Most hormesis research has focused on short-term physiological responses in plants. Whether such transient stimulation translates into sustained biomass gain, and how far the rhizosphere microbiome mediates this process, remain poorly understood. In this study, we exposed the hyperaccumulator Sedum alfredii Hance to a low dose of cadmium (Cd) at three distinct developmental stages: seedling stage (SS), rapid growth stage (RS), and stable growth stage (ZS). A control group (CK) received no Cd throughout the experiment. Cadmium was applied once to the cultivation substrate at the designated stage, and plants were then grown on to the end of a 100-day observation period. Integrating longitudinal growth monitoring with 16S rRNA amplicon sequencing and predictive functional profiling (PICRUSt2), we assessed the long-term consequences of hormetic stimulation and its underlying microecological mechanisms. Results show maximum biomass stimulation amplitudes of 40.7%, 24.4%, and 29.6% under SS, RS, and ZS, respectively. Long-term outcomes, however, diverged sharply: total plant biomass after 100 d exceeded that of CK by 67.7% (SS) and 54.8% (ZS) (p < 0.05), whereas RS showed no statistically significant deviation from CK, and belowground biomass remained comparable across all treatments. Short-term stimulation amplitude therefore does not predict long-term biomass gain; rather, the developmental timing of stress exposure governs the outcome. Low-dose Cd alters rhizosphere organic acid profiles: SS and ZS significantly increase secretion of malic, shikimic, and fumaric acids, driving functional reprogramming of microbial communities. SS upregulates pathways for pigment and vitamin biosynthesis while suppressing defensive functions such as antibiotic synthesis, reallocating resources from defense to growth. ZS activates complex carbon degradation pathways and downregulates lipopolysaccharide synthesis, facilitating compensatory growth in later stages. By contrast, RS exhibits broad suppression of most organic acids relative to CK, leading to weak coupling between initial stimulation and microbial responses—and thus its transient advantage is lost over time.
Stomata regulate water loss and carbon assimilation in response to environmental changes such as soil water deficit and high air temperature. The effects of these environmental stresses on tree growth and ecophysiological parameters linked with photosynthesis and gas exchange, such as stomata, are mostly studied separately, even though they often occur concurrently in nature. Two Populus euramericana genotypes grown under controlled chamber were first subjected to soil water deficit at ambient air temperature and then to high temperature. We measured leaf gas exchange and stomatal conductance (g sw ) dynamics in response to changes in irradiance or vapor pressure deficit. Physiological and morphological traits were assessed in relation to stomatal responses. At elevated temperature, stomata exhibited a two-step (bimodal) response, characterized by an initial decline in g sw followed by a recovery. The genotypes differed slightly in g sw dynamics in response to irradiance and VPD, particularly after a high-temperature event. Faster stomatal responses did not appear to be linked to stomatal morphology. Our results reveal a trade-off between water loss and carbon gain under combined stresses.
The Earth’s geomagnetic field (GMF, 25-65 µT) modulates plant physiology, but responses to magnetic deprivation remain poorly understood. We investigated how a near-null magnetic field (NNMF, ∼30 nT) impacts Mentha longifolia , focusing on the interplay between primary physiology, stress signalling, and specialized metabolism, particularly essential oil yield, carvone biosynthesis and phenolic compounds. NNMF altered photosynthetic performance, reducing chlorophyll a and carotenoid contents, PSII quantum yield under illumination, and rapidly reversible thermal energy dissipation. This photosynthetic energy deficit coincided with transcriptional repression of MEP pathway genes including IspG and GDPS , and was associated with reduced essential oil yield and lower accumulation of major monoterpenes, particularly carvone. The altered photosynthetic performance was accompanied by organ-specific ROS responses, including an approximately 80% increase in root H 2 O 2 and a reduction in root protein content, together with transcriptional downregulation of genes encoding antioxidant enzymes, including CAT and APX . Phytohormone profiling revealed organ-specific responses to NNMF, including opposite changes in OPDA and cytokinin-related metabolites between roots and shoots, together with reduced SA levels in both organs. Consequently, phenylpropanoid metabolism was altered, causing a ∼50% reduction in total phenolics and CHI downregulation, alongside structural flavonoid changes. Overall, GMF deprivation was associated with a stress response characterized by altered photosynthetic performance, organ-specific ROS dynamics, hormonal remodelling, and changes in specialized metabolism, resulting in reduced essential oil production and altered phenolic composition in M. longifolia .
Abiotic and biotic stressors co-occur in cereal agroecosystems, but their combined effects on pest epidemiology and crop health remain unclear. This study evaluated the interactive effects of water stress (WS) at 100%, 75%, and 50% field capacity (FC), barley cultivar (drought-tolerant Sararoud versus drought-sensitive Afzal), and infection of barley plants with Barley yellow dwarf virus-PAV (BYDV-PAV) on the demographic performance of the aphid vector Rhopalosiphum padi. Results revealed that aphid demographic responses to WS depended on the infection status of the host plants and barley cultivar. At 50% FC, aphids feeding on BYDV-PAV-infected plants had fecundity values 195.6% and 202.4% higher, and adult longevity 22.4% and 19.4% longer, on Sararoud and Afzal, respectively, than aphids feeding on virus-free plants. The intrinsic rate of increase was also 25.8% and 24.0% higher on infected Sararoud and Afzal plants, respectively; under severe WS, the intrinsic rate of increase, finite rate of increase, and net reproductive rate were lower in aphids feeding on virus-free plants. Under WS, aphids feeding on BYDV-PAV-infected plants showed higher age-stage survival, life expectancy, and reproductive value than aphids feeding on virus-free plants, while Sararoud showed greater antioxidant enzyme activity and aphid demographic responses differed between cultivars. Under controlled greenhouse conditions, these findings indicate that cultivar identity is associated with differences in virus–plant–vector interactions and support evaluating combined stresses in future IPM studies.
Stomata regulate water loss and carbon assimilation in response to environmental changes such as soil water deficit and high air temperature. The effects of these environmental stresses on tree growth and ecophysiological parameters linked with photosynthesis and gas exchange, such as stomata, are mostly studied separately, even though they often occur concurrently in nature. Two Populus euramericana genotypes grown under controlled chamber were first subjected to soil water deficit at ambient air temperature and then to high temperature. We measured leaf gas exchange and stomatal conductance (gsw) dynamics in response to changes in irradiance or vapor pressure deficit. Physiological and morphological traits were assessed in relation to stomatal responses. At elevated temperature, stomata exhibited a two-step (bimodal) response, characterized by an initial decline in gsw followed by a recovery. The genotypes differed slightly in gsw dynamics in response to irradiance and VPD, particularly after a high-temperature event. Faster stomatal responses did not appear to be linked to stomatal morphology. Our results reveal a trade-off between water loss and carbon gain under combined stresses.
