IAA Content Research Articles

Comparative Transcriptome Analysis Reveals Hormone Signal Transduction and Sucrose Metabolism Related Genes Involved in the Regulation of Anther Dehiscence in Photo-Thermo-Sensitive Genic Male Sterile Wheat.

Anther dehiscence is an important process to release pollen and then is a critical event in pollination. In the wheat photo-thermo-sensitive genic male sterility (PTGMS) line, pollen cannot release from anther since the anther cannot dehisce during anther dehiscence stage in a sterile condition. In this study, we carried out RNA-sequencing to analyze the transcriptome of one wheat PTGMS line BS366 during anther dehiscence under fertile and sterile conditions to explore the mechanism. We identified 6306 differentially expressed genes (DEGs). Weighted gene co-expression network analysis (WGCNA) and KEGG analysis showed that DEGs were mainly related to “hormone signal transduction pathway” and “starch and sucrose metabolism”. We identified 35 and 23 DEGs related hormone signal transduction and sucrose metabolism, respectively. Compared with conventional wheat Jing411, there were some changes in the contents of hormones, including JA, IAA, BR, ABA and GA3, and sucrose, during three anther dehiscence stages in the sterile condition in BS366. We performed qRT-PCR to verify the expression levels of some critical DEGs of the hormone signaling pathway and the starch and sucrose metabolism pathway. The results showed disparate expression patterns of the critical DEGs of the hormone signaling pathway and the starch and sucrose metabolism pathway in different conditions, suggesting these genes may be involved in the regulation of the anther dehiscence in BS366. Finally, we conducted a hypothesis model to reveal the regulation pathway of hormones and sucrose on anther dehiscence. The information provided new clues to the molecular mechanisms of anther dehiscence in wheat and improved wheat hybrid breeding.

Biocontrol Activity of Yeasts against Alternaria solani and Plant Growth Promotion of Tomato Plants

Aim: Yeasts have emerged as a single celled biocontrol agent which are applicable in controlling many disease causing pathogens in plants. These yeasts also have growth promoting substances that help in the growth and development of plants.
 Materials and Methods: Yeast on tomato plants were isolated using standard plate count technique and observed under microscope for their cell shape and sizes. Biocontrol activity of yeast was evaluated by measuring diameter of zone of inhibition (mm) and estimating mycelial dry weights of pathogen. IAA production by yeasts was estimated in vitro and the plant growth and development was evaluated by measuring plant heights, number of leaves, number of days for flower initiation, shoot biomass, root mass, disease incidence and severity in pot culture experiments.
 Results: Yeast isolate TPL-I isolated from tomato plants was most effective in inhibiting Alternaria solani with diameter of zone of inhibition of 9.00 mm. Reduced mycelial dry weight of pathogen viz., 40.07 mg was exhibited by TPL-I under in vitro conditions. The maximum concentration of IAA was produced by TPL- I (0.11 μg/ml). The highest plant height, number of leaflets and number of days taken for flower initiation was recorded highest in T4 (Trichoderma harzianum) followed by T7 (Foliar spray of Alternaria solani + TPL- I + Trichoderma harzianum) at 30, 45 and 60 days after transplanting. Maximum dry weight of shoot (12.32 g/plant) and root (5.18 g/plant) was recorded in T4 (Foliar spray of Trichoderma harzianum) whereas, minimum dry weight of shoot (8.26 g/plant) and root (2.80 g/plant) was recorded in T2 (Foliar spray of Alternaria solani). Lowest disease incidence (33.33%) and disease severity (24.25%) was recorded in T5 (Foliar spray of Alternaria solani + TPL- I).

