revealed no changes in the overall form of the root tip, although there were changes in the diameter of the root cap, cell numbers and cell size. Hymenoscyphus ericae increased the duration of the metaphase index. Both AM fungal treatments increased the concentrations of soluble proteins in root extracts and modified the protein profiles by the elimination and addition of protein bands detected by PAGE analysis. We conclude that AM fungal inoculation influenced processes in the root system at different levels, but not all effects were due to improved P nutrition or increased physiological age.