Biology subjects

Senior, J.

Publications and source records attributed to Senior, J..

3 recordsLinked to original sources

bioRxiv2025

Electroencephalography, pupillometry, and behavioral evidence for locus coeruleus-noradrenaline system related tonic hyperactivity in older adults

Neuroimaging studies have shown that age-related dysregulation of the locus coeruleus-noradrenaline (LC-NA) system is associated with cognitive decline. However, due to limitations in directly measuring LC function in vivo, it remains unclear whether age-related alterations in humans reflect tonic LC-NA system hyper- or hypoactivity, constraining our understanding of underlying mechanisms and hampers the development of targeted preventative interventions. In this study, we tested the hypothesis that cognitively healthy older adults sustain tonic LC hyperactivity, by acquiring electrophysiological, pupillometric, and behavioral measures during a passive and active auditory oddball paradigm. We capitalized on the LC-NA systems role in arousal regulation and manipulated state arousal using the unpredictable threat of electric shock. We hypothesized that if older adults maintain elevated LC activity compared with young adults, task-evoked noradrenergic responses would be less responsive to arousal in older adults. Consistent with this hypothesis, arousal elicited weaker behavioral responses, pupil dilation responses, and P300 event-related potentials in older adults compared with young adults. Linear mixed models revealed an arousal by modality interaction, showing that arousal differentially modulated attentional control to salient but task-irrelevant distractors between both age groups. Collectively, these findings support the hypothesis that aging is associated with tonic LC-NA system hyperactivity in humans, with neuromodulatory consequences for mechanisms of attentional control. Furthermore, the multimodal approach underscores the potential of non-invasive physiological markers to assess LC-NA system function throughout aging and identify individuals at elevated risk for neurodegenerative progression prior to the emergence of clinical biomarkers. Highlights- Behavioral, pupil and EEG data indicate LC-NA tonic hyperactivity in older adults. - Arousal modulates attentional control differently in young vs. older adults. - Older adults show increased distractibility from reduced habituation. - Arousal differentially modulates alpha power and aperiodic activity across age groups. - Phasic noradrenergic responses are modulated by state, arousal, and attention.

neuroscience↗

bioRxiv2025

Amino acid biostimulant increases pine photosynthetic efficiency and growth through optimised mycobiome and nitrogen assimilation

BackgroundAmino-acid biostimulants have emerged as powerful alternatives to conventional inorganic nitrogen fertilisers, yet their potential in forestry species like radiata pine (Pinus radiata) remains largely unexplored. In this study, we reveal physiological mechanisms of enhanced growth of radiata pine seedlings that are achieved by substituting standard inorganic fertigation, either partially or entirely, with amino-acid-based biostimulants. ResultsAmino-acid fertigation notably increased shoot biomass, plant height, and collar diameter. Critically, this approach reshaped the root fungal community, selectively enriching fungi with diverse ecological roles, including several taxa known for auxin production. These microbial shifts correlated directly with elevated auxin concentrations observed in needle tissues, providing a plausible mechanism for the enhanced growth. Machine learning models further identified key fungal genera that strongly associated with plant biomass, reinforcing microbiome shifts as a contributing mechanism to enhanced growth. Additionally, amino-acid fertigation improved nitrogen assimilation, correlating positively with increased chlorophyll content and photosynthetic efficiency. ConclusionsOur findings highlight that the transition from inorganic source to amino-acid biostimulants not only enhances plant growth and nitrogen use but also promotes a beneficial root microbiome, thereby offering a sustainable pathway to nursery production of radiata pine.

plant biology↗

bioRxiv2023

Evolution of rarity and phylogeny determine above- and belowground biomass in plant-plant interactions

Rare species are often considered inferior competitors due to occupancy of small ranges, specific habitats, and small local populations. However, the phylogenetic relatedness and rarity level of interacting species in plant-plant interactions are not often considered when predicting the competitive response of rare plants. We used a common garden of 25 species of Tasmanian Eucalyptus, varying in rarity to allow us to differentiate the competitive abilities of rare versus common species when grown in mixtures varying in phylogenetic relatedness and rarity. We demonstrate increased biomass production of rare plant species when interacting with genetically intermediate neighbors through synergistic non-additive effects not seen in common species. Additionally, we also find that all plants, regardless of rarity status, maintain 47% greater aboveground and 69% greater belowground biomass when interacting with common species compared to the rarest species. However, species-specific interactions with one particular common species, E. globulus, yielded a 97% increase in biomass compared to average biomass yields in other interactions, suggesting the importance of E. globulus integration into rare species restoration plantings. These results are important because they suggest that the evolutionary processes driving species rarity and the phylogenetic divergence of traits interact to drive ecological dynamics of plant-plant interactions in non-additive ways. Through the ecological and evolutionary consideration of performance traits, rarity, and species-specific effects, we can more accurately predict plant-plant interaction dynamics varying in rarity and relatedness across the landscape.

ecology↗