Influence of growth regulators and length of cuttings on the propagation potential of Piper pedicellatum C. DC. – A threatened wild leafy vegetable of North-East India

Piper pedicellatum C. DC. is a wild leafy vegetable belonging to the family Piperaceae and is categorized as threatened species. It is one of the widely used popular leafy vegetable in Arunachal Pradesh, Manipur, and Sikkim, locally known as Rahre, Raro or Rori. The species is rich in vitamin A, Vitamin C, minerals, dietary fibre, antioxidants, protein, and energy and is also used as an ethnomedicinal plant. An experiment was conducted to study the effect of growth regulators IBA and IAA and length of stem cuttings on propagation potential of P. pedicellatum C. DC in the Forestry Nursery of North Eastern Regional Institute of Science and Technology during the years 2018 and 2019. The experiment revealed that the performance of stem cuttings viz., time taken for first sprouting, maximum sprout per cutting, length of sprouted shoot, number of leaves per cutting, and maximum fresh weight of shoot are found better in the treatment of T4 (L1 + IBA 1500 ppm), T7 (L1 + IAA 1500 ppm), T11 (L2 + IBA 1500 ppm) and T14 (L2 + IAA 1500 ppm), respectively. Similarly, the maximum number of roots per cutting, root length, fresh and dry weight of roots were also recorded in the treatment of T4 (L2 + IAA 1500 ppm) at par with T11 (L1 + IBA 1500 ppm) during both the year. The mean maximum survival rate of cuttings with a higher rooting percentage was observed in T11, which is at par with T7, T14, and T4. Although L2 cuttings performed better than L1 cuttings, the difference was not so prominent. Stem cuttings, irrespective of their length, treated with IBA 1500 ppm and IAA 1500 ppm showed significantly superior performance over the cuttings treated with lower concentrations of IBA and IAA. The outcome of the present study indicated that the P. pedicellatum is a promising wild leafy vegetable plant that can be exploited for conservation, domestication, and cultivation through the vegetative propagation technique, with standardization of its production technology for the adoption of commercial cultivation of the threatened species.

Inoculation with carbofuran-degrading rhizobacteria promotes maize growth through production of IAA and regulation of the release of plant-specialized metabolites

Toxic residues of the insecticide carbofuran in farmland is an urgent problem, and high concentrations of carbofuran have been found in the rhizoshperic soil of maize treated with seed coating agents 120–180 days after planting. Using an enrichment co-culture method, we identify a bacterial strain obtained from these carbofuran-contaminated rhizosphere soils as Leclercia adecarboxylata MCH-1. This strain exhibited a significant ability to degrade both carbofuran and 3-keto carbofuran, with total degradation of 55.6 ± 4.6% and 75.7 ± 3.4%, respectively, 24 h following start of co-culture. Further activity screening revealed that the inoculation of maize roots with L. adecarboxylata MCH-1 promoted maize seedling growth. Quantitative analysis demonstrated that this bacterial strain had the ability to synthesize the phytohormone IAA. Simultaneously, the concentration of IAA in the rhizospheric soil increased following inoculation of maize roots with L. adecarboxylata MCH-1. Moreover, the concentrations of plant specialized metabolites, including phenolics, terpenoids, and alkaloids, decreased in maize seedlings and were elevated in the rhizospheric soil after maize roots had been inoculated with the MCH-1 strain. Interestingly, the growth of the strain MCH-1 was improved by co-culture with root exudates obtained from the rhizospheric soil, specifically 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, and zealexin A1 (ZA1). Taken together, our results suggest that the carbofuran-degrading rhizobacterium L. adecarboxylata MCH-1 is able to interact with maize plants through the regulation of maize root exudates. Moreover, inoculation with L. adecarboxylata MCH-1 promotes maize growth through the production of IAA and regulation of the release of plant specialized metabolites. Our results provide a new model organism for the remediation of farmland soils from pollution with carbofuran residues.

