Phytohormone Profiles Research Articles

The effects of humic substances application on the phytohormone profile in Lactuca sativa L.

AbstractHumic substances (HS) are commonly employed as plant biostimulants to enhance crop yields. However, the HS mechanisms of action, as well as the differences between radicular and foliar modes of application, remain unclear. Here, we explored the changes in phytohormonal balance as possible mechanism of HS to enhance lettuce (Lactuca sativa L.) growth, and the difference between both modes of application. For this purpose, BLACKJAK®, a HS‐based product was applied as radicular (R) and foliar (F) at the concentrations (mL/L): 0.20 (R1), 0.40 (R2), 0.60 (R3), 0.80 (R4), 5.00 (F1), 7.50 (F2), 10.00 (F3), and 12.50 (F4). The experiment was performed in pots filled with vermiculite:perlite (3:1) and HS were applied three times with a periodicity of 10 days. Shoot and root growth parameters were measured. In addition, the phythormones indole‐3‐acetic acid (IAA), gibberellins (GAs), trans‐zeatine (tZ), isopentenyl adenine (iP), 1‐aminocyclopropane‐1‐carboxylic acid (ACC), abscisic acid (ABA), jasmonic acid (JA), and salicylic acid (SA), were analysed by U‐HPLC‐MS. BLACKJAK® application resulted in higher shoot growth at doses R1, R2, R3, F2, and F3, whereas root biomass was increased at R2, R3, F2, F3, and F4, showing radicular better plant growth than foliar applications. Furthermore, HS changed phytohormonal balance in shoots and roots. However, it was with radicular applications, especially at R2, where phytohormonal profile was best associated with plant growth due to the increases observed in IAA, GAs, JA, SA, tZ, and decreased ABA. However, further research is needed to clarify the involvement of hormones in the growth‐promoting action of HS.

Herbivory by Leaf-Cutting Ants: Exploring the Jasmonate Response in Host and Non-Host Plants.

Leaf-cutting ants (Formicidae; Atta spp., Acromyrmex spp.) cut off pieces of leaves and other plant tissue and feed it to their symbiotic fungi. As this foraging behavior poses an imminent threat to agriculture, leaf-cutting ants are considered as pests of huge ecologically and economically importance. Consequently, research on leaf-cutting ants focused on their foraging decisions and interactions with their cultivated symbiotic fungi, whereas their effect on the attacked plants, apart from the loss of plant tissue, remains largely unknown. In this study, we investigated the consequences of an attack by leaf-cutting ants and analyzed the plants' defense responses in comparison to chewing caterpillars and mechanical damage. We found that an attack by leaf-cutting ants induces the production of jasmonates in several host and non-host plant species (Arabidopsis thaliana, Vicia faba, Phaseolus lunatus, Tococa quadrialata). Additionally, we showed in the natural host plant lima bean (P. lunatus) that leaf-cutting ant damage immediately leads to the emission of typical herbivory-induced plant volatiles, including green leaf volatiles and terpenoids. Further data exploration revealed clear differences in the defense-related phytohormone profile in plant species of Neotropical and Eurasian origin. Taken together, we show that leaf-cutting ant infestation and their way of clipping the plants' tissues induce jasmonate and jasmonates-mediated responses and do not differ from those to mechanical injury or larval feeding.

Integrating histology and phytohormone/metabolite profiling to understand rooting in yellow camellia cuttings

