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The herbicide fluridone (1-methyl-3-phenyl-5-[3-trifluoromethyl (phenyl)]-4(1H)-pyridone) interferes with carotenoid biosynthesis in plants by inhibiting the conversion of phytoene to phytofluene. Fluridone also indirectly inhibits the biosynthesis of abscisic acid and strigolactones, and therefore, our study indirectly addresses the effect of reduced ABA on the roots and leaf buds development in stem cuttings of Salix babylonica L. 'Tortuosa'. The stem cuttings were kept in distilled water (control) or in a solution of fluridone (10 mg/L) in natural greenhouse light and temperature conditions. During the experiments, morphological observations were carried out on developing roots and leaf buds, as well as their appearance and growth. After three weeks of continuous treatments, adventitious roots and leaf buds were collected and analysed. Identification and analysis of anthocyanins were carried out using micro-HPLC-MS/MS-TOF, while HPLC-MS/MS was used to analyse phenolic acids, flavonoids and salicinoids. The fluridone applied significantly inhibited root growth, but the number or density of roots was higher compared to the control. Contents of salicortin and salicin were several dozen times higher in leaf buds than in roots of willow. Fluridone increased the content of salicortin in roots and leaf buds and declined the level of salicin in buds. Fluridone also declined the content of most anthocyanins in roots but enhanced their content in buds, especially cyanidin glucoside, cyanidin galactoside and cyanidin rutinoside. Besides, fluridone markedly decreased the level of chlorophylls and carotenoids in the leaf buds. The results indicate that applied fluridone solution reduced root growth, caused bleaching of leaf buds, and markedly affected the content of secondary metabolites in the adventitious roots and leaf buds of S. babylonica stem cuttings. The paper presents and discusses in detail the significance of fluridone's effects on physiological processes and secondary metabolism. [ABSTRACT FROM AUTHOR]

Rice (Oryza sativa L.) is a main food crop in China and is crucial for the maintenance of national food security. The growth of rice seedling roots is regulated by a variety of genes and is closely related to abscisic acid (ABA) metabolism and ABA signaling pathways. In this study, we found that OsABT could increase the length of rice root tip meristem cells and upregulate root development-related genes, thereby alleviating ABA's inhibitory effects on rice root growth and seed germination. The overexpression of OsABT reduced the ABA content by downregulating ABA synthesis genes (OsNCED3 and OsNCED5) and upregulating the ABA catabolic gene (OsABA8ox2). In addition, OsABT interacted with OsPYL4, OsPYL10, and OsABIL2 via the ABA signal transduction pathway. By inhibiting the expression of positive regulatory genes (OsPYL9 and Rab16a) and increasing the expression of a negative regulatory gene (OsABIL1), OsABT negatively regulates the ABA signal transduction pathway. Transcriptome analysis revealed that OsABT inhibited the activity of Gene Ontology entries in response to ABA. Thus, OsABT increased the length of the rice root meristem, reduced the accumulation of ABA in the roots, and negatively regulated the ABA signal transduction pathway by interacting with key proteins in this pathway, ultimately relieving the inhibitory effect of ABA on rice root length and seed germination. [ABSTRACT FROM AUTHOR]

