Interaction Of Auxin Research Articles

Gibberellic Acid and Abscisic Acid Effects on Germination Across Arabidopsis Genotypes: Confirmation of Compound Identity and Genotypic Responses

It is well known that plant growth depends on the interaction of auxin and hormones, but whether different hormones have different effects on seed growth in different varieties is not fully understood. This study used a controlled experimental setup in which seeds from three different genotypes (assumed to be wild-type, abscisic acid (ABA) insensitive, and gibberellic acid (GA) deficient) were exposed to treatments of these compounds (labeled compounds A and B), as well as a control treatment using ethanol. Our results confirm the identities of Compound A as gibberellic acid and Compound B as abscisic acid through their consistent effects on seed germination. Gibberellic acid (Compound A) significantly enhanced germination across all genotypes. With the help of Gibberellic acid, GA-deficient genotype also showed a dramatic increase in germination rates which suggested a compensatory effect. Conversely, abscisic acid (Compound B) markedly inhibited germination, with the most pronounced effect observed in the wild-type genotype. The ABA-insensitive genotype demonstrated reduced susceptibility to Compound B, supporting its phenotypic characterization. The study highlights the key antagonistic role of gibberellic acid and abscisic acid in seed germination, providing valuable insights into defining genotypic-phenotypic interactions in plant responses to environmental and chemical signals.

Enhancement of developmental defects in the boron‐deficient maize mutanttassel‐less1by reduced auxin levels

AbstractBackgroundPlant responses to deficiencies of the micronutrient boron are diverse and go beyond the well‐characterized function of boron in cell wall crosslinking. To explain these phenotypic discrepancies, hypotheses about interactions of boron with various phytohormones have been proposed, particularly auxin. While these hypotheses are intensely tested in the root meristem of the model species,Arabidopsis thaliana, studies in crop species and the shoot are limited.AimsTo address potential boron–auxin interactions during the vegetative and reproductive development of the crop maize (Zea mays), we utilized the boron‐deficienttassel‐less1(tls1) mutant and the auxin‐deficientvanishing tassel2(vt2) mutant. We investigated interactions of boron and auxin on the levels of auxin biosynthesis and auxin transport in leaves and shoot meristems.Methods and ResultsBy using genetic interaction analysis, hormone quantification, and confocal microscopy, we show that boron‐deficient leaf phenotypes intls1are enhanced in double mutants withvt2in both greenhouse and field conditions. However, auxin levels are not altered in developing leaves intls1. Rather, the localization ofZmPIN1a:YFP, a marker for auxin transport, is altered in young tassel meristems and is absent from organ initiation sites during vegetative development.ConclusionsOur data suggest a link between polar auxin transport and phenotypic consequences in boron‐deficient conditions and further show that boron deficiency‐induced developmental defects are sensitive to low auxin levels. Our study, therefore, offers new insight into nutrient–hormone interactions to regulate crop development.

Insight into regulation of adventitious root formation by arbuscular mycorrhizal fungus and exogenous auxin in tea plant (Camellia sinensis L.) cuttings.

Adventitious root (AR) development, affected by various biotic and abiotic factors, is the most important procedure in tea plant (Camellia sinensis L.) cutting propagation. Establishing symbiotic relationships with most terrestrial plants, AMF (Arbuscular mycorrhizal fungus) can mediate the AR formation of several herbaceous and woody plants in previous studies. In this paper, effects of combined application of AMF and exogenous auxin on AR formation of cuttings from different tea plant varieties ('Pingyangtezao', 'Longjing 43' and 'Longjingchangye') were studied. Then we also performed RNA-Seq analysis with 'Pingyangtezao' cuttings aiming to find the possible auxin-related pathway of AM fungal regulation on AR formation. To accurately uncover the regulatory mechanism of AMF on AR formation of tea cuttings, rooting process were separated into four stages (S0, non-rooting; S1, AR protrusion; S2, AR formation and S3, AR elongation) at the same sampling time. Results showed that IBA treatment increased the mycorrhizal colonization rate, especially in 'Pingyangtezao' variety (from 37.58% to 46.29%). Both inoculating AMF and addition of IBA promoted the AR formation, and rooting of different tea plant varieties showed different dependence on auxin. AMF could alleviate the effect of auxin-related inhibitors (2,3,5-triiodobenzoic acid, L-α-(Aminooxy)-β-phenylpropionic acid and α-(phenylethyl-2-oxo)-IAA) on rooting of tea cuttings, even though the colonization of AMF was hindered at various degrees. Transcriptomic analysis showed that different numbers of differentially expressed genes (DEGs) at various rooting stages of tea cuttings with the most at S2 stage (1360 DEGs), indicating the increasing regulation by AMF with the development of AR. Similar trend was found in auxin-related DEGs, and family genes of YUC, GH, PIN, LAX, SAUR, AUX, and ABP involved in the AM fungal regulation on AR formation of tea cuttings. Additionally, AMF strongly mediated auxin transport and signal transduction pathways in tea cuttings as showed by the results of correlation analysis. Overall, interaction of AMF and exogenous auxin in promoting rooting and the preliminary mechanism of AMF regulating AR formation of tea cuttings was deciphered in this paper, which may provide a basis for further deep mechanistic research and cutting propagation of tea production.