Vegetative propagation through cutting is a widely used clonal approach for maintaining desired genotypes. However, some woody species have difficulty forming adventitious roots (ARs) with this approach, including yellow camellia (YC) C. nitidissima. Yellow camellias, prized for their ornamental value and potential health benefits in tea, remain difficult to propagate clonally due to this rooting recalcitrance. As part of the efforts to understand YC cuttings’ recalcitrance, we conducted a detailed investigation into AR formation in yellow camellia cuttings via histology and endogenous phytohormone dynamics during this process. We also compared YC endogenous phytohormone and metabolite phytohormone profiles with those of easy-to-root poplar and willow cuttings. Our results indicate that the induction of ARs in YC cuttings is achievable through auxin treatment, and YC ARs are initiated from cambial derivatives and develop a vascular system connected with that of the stem. During AR induction, endogenous hormones showed a dynamic profile, with IAA continuing to increase starting 9 days after auxin induction. JA, JA-Ile, and OPDA showed a similar trend as IAA but decreased by the 45th day. Cytokinin first decreased to its lowest level by the 18th day and then increased. SA largely exhibited an increasing trend with a drop on the 36th day, while ABA first increased to its peak level by the 18th day and then decreased. Compared to poplar, YC cuttings had a low level of IAA, IAA-Asp, and OPDA, and a high level of cytokinin and SA. Metabolite profiling highlighted significant down-accumulation of compounds associated with AR formation in yellow camellias, such as citric and ascorbic acid, fructose, sucrose, flavonoids, and phenolic acid derivatives. Our study reveals the unfavorable endogenous hormone and metabolite profiles underlying the rooting recalcitrance of YC cuttings, providing valuable knowledge for addressing this challenge in clonal propagation.

Xylooligosaccharides Enhance Lettuce Root Morphogenesis and Growth Dynamics.

Enhancing root development is pivotal for boosting crop yield and augmenting stress resilience. In this study, we explored the regulatory effects of xylooligosaccharides (XOSs) on lettuce root growth, comparing their impact with that of indole-3-butyric acid potassium salt (IBAP). Treatment with XOS led to a substantial increase in root dry weight (30.77%), total root length (29.40%), volume (21.58%), and surface area (25.44%) compared to the water-treated control. These enhancements were on par with those induced by IBAP. Comprehensive phytohormone profiling disclosed marked increases in indole-3-acetic acid (IAA), zeatin riboside (ZR), methyl jasmonate (JA-ME), and brassinosteroids (BRs) following XOS application. Through RNA sequencing, we identified 3807 differentially expressed genes (DEGs) in the roots of XOS-treated plants, which were significantly enriched in pathways associated with manganese ion homeostasis, microtubule motor activity, and carbohydrate metabolism. Intriguingly, approximately 62.7% of the DEGs responsive to XOS also responded to IBAP, underscoring common regulatory mechanisms. However, XOS uniquely influenced genes related to cutin, suberine, and wax biosynthesis, as well as plant hormone signal transduction, hinting at novel mechanisms of stress tolerance. Prominent up-regulation of genes encoding beta-glucosidase and beta-fructofuranosidase highlights enhanced carbohydrate metabolism as a key driver of XOS-induced root enhancement. Collectively, these results position XOS as a promising, sustainable option for agricultural biostimulation.

Integrated analyses of ionomics, phytohormone profiles, transcriptomics, and metabolomics reveal a pivotal role of carbon-nano sol in promoting the growth of tobacco plants

BackgroundCarbon nano sol (CNS) can markedly affect the plant growth and development. However, few systematic analyses have been conducted on the underlying regulatory mechanisms in plants, including tobacco (Nicotiana tabacum L.).ResultsIntegrated analyses of phenome, ionome, transcriptome, and metabolome were performed in this study to elucidate the physiological and molecular mechanisms underlying the CNS-promoting growth of tobacco plants. We found that 0.3% CNS, facilitating the shoot and root growth of tobacco plants, significantly increased shoot potassium concentrations. Antioxidant, metabolite, and phytohormone profiles showed that 0.3% CNS obviously reduced reactive oxygen species production and increased antioxidant enzyme activity and auxin accumulation. Comparative transcriptomics revealed that the GO and KEGG terms involving responses to oxidative stress, DNA binding, and photosynthesis were highly enriched in response to exogenous CNS application. Differential expression profiling showed that NtNPF7.3/NtNRT1.5, potentially involved in potassium/auxin transport, was significantly upregulated under the 0.3% CNS treatment. High-resolution metabolic fingerprints showed that 141 and 163 metabolites, some of which were proposed as growth regulators, were differentially accumulated in the roots and shoots under the 0.3% CNS treatment, respectively.ConclusionsTaken together, this study revealed the physiological and molecular mechanism underlying CNS-mediated growth promotion in tobacco plants, and these findings provide potential support for improving plant growth through the use of CNS.

