Drought and nitrogen deposition are global change factors that influence forest dynamics by altering tree physiology and growth. Nevertheless, their interactive effects on tree physiology (especially leaf photosynthetic traits) remain poorly understood. Here, we examined the effects of drought (D), nitrogen addition (N) and their combination (DN) on the leaf photosynthetic traits of two dominant evergreen broadleaved tree species (Schima superba and Michelia macclurei) in a subtropical forest in southern China following a 2-year treatment period. For S. superba, compared to the control (CK), D significantly decreased the leaf photosynthetic rate (Asat), stomatal conductance (gs), stomatal size (SS) and leaf nitrogen content (LNC), but increased soluble sugar content (LSS). Although N exerted no significant effects on any leaf functional traits relative to CK, DN significantly alleviated drought-induced declines in Asat, gs, SS and LNC of S. superba when compared with D. This indicates a significant interactive effect between drought and nitrogen supply: nitrogen addition only mitigated drought stress damage under water limitation, rather than improving leaf photosynthetic performance under well-watered conditions. In contrast, M. macclurei showed no significant differences in leaf photosynthesis-related traits across the D, N, DN and CK treatments. The divergent responses of the two species to D might be related to inherent differences in their hydraulic traits (turgor loss point-TLP and minimum conductance-gmin) and root characteristics. The deep-rooted S. superba displayed significantly higher TLP and gmin than the shallow-rooted M. macclurei. Overall, our results suggest that S. superba is more sensitive to D than M. macclurei. The negative effects of D on leaf photosynthesis of S. superba were significantly alleviated by N in this subtropical forest.
Increasing variability in water availability, caused by changing climatic conditions, is a major constraint for onion production. The present study investigated the physiological, metabolic and molecular responses of the diploid onion Allium cepa L. and the triploid hybrid Allium × cornutum Clementi ex Visiani under drought and waterlogging. Plants were exposed to controlled stress conditions, and responses were evaluated through relative water content (RWC), electrolyte leakage (EL), photosynthetic pigments, amino acid composition, total phenolic content (TPC), individual phenolic compounds and expression of antioxidant genes (CAT, SOD, AOX). Allium × cornutum showed a more pronounced response to drought, characterized by higher RWC, stable chlorophyll and carotenoid levels, increased accumulation of free amino acids and phenolic compounds, especially chlorogenic acid and quercetin glycosides, with significant upregulation of the antioxidant genes SOD and CAT. Allium cepa responded more strongly to waterlogging, showing increased amino acid levels, accumulation of quercetin and its glycosides, a marked increase in α-aminobutyric acid (AABA) concentration and higher expression of CAT and SOD. These results show distinct metabolic responses and physiological changes to drought and waterlogging, reflecting stress-specific adjustments under extreme water conditions and contributing to a better understanding of water stress adaptation in Allium species.
The evolutionary transition from autotrophy to full mycoheterotrophy is often viewed as a progressive loss of photosynthetic capacity, yet comparative studies of closely related leafless orchids that retain residual photosynthesis remain scarce. The Cremastra appendiculata species complex provides a valuable system for testing whether dependence on fungal carbon varies among leafless species. We compared the nutritional modes of two closely related leafless orchids, Cremastra aphylla and C. saprophytica, at flowering and fruiting using natural-abundance stable isotope analyses and measurements of chlorophyll concentration and fluorescence. Both species retained functional, albeit limited, photosynthetic capacity. From flowering to fruiting, chlorophyll concentrations and the maximum quantum yield of photosystem II increased, whereas δ13C values decreased, a pattern consistent with enhanced photosynthetic capacity during reproductive development. However, C. aphylla consistently showed greater 13C enrichment relative to autotrophic reference plants and had a significantly lower chlorophyll concentration during flowering than C. saprophytica, indicating greater dependence on fungal carbon. These results demonstrate that leaflessness does not necessarily imply full mycoheterotrophy and, more importantly, that dependence on fungal carbon can differ even between closely related leafless species. Together with developmental-stage-dependent changes within each species, these interspecific differences suggest that the transition from partial to full mycoheterotrophy can proceed through multiple incremental steps even after leaflessness has evolved.
