Plant Growth Retardants Research Articles

Efeito do regulador de crescimento paclobutrazol no ajuste do tamanho do manjericão como planta de vaso

Abstract Basil (Ocimum basilicum L., Lamiaceae) is an herbal species cultivated primarily for culinary and aromatherapy. Basil plant height could reach more than 60 cm, and the plants tend to elongate, particularly in low-light environments. Our current study examined the potential uses of plant growth retardant paclobutrazol to control sweet basil height and improve potted basil’s ornamental quality. The treatment tested was paclobutrazol concentration at 0, 5, 10, and 20 ppm, applied as 100 mL media drenching per pot five weeks after planting. The control plants were water-drenched using the same volume at the same time. Basil treated with PBZ at 10 ppm or 20 ppm had significantly shorter, smaller shoot canopy diameter, node and leaf number than the control, but had a similar number of branches to the control. Basil treated with PBZ at 10 ppm or 20 ppm showed a more compact and bushy pot plants with the height to pot ratio of 1.5. Higher leaf chlorophyll, indicated by a higher index value, was recorded only with the PBZ concentration of 20 ppm compared to the control and the other PBZ concentrations. Basil growth responses to PBZ at 10 ppm were not significantly different from those treated with PBZ at 20 ppm, therefore the use of PBZ at a lower concentration (10 ppm) is preferable. Further studies should examine whether repeated PBZ applications at lower concentration is more effective in producing shorter and more compact pot plants.

Experimental Evidence Questions the Relationship between Stress and Fluctuating Asymmetry in Plants

The eco-evolutionary theory of developmental instability predicts that small, non-directional deviations from perfect symmetry in morphological traits (termed fluctuating asymmetry, FA) emerge when an individual is unable to buffer environmental or genetic stress during its development. Consequently, FA is widely used as an index of stress. The goal of the present study was to experimentally test a seemingly trivial prediction derived from the theory of developmental instability—and from previous observational studies—that significant growth retardation (which indicates stress) in plants is accompanied by an increase in FA of their leaves. We induced stress, evidenced by a significant decrease in biomass relative to control, in cucumber (Cucumis sativus), sweet pepper (Capsicum annuum), and common bean (Phaseolus vulgaris) by applying water solutions of copper and nickel to the soil in which plants were grown. Repeated blind measurements of plant leaves revealed that leaf FA did not differ between stressed and control plants. This finding, once again, demonstrated that FA cannot be seen as a universal indicator of environmental stress. We recommend that the use of FA as a stress index is discontinued until the scope of the developmental instability theory is clarified and its applicability limits are identified.

Optical monitoring of the plant growth status using polarimetry

Polarimetry is a powerful characterization technique that uses a wealth of information from electromagnetic waves, including polarization. Using the rich information provided by polarimetry, it is being actively studied in biomedical fields such as cancer and tumor diagnosis. Despite its importance and potential in agriculture, polarimetry for living plants has not been well studied. A Stokes polarimetric imaging system was built to determine the correlation between the polarization states of the light passing through the leaf and the growth states of lettuce. The Stokes parameter s3 associated with circular polarization increased over time and was strongly correlated with the growth of lettuce seedlings. In the statistical analysis, the distribution of s3 followed the generalized extreme value (GEV) probability density function. Salt stress retarded plant growth, and the concentration of treated sodium chloride (NaCl) showed a negative correlation with the location parameter μ of GEV. The clear correlation reported here will open the possibility of polarization measurements on living plants, enabling real-time monitoring of plant health.

Hexavalent chromium-reducing plant growth-promoting rhizobacteria are utilized to bio-fortify trivalent chromium in fenugreek by promoting plant development and decreasing the toxicity of hexavalent chromium in the soil