The herbicide fluridone (1-methyl-3-phenyl-5-[3-trifluoromethyl(phenyl)]-4(1H)-pyridinone) affects processes related to plant growth and development. It interferes with carotenoid biosynthesis by inhibiting the activity of phytoene desaturase, which converts phytoene to phytofluene. Besides, fluridone indirectly inhibits abscisic acid (ABA) biosynthesis. The aim of the present study was to examine the effect of fluridone on plant pigments and proanthocyanidins in Muscari armeniacum leaves and on the dormancy of inflorescence shoots. In our experiments, uncooled M. armeniacum bulbs with fully differentiated adventitious roots were used. Three-week soaking of bulbs in water solutions of fluridone at concentrations of 5 and 10 mg dm-3 significantly inhibited the root growth of M. armeniacum plants. Besides, fluridone caused degradation of chlorophylls and carotenoids in the primary leaves of this species. Leaves obtained from fluridone--treated bulbs showed a pink colour due to the presence of anthocyanins, but histological analysis showed that these pigments were found only in the leaf parenchyma and not in the epidermis. Secondary leaves grew from bulbs after a long, 54-day treatment with fluridone contained almost no carotenoids and chlorophylls. This longer treatment of M. armeniacum bulbs also resulted in a large increase in the anthocyanin and proanthocyanidin content. The high anthocyanin content in leaves is a visible effect of fluridone-induced stress. Application of fluridone to M. armeniacum bulbs resulted also in breaking the dormancy of inflorescence shoots. [ABSTRACT FROM AUTHOR]

Invasive aquatic vegetation (IAV) is a management challenge in the Sacramento–San Joaquin Delta and the Suisun Marsh that has commanded major resource investment for 4 decades. We review the history and supporting science of chemical, biological, and mechanical control of IAV in the Delta and Suisun March, and in flowing waters outside the region. Outside the Delta, there is a significant history of research on IAV control in lotic systems, but few studies come from tidal environments, and we found no investigations at a spatial scale like that of the Delta. The science of control efforts in the Delta is nascent but has seen marked growth over the recent decade. Since 1983, control of invasive submerged and floating species has been centralized within the California State Parks Division of Boating and Waterways (CDBW). The program relies on herbicides, with an annual budget that has exceeded $12.5 million since 2015. However, the results have been mixed because of the challenge of applying herbicides effectively in a tidal system. In parallel, biological control agents for water hyacinth (Eichhornia crassipes) and giant reed (Arundo donax) have been released but have not provided an appreciable control benefit, likely because they are not suited for the temperate Delta climate. Over recent decades, regulatory complexity has increased, hampering efforts to innovate alternative methods or respond quickly to new invaders. Control efforts for giant reed and common reed (Phragmites australis), the main invasive emergent plants, have not been coordinated under a central program, and studies to investigate control strategies have only recently been permitted. As a result, no local studies have been published on control outcomes for these species. Based on this history and our review of the science, we develop recommendations for leadership and science actions to proactively manage IAV.

Rice (Oryza sativa L.) is a main food crop in China and is crucial for the maintenance of national food security. The growth of rice seedling roots is regulated by a variety of genes and is closely related to abscisic acid (ABA) metabolism and ABA signaling pathways. In this study, we found that OsABT could increase the length of rice root tip meristem cells and upregulate root development-related genes, thereby alleviating ABA’s inhibitory effects on rice root growth and seed germination. The overexpression of OsABT reduced the ABA content by downregulating ABA synthesis genes (OsNCED3 and OsNCED5) and upregulating the ABA catabolic gene (OsABA8ox2). In addition, OsABT interacted with OsPYL4, OsPYL10, and OsABIL2 via the ABA signal transduction pathway. By inhibiting the expression of positive regulatory genes (OsPYL9 and Rab16a) and increasing the expression of a negative regulatory gene (OsABIL1), OsABT negatively regulates the ABA signal transduction pathway. Transcriptome analysis revealed that OsABT inhibited the activity of Gene Ontology entries in response to ABA. Thus, OsABT increased the length of the rice root meristem, reduced the accumulation of ABA in the roots, and negatively regulated the ABA signal transduction pathway by interacting with key proteins in this pathway, ultimately relieving the inhibitory effect of ABA on rice root length and seed germination.

