Plant Responses Research Articles

Intercropping salt-sensitive Solanum lycopersicum L. and salt-tolerant Arthrocaulon macrostachyum in salt-affected agricultural soil under open field conditions: Physiological, hormonal, metabolic and agronomic responses

Salinity is one of the important environmental risks affecting agricultural production in the world. Under this condition and with the conventional cultivation methods, glycophyte plants, like tomato, are subjected to many stresses, such as ion toxicity, osmotic stress, nutritional disturbance, oxidative damage and metabolic disorders, which cause growth inhibition and yield reduction. In this context, the main objective of our study was to compare the physiological, hormonal, metabolic and agronomic responses of tomato plants (Solanum lycopersicum L.) grown in monoculture (TM) or intercropping (TH) with the halophytic species Arthrocaulon macrostachyum in a salt affected soil. The results showed that the intercropping system (TH) reduced the soil electrical conductivity, and Na+ and Cl- contents, improving mineral nutrition in tomato plants compared to TM. In addition, TH decreased the osmotic stress, improved water potential and increased water use efficiency in tomato plants, whereas the integrity of gas exchange parameters were maintained; as a consequence, an increase in tomato yield was achieved. Moreover, the ratio of stress hormones (ABA, SA and JA) to growth regulating hormones (GA, auxins and cytokinins) decreased under TH. Metabolomic analysis showed clear defined patterns of differentially accumulated metabolites. Some of the metabolites with higher abundance in TH were linked to phenylpropanoid biosynthesis and phenylalanine metabolism, whereas alanine, aspartate and glutamate metabolism, monoterpenoid biosynthesis and butanoate metabolism pathways were downregulated. Our results support the importance of A. macrostachyum in the desalination of salt-affected soils and in the improvement of tomato yield in mixed culture. Indeed, this intercropping system offers farmers a low-cost biosolution that improves yields while respecting the environment.

Identification and functional analysis of two serotonin N-acetyltransferase genes in maize and their transcriptional response to abiotic stresses.

Melatonin, a tryptophan-derived indoleamine metabolite with important roles in plant growth and defense, has recently been regarded as a new plant hormone. Maize is one of the most important cereal crops in the world. Although the melatonin receptor gene, ZmPMTR1, has already been identified, the genetic basis of melatonin biosynthesis in maize has still not been elucidated. Serotonin N-acetyltransferase (SNAT) is the enzyme that converts serotonin to N-acetylserotonin (NAS) or 5-methoxytryptamine (5MT) to melatonin in Arabidopsis and rice, but no SNAT encoding gene has been identified yet in maize. The bioinformatics analysis was used to identify maize SNAT genes and the enzyme activity of the recombinant proteins was determined through in vitro assay. The expression levels of ZmSNAT1 and ZmSNAT3 under drought and heat stresses were revealed by public RNA-seq datasets and qRT-PCR analysis. We first identified three maize SNAT genes, ZmSNAT1, ZmSNAT2, and ZmSNAT3, through bioinformatics analysis, and demonstrated that ZmSNAT2 was present in only eight of the 26 cultivars analyzed. We then determined the enzyme activity of ZmSNAT1 and ZmSNAT3 using their recombinant proteins through in vitro assay. The results showed that both ZmSNAT1 and ZmSNAT3 could convert serotonin to NAS and 5-MT to melatonin. Recombinant ZmSNAT1 catalyzed serotonin into NAS with a higher catalytic activity (K m, 8.6 mM; V max, 4050 pmol/min/mg protein) than ZmSNAT3 (K m, 11.51 mM; V max, 142 pmol/min/mg protein). We further demonstrated that the 228th amino acid Tyr (Y228) was essential for the enzymatic activity of ZmSNAT1. Finally, we revealed that the expression of ZmSNAT1 and ZmSNAT3 varied among different maize cultivars and different tissues of a plant, and was responsive to drought and heat stresses. In summary, the present study identified and characterized the first two functional SNAT genes in maize, laying the foundation for further research on melatonin biosynthesis and its regulatory role in plant growth and response to abiotic stresses.

Interactive Effects of Climate Change and Pathogens on Plant Performance: A Global Meta-Analysis.