Transcriptional modules and hormonal metabolic pathways reveal the critical role of TgHB12-like in the regulation of flower opening and petal senescence in Tulipa gesneriana

Tulips (Tulipa gesneriana) are one of the most widely cultivated bulbous plants with substantial ornamental value. However, the lack of well-documented reference genomes has limited the research progress and molecular breeding of tulips. In the present study, a full-length transcriptome of a commercial tulip cultivar was obtained using single-molecule long-read sequencing (PacBio Iso-Seq). In total, 244,357 full-length transcripts were identified, which had an average length of 2,044 bp and an N50 value of 3,861; 67,350 of these were annotated to databases. An inaugural integrated analysis of the transcriptome and phytohormone profiles during flower opening and petal senescence was performed using Illumina RNA-seq, coupled with Mfuzz (an R pakage, http://mfuzz.sysbiolab.eu) and weighted gene coexpression network analysis (WGCNA). A total of 16 gene coexpression and six transcription factor (TF) modules were constructed. Additionally, 26 hormone analogs were comprehensively profiled. Finally, a prominently novel gene, Tulipa gesneriana Homeobox12-like (TgHB12-like), which encodes an homeodomain–leucine zipper (HD-zip) TF, was identified as a pivotal regulator of petal senescence. Overall, this work facilitates the identification of hormones and TFs in plants related to flower opening and senescence in tulips. It also provides an important and valuable genetic basis for further research in them.

Characterization and Transcriptome Analysis Reveal Exogenous GA3 Inhibited Rosette Branching via Altering Auxin Approach in Flowering Chinese Cabbage

Branching is an important agronomic trait that is conducive to plant architecture and yield in flowering Chinese cabbage. Plant branching is regulated by a complex network mediated by hormones; gibberellin (GA) is one of the important hormones which is involved in the formation of shoot branching. Research on the regulatory mechanism of GA influencing rosette branch numbers is limited for flowering Chinese cabbage. In this study, the exogenous application of 600 mg/L GA3 effectively inhibited rosette branching and promoted internode elongation in flowering Chinese cabbage. RNA-Seq analysis further found that these DEGs were significantly enriched in ‘the plant hormone signal transduction’ pathways, and auxin-related genes were significantly differentially expressed between MB and MB_GA. The upregulation of auxin (AUX) and the upregulation of auxin/indole-3-acetic acid (AUX/IAA), as well as the downregulation of SMALL AUXIN-UPREGULATED RNA (SAUR), were found in the negative regulation of the rosette branching. The qRT-PCR results showed that the expression of AUX/IAA and SAUR from IAA gene family members were consistent with the results of transcriptome data. Phytohormone profiling by targeted metabolism revealed that endogenous auxin contents were significantly increased in MB_GA. Transcriptome and metabolome analysis clarified the main plant hormones and genes underlying the rosette branching in flowering Chinese cabbage, confirming that auxin could inhibit rosette branching. In this regard, the results present a novel angle for revealing the mechanism of gibberellin acting on the branching architecture in flowering Chinese cabbage.

Differential Morpho-Physiological, Ionomic, and Phytohormone Profiles, and Genome-Wide Expression Profiling Involving the Tolerance of Allohexaploid Wheat (Triticum aestivum L.) to Nitrogen Limitation.