The herbicide fluridone (1-methyl-3-phenyl-5-[3-trifluoromethyl (phenyl)]-4(1H)-pyridone) interferes with carotenoid biosynthesis in plants by inhibiting the conversion of phytoene to phytofluene. Fluridone also indirectly inhibits the biosynthesis of abscisic acid and strigolactones, and therefore, our study indirectly addresses the effect of reduced ABA on the roots and leaf buds development in stem cuttings of Salix babylonica L. ‘Tortuosa’. The stem cuttings were kept in distilled water (control) or in a solution of fluridone (10 mg/L) in natural greenhouse light and temperature conditions. During the experiments, morphological observations were carried out on developing roots and leaf buds, as well as their appearance and growth. After three weeks of continuous treatments, adventitious roots and leaf buds were collected and analysed. Identification and analysis of anthocyanins were carried out using micro-HPLC-MS/MS-TOF, while HPLC-MS/MS was used to analyse phenolic acids, flavonoids and salicinoids. The fluridone applied significantly inhibited root growth, but the number or density of roots was higher compared to the control. Contents of salicortin and salicin were several dozen times higher in leaf buds than in roots of willow. Fluridone increased the content of salicortin in roots and leaf buds and declined the level of salicin in buds. Fluridone also declined the content of most anthocyanins in roots but enhanced their content in buds, especially cyanidin glucoside, cyanidin galactoside and cyanidin rutinoside. Besides, fluridone markedly decreased the level of chlorophylls and carotenoids in the leaf buds. The results indicate that applied fluridone solution reduced root growth, caused bleaching of leaf buds, and markedly affected the content of secondary metabolites in the adventitious roots and leaf buds of S. babylonica stem cuttings. The paper presents and discusses in detail the significance of fluridone’s effects on physiological processes and secondary metabolism.

SUMMARY: Seeds of the root parasitic plant Striga hermonthica undergo a conditioning process under humid and warm environments before germinating in response to host‐released stimulants, particularly strigolactones (SLs). The plant hormone abscisic acid (ABA) regulates different growth and developmental processes, and stress response; however, its role during Striga seed germination and early interactions with host plants is under‐investigated. Here, we show that ABA inhibited Striga seed germination and that hindering its biosynthesis induced conditioning and germination in unconditioned seeds, which was significantly enhanced by treatment with the SL analog rac‐GR24. However, the inhibitory effect of ABA remarkably decreased during conditioning, confirming the loss of sensitivity towards ABA in later developmental stages. ABA measurement showed a substantial reduction of its content during the early conditioning stage and a significant increase upon rac‐GR24‐triggered germination. We observed this increase also in released seed exudates, which was further confirmed by using the Arabidopsis ABA‐reporter GUS marker line. Seed exudates of germinated seeds, containing elevated levels of ABA, impaired the germination of surrounding Striga seeds in vitro and promoted root growth of a rice host towards germinated Striga seeds. Application of ABA as a positive control caused similar effects, indicating its function in Striga/Striga and Striga/host communications. In summary, we show that ABA is an essential player during seed dormancy and germination processes in Striga and acts as a rhizospheric signal likely to support host infestation. Significance Statement: The root parasitic plant Striga hermonthica is a severe threat to cereal's yield, endangering global food security. Herein, we uncover a new role of known plant hormone abscisic acid as a rhizospheric signal released by germinated Striga seeds, allowing them to better compete with surrounding un‐conditioned seeds and facilitating host infestation. Our findings can help in developing strategies to control this parasite and mitigate its negative impact on food supply and income of smallholder farmers. [ABSTRACT FROM AUTHOR]