Plant health is increasingly threatened by abiotic and biotic stressors linked to anthropogenic global change. These stressors are frequently studied in isolation. However, they might have non-additive (antagonistic or synergistic) interactive effects that affect plant communities in unexpected ways. We conducted a global meta-analysis to summarize existing evidence on the joint effects of climate change (drought and warming) and biotic attack (pathogens) on plant performance. We also investigated the effect of drought and warming on pathogen performance, as this information is crucial for a mechanistic interpretation of potential indirect effects of climate change on plant performance mediated by pathogens. The final databases included 1230 pairwise cases extracted from 117 recently published scientific articles (from 2006) on a global scale. We found that the combined negative effects of drought and pathogens on plant growth were lower than expected based on their main effects, supporting the existence of antagonistic interactions. Thus, the larger the magnitude of the drought, the lower the pathogen capacity to limit plant growth. On the other hand, the combination of warming and pathogens caused larger plant damage than expected, supporting the existence of synergistic interactions. Our results on the effects of drought and warming on pathogens revealed a limitation of their growth rates and abundance invitro but an improvement under natural conditions, where multiple factors operate across the microbiome. Further research on the impact of climate change on traits explicitly defining the infective ability of pathogens would enhance the assessment of its indirect effects on plants. The evaluated plant and pathogen responses were conditioned by the intensity of drought or warming and by moderator categorical variables defining the pathosystems. Overall, our findings reveal the need to incorporate the joint effect of climatic and biotic components of global change into predictive models of plant performance to identify non-additive interactions.

The RNA helicase LOS4 regulates pre-mRNA splicing of key genes (EIN2, ERS2, CTR1) in the ethylene signaling pathway.

The Arabidopsis RNA helicase LOS4 plays a key role in regulating pre-mRNA splicing of the genes EIN2, CTR1, and ERS2 in ethylene signaling pathway. The plant hormone ethylene plays diverse roles in plant growth, development, and responses to stress. Ethylene is perceived by the membrane-bound ethylene receptors complex, and then triggers downstream components, such as EIN2, to initiate signal transduction into the nucleus, leading to the activation of ethylene-responsive genes. Over the past decades, substantial information has been accumulated regarding gene cloning, protein-protein interactions, and downstream gene expressions in the ethylene pathway. However, our understanding of mRNA post-transcriptional processing and modification of key genes in the ethylene signaling pathway remains limited. This study aims to provide evidence demonstrating the involvement of the Arabidopsis RNA helicase LOS4 in pre-mRNA splicing of the genes EIN2, CTR1, and ERS2 in ethylene signaling pathway. Various genetic approaches including RNAi gene silencing, CRISPR-Cas9 gene editing, and amino acid mutations were employed in this study. When LOS4 was silenced or knocked down, the ethylene sensitivity of etiolated seedlings was significantly enhanced. Further investigation revealed errors in the EIN2 pre-mRNA splicing when LOS4 was knocked down. In addition, aberrant pre-mRNA splicing was observed in the ERS2 and CTR1 genes in the pathway. Biochemical assays indicated that the los4-2 (E94K) mutant protein exhibited increased ATP binding and enhanced ATP hydrolytic activity. Conversely, the los4-1 (G364R) mutant had reduced substrate RNA binding and lower ATP binding activities. These findings significantly advanced our comprehension of the regulatory functions and molecular mechanisms of RNA helicase in ethylene signaling.

Modern pollen–plant diversity relationships for reliable pollen-based reconstruction of past plant taxonomic and functional diversity: A case study in southwest Shandong, China

Pollen diversity provides insights into our understanding of past plant diversity, a wide variety of diversity indices have been used to characterize plant diversity from sedimentary pollen. However, studies reported inconsistent associations between pollen-plant taxonomic diversity, this could be partly accounted for by biases due to interspecies differences in pollen production, pollen diffusion/deposition, and poorly specified dispersal distance of pollen-source plants. It is therefore crucial to improve the interpretation of the sedimentary pollen diversity by systematic studies of palynological and floristic diversity associations in contemporary landscapes.To test the reliability of pollen assemblages as a proxy of plant diversity, we collected pollen and vegetation from 36 surface sites in southwest Shandong. We detected the correlation between pollen-plant taxonomic and functional diversity indices from different spatial scales.Our results show pollen-plant correlations vary in spatial scales for different indices, the Spearman correlation analysis indicates significant and the strongest correlations between pollen-plant Shannon index around the RSAP (0.399 < ρ < 0.520), while the Pielou’s evenness shows significant and the highest correlations (0.411 < ρ < 0.425) around and beyond the RSAP, but only weak positive relationships can be detected between pollen-plant richness. Functional composition based on whole plant height and specific leave area and functional dispersion based on combined traits of whole plant height, specific leave area, seed mass, and leave dry mass shows significant positive pollen-plant associations, indicating that functional diversity may improve the pollen-plant link.Our results confirm that pollen data performs well in presenting plant taxonomic and functional diversity, which provides a solid theoretical basis for quantitative reconstruction of the long-term plant diversity dynamics and response of ecosystem functions to the environment in the future. Furthermore, the results demonstrate that the spatial scale of vegetation survey plays an important role in the representation of pollen diversity.