Common wheat (Triticum aestivum L.) is a global staple food, while nitrogen (N) limitation severely hinders plant growth, seed yield, and grain quality of wheat. Genetic variations in the responses to low N stresses among allohexaploid wheat (AABBDD, 2n = 6x = 42) genotypes emphasize the complicated regulatory mechanisms underlying low N tolerance and N use efficiency (NUE). In this study, hydroponic culture, inductively coupled plasma mass spectrometry, noninvasive microtest, high-performance liquid chromatography, RNA-seq, and bioinformatics were used to determine the differential growth performance, ionome and phytohormone profiles, and genome-wide expression profiling of wheat plants grown under high N and low N conditions. Transcriptional profiling of NPFs, NRT2s, CLCs, SLACs/SLAHs, AAPs, UPSs, NIAs, and GSs characterized the core members, such as TaNPF6.3-6D, TaNRT2.3-3D, TaNIA1-6B, TaGLN1;2-4B, TaAAP14-5A/5D, and TaUPS2-5A, involved in the efficient transport and assimilation of nitrate and organic N nutrients. The low-N-sensitivity wheat cultivar XM26 showed obvious leaf chlorosis and accumulated higher levels of ABA, JA, and SA than the low-N-tolerant ZM578 under N limitation. The TaMYB59-3D-TaNPF7.3/NRT1.5-6D module-mediated shoot-to-root translocation and leaf remobilization of nitrate was proposed as an important pathway regulating the differential responses between ZM578 and XM26 to low N. This study provides some elite candidate genes for the selection and breeding of wheat germplasms with low N tolerance and high NUE.

Integrative effects of phytohormones in the phenolic acids production in Salvia verticillata L. under multi-walled carbon nanotubes and methyl jasmonate elicitation

Salvia verticillata L. is a well-known herb rich in rosmarinic acid (RA) and with therapeutic values. To better understand the possible roles of phytohormones in the production of phenolic acids in S. verticillata, in this work, we investigated some physiological and biochemical responses of the species to methyl jasmonate (MJ) and multi-walled carbon nanotubes (MWCNTs) as two effective elicitors. The leaves were sprayed with aqueous solutions containing 100 mg L−1 MWCNTs and 100 µM MJ and then harvested during interval times of exposure up to 96 h. The level of abscisic acid, as the first effective phytohormone, was altered in the leaves in response to MJ and MWCNTs elicitation (2.26- and 3.06-fold more than the control, respectively), followed by significant increases (P ˂ 0.05) detected in jasmonic acid and salicylic acid contents up to 8 h after exposure. Obtained data revealed that simultaneously with changes in phytohormone profiles, significant (P ˂ 0.05) rises were observed in the content of H2O2 (8.85- and 9.74-folds of control), and the amount of lipid peroxidation (10.18- and 17.01-folds of control) during the initial times after exposure to MJ and MWCNTs, respectively. Later, the content of phenolic acids increased in the elicited leaves due to changes in the transcription levels of key enzymes involved in their biosynthesis pathways, so 2.71- and 11.52-fold enhances observed in the RA content of the leaves after exposure to MJ and MWCNTs, respectively. It is reasonable to conclude that putative linkages between changes in some phytohormone pools lead to the accumulation of phenolic acids in the leaves of S. verticillata under elicitation. Overall, the current findings help us improve our understanding of the signal transduction pathways of the applied stimuli that led to enhanced secondary metabolite production in medicinal plants.

Melatonin and fungal metabolites synergistically enhance tomato tolerance to Cd and disease resistance by regulating phytohormones

Mitigating biotic and abiotic stresses of plants through natural products is an environmental friendly and chemical free approach. In this study, the synergistic effect of exogenous application of melatonin (MT) and fungal metabolites (FM) were evaluated for their mitigation affects against bacterial wilt disease and cadmium toxicity in tomato plants. By using a multi-faceted approach including phytohormonal profiling, quantitative real-time PCR, biochemical assays, antibacterial test, and cadmium (Cd) content evaluation in plants, we presented evidence that MT and FM augmented disease resistance, tolerance to Cd toxicity and the combined treatment caused significantly increased effect by regulating phytohormone expression. Transcription of the genes related to the jasmonic acid (JA) and salicylic acid (SA) were enhanced while genes related to ethylene (ET) were decreased, which caused an increased JA and SA content and decrease in ET level. The plants treated with MT and FM showed significant reduction in disease intensity and Cd content compared to the control. Moreover, analyses indicated that the application of MT and FM reduced oxidative damage and increased antioxidant enzymes activity. The increased synergistic impact of MT and FM is supposed to be due to blending action mechanisms like resistance induction and enhanced growth impact of MT and antibacterial action of FM against R. solanacearum. These research findings emphasize the efficacy of a sustainable and comprehensive strategy in controlling bacterial wilt and Cd toxicity in tomato plants.