Selenium-induced modulations in growth, productivity and physiochemical responses to water deficiency in Quinoa (Chenopodium quinoa) grown in sandy soil

Water stress is one of the major global problems that limits the growth and production of various crops. The current investigation aims to study the possibilities of mitigating the effect of drought stress on Quinoa plant grown under sandy soil by foliar treatment with selenium through assessment growth, productivity, and many physiological and biochemical measurements. Selenium (SE) was exogenously-applied as a foliar treatment with concentrations SE25 mg/L and SE50 mg/L to Quinoa plants grown under (full irrigation I100 = 100%) and (deficit irrigation I60 = 60%) in open field in growing seasons (2019/2020 and 2020/2021). Exposure of Quinoa plants to water stress led to significant decreases in shoot growth, yield, chlorophyll a, chlorophyll b, carotenoids and indole acetic (IAA) comparing with full irrigation (I100). While, increased root length, fresh and dry weight, total phenolics, total soluble sugars TSS, proline and free amino acids (FAA). Furthermore, water deficit decreased yield and its components as well as carbohydrates, protein, nitrogen, phosphorus and potassium contents of the yielded Quinoa grains compared with those plants grown under normal irrigation (I100). However, foliar spraying with selenium particularly at 50 mg/L to stress plants significantly improved growth and productivity of Quinoa plants. Moreover, treatment Quinoa plant with different levels of selenium reduced the effect of water stress by enhancing growth and productivity of Quinoa plants through improving photosynthetic pigments, IAA, total phenolics, TSS, proline and FAA contents. As a result, this findings suggest using 25 or 50 mg/L selenium as a foliar application strategy for Quinoa plants grown under drought stress to maintain higher growth and the studied biochemical aspects and yield as well as yield components and mitigate the inhibitory action of water stress on plant growth and productivity.

Effects of Exogenous Strigolactone on Wheat Grain Filling and Yield Formation in Different Cultivation Densities

Wheat is one of the main crops in northern China, and drought has been a major problem in wheat cultivation. As a new type of plant hormone, Strigolactone (SLs), its effect on drought resistance of wheat needs to be studied extensively. In this study, the effects of SLs on the growth and development of wheat from florescence stage to maturity stage were determined by plant physiological and enzyme-linked immunoassay techniques. The results showed that, with the progress of reproductive development, leaf spraying exogenous SLs not only delayed the peak of ABA content, promoted the increase of IAA and GA content in the early stage, changed the metabolic balance of hormone in leaves, and thus changed the physiological metabolic process. Especially under the condition of high density, the effects of SLs were more obvious. And, with the change of the blade metabolic balance, its net photosynthetic rate and the level of carbon dioxide fixation increased, and SOD and POD activity enhanced, MDA content decreased, indicating that aging rate of leaves was slowed down and matter accumulation ability enhanced, so as to improve the filling rate and increase the weight of the mature grain, eventually promoted the yield of wheat. Through the above analysis, it can be seen that exogenous SLs can effectively improve the yield of wheat under high density condition, which provides reliable theoretical and technical support for its practical application in the field.

Induction Resistance in Chili (Capsicum frutescens L.) to the Geminivirus Disease by Pseudomonas fluorescens

This study included resistance induced by Pseudomonas fluorescens PGPR in chili (Capsicum frutescens L.) infected with Geminivirus. Geminivirus often attacks chili plants, causing disease with a yellowish color to the leaves, lobes, and stunting. Chili plants that have been attacked by the virus will experience crop failure and plant death. Virus prevention can be done with the application of PGPR by Pseudomonas fluorescens. The method used was 6 treatments on chili plants which were repeated 4 times. The analysis of variance was processed using R software. The results showed that cayenne pepper plants that were given the PGPR application had a shorter incubation period against Geminivirus attacks. Each concentration of Pseudomonas fluorescens has a mean incubation period that is not significantly different. The results also showed that there was a significant difference in the intensity of the disease that attacked the cayenne pepper plant. The application of 107 Pseudomonas fluorescens showed the most optimal results for phenol content, plant height, and number of plant leaves. The application of 109 Pseudomonas fluorescens showed optimal results for the content of IAA and the content of the peroxidase enzyme.