CsGAT1 modulates GABA metabolism and positively regulates cold resistance in tea plants

Tea plants (Camellia sinensis) are perennial woody economic crops that are often exposed to a range of abiotic stresses, especially low temperatures, during development. γ-Aminobutyric acid (GABA) is a nonprotein amino acid widely distributed in plants that is involved in the low-temperature response of plants. Here, we found that CsGAT1 was upregulated in tea leaves subjected to low-temperature stress according to transcriptomic data. Heterologous expression of CsGAT1 in a yeast mutant revealed that it specifically transports GABA. Subcellular localization assays revealed that CsGAT1 was located on the plasma membrane. The organizational localization experiments revealed that the expression level of CsGAT1 was relatively high in the old leaves and roots and relatively low in the flowers. Testing of different cold-tolerant tea germplasm resources revealed that cultivars with relatively low cold resistance presented relatively low CsGAT1 expression and GABA levels. In addition, Arabidopsis plants overexpressing CsGAT1 presented high levels of GABA accumulation and significant low-temperature resistance. In summary, we believe that CsGAT1 regulates the ability of tea plants to resist low-temperature stress by changing the concentration of GABA inside and outside the cell. This study provides a theoretical basis for breeding new tea cultivars with strong resistance to low-temperature stress during production.

Lower grass stomatal conductance under elevated CO2 can decrease transpiration and evapotranspiration rates despite carbon fertilization.

Anthropogenic increase in carbon dioxide (CO2) affects plant physiology. Plant responses to elevated CO2 typically include: (1) enhanced photosynthesis and increased primary productivity due to carbon fertilization and (2) suppression of leaf transpiration due to CO2-driven decrease in stomatal conductance. The combined effect of these responses on the total plant transpiration and on evapotranspiration (ET) has a wide range of implications on local, regional, and global hydrological cycles, and thus needs to be better understood. Here, we investigated the net effect of CO2-driven perennial ryegrass (Lolium perenne) physiological responses on transpiration and evapotranspiration by integrating physiological and hydrological (water budget) methods, under a controlled environment. Measurements of the net photosynthetic rate, stomatal conductance, transpiration rate, leaf mass per area, aboveground biomass, and water balance components were recorded. Measured variables under elevated CO2 were compared with those of ambient CO2. As expected, our results show that elevated CO2 significantly decreases whole-plant transpiration rates (38% lower in the final week) which is a result of lower stomatal conductance (57% lower in the final week) despite a slight increase in aboveground biomass. Additionally, there was an overall decline in evapotranspiration (ET) under elevated CO2, indicating the impact of CO2-mediated suppression of transpiration on the overall water balance. Although studies with larger sample sizes are needed for more robust conclusions, our findings have significant implications for global environmental change. Reductions in ET from ryegrass-dominated grasslands and pastures could increase soil moisture and groundwater recharge, potentially leading to increased surface runoff and flooding.

Comprehensive characterization of gibberellin oxidase gene family in Brassica napus reveals BnGA2ox15 involved in hormone signaling and response to drought stress