Flavonoids are frequently presented as health-beneficial plant metabolites, and their subclass anthocyanins is best known for striking flower colours. The biosynthesis of flavonoids has been studied for decades and has developed into a model system in plant biology. Despite thousands of publications about this pathway, there are still open questions about fundamental aspects of anthocyanin biosynthesis. Here, we review the evolution of anthocyanin biosynthesis and highlight key open questions-some of which are sitting in plain sight.
The phenomenon of Balkan high-mountain fen plant endemism, unique within Europe, remains poorly studied. We compiled an original dataset of wetland vegetation-plot data across nine countries where Balkan endemics and subendemics occur. We tested the diversity patterns for endemics, non-endemic habitat specialists of bryophytes and vascular plants and matrix-derived taxa with respect to climate, palaeoclimate, edaphic and topographic factors. We used Spearman correlations, Spatial Autoregressive Error Models, Canonical Correspondence Analysis and Principal Component Analysis of abiotic factors with richness patterns projected using Generalised Additive Models. Two major hotspots of fen endemism, centred around the Rila and Korab Mts, were identified. Species composition of endemics generally follows an east-to-west gradient that coincides with palaeoclimatic patterns. Palaeoclimate was influential for community-scale richness of bryophytes and narrow-range endemics, the latter being positively affected by the Bølling-Allerød precipitation peak and the wet-tundra climate during the glacial. The richness of other groups was affected by recent climate, edaphic factors and topography. Water pH differentiated major vegetation types and affected the richness of matrix-derived taxa and fen bryophytes, but had a minor impact on Balkan endemics, except those associated with serpentinite. Several endemic taxa usually co-exist even in small wetland patches. Palaeoclimate shows that fen endemics evidently experienced drier, warmer summers than today over the last 21,000 years; yet they were more affected by past precipitation. If we conserve Balkan high-mountain fens, their catchment properties and hydrology, and maintain moderate grazing, we increase the likelihood that their endemics will withstand ongoing climate change.
Strawberry micropropagation produces uniform, disease-free planting material. However, repeated in vitro subculturing can simplify the endophytic microbiome, reducing plant vigour and acclimatization success. This study investigated the impact of successive in vitro generations on the endomicrobiome of Fragaria × ananassa cv. San Andreas and determined if targeted biotization with beneficial rhizobacteria can enhance plant performance. Profiled endophytic bacterial and fungal communities were analysed in the mother plant and across three in vitro generations using amplicon sequencing of the 16S rRNA gene and ITS markers. Ten plant growth-promoting bacterial strains were tested in vitro. The most effective strains were combined into consortia, and their impact on growth, survival and phenolic and flavonoid accumulation was assessed under in vitro and ex vitro acclimatization conditions. Successive subcultures simplified the endophytic assemblage. The mother plant exhibited substantially higher bacterial alpha-diversity than in vitro generations, with richness and Shannon diversity declining significantly (P <0.001) across all subcultures. In vitro biotization with A. brasilense Ab-V5 and A. brasilense Ab-V6 increased total dry biomass from 190.63 mg in the control to 216.75 mg and 209.11 mg, respectively. Under ex vitro conditions, several inoculated treatments achieved 100% survival compared with 75% in the non-inoculated control. Prolonged in vitro maintenance reduces the complexity of the strawberry endomicrobiome by imposing a selective bottleneck. Targeted introduction of beneficial bacteria partially compensates by enhancing growth, survival and secondary metabolite accumulation, supporting microbiome-assisted strategies to improve tissue culture performance and ex vitro establishment.