Isolation of endophytic bacteria from cashew root and its ability as phosphate solubilizing and IAA-producing bacteria

This study aimed to isolate endophytic bacteria from cashew plant roots, and to determine their ability to dissolve phosphate and produce IAA. This research was conducted at the Microbiology Laboratory of the Faculty of Medicine, University of Mataram. This research was conducted by isolating the endophytic bacteria of cashew nut root and then testing the phosphate solubilizing ablity and testing the potential for IAA-producing bacteria. Based on the results of the study, there were 7 isolates of endophytic bacteria, all of which were able to solubilize inorganc phosphate with a low phosphate solubility index, ranging from 1 to 1.7. Of the 7 isolates, there were 2 isolates that were able to produce IAA, namely AJM 7 and AJM8 isolates with IAA concentrations ranging from 16 to 18 ppm. Based on the results above, it can be concluded that the endophytic bacterial isolates from the roots of the cashew plant have the potential to be a candidates for biofertilizer formulation.

Over-expression of a YUCCA-Like Gene Results in Altered Shoot and Stolon Branching and Reduced Potato Tuber Size

Auxin is known to be involved in various developmental processes, including meristem identity, shoot branching and initiation of potato tubers. The previously identified StYUCCA8 gene in potato that exhibits a peak in gene expression after tuber induction and prior to tuber swelling was cloned and over-expressed in order to study the effects of altered auxin content on shoot and stolon architecture and tuber development. The potato plants transformed with the 35S::StYUCCA8 construct exhibited increased shoot and stolon branching, reduced leaf size, lower average tuber fresh weight and enhanced adventitious and lateral root formation. Investigation of the IAA content revealed that the concentration of auxin was not altered in the shoot apex but was significantly lower in the basal part of the stem despite the several 100-fold increase of expression of the StYUCCA8 gene in three independent transgenic clones. This is the first time a potato YUCCA gene is used in an experiment in order to identify the role of endogenous auxin biosynthesis in potato plant development. Our research helps elucidate the importance of small changes of auxin content on several developmental events of the potato plant, such as shoot, stolon and root architecture.

New Insights Into the Activity of Apple Dihydrochalcone Phloretin: Disturbance of Auxin Homeostasis as Physiological Basis of Phloretin Phytotoxic Action.

Apple species are the unique naturally rich source of dihydrochalcones, phenolic compounds with an elusive role in planta, but suggested auto-allelochemical features related to “apple replant disease” (ARD). Our aim was to elucidate the physiological basis of the phytotoxic action of dihydrochalcone phloretin in the model plant Arabidopsis and to promote phloretin as a new prospective eco-friendly phytotoxic compound. Phloretin treatment induced a significant dose-dependent growth retardation and severe morphological abnormalities and agravitropic behavior in Arabidopsis seedlings. Histological examination revealed a reduced starch content in the columella cells and a serious disturbance in root architecture, which resulted in the reduction in length of meristematic and elongation zones. Significantly disturbed auxin metabolome profile in roots with a particularly increased content of IAA accumulated in the lateral parts of the root apex, accompanied by changes in the expression of auxin biosynthetic and transport genes, especially PIN1, PIN3, PIN7, and ABCB1, indicates the role of auxin in physiological basis of phloretin-induced growth retardation. The results reveal a disturbance of auxin homeostasis as the main mechanism of phytotoxic action of phloretin. This mechanism makes phloretin a prospective candidate for an eco-friendly bioherbicide and paves the way for further research of phloretin role in ARD.