Brassica napus is a well-known allopolyploid oil crop with high commercial potential. Gibberellin oxidase (GAox) is an essential enzyme that activates gibberellins, which regulate plant growth, and development, and have a significant impact on plant responses to abiotic stress. However, the comprehensive understanding of GAox genes and their evolution in Brassica plants remains elusive. Using advanced bioinformatics tools, this study identified 125 candidate GAox genes from the whole genomes of three key Brassica species. This study also investigated sequence characteristics, conserved motifs, exon/intron structures, cis-acting elements, syntenic analysis, duplication events and expression patterns. Subcellular localization analysis showed that the BnGA2ox14 and BnGA2ox15 proteins are located in the nucleus, whereas BnGA2ox26 is specifically localized to the chloroplast. Yeast one-hybrid and dual-luciferase assays demonstrated that MYELOCYTOMATOSIS 4 (BnMYC4) and ABA-INDUCIBLE BHLH-TYPE TRANSCRIPTION FACTOR (BnAIB) bind to the BnGA2ox15 promoter and activate its transcription. Molecular docking analysis further elucidated their interaction structures and identified potential binding sites. Roots transformations show that overexpression of BnGA2ox15 increased sensitivity to PEG-6000 treatment in rapeseed. In brief, this study reveals that BnGA2ox15 is a downstream target in JA and ABA signaling pathways, functioning as a negative regulator in responding to drought stress.

Relationship Between Genetic and Phenotypic Variations in Natural Populations of Perennial and Biennial Sagebrush.

Plant responses to environmental heterogeneity depend on life-history traits, which could relate to phenotypical and genetic characteristics. To elucidate this relationship, we examined the variation in population genetics and functional traits of short- and long-lived Artemisia species that are co-occurring in the steppes of Mongolia. Mongolian steppes represent stressful and water-limited habitats, demanding phenotypic modifications in the short term and/or genetic adaptation in the long term. However, detailed knowledge is missing about both plant phenotypic and genetic differentiation, and their interrelationships in temperate grasslands. Here, we investigated 21 populations of the widely distributed subshrub Artemisia frigida and the herbaceous biennial Artemisia scoparia. Genetic variation was assessed with newly developed simple sequence repeats (SSRs) markers. Functional trait data were collected from each individual, and data on environmental variables was collected for each population. We detected significantly higher genetic diversity in the biennial species (H E = 0.86) compared with the perennial (H E = 0.79). For both species, the largest share of genetic variation was partitioned within populations (96%). Population genetic structure in the biennial A. scoparia was weak, while the perennial A. frigida showed some spatial genetic structure, which was impacted by geographical factors, soil nutrients, and precipitation amount. Morphology-related functional traits (i.e., plant height) were predominantly associated with environmental variables rather than with genetic variation, whereas physiology-related trait (i.e., specific leaf area [SLA]) was partly genetically determined.

Unveiling the molecular symphony: microRNA160a-Auxin Response Factor 18 module orchestrates low potassium tolerance in banana (Musa acuminata L.)

Potassium (K) is an essential nutrient for the growth and development of most plants. In banana (Musa acuminata L.), microRNA160a (miR160a) is suggested to potentially contribute to the response to low K+ stress by modulating the auxin signaling pathway. However, further investigation is required to elucidate its specific regulatory mechanism. This study presents evidence highlighting the critical role of the miR160a-Auxin Response Factor 18 (ARF18) module in conferring low K+ tolerance in banana. Both miR160a and its predicted target gene ARF18 displayed elevated expression levels in banana roots, with their expression profiles significantly altered under low K+ stress. The inhibitory effect of mac-miR160a on the expression of MaARF18-like-2 was confirmed through tobacco transient transformation and dual-Luciferase reporter assay. Surprisingly, Arabidopsis lines overexpressing mac-miR160a (mac-miR160a OE) exhibited enhanced tolerance to low K+ stress. Conversely, Arabidopsis lines overexpressing MaARF18-like-2 (MaARF18-like-2 OE) displayed increased sensitivity to K+ deficiency. Additionally, RNA sequencing (RNA-seq) analysis revealed that MaARF18-like-2 mediates the response of Arabidopsis to low K+ stress by influencing the expression of genes associated with Ca2+, ion transport, and reactive oxygen species (ROS) signaling. In conclusion, our study provides novel insights into the molecular mechanism of the miR160a-ARF18-like-2 module in the plant response to low K+ stress.

Roles of Histone Acetylation and Deacetylation in Root Development

Roots are usually underground plant organs, responsible for anchoring to the soil, absorbing water and nutrients, and interacting with the rhizosphere. During root development, roots respond to a variety of environmental signals, contributing to plant survival. Histone post-translational modifications play essential roles in gene expression regulation, contributing to plant responses to environmental cues. Histone acetylation is one of the most studied post-translational modifications, regulating numerous genes involved in various biological processes, including development and stress responses. Although the effect of histone acetylation on plant responses to biotic and abiotic stimuli has been extensively reviewed, no recent reviews exist focusing on root development regulation by histone acetylation. Therefore, this review brings together all the knowledge about the impact of histone acetylation on root development in several plant species, mainly focusing on Arabidopsis thaliana. Here, we summarize the role of histone acetylation and deacetylation in numerous aspects of root development, such as stem cell niche maintenance, cell division, expansion and differentiation, and developmental zone determination. We also emphasize the gaps in current knowledge and propose new perspectives for research toward deeply understanding the role of histone acetylation in root development.