Drought is a key constraint on plant growth and development. Poplars and willows are dioecious plants, and sex-specific responses to drought differ across species. However, little is known about how xylem embolism drives sex-specific hydraulic failure. In this study, male and female Populus cathayana and Salix babylonica were used to investigate the role of embolism in sex-specific drought responses. Drought significantly reduced plant growth and photosynthetic capacity, increased membrane damage and reactive oxygen species accumulation, altered vessel structure and aggravated embolism. P. cathayana males maintained higher net photosynthetic rates than females, whereas S. babylonica females performed better than males under drought stress. P. cathayana males exhibited larger vessel area and diameter but lower density than females, while the opposite sex pattern was observed in S. babylonica. In terms of hydraulic function, male P. cathayana and female S. babylonica had lower embolism degrees, higher hydraulic conductivity and maintained more stable conductivity than their opposite sexes. Embolism degree was strongly correlated with both the standardized vessel structure index and the standardized photosynthetic index (R2 = 0.81 and 0.93 for P. cathayana; 0.78 and 0.91 for S. babylonica, respectively). Overall, male P. cathayana and female S. babylonica were more resistant to embolism, sustaining higher photosynthetic performance and growth. These findings suggest that drought alters xylem vessel structure, thereby inducing embolism and restricting growth, which forms the core mechanism underlying sex-specific drought responses in P. cathayana and S. babylonica.
Pollination shifts result in floral divergence, yet how such shifts influence variation and correlation among floral traits is unclear. We examine whether a transition from bee to hummingbird pollination in sister species of Neotropical spiral gingers - Costus kuntzei, with ancestral bee pollination, and Costus wilsonii, with derived hummingbird pollination - drives phenotypic variation, functional integration and morphological modularity. Using field measurements and observations, we assess pollinator assemblages and pollination syndrome divergence by quantifying a suite of floral traits related to shape, size, colour, scent and nectar reward. We then test whether the shift from bee to hummingbird pollination has led to differences in floral phenotypic variation and integration, and we use geometric morphometric analyses to evaluate modularity hypotheses based on floral function and genetic or developmental constraints. We find that C. wilsonii exhibits changes in, and loss of, multiple floral traits, along with extreme specialization on a single hermit hummingbird species. In contrast, C. kuntzei is visited by a more species-rich pollinator assemblage of euglossine bees and a tabanid fly. Both plant species show similar patterns of floral variation, integration and modularity, with reduced floral variation and modularity patterns concentrated in traits involved in pollinator fit and pollen transfer. The findings suggest that phenotypic patterns reflect functional traits shaped by divergent pollinator-mediated adaptation. This floral adaptation has resulted in stable patterns of trait variation and correlation, consistent with selection for efficient pollination and pollinator fit in both species.
Cyanobacteriochromes (CBCRs) are widely distributed photoreceptors in cyanobacteria, crucial for regulating light-responsive phenomena. CBCR GAF domains form a stable covalent bond with a linear tetrapyrrole chromophore via the canonical Cys residue and exhibit reversible photoconversion. The DXCF (Asp-Xxx-Cys-Phe) -type CBCRs, a dominant subgroup across various clades, are characterized by a highly conserved second Cys residue involved in both phycocyanobilin (PCB)-to-phycoviolobilin (PVB) isomerization and reversible ligation to the chromophore. The AM1_1499g1 GAF domain, categorized as a DXCF-type CBCR, is unique due to the evolutionary loss of this second Cys residue, which is substituted by Ser118. This domain exhibits an orange/green-reversible photocycle alongside thermochromism in its photoproduct state, suggesting a novel spectral tuning mechanism to be elucidated. To elucidate the molecular basis of the spectral tuning mechanism in AM1_1499g1, we performed saturation mutagenesis at the Ser118 position and comprehensively performed spectral analyses of the resulting S118X variants. Spectral analyses classified the S118X mutants into five distinct functional groups based on PCB-to-PVB isomerization activity, thermochromism and photocycle property. These results lead us to propose that the side chain property at Ser118, located near the chromophore centre, affects the chromophore conformation, especially the A-ring conformation, thereby controlling the domain's spectral properties. Framed within the evolutionary transition of AM1_1499g1, our findings demonstrate that single-site mutagenesis at Ser118 is sufficient to recapitulate a broad range of spectral properties. This variation functionally mimics the natural evolutionary divergence of XRG (extended red/green)-type CBCR domains, highlighting the exceptional molecular plasticity of this photoreceptor family.