BackgroundFenugreek is known to have good anti-diabetes properties. Moreover, several studies accounted that the trivalent form of chromium [Cr(III)] also have anti-diabetic properties. However, its hexavalent form i.e., Cr(VI) is known to be highly toxic and carcinogenic to living beings and retarded plant growth even if it is present in low concentration in soil. Many plant growth-promoting rhizobacteria (PGPR) are reported to have the potential to reduce the Cr(VI) into Cr(III) in soil. In view of the above, the present objective was designed to effectively utilize Cr(VI) reducing PGPRs for the growth and development of fenugreek plant in Cr(VI) amended soil, apart from reducing Cr(VI) in soil and fortification of Cr(III) in the aerial part of plants. MethodsThe experiment was carried out to evaluate the effect of Cr(VI)-reducing PGPRs viz. Bacillus cereus (SUCR44); Microbacterium sp. (SUCR140); Bacillus thuringiensis (SUCR186) and B. subtilis (SUCR188) on growth, uptake and translocation of Cr as well as other physiological parameters in fenugreek grown under artificially Cr(VI) amended soil (100 mg kg−1 of Cr(VI) in soil). ResultsThe aforementioned concentration of Cr(VI) in soil cause severe reduction in root length (41 %), plant height (43 %), dry root (38 %) and herb biomass (48 %), when compared with control negative (CN; uninoculated plant not grown in Cr(VI) contaminated soil). However, the presence of Microbacterium sp.˗SURC140 (MB) mitigates the Cr toxicity resulting in improved root length (92 %), plant height (86 %), dry root (74 %) and herb biomass (99 %) as compared with control positive (CP; uninoculated plants grown in Cr(VI) contaminated soil). The maximum reduction in bioavailability (82 %) of Cr(VI) in soil and its uptake (50 %) by the plant were also observed in MB-treated plants. However, All Cr(VI)-reducing PGPRs failed to decrease the translocation of Cr to the aerial parts. Moreover, the plant treated with MB observed diminution in relative water content (13 %), electrolyte leakage (16%) and lipid peroxidation (38 %) as well as higher chlorophyll (37 %) carotenoids (17 %) contents and antioxidants (18%) potential. ConclusionThis study demonstrates that MB can lower the Cr(VI) toxicity to the plant by reducing the bioavailable Cr(VI), consequently reducing the Cr(VI) toxicity level in soil and helping in improving the growth and yield of fenugreek. Additionally, Cr(III) uptakes and translocation may improve the effectiveness of fenugreek in treating diabetes.

Co-crystalization reveals the interaction between AtYchF1 and ppGpp.

AtYchF1 is an unconventional G-protein in Arabidopsis thaliana that exhibits relaxed nucleotide-binding specificity. The bindings between AtYchF1 and biomolecules including GTP, ATP, and 26S rRNA have been reported. In this study, we demonstrated the binding of AtYchF1 to ppGpp in addition to the above molecules. AtYchF1 is a cytosolic protein previously reported as a negative regulator of both biotic and abiotic stresses while the accumulation of ppGpp in the cytoplasm induces retarded plant growth and development. By co-crystallization, in vitro pull-down experiments, and hydrolytic biochemical assays, we demonstrated the binding and hydrolysis of ppGpp by AtYchF1. ppGpp inhibits the binding of AtYchF1 to ATP, GTP, and 26S rRNA. The ppGpp hydrolyzing activity of AtYchF1 failed to be activated by AtGAP1. The AtYchF1-ppGpp co-crystal structure suggests that ppGpp might prevent His136 from executing nucleotide hydrolysis. In addition, upon the binding of ppGpp, the conformation between the TGS and helical domains of AtYchF1 changes. Such structural changes probably influence the binding between AtYchF1 and other molecules such as 26S rRNA. Since YchF proteins are conserved among different kingdoms of life, the findings advance the knowledge on the role of AtYchF1 in regulating nucleotide signaling as well as hint at the possible involvement of YchF proteins in regulating ppGpp level in other species.

Phytotoxicity level and accumulation ability of pot marigold (Calendula officinalis L.) to zinc

The study aims to reveal the effects of different Zn levels on pot marigold. We determined some germination and young seedling properties in the first experiment, and morphological, stomatal, and physiological parameters besides uptake profiles of both Zn and other plant nutrients in the second one. We supplied the water requirement of the seeds with Zn solutions (0, 250, 500, 750, and 1,000 mg l−1) in the first experiment, and We added the same zinc doses as mg kg−1 to the soil of the pots where the plants would grow in the second one. As a result, the inhibitory effects were more prominent in the early seedling stage (especially at 1,000 mg l−1 Zn) than in the germination one. We determined plant growth retardation, decreases in leaf water contents, and increases in membrane damages with higher Zn (≥500 mg kg−1) in the experiment conducted by potting soil. We detected decreases in chlorophyll parameters parallel with the increases in Zn. The alterations in plant zinc contents revealed the accumulation capacity of pot marigold in potting conditions. That TF value >1 in Zn treatments up to 500 mg kg−1 points to the efficiency limit of pot marigold as a Zn-accumulator plant.