Cross compatibility and endogenous phytohormone profiles in interspecific hybridization between Iris tectorum and Iris germanica

In order to introduce new valuable trait to other species, the interspecific hybridization is used in ornamental breeding. The success of interspecific hybridization is hindered by incompatibility occurring at various stages of hybridization. To character the barriers of interspecific hybridization between Iris tectorum and Iris germanica cultivars, this study investigated the compatibility of pre-fertilization and post-fertilization, and profiles of endogenous phytohormones in ovary of self-pollination and interspecific hybridization. After pollination, pollen tubes germinated, grew through style, and entered ovules in both self-pollination and interspecific hybridization. Thus, the interspecific incompatibility between I. tectorum and I. germanica cultivars were not caused by pre-fertilization barrier. The observations of embryo and endosperm development revealed that incompatibility of interspecific-hybridization occurred at post-fertilization stage during the development of the embryo. The degeneration of endosperms was observed at 15 days after pollination and no embryo was observed in the interspecific hybridization. The abnormal development of embryos and endosperms indicates that reproductive barriers between I. tectorum and I. germanica cultivars happened at post-fertilization stage. To character the profiles of endogenous phytohormones in the ovary of self-pollination and interspecific hybridization, concentration of auxins, cytokinins (CKs), gibberellins (GAs), abscisic acid (ABA), Jasmonate (JA), salicylic acid (SA), and their derivatives were analyzed by UPLC-ESI-MS/MS. The results showed concentrations of indole-3-acetic acid (IAA) and bioactive free based of CKs were highest in ovary of I. tectorum self-pollination (IT-Self), which has normally developed embryos and endosperms. Four bioactive forms of GAs were identified in this study, while the patterns of their concentration changes were not constant among different materials. Besides, the concentration of ABA was highest in unfertilized ovary of I. tectorum (IT-CK). According to the profiles of endogenous phytohormones, the abnormal development of embryos in interspecific hybridization might be caused by the low concentration of IAA and CKs, proper concentration of these phytohormone could be added into in vitro culture medium to rescue embryos of interspecific hybridization. The investigation of cross compatibility and endogenous phytohormone profiles in this study will provide insight for overcoming the barrier of interspecific hybridization and embryo rescue in Iris genus.

Limited efficacy of a commercial microbial inoculant for improving growth and physiological performance of native plant species.

Soil microbial inoculants are increasingly being explored as means to improve soil conditions to facilitate ecological restoration. In southwestern Western Australia, highly biodiverse Banksia woodland plant communities are increasingly threatened by various factors including climate change, land development and mining. Banksia woodland restoration is necessary to conserve this plant community. The use of microbial inoculation in Banksia woodland restoration has not yet been investigated. Here, we evaluated the efficacy of a commercial microbial inoculant (GOGO Juice, Neutrog Australia Pty Ltd) for improving the performance of 10 ecologically diverse Banksia woodland plant species in a pot experiment. Plants were subjected to one of two watering regimes (well-watered and drought) in combination with microbial inoculation treatments (non-inoculated and inoculated). Plants were maintained under these two watering treatments for 10weeks, at which point plants in all treatments were subjected to a final drought period lasting 8weeks. Plant performance was evaluated by plant biomass and allocation, gas exchange parameters, foliar carbon and nitrogen and stable isotope (δ15N and δ13C) compositions. Plant xylem sap phytohormones were analysed to investigate the effect of microbial inoculation on plant phytohormone profiles and potential relationships with other observed physiological parameters. Across all investigated plant species, inoculation treatments had small effects on plant growth. Further analysis within each species revealed that inoculation treatments did not result in significant biomass gain under well-watered or drought-stressed conditions, and effects on nitrogen nutrition and photosynthesis were variable and minimal. This suggests that the selected commercial microbial inoculant had limited benefits for the tested plant species. Further investigations on the compatibility between the microorganisms (present in the inoculant) and plants, timing of inoculation, viability of the microorganisms and concentration(s) required to achieve effectiveness, under controlled conditions, and field trials are required to test the feasibility and efficacy in actual restoration environments.