Salinity-Induced Photorespiration in Populus Vascular Tissues Facilitate Nitrogen Reallocation.

Adaptation to abiotic stress is critical for the survival of perennial tree species. Salinity affects plant growth and productivity by interfering with major biosynthetic processes. Detrimental effects of salinity may vary between different plant tissues and cell types. However, spatial molecular mechanisms controlling plant responses to salinity stress are not yet thoroughly understood in perennial trees. We used laser capture microdissection in clones of Populus tremula x alba to isolate palisade and vascular cells of intermediary leaf from plants exposed to 150 mM NaCl for 10 days, followed by a recovery period. Cell-specific changes in proteins and metabolites were determined. Salinity induced a vascular-specific accumulation of proteins associated with photorespiration, and the accumulation of serine, 3-phosphoglycerate and NH4 + suggesting changes in N metabolism. Accumulation of the GLUTAMINE SYNTHETASE 2 protein, and increased GS1.1 gene expression, indicated that NH4 + produced in photorespiration was assimilated to glutamine, the main amino acid translocated in Populus trees. Further analysis of total soluble proteins in stems and roots showed the accumulation of bark storage proteins induced by the salinity treatments. Collectively, our results suggest that the salt-induced photorespiration in vascular cells mediates N-reallocation in Populus, an essential process for the adaptation of trees to adverse conditions.

Jasmonates Regulate Auxin-Mediated Root Growth Inhibition in Response to Rhizospheric pH in Arabidopsis thaliana.

Rhizospheric pH, an important environmental cue, severely impacts plant growth and fitness, therefore, has emerged as a major determinant of crop productivity. Despite numerous attempts, the key questions related to plants response against rhizospheric pH remains largely elusive. The present study provides a mechanistic framework for rhizospheric pH-mediated root growth inhibition (RGI). Utilizing various genetic resources combined with pharmacological agents and high-resolution confocal microscopy, the study provides direct evidence for the involvement of jasmonates and auxin in rhizospheric pH-mediated RGI. We show that auxin maxima at root tip is tightly regulated by the rhizospheric pH. In contrast, jasmonates (JAs) abundance inversely correlates with rhizospheric pH. Furthermore, JA-mediated regulation of auxin maxima through GRETCHEN HAGEN 3 (GH3) family genes explains the pattern of RGI observed over the range of rhizospheric pH. Our findings revealed auxin as the key regulator of RGI during severe pH conditions, while JAs antagonistically regulate auxin response against rhizospheric pH.

Polymeric Nanocarriers Autonomously Cross the Plant Cell Wall and Enable Protein Delivery for Stress Sensing.

Delivery of proteins in plant cells can facilitate the design of desired functions by modulation of biological processes and plant traits but is currently limited by narrow host range, tissue damage, and poor scalability. Physical barriers in plants, including cell walls and membranes, limit protein delivery to desired plant tissues. Herein, a cationic high aspect ratio polymeric nanocarriers (PNCs) platform is developed to enable efficient protein delivery to plants. The cationic nature of PNCs binds proteins through electrostatic. The ability to precisely design PNCs' size and aspect ratio allowed us to find a cutoff of ≈14nm in the cell wall, below which cationic PNCs can autonomously overcome the barrier and carry their cargo into plant cells. To exploit these findings, a reduction-oxidation sensitive green fluorescent protein (roGFP) is deployed as a stress sensor protein cargo in a model plant Nicotiana benthamiana and common crop plants, including tomato and maize. In vivo imaging of PNC-roGFP enabled optical monitoring of plant response to wounding, biotic, and heat stressors. These results show that PNCs can be precisely designed below the size exclusion limit of cell walls to overcome current limitations in protein delivery to plants and facilitate species-independent plant engineering.