Plastid methylerythritol phosphate pathway participates in the hypersensitive response-related cell death in Nicotiana benthamiana.

Programmed cell death (PCD), a characteristic feature of hypersensitive response (HR) in plants, is an important cellular process often associated with the defense response against pathogens. Here, the involvement of LytB, a gene encoding 4-hydroxy-3-methylbut-2-enyl diphosphate reductase that participates in the final step of the plastid methylerythritol phosphate (MEP) pathway, in plant HR cell death was studied. In Nicotiana benthmiana plants, silencing of the NbLytB gene using virus-induced gene silencing (VIGS) caused plant growth retardation and albino leaves with severely malformed chloroplasts. In NbLytB-silenced plants, HR-related cell death mediated by the expression of either the human proapoptotic protein gene Bax or an R gene with its cognate Avr effector gene was inhibited, whereas that induced by the nonhost pathogen Pseudomonas syringae pv. syringae 61 was enhanced. To dissect the isoprenoid pathway and avoid the pleiotropic effects of VIGS, chemical inhibitors that specifically inhibit isoprenoid biosynthesis in plants were employed. Treatment of N. benthamiana plants with fosmidomycin, a specific inhibitor of the plastid MEP pathway, effectively inhibited HR-related PCD, whereas treatment with mevinolin (a cytoplasmic mevalonate pathway inhibitor) and fluridone (a carotenoid biosynthesis inhibitor) did not. Together, these results suggest that the MEP pathway as well as reactive oxygen species (ROS) generation in the chloroplast play an important role in HR-related PCD, which is not displaced by the cytosolic isoprenoid biosynthesis pathway.

Reduced stem nonstructural carbohydrates caused by plant growth retardant had adverse effects on maize yield under low density.

Enhancing maize lodging resistance with plant growth retardants (PGRs) is common in maize production. However, the underlying mechanisms of yield formation as affected by PGRs are still poorly understood. A field experiment contained PGR application (a mixture of ethephon and cycocel, EC) with normal (T1) and double (T2) doses and water control (CK) was conducted at four maize plant densities (4.5, 6.0, 7.5, and 9.0 plants m-2) in 2020 and 2021. In this two-year study, the grain yield and kernel number per ear (KNE) of EC treatments were reduced by 4.8-9.0% and 3.3-12.2%, respectively, compared with CK under densities of 4.5, 6.0, and 7.5 plants m-2 without lodging. However, under the density of 9.0 plants m-2, EC treatments had no pronounced effects on grain yield and yield components. Across all densities, EC significantly decreased the leaf area index (LAI), and the lowest LAI was recorded in T2. The concentrations of nonstructural carbohydrates (NSCs; starch and soluble sugar) in the stem were significantly decreased by 9.9-10.2% in T2 averaged all densities. The sucrose and starch concentrations in grains also declined in the EC treatments. The key enzymes (cell wall acid invertase, sucrose synthase, and adenosine diphosphate pyrophosphorylase) and grain polyamine concentrations showed a slight downward trend under EC treatments compared to CK. NSCs in stems and grains, kernel enzyme activities, and polyamines in grains presented significant positive correlations with KNE. Additionally, structural carbohydrate (SC; including cellulose, hemicellulose, and lignin) concentrations in stems were improved with enhanced lodging resistance by spraying EC. Significant negative relationships were observed between SC with kernel number m-2 (KNM) and yield, suggesting that improved SC in stems might affect the availability of NSCs for kernel set. Although the lowest kernel weight and KNE were obtained at 9.0 plant m-2, relatively high LAI still ensured high KNM and high yield. Collectively, EC treatment increased SC in stems, enhanced lodging resistance of maize and reduced NSC availability for kernels, ultimately presenting adverse effects on maize kernel number and yield under relative low density.

Integrated Metabolome and Lipidome Strategy to Reveal the Action Pattern of Paclobutrazol, a Plant Growth Retardant, in Varying the Chemical Constituents of Platycodon Root.