Poor shoot and leaf growth in Huanglongbing-affected sweet orange is associated with increased investment in defenses.

Citrus disease Huanglongbing (HLB) causes sparse (thinner) canopies due to reduced leaf and shoot biomass. Herein, we present results demonstrating the possible mechanisms behind compromised leaf growth of HLB-affected 'Valencia' sweet orange trees by comparing morphological, transcriptome, and phytohormone profiles at different leaf development phases (1. buds at the start of the experiment; 2. buds on day 5; . 3. leaf emergence; 4. leaf expansion; and 5. leaf maturation) to healthy trees. Over a period of 3 months (in greenhouse conditions), HLB-affected trees had ≈40% reduction in growth traits such as tree height, number of shoots per tree, shoot length, internode length, and leaf size compared to healthy trees. In addition, buds from HLB-affected trees lagged by ≈1 week in sprouting as well as leaf growth. Throughout the leaf development, high accumulation of defense hormones, salicylic acid (SA) and abscisic acid (ABA), and low levels of growth-promoting hormone (auxin) were found in HLB-affected trees compared to healthy trees. Concomitantly, HLB-affected trees had upregulated differentially expressed genes (DEGs) encoding SA, ABA, and ethylene-related proteins in comparison to healthy trees. The total number of cells per leaf was lower in HLB-affected trees compared to healthy trees, which suggests that reduced cell division may coincide with low levels of growth-promoting hormones leading to small leaf size. Both bud dieback and leaf drop were higher in HLB-affected trees than in healthy trees, with concomitant upregulated DEGs encoding senescence-related proteins in HLB-affected trees that possibly resulted in accelerated aging and cell death. Taken together, it can be concluded that HLB-affected trees had a higher tradeoff of resources on defense over growth, leading to sparse canopies and a high tree mortality rate with HLB progression.

Construction and analysis of the tapping panel dryness-related lncRNA/circRNA-miRNA-mRNA ceRNA network in latex of Hevea brasiliensis

Tapping panel dryness (TPD) results in a severe reduction in latex yield in Hevea brasiliensis. However, the molecular regulatory mechanisms of TPD occurrence are still largely unclear. In this study, whole-transcriptome sequencing was carried out on latex from TPD and healthy trees. In total, 7078 long noncoding RNAs (lncRNAs), 3077 circular RNAs (circRNAs), 4956 miRNAs, and 25041 mRNAs were identified in latex, among which 435 lncRNAs, 68 circRNAs, 320 miRNAs, and 1574 mRNAs were differentially expressed in the latex of TPD trees. GO and KEGG analyses indicated that plant hormone signal transduction, MAPK signaling pathway, and ubiquitin-mediated proteolysis were the key pathways associated with TPD onset. Phytohormone profiling revealed significant changes in the contents of 28 hormonal compounds, among which ACC, ABA, IAA, GA, and JA contents were increased, while SA content was reduced in TPD latex, suggesting that hormone homeostasis is disrupted in TPD trees. Furthermore, we constructed a TPD-related competitive endogenous RNA (ceRNA) regulatory network of lncRNA/circRNA-miRNA-mRNA with 561 edges and 434 nodes (188 lncRNAs, 5 circRNAs, 191 miRNAs, and 50 mRNAs) and identified two hub lncRNAs (MSTRG.11908.1 and MSTRG.8791.1) and four hub miRNAs (hbr-miR156, miR156-x, miRf10477-y, and novel-m0452-3p). Notably, the lncRNA-miR156/157-SPL module containing three hubs probably plays a crucial role in TPD onset. The expression of network hubs and the lncRNA-miR156/157-SPL module were further validated by qRT-PCR. Our results reveal the TPD-associated ceRNA regulatory network of lncRNA/circRNA-miRNA-mRNA in latex and lay a foundation for further investigation of molecular regulatory mechanisms for TPD onset in H. brasiliensis.