Integrated transcriptomic and proteomic analysis revealed the regulatory role of 5-azacytidine in kenaf salt stress alleviation

Salinity stress limits agricultural production. The DNA methyltransferase inhibitor, 5-azacitidine (5-azaC), plays a role in plant abiotic stress regulation, but its molecular basis in mediating salinity tolerance in kenaf remains unclear. To investigate the effects on 5-azaC on alleviating salt stress, kenaf seedlings were pre-treated with 0, 50, 100, 150, and 200 μM 5-azaC and then exposed to 150 mM NaCl in a nutrient solution. Physiological, transcriptomic, and proteomic analyses were conducted on the root system to understand the regulatory mechanism of 5-azaC (comparing 5-azaC150 and control group 5-azaC0) under salt stress. The results indicated that 5-azaC significantly mitigated salt stress in kenaf by activating the antioxidant system, reducing reactive oxygen species (ROS), and increasing starch, soluble sugars, and adenosine triphosphate (ATP) content. A total of 14,348 differentially expressed genes (DEGs) and 313 differentially abundant proteins (DAPs) were identified. Combined proteomic and transcriptomic analysis revealed 27 DEGs/DAPs, with jointly up-regulated proteins (genes) including HcTHI1, HcBGLU11, and HcCBL1, and jointly down-regulated proteins (genes) including HcGAPDH, HcSS, and HcPP2C52. Overexpression and virus-induced gene silencing (VIGS) of HcPP2C52 demonstrated its role as a negative regulator of salt tolerance. These findings provide insights into the regulatory role of 5-azaC in plant responses to abiotic stresses. SignificanceThe specific molecular mechanism by which 5-azaC affects gene expression and protein activity of kenaf has been revealed, leading to enhanced salt tolerance.

A putative NF-Y complex interacting with ERD15 may positively regulate the expression of a peroxidase gene in response to stress in rapeseed (Brassica napus L.)

Drought stress is one of the major constraints on crop productivity, including rapeseed (Brassica napus L.). Nuclear factors Y (NF-Ys) are important transcription factors involved in plant responses to drought and other stresses. However, the underlying molecular mechanisms remain unclear in rapeseed. By silencing BnaNF-YA9 in rapeseed and transforming BnaNF-YA9 into the Arabidopsis mutant Atnf-ya5, we demonstrated that BnaNF-YA9 plays a positive role in drought resistance. To explore its regulatory mechanism, we performed protein-protein interaction analyses using various approaches. Our study revealed complex interactions among BnaNF-YA9, BnaNF-YB2, BnaNF-YC4, and EARLY RESPONSIVE TO DEHYDRATION 15 (ERD15), suggesting that these proteins form a multimember complex. We also showed that BnaNF-YA9 binds to the CCAAT element in the promoter of a BnaPRX gene, which encodes a peroxidase. Interestingly, overexpression of BnaNF-YC4 or BnaERD15 in Arabidopsis increased sensitivity to salt stress, drought, and abscisic acid. Our results support an NF-Y/ERD15/PRX cascade and suggest a complex regulatory network in rapeseed that may be important in maintaining ROS homeostasis during abiotic stress responses. Our findings provide insights into potential targets for improving drought resilience in crops.

RNA-Binding Protein-Mediated Alternative Splicing Regulates Abiotic Stress Responses in Plants.

The alternative splicing of pre-mRNA generates distinct mRNA variants from a pre-mRNA, thereby modulating a gene's function. The splicing of pre-mRNA depends on splice sites and regulatory elements in pre-mRNA, as well as the snRNA and proteins that recognize these sequences. Among these, RNA-binding proteins (RBPs) are the primary regulators of pre-mRNA splicing and play a critical role in the regulation of alternative splicing by recognizing the elements in pre-mRNA. However, little is known about the function of RBPs in stress response in plants. Here, we summarized the RBPs involved in the alternative splicing of pre-mRNA and their recognizing elements in pre-mRNA, and the recent advance in the role of RBP-mediated alternative splicing in response to abiotic stresses in plants. This review proposes that the regulation of pre-mRNA alternative splicing by RBPs is an important way for plants to adapt to abiotic stresses, and the regulation of alternative splicing by RBPs is a promising direction for crop breeding.