Platycodon root, a medicinal food homology species which has been used in Asian countries for hundreds of years, is now widely cultivated in China. Treatment with paclobutrazol, a typical plant growth retardant, has raised uncertainties regarding the quality of Platycodon root, which have been rarely investigated. In the present study, metabolomic and lipidomic differences were revealed by ultra-high performance liquid chromatography coupled to ion mobility-quadrupole time of flight mass spectrometry (UPLC-IM-QTOF-MS). A significant decrease of platycodigenin-type saponins was observed in the paclobutrazol-treated sample. Carrying out a comprehensive quantitative analysis, the contents of total saponins and saccharides were determined to illustrate the mode of action of paclobutrazol on Platycodon root. This study demonstrated an exemplary research model in explaining how the exogenous matter influences the chemical properties of medicinal plants, and therefore might provide insights into the reasonable application of plant growth regulators.

Morphological characterization and transcriptome analysis of leaf angle mutant bhlh112 in maize [Zea mays L.

Leaf angle is an important agronomic trait in maize [Zea mays L.]. The compact plant phenotype, with a smaller leaf angle, is suited for high-density planting and thus for increasing crop yields. Here, we studied the ethyl methane sulfonate (EMS)-induced mutant bhlh112. Leaf angle and plant height were significantly decreased in bhlh112 compared to the wild-type plants. After treatment of seedlings with exogenous IAA and ABA respectively, under the optimal concentration of exogenous hormones, the variation of leaf angle of the mutant was more obvious than that of the wild-type, which indicated that the mutant was more sensitive to exogenous hormones. Transcriptome analysis showed that the ZmbHLH112 gene was related to the biosynthesis of auxin and brassinosteroids, and involved in the activation of genes related to the auxin and brassinosteroid signal pathways as well as cell elongation. Among the GO enrichment terms, we found many differentially expressed genes (DEGs) enriched in the cell membrane and ribosomal biosynthesis, hormone biosynthesis and signaling pathways, and flavonoid biosynthesis, which could influence cell growth and the level of endogenous hormones affecting leaf angle. Therefore, ZmbHLH112 might regulate leaf angle development through the auxin signaling and the brassinosteroid biosynthesis pathways. 12 genes related to the development of leaf were screened by WGCNA; In GO enrichment and KEGG pathways, the genes were mainly enriched in rRNA binding, ribosome biogenesis, Structural constituent of ribosome; Arabidopsis ribosome RNA methyltransferase CMAL is involved in plant development, likely by modulating auxin derived signaling pathways; The free 60s ribosomes and polysomes in the functional defective mutant rice minute-like1 (rml1) were significantly reduced, resulting in plant phenotypic diminution, narrow leaves, and growth retardation; Hence, ribosomal subunits may play an important role in leaf development. These results provide a foundation for further elucidation of the molecular mechanism of the regulation of leaf angle in maize.

Effect of Plant Growth Retardants on Growth and Flowering of Dahlia (Dahlia variabilis L.) CV. Edinburgh

The present investigation was conducted in the Research Field, Department of Horticulture, Sam Higginbottom University of Agriculture, Technology and Sciences, Prayagraj, from November 2021 to March 2022 to study the effect of plant growth retardants on the growth and flowering of dahlia (Dahlia variabilis L.) cv. Edinburgh. The seedlings were planted at a spacing of 50cm x 50cm from row to row and plant to plant to accommodate nine plants per 3- meter square area. The experiment's design used a Randomized Block Design with thirteen treatments that were duplicated three times. The plants were watered immediately after planting and at weekly intervals during the growing period. Based on the present investigation, the treatment T12 maleic hydrazide@1200ppm was found best in terms of plant growth parameters, flower, and yield of Dahlia. In terms of economics, the maximum Cost Benefit ratio (1: 2.62) was also found in treatment T12 maleic hydrazide@1200ppm, whereas the minimum Cost benefit ratio (1:1.33) was recorded in treatment T0 (Control).

Histidine-Containing Dipeptides Mitigate Salt Stress in Plants by Scavenging Reactive Carbonyl Species.

Reactive oxygen species (ROS) are critical factors that cause damage in salt-stressed plants, but their mechanisms of action in living cells are largely unknown. We investigated the roles of reactive carbonyl species (RCS), i.e., the lipid peroxide-derived α,β-unsaturated aldehydes and ketones, in plant growth retardation under salt stress. When Arabidopsis thaliana Col-0 seeds were exposed to 100 mM NaCl, germination was delayed and the levels of ROS, RCS, and protein carbonylation in the seedlings were increased. Adding the histidine-containing dipeptides carnosine, N-acetylcarnosine, and anserine, which are reported RCS scavengers, restored the germination speed and suppressed the increases in RCS and protein carbonylation but did not affect the ROS level. Increases in the levels of the RCS acrolein, crotonaldehyde, (E)-2-pentenal, and 4-hydroxy-(E)-2-nonenal were positively correlated with the delay of germination and growth inhibition. These RCS, generated downstream of ROS, are thus primarily responsible for the salt-stress symptoms of plants.