Excessive nitrogen in field-grown rice suppresses grain filling of inferior spikelets by reducing the accumulation of cytokinin and auxin

Excessive nitrogen fertilizer is often applied to achieve higher rice yield in many regions of the world. However, the effect of excessive nitrogen on grain filling of inferior spikelets and its underlying mechanisms are still poorly understood. A three-year field experiment was conducted to reveal the mechanisms by which excessive nitrogen application regulated grain filling. We found that excessive application of nitrogen reduced the starch biosynthesis and grain weight of inferior spikelets but not superior spikelets. Plant hormone detection revealed that both cytokinin (CTK) and 3-Indoleacetic acid (IAA) were reduced by excessive nitrogen at the early stage of grain filling in inferior spiekelts. Quantitative real-time PCR results showed that inhibition of biosynthesis genes led to a decrease in IAA content, while elevation of CTK oxidase genes resulted in a lower level of CTK under excessive nitrogen treatment. Application of exogenous IAA or CTK significantly impaired the inhibitory effect of excessive nitrogen on starch accumulation and grain weight of inferior spikelets. Further enzyme assays revealed that excessive nitrogen application significantly suppressed the enzyme activities of sucrose synthase (SuS), adenosine diphosphate glucose pyrophosphorylase (AGP) and starch synthase (StS) in inferior spikelets. Application of exogenous IAA or CTK to the panicle under excessive nitrogen treatment significantly increased the enzyme activities of SuS, AGP and StS. Taken together, our results revealed that excessive nitrogen application in field-grown rice suppressed grain filling of inferior spikelets by reducing the accumulation of cytokinin and auxin. • Grain filling of inferior spikelets was reduced by excessive nitrogen application. • HN application reduced the contents of CTK and auxin in inferior spikelets at 6 DAA. • Exogenous CTK and auxin both increased grain filling under HN conditions. • HN downregulated auxin biosynthesis genes while upregulated CTK catabolism genes. • Activities of key enzymes for starch biosynthesis were regulated by CTK and auxin.

Effect of IAA Addition and Some Organic Supplements on Growth and Rooting of Cavendish Banana (Musa Acuminata, AAA) In-Vitro

In vitro propagation of Cavendish banana is an alternative to produce healthy, uniform and sufficient plant materials of high qualities. Appropriate culture media formulation is needed for shoot growth and rooting stage. This experiment aimed to study effects of IAA and organic supplements on in vitro shoot growth and rooting. Explants were subjected to MS medium with IAA and various organic supplements, in a factorial arrangement of a completely randomized design. The first factor was IAA concentrations (0; 0.5; 1 and 1.5 mg.L-1), and the second factor was types of organic supplement (control, coconut water, potato extract and banana extract). At 8 weeks after planting, shoot growth and root performance of plantlets were recorded. The results showed that addition of IAA did not affect shoot height. Addition of potato extract and banana homogenate resulted in the highest plantlets. Medium with IAA at 1 mg.L-1 resulted in the highest number of roots. The highest number of shoots was produced on media with IAA 1 mg.L-1 + coconut water and IAA 1.5 mg.L-1 + potato extract. The highest number of roots was produced in medium with potato extract. The longest roots were produced in media with 0.5 mg.L-1 IAA + banana homogenate. Keywords: Banana extract, Cavendish, Coconut water, IAA, Potato extract

Exogenous Hemin alleviates cadmium stress in maize by enhancing sucrose and nitrogen metabolism and regulating endogenous hormones

Cadmium (Cd) stress restricts maize growth and productivity severely. We aimed to investigate the effects of Hemin on the metabolism of sucrose and nitrogen and endogenous hormones in maize under cadmium stress. Maize varieties ‘Tiannong 9’ (cadmium tolerant) and ‘Fenghe 6’ (cadmium sensitive) were grown in nutrient solutions to study the effects of Hemin on maize physiological and ecological mechanisms under cadmium stress. The results showed that Hemin mediated the increase of sucrose content and the activities of key enzymes sucrose phosphate synthase (SPS) and sucrose synthase (SS) in maize leaves under cadmium stress. Soluble acid invertase (SAInv) and basic/neutral invertase (A/N-Inv) enzyme activities in leaves were decreased significantly, and sucrose accumulation in leaves was increased. Hemin also mediated the increase of NO3 − content in leaves, the decrease of NH4 + content and the increase of nitrate reductase (NR), glutamine synthetase (GS), glutamate synthase activity (GOGAT) and glutamate dehydrogenase (GDH) enzyme activities under cadmium stress. The contents of IAA, ZR, and GA in leaves and roots increased, ABA, MeJA, and SA decreased, and IAA/ABA, ZR/ABA, and GA/ABA increased under cadmium stress. Our study showed Hemin can alleviate cadmium stress in maize by enhancing sucrose and nitrogen metabolism and regulating endogenous hormones.