Morpho-physiological response to micronutrient deficiencies and nickel addition of passion fruit plants

Ultrastructural changes and visual symptoms resulting from nutritional disorders involving boron, manganese, iron, zinc, copper, molybdenum, and nickel depend on the species of the plant, and are unknown in passion fruit plants (Passiflora edulis Sims). A hydroponic experiment evaluated the symptoms of nickel addition and micronutrient deficiency in passion fruit seedlings “BRS Gigante Amarelo” and determined the micronutrient contents in leaf and root tissue, root development, ultrastructural changes (leaf tissue deformations) and dry matter accumulation when visual symptoms were observed. Results showed that the order of manifestation of deficiencies was Fe > Mn > Zn > Cu > Mo > B. Nickel toxicity appeared 40 days after the experiment was started, presenting chlorosis in the new leaves followed by general yellowing and some white parts. Boron omission of resulted in deformations in the leaf limbus and loss of apical dominance, showing deformation of the growth points. Mn omission caused reduction of growth and generalized chlorosis of young leaves with a thick reticulum. Iron omission of resulted in internerval chlorosis with a fine lattice appearance. Omission of zinc and copper resulted in deformation and elongation of the leaves, reducing height and root development. Molybdenum omission caused chlorosis in the older leaves, which was observed to spread over time. Iron was the nutrient that most reflected symptoms of deficiency by the formation of root hairs. The findings of this research suggest that the knowledgement of plant micronutrients status permits an understanding of the physiological responses of passion fruit plants to crop fertilization.

The Effect Addition of Soil Amandments and PGPR (Plant Growth Promoting Rhizobacteria) on the Growth and Yield of Cotton Plants Intercropped with Corn Plants in Dry Land of North Lombok Regency of Indonesia

This research investigates the effect of soil amendments in the form of cow, form goat manures and PGPR biofertilizer on cotton plants intercropped with corn in the dry lands of North Lombok Regency. The research aims is to determine the growth and yield response of cotton plants due to the application of soil amendments and PGPR in an intercropped system with corn in dryland areas. The research was conducted from December 2023 to June 2024 in Andalan Village, Bayan District, North Lombok Regency. The method used is an experimental method with field trials. The design used was Randomized Block Design (RBD), incorporating two factors: soil amendment treatment (P) as the main plot and PGPR (K) concentration treatments as the subplot. Soil amendments consisted of three levels: P0 (no cow manure and no goat manure), P1 (20 tons/ha cow manure), P2 (20 tons/ha goat manure). PGPR concentration consisted of four levels: K0 (without PGPR), K1 (20 ml/liter PGPR application), K2 (30 ml/liter PGPR application), and K3 (40 ml/liter PGPR application). The research results indicated that the application of 20 tons/ha of goat manure (P2) produced the highest average across all observed parameters (plant height, number of leaves, branch number, stem diameter, and plant yield). Similarly, the application of 40 ml/liter PGPR produced the highest average for these observed parameters. Based on the results of the land equivalent ratio (LER) analysis, this integration system shows highly suitable and relevant to be applied in the dry lands of North Lombok.

γ-aminobutyric acid contributes to a novel long-distance signaling in figleaf gourd rootstock-induced cold tolerance of grafted cucumber seedlings

Long-distance signals play a vital role in plant stress response. γ-aminobutyric acid (GABA) has been proposed to be a signal and protects crops against diverse stresses. However, whether GABA acts as a long-distance signal to plant response to stresses remains unknown. Here, we found that the GABA content in cucurbita rootstocks, especially figleaf gourd, was significantly higher than that in cucumber. Figleaf gourd rootstock obviously enhanced cold tolerance and GABA accumulation in roots, xylem sap and leaves of grafting cucumber seedlings. Conversely, GABA synthesis inhibitor 3-mercaptopropionic acid (3-MPA) irrigation was more effective than its foliar application in inhibiting grafting-induced cold tolerance. Moreover, fluorescence microscopy confirmed that GABA can be transported from root to shoot through the xylem when the roots of grafted seedlings were fed with fluorescein isothiocyatate-labeled GABA under normal and cold stress conditions. Importantly, 3-MPA irrigation attenuated grafting-induced cold tolerance, as revealed by a decline in the GABA accumulation, the transcripts of ICE1, CBF1 and COR47, the activities of the antioxidant enzymes, and an increase in stomatal aperture. Collectively, our findings strongly support that GABA functions as a novel long-distance signal in figleaf gourd rootstock-induced cold tolerance of grafted cucumber seedlings by modulating CBF-signalling pathways, antioxidant system and stomatal aperture, providing new evidence for long-distance signaling-mediated cold response of plants.