Long-Term Fertilization Strategy Impacts Rhizoctonia solani-Microbe Interactions in Soil and Rhizosphere and Defense Responses in Lettuce.

The long-term effects of agricultural management such as different fertilization strategies on soil microbiota and soil suppressiveness against plant pathogens are crucial. Therefore, the suppressiveness of soils differing in fertilization history was assessed using two Rhizoctonia solani isolates and their respective host plants (lettuce, sugar beet) in pot experiments. Further, the effects of fertilization history and the pathogen R. solani AG1-IB on the bulk soil, root-associated soil and rhizosphere microbiota of lettuce were analyzed based on amplicon sequencing of the 16S rRNA gene and ITS2 region. Organic fertilization history supported the spread of the soil-borne pathogens compared to long-term mineral fertilization. The fertilization strategy affected bacterial and fungal community composition in the root-associated soil and rhizosphere, respectively, but only the fungal community shifted in response to the inoculated pathogen. The potential plant-beneficial genus Talaromyces was enriched in the rhizosphere by organic fertilization and presence of the pathogen. Moreover, increased expression levels of defense-related genes in shoots of lettuce were observed in the soil with organic fertilization history, both in the absence and presence of the pathogen. This may reflect the enrichment of potential plant-beneficial microorganisms in the rhizosphere, but also pathogen infestation. However, enhanced defense responses resulted in retarded plant growth in the presence of R. solani (plant growth/defense tradeoff).

Effects of plant growth retardant daminozide (Alar) on neuromuscular co-ordination behavior in Drosophila melanogaster

ABSTRACT Daminozide (alar), a plant growth retardant, is used in different fruit orchard to make fruits attractive and reduce pre-harvest losses. Previously data demonstrated that acute daminozide exposure affected reproductive fitness and produced neurodegeneration in Drosophila melanogaster. The goal of this study was to determine whether continuous exposure to daminozide affects neuromuscular co-ordination in D. melanogaster as manifested in various behavioral responses. Fruit flies were exposed to 200 or 400 mg/L concentration of daminozide for two successive generations. Treated D. melanogaster were examined for the behaviors indicative of neuromuscular coordination and cognitive abilities, that include climbing, social interaction, adult grooming, migration, flight, male aggression, and adult courtship. Aberrant behavioral responses were noted among treated D. melanogaster of both sexes as evidenced by the following parameters: reduction in flight duration, abnormal social interaction, altered copulatory acts, and over-aggressiveness. Data suggest that daminozide produces impairment in neuromuscular coordination and cognitive ability in Drosophila, which was reflected as altered behavioral patterns. As Drosophila is considered as a reliable in vivo model utilized in toxicity testing, our findings may help us to anticipate and monitor potential daminozide-induced toxicity in animals and humans.

Ectopic expression of WRINKLED1 in rice improves lipid biosynthesis but retards plant growth and development.

WRINKLED1 (WRI1) is a transcription factor which is key to the regulation of seed oil biosynthesis in Arabidopsis. In the study, we identified two WRI1 genes in rice, named OsWRI1a and OsWRI1b, which share over 98% nucleotide similarity and are expressed only at very low levels in leaves and endosperms. The subcellular localization of Arabidopsis protoplasts showed that OsWRI1a encoded a nuclear localized protein. Overexpression of OsWRI1a under the control of the CaMV 35S promoter severely retarded plant growth and development in rice. Expressing the OsWRI1a gene under the control of the P1 promoter of Brittle2 (highly expressed in endosperm but low in leaves and roots) increased the oil content of both leaves and endosperms and upregulated the expression of several genes related to late glycolysis and fatty acid biosynthesis. However, the growth and development of the transgenic plants were also affected, with phenotypes including smaller plant size, later heading time, and fewer and lighter grains. The laminae (especially those of flag leaves) did not turn green and could not unroll normally. Thus, ectopic expression of OsWRI1a in rice enhances oil biosynthesis, but also leads to abnormal plant growth and development.