Indirect regeneration in Ficus lyrata Warb. and metabolite profiles influenced by nitric oxide and Plant growth regulators

BackgroundTo establish an indirect regeneration protocol in Ficus lyrata, a three-phase experiment (callus induction, morphogenic callus induction, and plant regeneration) based on auxin, cytokinin, and nitric oxide interactions was designed and implemented using leaf explants. The metabolite profiles (amino acid profile, total phenolic content, total soluble sugars, and total antioxidant activity) alteration patterns were also investigated to determine the metabolites contributing to the progress of each phase.ResultsResults demonstrated that 11 out of 48 implemented treatments resulted in morphogenic callus induction (morphogenic treatments), and nitric oxide played a key role in increasing efficiency from 13 to 100%. More importantly, nitric oxide cross-talk with cytokinins was necessary for shoot regeneration from morphogenic calli. Only 4 out of all 48 implemented treatments were capable of shoot regeneration (regenerative treatments), and among them, PR42 treatment led to the highest shoot regeneration rate (86%) and maximum mean number of shoot/explant (10.46). Metabolite analyses revealed that the morphogenic and regenerative treatments followed similar metabolite alterations, which were associated with increased biosynthesis of arginine, lysine, methionine, asparagine, glutamine, histidine, threonine, leucine, glycine, serine amino acids, total soluble sugars content, and total antioxidant activity. On the contrary, non-morphogenic and non-regenerative treatments caused the accumulation of a significantly greater total phenolic content and malondialdehyde in the explant cells, which reflexed the stressful condition of the explants.ConclusionsIt could be concluded that the proper interactions of auxin, cytokinins, and nitric oxide could result in metabolite biosynthesis alterations, leading to triggering cell proliferation, morphogenic center formation, and shoot regeneration.

Novel insights into maize (Zea mays) development and organogenesis for agricultural optimization

In maize, intrinsic hormone activities and sap fluxes facilitate organogenesis patterning and plant holistic development; these hormone movements should be a primary focus of developmental biology and agricultural optimization strategies. Maize (Zea mays) is an important crop plant with distinctive life history characteristics and structural features. Genetic studies have extended our knowledge of maize developmental processes, genetics, and molecular ecophysiology. In this review, the classical life cycle and life history strategies of maize are analyzed to identify spatiotemporal organogenesis properties and develop a definitive understanding of maize development. The actions of genes and hormones involved in maize organogenesis and sex determination, along with potential molecular mechanisms, are investigated, with findings suggesting central roles of auxin and cytokinins in regulating maize holistic development. Furthermore, investigation of morphological and structural characteristics of maize, particularly node ubiquity and the alternate attachment pattern of lateral organs, yields a novel regulatory model suggesting that maize organ initiation and subsequent development are derived from the stimulation and interaction of auxin and cytokinin fluxes. Propositions that hormone activities and sap flow pathways control organogenesis are thoroughly explored, and initiation and development processes of distinctive maize organs are discussed. Analysis of physiological factors driving hormone and sap movement implicates cues of whole-plant activity for hormone and sap fluxes to stimulate maize inflorescence initiation and organ identity determination. The physiological origins and biogenetic mechanisms underlying maize floral sex determination occurring at the tassel and ear spikelet are thoroughly investigated. The comprehensive outline of maize development and morphogenetic physiology developed in this review will enable farmers to optimize field management and will provide a reference for de novo crop domestication and germplasm improvement using genome editing biotechnologies, promoting agricultural optimization.