Crassulacean acid metabolism (CAM) photosynthesis is a water-conserving pathway of photosynthesis that typically occurs in leaf- or stem-succulent plants of warm, water-limited habitats. Key features of CAM photosynthesis are nocturnal CO2 uptake and nocturnal increases in tissue acidity. CAM photosynthesis was recently reported in water-deficit stressed carnivorous plants of the genus Pinguicula (Lentibulariaceae). The report is remarkable because CAM has neither been documented in the Lentibulariaceae nor in a carnivorous species before. Furthermore, Pinguicula plants are vastly different in appearance from archetypal CAM plants like cacti and agaves. Evidence of CAM activity in Pinguicula was solely based on small nocturnal increases in leaf titratable acidity. Day-night CO2 gas exchange was measured, but results were inconclusive. To independently verify the presence of CAM in Pinguicula, net-CO2 exchange during 12 h light/12 h dark cycles was measured in plants exposed to different degrees of water-deficit stress using a custom-designed stationary gas-exchange system which enables long-term CO2 monitoring and the detection of small CO2 fluxes. Measurements included eight plants of Pinguicula 'Weser' and encompassed 36 day-night cycles of CO2 exchange. Net CO2 uptake occurred largely in the light via C3 photosynthesis. However, distinct transient reductions in the rate of nocturnal CO2 release were regularly observed during dark periods, as were transient reductions of net CO2 uptake during light periods. In the middle of 14 of 36 dark periods, transient reductions in CO2 release eventually turned into small rates of net dark CO2 fixation. These results provide unequivocal evidence of CAM activity and confirm previous suggestions of low-level CAM in Pinguicula.
Sugarcane (Saccharum spp.) is an important crop for food and energy security. Identifying SNPs and genes associated with sugarcane yield and related traits is crucial for developing high - yielding sugarcane cultivars through molecular breeding. Here, we measured nine phenotypic traits across 160 sugarcane genotypes and employed multiple statistical models (namely MLM, CMLM, MLMM, FarmCPU and SUPER) in GWAS to identify stable and pleiotropic loci. A total of 200 SNPs corresponding to 137 QTLs were detected to be significantly associated with nine traits using multiple statistical models, among which 18 QTLs were consistently identified by two or more models. Notably, the SNP S9A_47793177 on chromosome 9A showed the strongest association with phenotypic variation in aboveground biomass, with a phenotypic explanation rate of 70.54%. Additionally, several QTLs significantly associated with tillering - related traits were identified, suggesting that these QTLs may play crucial roles in the regulation of tillering. The QTLs and SNPs identified in this study provide a significant foundation for molecular marker - assisted breeding in sugarcane. This advancement can significantly enhance the efficiency of genetic improvement for sugarcane yield and tillering - related traits.
Insufficient light intensity diminishes stem mechanical strength of Paeonia lactiflora, adversely affecting the quality of cut flowers. However, the underlying mechanisms remain poorly understood. Through anatomical analysis and matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) combined with LC-MS, the shading-induced changes of morphology and metabolism in fibre cells of P. lactiflora stems were comprehensively characterized for the first time. The results showed that shading inhibited secondary cell wall (SCW) thickening in fibre cells, leading to thinner SCWs and low stem mechanical strength. A total of 931 metabolites were detected in the full-sun and shade groups of P. lactiflora stem sections by MALDI MSI, and 25 significant differential metabolites were identified in the stem fibre cell zones by MS/MS fragmentations. The shading-induced differential metabolites in the fibre cell zones were primarily concentrated on various secondary metabolites with antioxidant defence properties, with their synthesis triggered by shade stress. It indicated that shading reduced P. lactiflora stem mechanical strength by inhibiting fibre SCW thickening, and this inhibition was closely correlated with an enhanced synthesis of defence metabolites in the fibre cells. This study lays a foundation for elucidating the cytological mechanism underlying shading that affects stem mechanical strength.