Rhodotypos scandens (Thunb.) Makino is known to have a seed dispersal that is thick and stony (endocarp + seeds) and has potential as a landscaping tree seed. In several Rosaceae species, seeds are covered with a hard endocarp, making the internal seeds water-impermeable and germination difficult. Here, we analyzed the morphoanatomical traits and germination properties of R. scandens seeds. To identify ideal seed propagation conditions, we immersed R. scandens seeds in sulfuric acid for varying durations and subjected them to phytohormone (gibberellic acid A3 and fluridone) and a cold stratification (CS) (5 °C) treatment after endocarp removal (ER). The R. scandens stony seeds did not increase in mass by ≥25.0%. Following ER, the seed mass increased by ≥50.0% with water absorption when compared to the initial dry mass. Seed surfaces showed damage and cracks through scarification after 1 h of immersion in sulfuric acid, failing to germinate. A combination of ER, phytohormone treatment, and CS improved seed germination compared to ER alone (26.0 ± 5.3%). Overall, R. scandens seeds showed a dispersal with a hard endocarp from the parent plant, and a pre-treatment with ER, phytohormones, and CS was required for effective seed propagation. [ABSTRACT FROM AUTHOR]

The obligate root parasite Cistanche armena is a recently rediscovered, extremely rare endangered species endemic to Armenia, specifically parasitizing camelthorn (Alhagi maurorum , Fabaceae) and saltwort (Salsola dendroides , Chenopodiaceae). Its populations are reputedly declining due to habitat destruction and biotic impacts. Since the only known means of its reproduction is via the seeds, understanding the mechanisms of breaking C. armena seed dormancy and germination along with the related aspects of the species' biology is highly important both from fundamental (functional ecology and evolution) and applied (conservation and management) perspectives. Here, we present the first in vitro seed germination protocol for C. armena involving fluridone, a systemic herbicide targeting the carotenoid biosynthetic pathway. In addition, the seed micromorphology of C. armena is described using both light microscopy and lignin autofluorescence visualized by confocal laser scanning microscopy. The actin cytoskeleton in radicle cells of germinated C. armena seedlings is described for the first time, being the proof of seed viability. Further elaboration and application of the proposed germination protocol with the cultivation of C. armena on susceptible hosts are altogether seen as a valuable tool for the conservation of this species. [ABSTRACT FROM AUTHOR]

Invasive aquatic macrophytes are a major threat to estuarine ecosystems globally, posing difficult control challenges for resource managers. This study examined the efficacy of a fluridone treatment program to control invasive submerged aquatic vegetation (SAV). We leveraged four datasets to examine efficacy of fluridone treatment in the Sacramento–San Joaquin Delta, a freshwater tidal estuary in California, from 2014 to 2018. Annual SAV coverage maps derived from spectroscopy data were used in conjunction with fluridone application data and water current speed predicted by a 3-D hydrodynamic model of the study system. Our objective was to determine if the probability of SAV occurrence in treated sites was significantly different from untreated sites. We examined whether efficacy was influenced by the amount of herbicide applied at a site, the local current speed, and the treatment history of the site. We found that treatment efficacy was positively associated with the amount of herbicide applied per unit area, but this effect was mediated by a negative association with current speed. The efficacy of treatment did not improve when a site was treated for multiple consecutive years. Finally, we did not detect legacy effects one year after cessation of treatment. Our results suggest the need for careful selection of treatment sites to ensure that the amount of fluridone applied is likely to have significant impact given local current speeds. Our study underscores the need for development of additional treatment methodologies for hydrologically dynamic systems such as estuaries, particularly when control is needed year-round and for multiple years. [ABSTRACT FROM AUTHOR]

Rhodotypos scandens (Thunb.) Makino is known to have a seed dispersal that is thick and stony (endocarp + seeds) and has potential as a landscaping tree seed. In several Rosaceae species, seeds are covered with a hard endocarp, making the internal seeds water-impermeable and germination difficult. Here, we analyzed the morphoanatomical traits and germination properties of R. scandens seeds. To identify ideal seed propagation conditions, we immersed R. scandens seeds in sulfuric acid for varying durations and subjected them to phytohormone (gibberellic acid A3 and fluridone) and a cold stratification (CS) (5 °C) treatment after endocarp removal (ER). The R. scandens stony seeds did not increase in mass by ≥25.0%. Following ER, the seed mass increased by ≥50.0% with water absorption when compared to the initial dry mass. Seed surfaces showed damage and cracks through scarification after 1 h of immersion in sulfuric acid, failing to germinate. A combination of ER, phytohormone treatment, and CS improved seed germination compared to ER alone (26.0 ± 5.3%). Overall, R. scandens seeds showed a dispersal with a hard endocarp from the parent plant, and a pre-treatment with ER, phytohormones, and CS was required for effective seed propagation.