Физиологические аспекты созревания и продления срока хранения сочных плодов

This review discusses the physiological aspects of the ripening of juicy fruits in relation to the problem of extending the shelf life of horticultural products. The achievements of molecular biology in the field of genetic regulation of plant quality formation processes are used. Particular attention is paid to the hormonal regulation of the accumulation of nutrients and biologically active substances in fruits. The role of ARF/IAA and DELLA receptor proteins in the interaction of auxin and GA signalling pathways during the growth of tomato, strawberry, and grape fruits is demonstrated. The involvement of DELLA proteins in integrating the function of other phytohormones – cytokinin, ethylene, abscisic acid, brassinosteroids and jasmonic acid – is noted. Evidence is presented for the interaction of cytokinin with auxin and GA in the regulation of early development and fruit size. The combination of transcription factors and epigenetic modifications during fruit development and senescence is considered. The involvement of mechanisms of senescence and loss of fruit shelf life in the absence of external signs is shown. The ripening characteristics of climacteric and nonclimacteric fruits are considered. One of the key regulators of the ripening process in both climacteric and non-climacteric fruits is the MADS domain transcription factor RIPENING INHIBITOR (RIN). The regulation of non-climacteric fruit ripening is reviewed using grape and strawberry as examples. Special attention is paid to growth processes, water exchange, photosynthesis, primary and secondary metabolism of developing and ripening fruits. The formation of integuments and cell walls as a structural basis for the physical properties of products is considered. Promising methods of using regulators of vital processes in the post-harvest period to slow down the fruit senescence are given. Increased knowledge of genetic, hormonal and metabolic networks opens up broad prospects for improving and maintaining the quality of fleshy horticultural products.

Increased growth of Porang (Amorphophallus muelleri Blume) seedlings on various bulbil weights with auxin application

Porang is a plant that contains quite high glucomannan. In 2021 the export value of porang has increased by 160% from 2019. The increase in demand for porang is still not supported by the availability of porang tubers so porang exports cannot be maximized. Efforts to meet the availability of porang tubers are to maximize the technical cultivation factory with the availability of quality seeds. This study aims to determine the interaction of bulbil weight and auxin, obtain the best combination of auxin and bulbil weight, as well as the effect of knowing auxin, and the effect of bulbil weight on increasing the growth of porang seedlings. The research was carried out experimentally in the form of a 3 x 4 factorial, arranged using a completely randomized design. Factor I, bulbil weight (5 – 11, >11 – 17, and >17 – 23 g per bulbil). Factor II, auxin concentration (0, 150, 300, and 450 mg.l-1). From these two factors, 12 combinations were obtained, and each combination was repeated 3 times to obtain 36 experimental units. Each experimental unit contained 3 plants in 3 polybags so a total of 108 plants were observed. Parameters observed were the days of shoot emergence, height, stem diameter, root volume, and fresh seedling weight. The results showed that the combination of bulbil weight >17 – 23 g and an auxin concentration of 300 mg.l-1 gave the best results for the growth of porang seedlings on all observation parameters. Bulbil weight > 17 – 23 g markedly increased seedling growth in all observation parameters, and administration of auxin concentration of 300 mg/l-1 also significantly increased porang seedling growth in all observed parameters.

Comprehensive analyses of plant hormones in etiolated pea and maize seedlings grown under microgravity conditions in space: Relevance to the International Space Station experiment “Auxin Transport”