Rapid fluctuations in light intensity require swift regulatory adjustments of photosynthesis. Although the major plant regulators of fast photosynthetic responses have been identified, additional genes with conditional or subtle effects are likely still undiscovered. We hypothesized that genes co-expressed with the core regulators PGR5, KEA3, STN7 and ZEP also participate in photosynthetic regulation. Transcriptome co-expression analysis defined a set of 'CERP' (CO-EXPRESSED-WITH-REGULATION-OF-PHOTOSYNTHESIS) candidate genes. Arabidopsis thaliana T-DNA insertion mutants for selected CERP loci were isolated. Spectroscopic measurements of whole plants and isolated thylakoid membranes, pigment analyses, native/denaturing gel electrophoresis coupled with immunoblotting and fluorescence microscopy were used to assess photosynthetic parameters under constant light and under rapidly fluctuating light regimes and determine photosynthetic complex composition, as well as localize the proteins. Two mutants showed alterations in non-photochemical quenching (NPQ) during light fluctuations. Mutants lacking CERP1, also known as AAF, showed delayed NPQ relaxation after high-to-low light transitions. Mutants lacking CERP4b, also known as FLAP1, exhibited a higher NPQ during high light phases. These NPQ phenotypes were linked to changes in leaf pigment content and composition. Further characterization of CERP4b/FLAP1 points towards a function of this protein in the formation or composition of the PSII supercomplex. Co-expression mining successfully uncovered additional components that contribute to rapid photoprotective acclimation. CERP1/AAF is essential for fast NPQ relaxation, while CERP4b/FLAP1 contributes to NPQ in high light, likely through effects on PSII antenna. These findings broaden the known regulatory network governing NPQ by including two components that modulate leaf pigment content and composition.
Despite the increasing body of knowledge concerning the influence of the lunar cycle on various components of the biosphere, how living organisms respond to environmental factors across this cycle remains unclear. Recent evidence that cryptochromes are involved in the perception of both magnetic fields and moonlight suggests a potential mechanistic link, whereby plant sensitivity to the geomagnetic field may vary with lunar phase. Here, we test the hypothesis that geomagnetic sensitivity of plant growth is modulated during the lunar cycle. Growth dynamics of Sphagnum riparium were analysed using a long-term field dataset obtained from Karelian mires (Russia). Monitoring was conducted at 2-day intervals over 10 full growing seasons, yielding 1795 growth rate estimates derived from measurements of 245860 shoots. Although no significant relationship between growth rate and the geomagnetic Kp index was detected across the full dataset, phase-resolved analysis revealed a different pattern. Near both the full moon and the new moon, the growth response to geomagnetic variations became significant and exhibited a characteristic flip-flop pattern, with a positive response preceding the lunar phase and a negative response immediately following it. These responses were confined to narrow time windows. The results support the hypothesis of lunar modulation of geomagnetic sensitivity in plants and demonstrate that this sensitivity is temporally gated within specific phases of the lunar cycle. The emergence of a half-lunar (~14.8-day) periodicity in geomagnetic response, absent in the growth rate itself, suggests that this mechanism may function as a regulatory layer synchronizing plant-environment interactions rather than directly controlling growth.
Anthocyanins and betalains are hydrophilic plant pigments with numerous physiological and ecological functions. The biosynthesis routes of anthocyanins and betalains differ, with anthocyanins being synthesized from phenylalanine via the general phenylpropanoid pathway, whereas betalains are derived from tyrosine. Although the precursors phenylalanine and tyrosine are present in all plants, there is no known plant in which both these pigments are co-accumulated. Most plants synthesize anthocyanins, while certain families in the order Caryophyllales produce betalains. There is an apparent mutual exclusion of these two plant pigments. Over the past five decades, evidence has accumulated supporting this theory of mutual exclusion of the two pigments. However, recently published reports claim the presence of anthocyanins in well-known betalain-pigmented plants without providing the necessary evidence. Here, we critically evaluate the origins of such claims, show how methodological limitations and analytical misinterpretations have led to unsupported reports of anthocyanin-betalain co-occurrence, and provide recommendations to ensure robust evidence standards in future studies of plant pigment biosynthesis.