Hormonal Interplay Leading to Black Knot Disease Establishment and Progression in Plums.

Black Knot (BK) is a deadly disease of European (Prunus domestics) and Japanese (Prunus salicina) plums caused by the hemibiotrophic fungus Apiosporina morbosa. After infection, the appearance of warty black knots indicates a phytohormonal imbalance in infected tissues. Based on this hypothesis, we quantified phytohormones such as indole-3-acetic acid, tryptophan, indoleamines (N-acetylserotonin, serotonin, and melatonin), and cytokinins (zeatin, 6-benzyladenine, and 2-isopentenyladenine) in temporally collected tissues of susceptible and resistant genotypes belonging to European and Japanese plums during of BK progression. The results suggested auxin-cytokinins interplay driven by A. morbosa appears to be vital in disease progression by hampering the plant defense system. Taken together, our results indicate the possibility of using the phytohormone profile as a biomarker for BK resistance in plums.

Phytohormone Profiling of Potato (Solanum tuberosum L.) Exposed to French Marigold (Tagetes patula L.) Essential Oil

Phytohormone Profiling of Potato (Solanum tuberosum L.) Exposed to French Marigold (Tagetes patula L.) Essential Oil

Fertiliser supplementation with a biostimulant complex of fish hydrolysate, Aloe vera extract, and kelp alters cannabis root architecture to enhance nutrient uptake

Biostimulants are non-nutritive fertiliser additives which have demonstrated improvements to growth outputs of various agricultural crops. As a result, they have gained attention as sustainable components in cultivation practices, particularly in the rapidly emerging cannabis spheres, including medicinal and industrial cannabis cultivation. One point of focus to cannabis cultivators is the plant's efficiency of nutrient utilisation, attributed to the growth vigour and activity of roots. Despite the interest in this topic, due to the concealment of plant roots within substrates, exploration of plant roots is generally challenging and as such has hampered understanding of the impacts of biostimulants to plant root activity and associated nutrient utilisation efficiency. This project aimed to characterise the impacts and modes of action of the biostimulants kelp, Aloe vera extract, and fish hydrolysate to cannabis growth through exploration of their impacts individually, and as a biostimulant complex (BC). To overcome the limitations of root analyses, substrate-free hydroponic growth systems such as aeroponics, deep water culture (DWC), and the Root-TRAPR system were utilized. These systems allowed for the measurement of changes in root architecture and nutrient utilisation induced by the biostimulants. The results demonstrated that application of BC significantly enhanced root development, as indicated by increased root branching (P = 0.038) and increased total length (P = 0.046). In addition, BC treatment resulted in significant increases in the uptake of phosphorous (P = 0.038) and potassium (P = 0.040) by the plant. Metabolite and phytohormone profiling revealed that kelp and Aloe vera extract induced general plant stress-response mechanisms, whilst fish hydrolysate induced mechanisms associated with the plant pathogen defence response. However, when applied together as BC, the induced molecular mechanisms were associated with phosphorous deficiency without induction of general stress response mechanisms, potentially driving the increased uptake of phosphorous observed. These novel characterisations of biostimulant mechanisms and efficacies provide valuable insights to establishing optimised usage of biostimulants within cannabis cultivation, leading to increased production efficiency through sustainable practises.