Integrated Methylome and Transcriptome Analysis Provides Insights into the DNA Methylation Underlying the Mechanism of Cytoplasmic Male Sterility in Kenaf (Hibiscus cannabinus L.).

Cytoplasmic male sterility (CMS) is widely exploited in hybrid seed production. Kenaf is an important fiber crop with high heterosis. The molecular mechanism of kenaf CMS remains unclear, particularly in terms of DNA methylation. Here, using the anthers of a kenaf CMS line (P3A) and its maintainer line (P3B), comparative physiological, DNA methylation, and transcriptome analyses were performed. The results showed that P3A had considerably lower levels of IAA, ABA, photosynthetic products and ATP contents than P3B. DNA methylome analysis revealed 650 differentially methylated genes (DMGs) with 313 up- and 337 down methylated, and transcriptome analysis revealed 1788 differentially expressed genes (DEGs) with 558 up- and 1230 downregulated genes in P3A compared with P3B. Moreover, 45 genes were characterized as both DEGs and DMGs, including AUX, CYP, BGL3B, SUS6, AGL30 and MYB21. Many DEGs may be regulated by related DMGs based on methylome and transcriptome studies. These DEGs were involved in carbon metabolism, plant hormone signal transduction, the TCA cycle and the MAPK signaling pathway and were shown to be important for CMS in kenaf. These results provide new insights into the epigenetic mechanism of CMS in kenaf and other crops.

A One-Step Polyphenol Removal Approach for Detection of Multiple Phytohormones from Grape Berry

Phytohormones play an important role in regulating the maturation process and the quality-related metabolite accumulation of fruits, and their concentration variation has always been concerned during fruit development. However, berry fruits, such as grape berries, are rich in a large number of secondary metabolites, which brings great challenges to the isolation and determination of hormones. In this work, we used grapes as experimental materials and proposed a solid-phase extraction (SPE) protocol to efficiently isolate multiple hormones from phenol-rich matrix using a mixture of dichloromethane, methanol and formic acid as eluent. A highly sensitive method based on ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS) was developed to quantify a total of 11 plant growth regulators, including the recognized phytohormones, in grape pericarp and seed. The established method showed satisfactory precision (RSD < 11.3%) and linearity (R2 > 0.9980). The limits of detection (LOD) and the limit of quantification (LOQ) were 0.001–0.75 ng/mL and 0.004–2.5 ng/mL, respectively. The recovery for the three levels of analytes spiked ranged from 63% to 118%, and the matrix effect was between 73% and 119%. Finally, the proposed method was applied to investigate the dynamic hormone concentration in Vitis vinifera L. cv. Cabernet Sauvignon berries from different vineyards, and assess the changes in endogenous hormones in grapes after treatment with exogenous growth regulators. We found that the contents of IP, ABA and IAA in pericarp and IP, IAA, IBA and SA in seed were significantly down-regulated after 10 days of treatment with NAA concentrations of 10 mg/L and 40 mg/L. In conclusion, this method helps to elucidate the role played by phytohormones in the maturation process and the accumulation of quality-related metabolites in phenol-rich fruits.