Tomato SlYTH1 encoding a putative RNA m6A reader affects plant growth and fruit shape

N6-methyladenosine (m6A), the most abundant and common modification on eukaryotic mRNA, plays crucial roles in multiple biological processes through controlling endogenous gene activity in organisms. The m6A reader specifically recognizes the m6A mark to mediate the regulation of m6A on mRNA, and determines the fate of its target mRNA. In plants, the currently confirmed m6A readers are YTH (YT521B homology) domain-containing proteins. We previously reported that tomato contains 9 YTH genes, of which SlYTH1 has the strongest expression. The present study reports the functional characterization of SlYTH1 in tomato. SlYTH1 mutants generated via CRISPR/Cas9 technology exhibited pleiotropic phenotypes, including low seed germination rate, shortened seedling root, retarded plant growth and development during vegetative development, and elongated and longitudinally flattened fruit with reduced the locule number. SlYTH1 knockout reduced GA3 content and downregulated the expression of related genes in gibberellin biosynthesis pathway. Moreover, exogenous GA3 application could partially restore the phenotypic defects caused by SlYTH1 mutations. SlYTH1 knockout could alleviate the inhibition of seedling root elongation by exogenous GA3 application at relatively low concentration. These facts indicated SlYTH1 is involved in regulating gibberellin biosynthesis and plays important roles in multiple physiological processes in tomato.

Effects of Different Forms of Tagetes erecta Biofumigation on the Growth of Apple Seedlings and Replanted Soil Microbial Environment

Apple replant disease (ARD) is a common soil disease that occurs in apple-growing areas around the world, causing root tip rot and necrosis, plant growth retardation and even plant death. Biofumigation is a promising strategy for controlling ARD due to its advantages of convenient application and being environmentally friendly. Tagetes erecta is an effective biological fumigant, but its effect on ARD is unclear. In the present study, we used Malus hupehensis Rehd. seedlings as the test material to detect the mitigating effects of different forms of T. erecta: air-dried sample (DS), fresh samples (FS) and fresh sample infusion solution (IS) on ARD. The effects of different forms of T. erecta on the growth of apple seedlings, leaf photosynthesis, root antioxidant enzyme, soil enzymatic activity and microbial environment were investigated. Compared with the CK treatments, DS, FS, and IS treatments all significantly increased the biomass of apple seedlings and promoted root growth under replanting conditions. Among them, DS showed the best results. The activity of antioxidant enzyme including superoxide dismutase, peroxidase and catalase were significantly increased in roots grown in soils treated with T. erecta. Moreover, T. erecta treatment also increased the activity of soil urease, phosphatase, sucrase and catalase enzyme, significantly altered the abundance of soil fungal communities and, in particular, reduced the abundance of Fusarium oxysporum, the main causal fungus of ARD. Therefore, our results suggest that biofumigation of different forms of T. erecta enhanced the resistance of ARD by regulating root reactive oxygen levels and improving the soil fungal communities.

In Vitro Techniques for Shipping of Micropropagated Plant Materials

Shipping of in vitro micro-cuttings in tubes or jars is a frequently used method as the plants are more likely to quickly reproduce and comply with quarantine regulations in plant germplasm distribution. However, these containers are fragile during transportation. To diminish the risk associated with the long-distance shipping of in vitro plants, a safe and widely applicable packing and conservation technique based on microplate and slow growth was developed in this study. Potato cultivar ZHB and ginger cultivar G-2 were used to optimize the system with microplates (96 wells), vacuum-sealed packaging, and slow-growth techniques. Under regular culture conditions, packing in vacuum-sealed microplates reduced the survival of ZHB and G-2 micro-cuttings to 85.8% and 20.0%, respectively, and regeneration to 61.8% and 0%, respectively. Reducing the temperature to 10 °C maintained the survival of ZHB and G-2 micro-cuttings in the range of 83.3–100% after 60 days. Exposure to darkness decreased the survival of G-2 and inhibited regrowth. Thus, conservation in darkness at 10 °C is suggested. The effects of iron concentration and plant growth retardants were further assessed. The addition of 1/4 MS medium combined with 100 mg/L chlormequat chloride (CCC) resulted in full survival and growth inhibition of plantlets, without malformation identified. Finally, incubation with 1/4 MS medium supplemented with 100 mg/L CCC in vacuum-sealed microplates at 10 °C in the dark resulted in high survival and suppressed germination. Sweet potato HXS was incubated as well to test the broad-spectrum applications of the technique; 100% survival and 6.7% germination was gained. Morphological indices of released cuttings recovered to control levels after two cycles of subculture in MS medium. A 0.1–0.2% genetic variation was detected by SSR and ISSR, suggesting genetic stability of the conserved samples. Finally, micro-cuttings were safely transported to cities located thousands of kilometers away without package and sample damage. Our results enable easy distribution of in vitro plant germplasms.