Fluridone is widely used as a herbicide for controlling invasive aquatic plants such as hydrilla in surface water bodies. When applied on surface waters fluridone can attach to bed sediment, requiring rigorous extraction methods prior to analysis. Currently, very limited information exists in terms of fluridone residue detection in delta sediment. In this study, we researched fluridone detection in both water and sediment. To extract fluridone from sediment, here we have tested two extraction methods: (1) a rotavapor method (RM); and (2) a quick, easy, cheap, effective, rugged and safe (QuEChERS) method (QM). The extraction results of RM were compared with those of QM. To quantify fluridone concentrations in extracts, a high-performance liquid chromatography (HPLC)-UV detector was used. HPLC separation was achieved using an Allure C18 5 µm 150 × 4.6 mm column with a mobile phase composed of acetonitrile and water (60:40, v/v). The UV detector was operated at 237 nm. The method was tested and validated using a series of water and sediment samples taken from Sacramento-San Joaquin Delta in California. The average recovery of fluridone was 73% and 78% using RM and QM respectively. The proposed method can be used for testing fluridone in water and sediment samples.

The phytohormone abscisic acid (ABA) inhibits seed germination and seedling growth and is required for the inception of dormancy. Xanthoxal (also known as xanthoxin) is the first specific biosynthetic precursor of ABA. In this study, a modified method to produce xanthoxal is described. I tested the ability of either xanthoxal or ABA to reinstate dormancy in dormant red rice seeds whose dormancy was broken by fluridone (an inhibitor of the synthesis of carotenoids and, subsequently, ABA). Xanthoxal was shown to have a stronger inhibitory effect on germination than ABA when exogenously provided. Although this could indicate an additional effect of xanthoxal above that expected if xanthoxal were simply converted to ABA in the seed, alternative hypotheses cannot be excluded. One alternative is that exogenous xanthoxal may be trapped inside the cells to a greater extent than exogenous ABA, resulting in an intracellular level of ABA higher than that reached with a direct application of ABA. As a further alternative, exogenous xanthoxal may interfere with ABA action in the apoplast. In this study, following germination, early seedling growth was delayed only if ABA was applied. This suggests that inhibition of early seedling growth, but not of germination, requires extracellular ABA. [ABSTRACT FROM AUTHOR]

Haematococcus pluvialis has high economic value because of its high astaxanthin-producing ability. The mutation breeding of Haematococcus pluvialis is an important method to improve the yield of astaxanthin. Fluoridone, an inhibitor of phytoene dehydrogenase, can be used as a screening reagent for mutation breeding of Haematococcus pluvialis. This study describes the effect of fluridone on the biomass, chlorophyll, and astaxanthin content of Haematococcus pluvialis at different growth stages. Five fluridone concentrations (0.00 mg/L, 0.25 mg/L, 0.50 mg/L, 1.00 mg/L, and 2.00 mg/L) were set to treat Haematococcus pluvialis. It was found that fluridone significantly inhibited the growth and accumulation of astaxanthin in the red dormant stage. In addition, transcriptome sequencing was used to analyze the expression of genes related to four metabolic pathways in photosynthesis, carotenoid synthesis, fatty acid metabolism, and cellular antioxidant in algae after fluridone treatment. The results showed that six genes related to photosynthesis were downregulated. FPPS, lcyB genes related to carotenoid synthesis are downregulated, but carotenoid β-cyclic hydroxylase gene (LUT5), which plays a role in the conversion of carotenoid to abscisic acid (ABA), was upregulated, while the expression of phytoene dehydrogenase gene did not change. Two genes related to cell antioxidant capacity were upregulated. In the fatty acid metabolism pathway, the acetyl-CoA carboxylase gene (ACACA) was downregulated in the green stage, but upregulated in the red stage, and the stearoyl-CoA desaturase gene (SAD) was upregulated. According to the transcriptome results, fluridone can affect the astaxanthin accumulation and growth of Haematococcus pluvialis by regulating the synthesis of carotenoids, chlorophyll, fatty acids, and so on. It is expected to be used as a screening agent for the breeding of Haematococcus pluvialis. This research also provides an experimental basis for research on the mechanism of astaxanthin metabolism in Haematococcus pluvialis. [ABSTRACT FROM AUTHOR]

