Global warming generates intensifying risks to floral organs, whereas most floral heat stress research concentrates on species with low floral resource allocation. This study explores heat response mechanisms in high-floral-allocation orchids using Oncidium and its related germplasm (dancing lady orchids) as experimental materials. Two core physiological indicators were adopted to quantify floral thermotolerance: cell membrane thermostability (T50) and perianth cuticular phase transition temperature (Tp). We further correlated these two indices with floral allocation and hydraulic traits, compared the divergent thermal responses driven by structural heterogeneity across sepals, petals, and labella, and characterized shifts in floral volatile metabolites under sequential high-temperature gradients. No significant correlation was detected between floral T50 and Tp values. Phylogenetic signal analysis revealed that T50 was weakly constrained by phylogenetic relationships, whereas Tp exhibited no phylogenetic dependence. T50 displayed significant negative correlations with flower area and fresh mass, implying divergent membrane thermal protection capacity across flowers with varying structural construction costs. Tp was negatively associated with floral longevity, and orchid flowers exhibited lower cuticular phase transition temperatures relative to non-orchid angiosperms, which may facilitate evaporative cooling through enhanced water loss. The structural traits of sepals, petals, and labella showed different modular linkage with floral heat tolerance in network analysis. Volatile compounds with low water solubility displayed a unimodal accumulation pattern, rising initially, then declining under elevated temperatures. Taken together, floral thermotolerance is a multifactorially regulated trait that should be prioritized in germplasm conservation and breeding programs for dancing lady orchids.
Capsaicinoid biosynthesis in chilli pepper requires the conversion of vanillin to vanillylamine, a reaction catalyzed by vanillin aminotransferase, VAMT, previously annotated as pAMT. Recent work identified VAMT as a specialized member of the Solanaceae cytosolic GABA-aminotransferase lineage and showed that closely related enzymes can differ markedly in activity despite high overall sequence similarity. However, it remains unclear whether VAMT-like vanillylamine-forming activity is functionally restricted to Capsicum or more broadly retained among related Solanaceae homologues when tested in a plant context.Here, we used VAMT protein sequences from Capsicum chinense cv. red habanero and Capsicum annuum cv. Yume-matsuri to identify homologous aminotransferases from tomato and tobacco and compared their capacity to support vanillylamine accumulation in a transient Nicotiana benthamiana leaf assay following vanillin feeding. First, we established an LC-MS/MS workflow for the detection of vanillin, vanillylamine, and vanillyl alcohol in plant extracts, and optimised precursor feeding conditions for the transient assays using the two Capsicum reference enzymes. Under the tested conditions, tomato VAMT-like homologues SlVAMT1 and SlVAMT2 led to substantially higher vanillylamine accumulation than the reference Capsicum enzyme, whereas SlVAMT3 did not result in detectable vanillylamine accumulation above the empty vector control. Furthermore, evaluation of the Nicotiana VAMT-like homologues revealed substantial variation, with NtVAMT1 supporting increased vanillylamine accumulation, while NtVAMT2 and the tested N. benthamiana homologues did not increase accumulation above the control. These results demonstrate that tomato VAMT-like homologues previously shown to possess vanillylamine-forming activity in recombinant assays can enable unexpectedly high vanillylamine accumulation in a transient plant system and provide the first plant-based assessment of the tested Nicotiana homologues. Together, the data show that closely related VAMT-like homologues differ in their effects on vanillylamine accumulation under transient expression conditions.
Aluminum (Al) toxicity constrains plant productivity on ≈30% of arable acidic soils, yet woody species show cultivar-specific regulation of conserved Al-resistance mechanisms. We dissected physiological, biochemical and molecular responses that underpin Al resistance in three highbush blueberry (Vaccinium corymbosum L.) cultivars “Cargo” (Al-tolerant), “Star” (Al-sensitive) and “Liberty” (uncharacterized). One-year-old plants were hydroponically exposed to 0, 200, 400 or 800 μM AlCl3 (pH 4.5) for 0–48 h. We quantified Al accumulation, gas exchange, antioxidant metrics, TCA-cycle enzymes (NAD-IDH, NAD-MDH) and the expression of VcMATE and VcALMT transporter genes. “Cargo” accumulated up to 18-fold more Al in roots than in shoots yet maintained photosynthetic rate (−21% at 800 μM after 48 h) and pigment integrity, coincident with a 2- to 3-fold surge in root NAD-MDH activity and stable ASC/DHA ratios. “Star” accumulated less root Al but showed marked declines in net photosynthesis (−33%) and increased lipid peroxidation (2-fold). “Liberty” displayed concentration dependent phenotypes intermediate at low to moderate Al doses (200-400 μM) but exhibiting the greatest net photosynthesis decline at 48 h (800 μM), indicated of high dose sensitivity. VcMATE was transiently repressed at 24 h in all cultivars; a transient recovery (≈2-fold at 48 h, 400 μM) was observed in “Liberty”, while “Cargo” roots-maintained suppression, consistent with an internal tolerance strategy. VcALMT was generally down-regulated across cultivars and time points. Blueberry Al tolerance hinges on rapid root sequestration, sustained redox buffering and TCA-cycle up-regulation that preserves carbon flux to organic-acid detoxification. These findings provide a mechanistic framework for improving Al resistance in woody plants, with direct relevance for cultivar selection and orchard management on acid soils, particularly in volcanic regions such as southern Chile.
Nitrification is a major route of nitrogen loss from agricultural soils, yet it is increasingly clear that plants are important for microbial nitrogen cycling. Through nitrogen-form sensing, proton extrusion and selective root exudation, roots can actively remodel the chemical and biological environment in which nitrifiers operate. Biological nitrification inhibition (BNI), the suppression of nitrifier activity by root-derived compounds and associated rhizosphere processes, provides a compelling example of plant-mediated control over soil nitrogen cycling. Here, we critically synthesize BNI from a plant physiology and biochemistry perspective, focusing on how ammonium nutrition, rhizosphere acidification, plasma-membrane H+-ATPase activity, and exudate transport regulate BNI release. We integrate the chemistry of hydrophilic and hydrophobic BNIs with their mobility, persistence, and accessibility to ammonia-oxidizing bacteria, ammonia-oxidizing archaea, comammox Nitrospira, and nitrite-oxidizing bacteria. Characterized BNIs act through multiple mechanisms, including inhibition of nitrification enzymes (AMO, HAO, and NXR), redox modulation, reactive oxygen and nitrogen species interactions, and trace-metal interference. This diversity suggests that BNI is not a single-compound effect, but an inducible rhizosphere trait shaped by plant metabolism, root transport, and microbial target specificity. We propose a plant-centered framework linking nitrogen sensing, secondary metabolite biosynthesis, exudate delivery, and nitrifier responses. This review highlights the need to resolve the biosynthetic pathways, transporter systems, and regulatory signals that control BNI release, and to validate their functions under realistic plant-soil conditions. By framing BNI as a plant-regulated biochemical trait, we provide a basis for understanding how roots influence rhizosphere nitrogen availability and for developing crops with improved nitrogen acquisition and reduced nitrification losses.