Global climate change has intensified extreme heat and drought events worldwide. Leaf potassium (K), calcium (Ca) and magnesium (Mg) are critical for maintaining plant physiological functions and stress resistance. However, the large-scale distributions, stoichiometric relationships and future climate-change dynamics of these three elements in plants remain unclear. Here, we explored the spatial and temporal variations in leaf K/Ca/Mg concentration and their stoichiometry of woody angiosperm plants in China, and the underlying potential drivers, based on climate and soil variables and CMIP6 future climate data. We found that leaf K and Mg concentrations increased from south-eastern to north-western China, primarily regulated by precipitation, with soil showing limited contribution. Leaf Ca peaked in central China and showed a unimodal relationship with temperature and precipitation, with drought and cold reducing Ca uptake by limiting transpiration. Leaf K and Mg were strongly coupled across China, whereas Ca was coupled with them only in humid and warm regions but became decoupled in arid and cold regions. Under future climate, scenario-based projections suggested that the overall patterns and relationships of leaf K-Ca-Mg may remain similar to current ones, while leaf Ca concentration may increase and become increasingly decoupled from leaf Mg. These findings contribute to our understanding of the nutrient-adaptive strategies of woody plants and provide critical insights for evaluating potential changes in nutrient cycling and forest productivity under global change.
Drought and heavy metal (HM) contamination severely constrain maize productivity in dryland agriculture. While ascorbic acid (AA) and salicylic acid (SA) are recognized as protective agents against abiotic stress, their comparative efficacy and synergistic potential under combined stress remain poorly understood. This study evaluated individual and combined applications of AA (100 mg·L-1, equivalent to 0.57 mM) and SA (0.5 mM) on maize ('Zhengdan No. 16') subjected to four water regimes: well-watered (WW 100%), mild water stress (MWS 75%), moderate water stress (MoWS, 50%), and severe water stress (SWS, 30% field capacity), with or without Pb (200 μM) or Cd (100 μM) exposure. Photosynthetic pigments, gas exchange, phytohormones (ABA, IAA), oxidative stress markers (H2O2, SOD), and macronutrient uptake (N, P, K) were quantified. The Pb concentration (200 μM) was selected based on preliminary dose-response experiments (0, 100, 200, 400 μM), where 200 μM caused significant but non-lethal growth inhibition (30%-40% biomass reduction), allowing assessment of AA/SA mitigation without complete growth arrest. Under WW conditions, AA increased chlorophyll a by 11.0% and SA by 14.5% versus controls. Combined AA+SA + Cd improved selected nutrient responses, including a 2.8% increase in leaf N and a 4.5% increase in leaf K relative to Cd alone under WW conditions; however, leaf P did not increase under all water regimes. AA reduced Cd-triggered H2O2 by approximately 30% and Pb-triggered H2O2 by approximately 18% (P < 0.05). Under SWS, combined treatments improved selected photoprotective responses, including a 14.3% increase in carotenoid content, although Chl a responses were treatment and metal-specific. Exogenous AA and SA, particularly in combination, enhance dryland maize resilience to combined drought and HM stress through improved photosynthesis, reduced oxidative damage, and optimized nutrient acquisition. These findings support antioxidant biostimulants as sustainable tools for crop stress.