Abstract Fluridone is widely used as a herbicide for controlling invasive aquatic plants such as hydrilla in surface water bodies. When applied on surface waters fluridone can attach to bed sediment, requiring rigorous extraction methods prior to analysis. Currently, very limited information exists in terms of fluridone residue detection in delta sediment. In this study, we researched fluridone detection in both water and sediment. To extract fluridone from sediment, here we have tested two extraction methods: (1) a rotavapor method (RM); and (2) a quick, easy, cheap, effective, rugged and safe (QuEChERS) method (QM). The extraction results of RM were compared with those of QM. To quantify fluridone concentrations in extracts, a high-performance liquid chromatography (HPLC)-UV detector was used. HPLC separation was achieved using an Allure C18 5 µm 150 × 4.6 mm column with a mobile phase composed of acetonitrile and water (60:40, v/v). The UV detector was operated at 237 nm. The method was tested and validated using a series of water and sediment samples taken from Sacramento–San Joaquin Delta in California. The average recovery of fluridone was 73% and 78% using RM and QM respectively. The proposed method can be used for testing fluridone in water and sediment samples.

Nitrogen availability in Buglossoides arvensis mother plants influences seed dormancy level. Abscisic acid (ABA) levels chiefly determine primary dormancy during embryo maturation and its maintenance depends on ABA/gibberellic acid (GA) balance. We hypothesised that soil nitrogen fertilisation of B. arvensis mother plants affects seed sensitivity to hormonal germination promotors and inhibitors. The purpose of the present work was therefore to investigate to what extent the changes that occur in seed germinability as a result of maternal nitrogen fertilisation (with ‐N(+)‐ and without ‐N(−)‐) are paralleled by changes in ABA or GAs de novo synthesis and embryonic sensitivity to ABA or GAs. Seed germinability was assessed under a gradient of ABA and GA3 and their corresponding de novo synthesis inhibitors (fluridone ‐FLU‐ and paclobutrazol ‐PBZ‐). B. arvensis seeds were incubated at suboptimal (7°C), optimal (15°C) and supraoptimal (20°C) temperatures. Results indicated a higher germination of N(+) seeds, irrespective of hormone type, dose or incubation temperature. N(−) seeds were more sensitive to FLU at 7°C and to GA3 at 15°C, whereas N(+) seeds were more sensitive to FLU at 15‐20°C and to PBZ at 7°C. At 20°C, N(+) seed germinability was stimulated by GA3 counteracting the thermo‐inhibitory effect. The higher seed germinability recorded from nitrogen‐fertilised plants could be associated to a decrease in seed dormancy levels due to lower ABA levels during embryogenesis, thus requiring a lower amount of GAs to germinate. Further studies are required to confirm this hypothesis. [ABSTRACT FROM AUTHOR]