Zinc deficiency in cucumber plants can be alleviated by fullerenol

Zinc (Zn) deficiency is one of the most limiting factors in plant growth and productivity worldwide. Among carbon-based nanomaterials, water-soluble fullerene derivates offer unique opportunities to increase crop productivity and protection. In this work, we evaluated the stress mitigation effects of fullerenol in cucumber plants (Cucumis sativus L.) submitted to Zn deficiency conditions. Cucumber plants were grown hydroponically, either with (+Zn) or without (−Zn) a Zn supply, with (+F) or without (−F) a fullerenol supply. Fullerenol was added in a nutrient solution either before the beginning of Zn deficiency (plant priming) or at its start. A nutrient imbalance, leaf yellowing and spotting, a reduced electron transport rate (ETR), enhanced oxidative damage by excessive production of malondialdehyde (MDA) and retarded plant growth were found in Zn-deficient plants. After fullerenol treatment, some symptoms of Zn deficiency were alleviated. Overall, fullerenol decreased leaf MDA and spotting (visual observations). When fullerenol was added in a Zn-free solution, plants exhibited enhanced leaf chlorophyll or shoot dry biomass compared with non-treated plants. Also, an increase in xylem sap or young leaf Zn was observed in fullerenol-treated plants under Zn deficiency. With the exception of the MDA responses and spotting, these effects appear to occur in a dose-dependent manner. In contrast, the Zn-fed plants remained phenotypically unaffected by fullerenol. Thus, fullerenol probably alleviated Zn deficiency due to an improvement in Zn remobilization and the antioxidant capacity of the plants, in turn decreasing lipid peroxidation.

Cadmium accumulation regulated by a rice heavy-metal importer is harmful for host plant and leaf bacteria

IntroductionCadmium (Cd), one of the major toxic heavy metals, causes severe deleterious effects on all living organisms from prokaryotes to eukaryotes. Cadmium deposition affects bacterial diversity and bacterial population in soil. Cadmium accumulation in plants is mainly controlled by transporters and the resulting Cd enrichment gives rise to phytotoxicity. ObjectiveThis study aimed to mine transporters that control Cd import or accumulation in rice and uncover the underlying mechanisms that how accumulated Cd poses risks to host plant and leaf bacteria. MethodsRNA-seq analysis, histochemical assays, and elemental quantification were carried out to reveal the biological roles of OsABCG43 for Cd import. Pathogen inoculation, IC50 value, and bacterial virulence assays were conducted to disclose the effects of Cd on leaf bacteria. ResultsOsABCG43 is characterized as a Cd importer controlling Cd accumulation in rice. OsABCG43 was induced under Cd stress and specifically expressed in the vasculature of leaves and roots. Overexpression of OsABCG43 caused Cd accumulation which inhibits photosynthesis and development and alters the antioxidant system, resulting in phytotoxicity. Moreover, overexpression of OsABCG43 resulted in retarded plant growth and enhanced rice sensitivity to Cd stress. Numerous differentially expressed genes were identified via RNA-seq analysis between the OsABCG43-overexpressing plants and wild type, which functioned in Cd or reactive oxygen species (ROS) homeostasis. In addition, OsABCG43 transcripts were induced by leaf bacteria Xanthomonas oryzae pv. oryzicola (Xoc) and X. oryzae pv. oryzae (Xoo). The enriched Cd directly impaired the formation of virulence factors for the leaf bacteria, preventing colonization or proliferation of Xoc or Xoo in rice leaves. ConclusionThis work reveals that OsABCG43 is expressed specifically in the vascular and plasma membrane-localized OsABCG43 functions as a Cd importer. OsABCG43-mediated import of Cd is harmful for both rice and the corresponding leaf bacteria.