Mistletoe-frugivore interactions stand out as one of the classic examples of specialized and reciprocal relationships in ecology and evolutionary biology. Additionally, many theoretical advances have been made by using the interactions between mistletoes and their seed dispersers as study models. Although generally well-studied, there is no single global review on mistletoe frugivory and seed dispersal, creating an opportunity to synthesize existing knowledge, identify major gaps, and advance unresolved and new research questions. We conducted a systematic review of studies on mistletoe frugivory and seed dispersal, focusing on taxonomic, geographic, and methodological patterns, showcasing the plant perspective, which has been comparatively underappreciated relative to seed dispersers' perspective. The number of studies (n = 58) and species studied (n = 36) was proportional to the number of species per genus, although several diverse genera remain understudied. We found very few studies in the tropical rainforests and in the north temperate forests. No endangered mistletoe species (n = 58) have been studied, and only one species has been studied in urban areas. Methodologically, searching for seeds or seedlings in potential recruitment sites predominated, while tracking movements of seed dispersers with radio or GPS devices remains poorly used. Mistletoe-frugivore interactions offer excellent study models for exploring a different suite of ecological questions, yet substantial gaps persist across taxa, regions, and biomes. Future studies should prioritize rarer species, especially those threatened and endemic. Studies should also prioritize understudied biomes, such as the tropical rainforests and north temperate forests. We further believe that many unanswered research questions could be clarified using appropriate and modern methods to assess and record interactions between mistletoes and frugivores, thereby advancing the use of these systems as model frameworks for studying the ecological and evolutionary consequences of seed dispersal.
In alpine conifer forests, nutrient acquisition is shaped by nitrogen (N), phosphorus (P) and cold soils, but the elevational adjustment of nutrient-acquisition traits in Abies fabri is still poorly known. Along the Gongga Mountain transect (2,800-3,400 m), soil inorganic N declined markedly with elevation, whereas available phosphorus, defined here as Bray-1 extractable P, did not differ significantly among elevations. Forests at 2,800, 3,100 and 3,400 m were sampled for soil nutrients, leaf N:P, foliar N and P fractions, root morphology, root exudation, mycorrhizal colonisation, root enzyme activities and non-structural carbohydrates (NSC) to test how leaf nutrient status was linked to belowground acquisition traits. The trait pattern did not follow a directional available-P gradient. With elevation, foliar N allocation shifted from Rubisco towards cell-wall pools, while foliar P shifted towards metabolic and nucleic-acid pools. Fine roots showed a more conservative morphology, with lower specific root length (SRL) and specific root area (SRA), whereas fine-root acid phosphatase (APase) and N-assimilating enzyme activities increased. With the high-elevation decline in leaf N:P, A. fabri responses reflected N-P stoichiometric context, internal nutrient allocation and root-trait coordination rather than a simple soil-P availability gradient.
Phytic acid (PA, InsP6) is the primary phosphorus storage form in seeds, but its poor digestibility in monogastric animals and strong chelation of essential minerals reduce nutritional value, while undigested PA contributes to environmental eutrophication. Developing low phytic acid (LPA) crops is critical for sustainable agriculture, yet LPA genotypes typically exhibit pleiotropic growth defects that limit breeding applications. We employed a forward genetic suppressor screen to identify suppressor mutations in the Arabidopsis ipk1-1 mutant background. Suppressor lines were characterized through mapping-by-sequencing, complementation analysis, and phenotypic assessment including phosphate quantification, gene expression profiling and phytic acid measurement. We discovered that LPA triggers constitutive activation of the phosphate starvation response (PSR), leading to excessive phosphate accumulation and elevated salicylic acid (SA) biosynthesis that drives premature leaf senescence. Loss-of-function mutations in PHR1/PHL1 block this hyperactive signalling cascade, normalizing SA levels and suppressing senescence-associated gene expression while maintaining the low phytic acid phenotype. Our findings provide independent genetic evidence, obtained through a forward suppressor screen, that loss of PHR1/PHL1 function blocks the aberrant PSR and SA accumulation triggered by IPK1 deficiency, thereby preventing premature senescence while maintaining the LPA phenotype. This work extends the established framework of PHR1/PHL1-dependent signalling to include seed yield, germination, and senescence, offering a refined strategy for developing low phytic acid crops with minimal agronomic penalties.