Functional relationships between endogenous levels of plant hormones in the growth and development of shoots in etiolated Alaska pea and etiolated Golden Cross Bantam maize seedlings under different gravities were investigated in the “Auxin Transport” experiment aboard the International Space Station (ISS). Comprehensive analyses of 31 species of plant hormones of pea and maize seedlings grown under microgravity (μg) in space and 1 g conditions were conducted. Principal component analysis (PCA) and a multiple regression analysis with the dataset from the plant hormone analysis of the etiolated pea seedlings grown under μg and 1 g conditions in the presence and absence of 2,3,5-triiodobenzoic acid (TIBA) revealed endogenous levels of auxin correlated positively with bending and length of epicotyls. Endogenous cytokinins correlated negatively with them. These results suggest an interaction of auxin and cytokinins in automorphogenesis and growth inhibition of etiolated Alaska pea epicotyls grown under μg conditions in space. Less polar auxin transport with reduced endogenous levels of auxin increased endogenous levels of cytokinins, resulting in changing the growth direction of epicotyls and inhibiting growth. On the other hand, almost no close relationship between endogenous plant hormone levels and growth and development in etiolated maize seedlings grown was observed under μg conditions in space, as per Schulze et al. (1992). However, endogenous levels of IAA in the seedlings grown under μg conditions in space were significantly higher than those grown on Earth, similar to the cases of polar auxin transport already reported.

Cell- and noncell-autonomous AUXIN RESPONSE FACTOR3 controls meristem proliferation and phyllotactic patterns.

In cell-cell communication, noncell-autonomous transcription factors play vital roles in controlling plant stem cell fate. We previously reported that AUXIN RESPONSE FACTOR3 (ARF3), a member of the ARF family with critical roles in floral meristem maintenance and determinacy, has a distinct accumulation pattern that differs from the expression domain of its encoding gene in the shoot apical meristem (SAM). However, the biological meaning of this difference is obscure. Here, we demonstrate that ARF3 expression in Arabidopsis (Arabidopsis thaliana) is mainly activated at the periphery of the SAM by auxin where ARF3 cell autonomously regulates the expression of meristem-organ boundary-specific genes, such as CUP-SHAPED COTYLEDON1-3 (CUC1-3), BLADE ON PETIOLE1-2 (BOP1-2), and TARGETS UNDER ETTIN CONTROL3 (TEC3) to regulate the arrangement of organs in regular pattern, a phenomenon referred to as phyllotaxis. We also show that ARF3 is translocated into the organizing center where it represses cytokinin activity and WUSCHEL expression to regulate meristem activity noncell-autonomously. Therefore, ARF3 acts as a molecular link that mediates the interaction of auxin and cytokinin signaling in the SAM while coordinating the balance between meristem maintenance and organogenesis. Our findings reveal an ARF3-mediated coordination mechanism through cell-cell communication in dynamic SAM maintenance.

Regulation of cytokinin biosynthesis using PtRD26pro -IPT module improves drought tolerance through PtARR10-PtYUC4/5-mediated reactive oxygen species removal in Populus.

Drought is a critical environmental factor which constrains plant survival and growth. Genetic engineering provides a credible strategy to improve drought tolerance of plants. Here, we generated transgenic poplar lines expressing the isopentenyl transferase gene (IPT) under the driver of PtRD26 promoter (PtRD26pro -IPT). PtRD26 is a senescence and drought-inducible NAC transcription factor. PtRD26pro -IPT plants displayed multiple phenotypes, including improved growth and drought tolerance. Transcriptome analysis revealed that auxin biosynthesis pathway was activated in the PtRD26pro -IPT plants, leading to an increase in auxin contents. Biochemical analysis revealed that ARABIDOPSIS RESPONSE REGULATOR10 (PtARR10), one of the type-B ARR transcription factors in the cytokinin pathway, was induced in PtRD26pro -IPT plants and directly regulated the transcripts of YUCCA4 (PtYUC4) and YUCCA5 (PtYUC5), two enzymes in the auxin biosynthesis pathway. Overexpression of PtYUC4 enhanced drought tolerance, while simultaneous silencing of PtYUC4/5 evidently attenuated the drought tolerance of PtRD26pro -IPT plants. Intriguingly, PtYUC4/5 displayed a conserved thioredoxin reductase activity that is required for drought tolerance by deterring reactive oxygen species accumulation. Our work reveals the molecular basis of cytokinin and auxin interactions in response to environmental stresses, and shed light on the improvement of drought tolerance without a growth penalty in trees by molecular breeding.

Flavonoids are involved in phosphorus-deficiency-induced cluster-root formation in white lupin.