Cultivation of heterotrophic Euglena gracilis: The effects of recycled media on culture growth and associations with growth regulating phytohormone profiles

Cultivation of heterotrophic Euglena gracilis: The effects of recycled media on culture growth and associations with growth regulating phytohormone profiles

Jasmonate-mediated gibberellin catabolism constrains growth during herbivore attack in rice.

Plant defense against herbivores is costly and often associated with growth repression. The phytohormone jasmonate (JA) plays a central role in prioritizing defense over growth during herbivore attack, but the underlying mechanisms remain unclear. When brown planthoppers (BPH, Nilaparvata lugens) attack rice (Oryza sativa), growth is dramatically suppressed. BPH infestation also increases inactive gibberellin (GA) levels and transcripts of GA 2-oxidase (GA2ox) genes, 2 (GA2ox3 and GA2ox7) of which encode enzymes that catalyze the conversion of bioactive GAs to inactive GAs in vitro and in vivo. Mutation of these GA2oxs diminishes BPH-elicited growth restriction without affecting BPH resistance. Phytohormone profiling and transcriptome analyses revealed that GA2ox-mediated GA catabolism was enhanced by JA signaling. The transcript levels of GA2ox3 and GA2ox7 were significantly attenuated under BPH attack in JA biosynthesis (allene oxide cyclase [aoc]) or signaling-deficient (myc2) mutants. In contrast, GA2ox3 and GA2ox7 expression was increased in MYC2 overexpression lines. MYC2 directly binds to the G-boxes in the promoters of both GA2ox genes to regulate their expression. We conclude that JA signaling simultaneously activates defense responses and GA catabolism to rapidly optimize resource allocation in attacked plants and provides a mechanism for phytohormone crosstalk.

Drought attenuates plant responses to multiple rhizospheric pathogens: A study on a dry root rot-associated disease complex in chickpea fields

Root rots, a major factor contributing to yield loss in chickpea, often occur in disease complexes. Plant responses to disease complexes are not well elucidated. We sought a clear understanding of a newly identified disease complex in chickpea, dry root rot (DRR)–wilt disease complex, in the field and studied the effect of drought on the severity of the complex and its effect on yield. We compared plant responses to DRR alone and the disease complex under drought and determined the phytohormones involved in plant defense against the disease complex. We compared the effect of 14 environments (two soil moisture regimes at seven locations) on the incidence of the disease complex and yield loss in four chickpea genotypes. We also studied the effect of drought on rhizospheric and root endo-microbial communities by whole-genome and metagenomic sequencing and performed LC-MS-based phytohormonal profiling of chickpea roots. Soil moisture and plant genetic variability were critical in modulating disease incidence in field conditions. DRR was the primary driver of the disease complex under drought stress. Drought aggravated the yield reductions caused by the disease complex from 35% to 60% in susceptible genotypes. Further, drought-tolerant genotypes performed better under combined disease complex infection and drought stress and exhibited lesser yield losses than susceptible genotypes. Pathogenic fungi such as Macrophomina phaseolina, Fusarium oxysporum, and Rhizoctonia solani were enriched in the chickpea rhizosphere, and M. phaseolina was predominant in infected chickpea roots under both well-watered and drought conditions. Symbiotic associations of chickpea with nitrogen-fixing bacteria were suppressed under drought stress. Abscisic acid, jasmonic acid, and salicylic acid were found to be involved in defense against the disease complex across various stages of plant growth. We highlight the interaction between drought and soil pathogens affecting chickpea yield and suggest the utilization of drought-tolerant root traits as donor traits for improving combined stress resistance. We also demonstrate growth stage–dependent phytohormonal responses elicited by DRR and the DRR–wilt disease complex. The identification and management of root rots is essential, and our findings offer valuable new insights into a lesser-known but highly significant disease complex of chickpea. Manuscript data is available at Supplementary File S1. The soil microbe whole-genome and metagenome and root-microbe 16 S and ITS sequencing data are available at NCBI PRJNA871091 and PRJNA895851.