Potassium application promote cotton acclimation to soil waterlogging stress by regulating endogenous protective enzymes activities and hormones contents

To investigate the effect of potassium application on cotton damage mitigation after waterlogging stress, experiments were conducted under two potassium application levels (0 and 150 kg K2O hm−2) with three types of soil waterlogging treatments (0d, 3d and 6d) during cotton flowering stage. The results showed that: (a) under simple soil waterlogging stress, the increments of endogenous hormones contents of IAA, GA3 and ZR in cotton leaves were decreased as days of soil waterlogging. On the contrary, the soluble protein, MDA and ABA contents were significantly increased, while ZR/ABA, IAA/ABA and GA3/ABA were decreased. CAT and POD enzyme activities were increased although SOD activity decreased with the duration of soil waterlogging. (b) Potassium application combined with soil waterlogging significantly affected the antioxidant enzymes activity and endogenous hormones balance compared with soil waterlogging alone, leading to a significant increase in soluble protein and a pronounced decrease in H2O2 content, O2− generation rate, and MDA content, a significant increase in IAA, GA3 and ZR contents while a decrease in ABA content. Besides, it also kept higher SOD, CAT activities and slowly increased POD activity. (c) There was an obvious compensatory effect in cotton after 3d soil waterlogging under potassium application, which promoted rapidly recovery of physiological enzymes activities and ABA content. However, 6d soil waterlogging required a longer time for recovery. These findings were expected to provide a scientific and theoretical basis for reducing flood damage and improving cotton yield.

Water Uptake and Hormone Modulation Responses to Nitrogen Supply in Populus simonii under PEG-Induced Drought Stress

In the present study, the effects of nitrogen (N) supply on water uptake, drought resistance, and hormone regulation were investigated in Populus simonii seedlings grown in hydroponic solution with 5% polyethylene glycol (PEG)-induced drought stress. While acclimating to drought, the P. simonii seedlings exhibited a reduction in growth; differential expression levels of aquaporins (AQPs); activation of auxin (IAA) and abscisic acid (ABA) signaling pathways; a decrease in the net photosynthetic rate and transpiration rate; and an increase in stable nitrogen isotope composition (δ15N), total soluble substances, and intrinsic water use efficiency (WUEi), with a shift in the homeostasis of reactive oxygen species (ROS) production and scavenging. A low N supply (0.01 mM NH4NO3) or sufficient N supply (1 mM NH4NO3) exhibited distinct morphological, physiological, and transcriptional responses during acclimation to drought, primarily due to strong responses in the transcriptional regulation of genes encoding AQPs; higher soluble phenolics, total N concentrations, and ROS scavenging; and lower transpiration rates, IAA content, ABA content, and ROS accumulation with a sufficient N supply. P. simonii can differentially manage water uptake and hormone modulation in response to drought stress under deficient and sufficient N conditions. These results suggested that increased N may contribute to drought tolerance by decreasing the transpiration rate and O2− production while increasing water uptake and antioxidant enzyme activity.

The Involvement of Antioxidant Enzyme System, Nitrogen Metabolism and Osmoregulatory Substances in Alleviating Salt Stress in Inbred Maize Lines and Hormone Regulation Mechanisms.

Salt stress inhibited the growth of maize. B46 and NC236 were chosen as materials and NaCl concentrations (0, 55, 110, 165, and 220 mmol L−1) were set. We found the activities of SOD, POD, CAT, APX, GR, MDHAR, and DHAR decreased under NaCl stress. Compared with NC236, the contents of AsA and GSH, AsA/DHA and GSH/GSSG of B46 decreased. The content of O2−, H2O2, MDA, and EL of B46 increased. The contents of NO3− and NO2− decreased, while the content of NH4+ increased under high NaCl concentration. The activities of NR and NiR decreased, while the activities of GS and GOGAT increased first and then decreased. For B46 and NC236, the maximum of NADH-GDH and NAD-GDH appeared at 165 and 110 mmol L−1 NaCl concentration, respectively. Compared with B46, and the GOT and GPT activities of NC236 increased first and then decreased. With the increase of NaCl concentration, the contents of proline, soluble protein, and soluble sugar were increased. The Na+ content of B46 and NC236 increased, and the K+ content and K+/Na+ decreased. Compared with NC236, B46 had higher IAA content in leaf, higher Z + ZR content in leaf and root, and lower ABA content in leaf and root.