Initiation of cluster roots in white lupin (Lupinus albus) under phosphorus (P) deficiency requires auxin signalling, whereas flavonoids inhibit auxin transport. However, little information is available about the interactions between P deficiency and flavonoids in terms of cluster-root formation in white lupin. Hydroponic and aeroponic systems were used to investigate the role of flavonoids in cluster-root formation, with or without 75 μm P supply. Phosphorus-deficiency-induced flavonoid accumulation in cluster roots depended on developmental stage, based on in situ determination of fluorescence of flavonoids and flavonoid concentration. LaCHS8, which codes for a chalcone synthase isoform, was highly expressed in cluster roots, and silencing LaCHS8 reduced flavonoid production and rootlet density. Exogenous flavonoids suppressed cluster-root formation. Tissue-specific distribution of flavonoids in roots was altered by P deficiency, suggesting that P deficiency induced flavonoid accumulation, thus fine-tuning the effect of flavonoids on cluster-root formation. Furthermore, naringenin inhibited expression of an auxin-responsive DR5:GUS marker, suggesting an interaction of flavonoids and auxin in regulating cluster-root formation. Phosphorus deficiency triggered cluster-root formation through the regulation of flavonoid distribution, which fine-tuned an auxin response in the early stages of cluster-root development. These findings provide valuable insights into the mechanisms of cluster-root formation under P deficiency.

Synergistic interaction of exogenous auxin and reduced level of stockplant irradiance on the rooting of cola acuminata (Pal. De Beauv.) stem cuttings: applications for agroforestry trees domestication

ABSTRACT The establishment of an efficient propagation protocol is one of the most important steps in the domestication of agroforestry trees. Using Cola acuminata as a biological model, the present study investigated the interaction between exogenous auxin and reduced levels of stockplant irradiance for its effect on the rooting of stem cuttings. In a 3 × 4 factorial experiment, three levels of stockplant irradiance and four concentrations of indole 3-butyric acid (IBA) were tested for their effect on the rooting potential of leafy stem cuttings. Relationship between flavonoid content of stockplants and rooting potential of stem cuttings was also investigated. Results showed that percentage of cuttings rooted significantly increased, as did the mean number of roots, with decreasing levels of stockplant irradiance. Likewise, rooting was enhanced by all applications of IBA. 100% rooting was achieved under the combination of 50% and 25% ambient irradiance together with 2% and 4% IBA. The mean number of roots was greatest (11.4 ± 0.2) when 4% IBA was combined with 25% ambient sunlight. Flavonoid content of plant extracts decreased with stockplant irradiance. There were significant negative correlations between flavonoid content of plant extracts and the rooting parameters of cuttings.

Systematic enhancement of L-DOPA and Secondary metabolites from Mucuna imbricata: Implication of precursors and elicitors in Callus culture

The bioprocess methodology for the enhanced production of phytochemicals using plant cultures predominantly depends on the elicitors and precursors. The drug L-DOPA (anti-Parkinson's drug) (L-3, 4-dihydroxyphenylalanine) has been chiefly isolated from the popular medicinal plant species Mucuna. The present study has been carried out to enhance the production of L-DOPA and other secondary metabolites in the presence of the optimized concentration of growth promoters, elicitors and precursor's in vitro callus culture of Mucuna imbricata. Results revealed that there is a positive influence of Methyl Jasmonate (MJC) and Salicylic Acid (SAC) on the accumulation of L-DOPA and other secondary metabolites (Nutritional and anti-nutritional factors), which enhances their production by more than two folds. The highest accumulation of L-DOPA was noticed in the elicitation of 1 mM MJC (4.3 ± 0.4 %) followed by 1 mM SAC (3.4 ± 0.08 %) on 45th and 30th days respectively. Results also illustrated a significant increase of callus biomass (dry and moist weight) as well as total phenolics, flavonoids and antioxidants values in the elicited callus from day 30th to day 45th of explant inoculation which indicates a synergistic interaction of auxin, cytokinins with elicitors and precursors respectively. Additionally, results revealed that improved accumulation of carbohydrates was positively correlated with an increase in L-DOPA content in the elicited callus. Hence the protocol formulated delivers an effective alternative for mass production of L-DOPA from callus culture with improved metabolite content.

RNA-seq analysis of laser microdissected Arabidopsis thaliana leaf epidermis, mesophyll and vasculature defines tissue-specific transcriptional responses to multiple stress treatments.

Acclimation of plants to adverse conditions requires the coordination of gene expression and signalling pathways between tissues and cell types. As the energy and carbon capturing organs, leaves are significantly affected by abiotic and biotic stresses. However, tissue- or cell type-specific analyses of stress responses have focussed on the Arabidopsis root. Here, we comparatively explore the transcriptomes of three leaf tissues (epidermis, mesophyll, vasculature) after induction of diverse stress pathways by chemical stimuli (antimycin A, 3-amino-1,2,4-triazole, methyl viologen, salicylic acid) and ultraviolet light in Arabidopsis using laser capture microdissection followed by RNA sequencing. Stimulation of stress pathways caused an overall reduction in the number of genes expressed in a tissue-specific manner, though a small subset gained or changed their tissue specificity. We find no evidence of a common stress response, with only a few genes consistently responsive to two or more treatments in the analysed tissues. However, differentially expressed genes overlap between tissues for individual treatments. A focussed analysis provided evidence for an interaction of auxin and ethylene that mediates retrograde signalling during mitochondrial dysfunction specifically in the epidermis, and a gene regulatory network defined the hierarchy of interactions. Taken together, we have generated an extensive reference dataset that will be valuable for future experiments analysing transcriptional responses on a tissue or single-cell level. Our results will enable the tailoring of the tissue-specific engineering of stress-tolerant plants.

Auxin Interactions with Other Hormones in Plant Development.

Auxin is a crucial growth regulator that governs plant development and responses to environmental perturbations. It functions at the heart of many developmental processes, from embryogenesis to organ senescence, and is key to plant interactions with the environment, including responses to biotic and abiotic stimuli. As remarkable as auxin is, it does not act alone, but rather solicits the help of, or is solicited by, other endogenous signals, including the plant hormones abscisic acid, brassinosteroids, cytokinins, ethylene, gibberellic acid, jasmonates, salicylic acid, and strigolactones. The interactions between auxin and other hormones occur at multiple levels: hormones regulate one another's synthesis, transport, and/or response; hormone-specific transcriptional regulators for different pathways physically interact and/or converge on common target genes; etc. However, our understanding of this crosstalk is still fragmentary, with only a few pieces of the gigantic puzzle firmly established. In this review, we provide a glimpse into the complexity of hormone interactions that involve auxin, underscoring how patchy our current understanding is.

Complex-Type N-Glycans Influence the Root Hair Landscape of Arabidopsis Seedlings by Altering the Auxin Output.

Roots supply plants with nutrients and water, besides anchoring them in the soil. The primary root with its lateral roots constitutes the central skeleton of the root system. In particular, root hairs increase the root surface, which is critical for optimizing uptake efficiency. During root-cell growth and development, many proteins that are components of, e.g., the cell wall and plasma membrane are constitutively transported through the secretory system and become posttranslationally modified. Here, the best-studied posttranslational modification is protein N-glycosylation. While alterations in the attachment/modification of N-glycans within the ER lumen results in severe developmental defects, the impact of Golgi-localized complex N-glycan modification, particularly on root development, has not been studied in detail. We report that impairment of complex-type N-glycosylation results in a differential response to synthetic phytohormones with earlier and increased root-hair elongation. Application of either the cytokinin BAP, the auxin NAA, or the ethylene precursor ACC revealed an interaction of auxin with complex N-glycosylation during root-hair development. Especially in gntI mutant seedlings, the early block of complex N-glycan formation resulted in an increased auxin sensitivity. RNA-seq experiments suggest that gntI roots have permanently elevated nutrient-, hypoxia-, and defense-stress responses, which might be a consequence of the altered auxin responsiveness.

Reaction Wood Anatomical Traits and Hormonal Profiles in Poplar Bent Stem and Root.