Halotolerant N-Fixing Bacteria Isolates for Increasing the Biochemical Activity, Total Bacteria Population, N-Uptake and Rice Seedling Growth

Rice farming is hampered by saline soil, which contains a large amount of soluble salt. The high salt content inhibits plant growth and causes nitrogen nutrient deficiency, as well as sodium and chlorine ion poisoning. Beneficial microbes that have adapted to saline ecosystems (halotolerant) can reduce salinity’s impact on rice growth. Microorganisms known as halotolerant bacteria can survive in high salt environments by maintaining an osmotic balance. The use of halotolerant N-fixing bacteria (HNB) as biofertilizers is an attempt to boost nitrogen nutrients and rice plant productivity in saline land. The goal of this study was to see how effective HNB isolates were at increasing rice plant growth. The experiment was conducted in the greenhouse of Universitas Padjadjaran’s Faculty of Agriculture, using a randomized block design with 16 treatments (control, single, and consortia of inoculant) and was repeated three times. Rice seedlings were inoculated with HNB isolates and grown in a Fahraeus saline medium. The HNB consortium application increased plant height by 9.03 cm, root-shoot ratio by 0.92, IAA content by 0.475 g/mL, nitrogen content by 2.94%, and the total number of HNB isolates (Azotobacter, Azospirillum, Bacillus, and Stenotrophomonas) by 8.10x107 CFU/mL.
 Keywords: Biofertilizer, consortia inoculum, N-fixing bacteria, rice seedling

DPC can inhibit cotton apical dominance and increase seed yield by affecting apical part structure and hormone content

The plant growth regulator mepiquat chloride (1,1-dimethylpiperidinium chloride, DPC) has been successfully used worldwide in cotton production. Fortified DPC (DPC+) can slightly damage young tissues of the epidermis, which has shown potential in cotton chemical topping in China. The underlying mechanism remains unclear. We investigated whether apical meristem and leaf morpho-physiological traits contribute to delayed growth of the main stem and increased seed yield in DPC or DPC+ as a chemical inhibitor. Two different DPC-sensitive varieties (Xinluzao 60, L60; Jinken 1402, JK1402) were field-grown using three different topping treatments manual topping (MT), no topping (NT) and chemical topping (DPC+ and DPC) in irrigated arid lands of Xinjiang for two years. The plant height decreased by 1.4–13.6% for the DPC+ and DPC treatments compared with the NT treatment and increased by 3.8 –9.2% compared with the MT treatment. The thickness of the leaves, palisade tissue (Pt) and spongy tissue (St) increased by 5.1–21.5% under DPC treatment compared with other treatments. The 3-indoleacetic acid (IAA) content of the leaves significantly increased by 25.0–93.8% at 10 days under the DPC treatment compared with that under the MT and NT treatments. The zeatin riboside (ZR) content of the leaves and apical buds increased up to 7.5 times at 40 days under the DPC+ and DPC treatments compared with that under the NT treatment. The accumulation of reproductive organ biomass and proportion of reproductive organ dry matter to total dry matter under the DPC+ and DPC treatments increased by 2.0–39.7% compared with that under the MT and NT treatments. The seed cotton yield between the DPC+ and DPC treatments showed no significant difference. However, the seed cotton yield of JK1402 under the DPC+ and DPC treatments significantly increased by 9.5–11.7% compared with that under the MT and NT treatments. The main stem length was significantly correlated with the stem length of the upper part and gibberellin (GA) content in the apical buds. The leaf Pt and ZR contents were significantly correlated with the boll weight and seed cotton yield. Collectively, the data suggest that improved morpho-physiological traits of the apical part, such as an increase in the IAA and GA contents in the apical buds, leaf Pt and ZR contents, and boll weight, inhibited growth of the main stem and increased seed cotton yield for DPC, which is cheaper than DPC+ as a chemical inhibitor under chemical regulation during the whole growth period.