Reaction wood (RW) formation is an innate physiological response of woody plants to counteract mechanical constraints in nature, reinforce structure and redirect growth toward the vertical direction. Differences and/or similarities between stem and root response to mechanical constraints remain almost unknown especially in relation to phytohormones distribution and RW characteristics. Thus, Populus nigra stem and root subjected to static non-destructive mid-term bending treatment were analyzed. The distribution of tension and compression forces was firstly modeled along the main bent stem and root axis; then, anatomical features, chemical composition, and a complete auxin and cytokinin metabolite profiles of the stretched convex and compressed concave side of three different bent stem and root sectors were analyzed. The results showed that in bent stems RW was produced on the upper stretched convex side whereas in bent roots it was produced on the lower compressed concave side. Anatomical features and chemical analysis showed that bent stem RW was characterized by a low number of vessel, poor lignification, and high carbohydrate, and thus gelatinous layer in fiber cell wall. Conversely, in bent root, RW was characterized by high vessel number and area, without any significant variation in carbohydrate and lignin content. An antagonistic interaction of auxins and different cytokinin forms/conjugates seems to regulate critical aspects of RW formation/development in stem and root to facilitate upward/downward organ bending. The observed differences between the response stem and root to bending highlight how hormonal signaling is highly organ-dependent.

Interaction of Auxin and Nitric Oxide Improved Photosynthetic Efficiency and Antioxidant System of Brassica juncea Plants Under Salt Stress

It is known that auxin and nitric oxide have the ability to ameliorate various abiotic stresses in plants individually. However, their interactive effects on the stress generated by salt in plants are not reported yet. Therefore, the present study was conducted to explore the effectiveness of sodium nitroprusside (SNP), a donor of nitric oxide and IAA (Indole acetic acid) individually and in combination on the photosynthetic efficiency, antioxidative enzyme activities, and plant biomass under salt stress. Twenty-five-day-old plants were exposed to SNP and IAA individually and in combination for 5 days continuously, and it was found that both SNP and IAA showed almost similar response at 30 and 45 days of old plants and increased studied parameters over their respective controls. However, the interactive effect of both SNP and IAA excelled over the individual response of SNP and IAA. On the other hand, the presence of salt in soil significantly decreased the parameters studied. Furthermore, stress generated by NaCl was overcome by the exogenous application of SNP, IAA alone as well as in combination at both the stages of samplings. However, the combination of IAA and SNP was more effective at 45 DAS where the value of plant biomass and photosynthetic efficiency was more in comparison to control plants. The level of antioxidant enzymes and proline was further enhanced by SNP and IAA and maximum values were reported in the plants received both SNP and IAA under NaCl stress. This enhanced antioxidant system and proline accumulation could ameliorate the stress induced by NaCl in plants that was reflected by the improved plant biomass, and photosynthetic efficiency in comparison to control plants.

Sugarcane of Rapid Multiplication by Callogenesis

The results showed that shoot apical meristem of sugarcane has the ability to stimulate and induction to callus in vitro by plant tissue culture. The results showed 2,4-D regulator 1.5 mg/L was more potent in the induction of the callus and callus subsequent growth. The effected interactions of auxin and cytokinin regulators were not significant with respect to the formation of callus. The best regeneration response was achieved by using growth regulators. In Co8371, best induction of the shoot response was found on MS medium with concentration of 1.0 mg/L BAP compared to Co85004. MS medium with the using of 0.5 mg/L BAP and 0.25 mg/L Kinetin regulator exhibited best organogenesis responding.

Abscisic acid-nitric oxide and auxin interaction modulates salt stress response in tomato roots

Integrated signaling network involving abscisic acid (ABA), nitric oxide (NO), and indole-acetic acid (IAA) controls root morphogenesis during salt stress by a mechanism still poorly understood. The present data unveiled an ABA-NO-IAA interaction underlying radicular morphological responses to salinity. Three Solanum lycopersicum genotypes were analyzed: wild type, ABA-insensitive mutant (sitiens), and auxin-responsive (DR5::GUS) plants. Nitric oxide fluorescence, nitrate reductase activity, auxin signaling, and some molecular analyses were performed. Pharmacological inhibitors and NO donor sodium nitroprusside were also used to evaluate NaCl-induced root morphological responses. Sodium nitroprusside inhibited primary root length, increased lateral root emergence, and rescued salt inhibited lateral root growth. The results showed that NO integrates the ABA-IAA signaling network of root system responses under salt stress, involving: (a) ABA and molybdenum-dependent enzymes as responsible for salt-induced NO production; (b) modulations of the plasma membrane H+-ATPase coupling and isoforms differential expression; and (c) ABA-mediated and NO-dependent antioxidative enzymes activities.