The phytohormone abscisic acid (ABA) inhibits seed germination and seedling growth and is required for the inception of dormancy. Xanthoxal (also known as xanthoxin) is the first specific biosynthetic precursor of ABA. In this study, a modified method to produce xanthoxal is described. I tested the ability of either xanthoxal or ABA to reinstate dormancy in dormant red rice seeds whose dormancy was broken by fluridone (an inhibitor of the synthesis of carotenoids and, subsequently, ABA). Xanthoxal was shown to have a stronger inhibitory effect on germination than ABA when exogenously provided. Although this could indicate an additional effect of xanthoxal above that expected if xanthoxal were simply converted to ABA in the seed, alternative hypotheses cannot be excluded. One alternative is that exogenous xanthoxal may be trapped inside the cells to a greater extent than exogenous ABA, resulting in an intracellular level of ABA higher than that reached with a direct application of ABA. As a further alternative, exogenous xanthoxal may interfere with ABA action in the apoplast. In this study, following germination, early seedling growth was delayed only if ABA was applied. This suggests that inhibition of early seedling growth, but not of germination, requires extracellular ABA.

Abstract Background Notopterygium incisum is an important Chinese medicinal plant. Its mature seeds have underdeveloped embryos and are physiological dormant. We found the seeds with full developed embryos can germinate after treated by fluridone (FL), an inhibitor of abscisic acid (ABA). In order to understand the molecular mechanisms underlying seed dormancy release by FL, we compared the transcriptomic changes in dormancy release induced by two different methods, FL and cold stratification (CS) in N. incisum. We further analyzed the gene expression patterns involved in seed germination and dormancy using quantitative reverse-transcription PCR. Results RNA-sequence analysis revealed more dramatic changes in the transcriptomes of FL than those in CS, particularly for genes involved in the biosynthesis and regulation of gibberellins (GAs) and ABA. The down-regulation of ABA biosynthesis genes and the dramatic up-regulation of NiCYP707As, an ABA catabolic gene, contributed to the reduced ABA levels in FL. The increased GA3 levels in CS-treated seeds were due to the up-regulation of NiGA3OX. Both NiABI5 (a positive ABA regulator) and NiGAI (a negative regulator of GA) were down-regulated in FL and CS. The upregulation of strigolactones (SLs; the metabolites with the same precursor as ABA) biosynthesis and regulatory genes in both FL- and CS-treated seeds indicates that SLs contribute positively to seed dormancy release in N. incisum. Conclusions Our results indicated that FL- and CS-seed dormancy release possibly depends on two totally different mechanisms: alleviation of the effects of ABA and potentiation of the effects of GA, respectively. However, NiABI5 and NiGAI probably function as common factors integrating the effects of ABA and GA on seed dormancy release.

The effects of fluridone on the content and composition of fatty acids and some other properties of tomato fruits during a 14-day period of ripening were studied. Mature green tomato fruits were used for the experiments. Fluridone at a 1.0% concentration in lanolin paste was applied as a 2-3 mm stripe from the top to the base of a tomato fruit, and a stripe of lanolin was applied in the same way on the opposite side of the frui as control. After 14 days of the experiment, the treated (yellow) and untreated (red) halves of the tomato were separately freeze-dried and powdered before analysis. Determination of the profile and content of fatty acids was carried out in a micro-HPLC-MS/MS system including a 5600 QTOF mass spectrometer. Fatty acids were identified, based on retention times of available standards and the MS/MS spectra. The degree of lipid peroxidation, DPPH radical scavenging activity, proline and soluble protein content were determined using spectrophotometric methods. The use of fluridone did not cause significant changes in the content of unbound fatty acids, although there was a tendency to increased amounts of unsaturated acids. Concerning total fatty acids, the use of fluridone significantly increased the ratio of oleic acid to stearic, as well as the ratio of total unsaturated acids to saturated acids in the treated pericarp of tomato fruits. Fluridone had not effect on the content of proline, total phenolic acids, MDA and antioxidant activity, but inhibited soluble protein accumulation and enhanced the content of total flavonoids. [ABSTRACT FROM AUTHOR]

Graptopetalum paraguayense E. Walther is an edible succulent plant that is native to Mexico. When leaves of G. paraguayense are detached from the mother plant, shoots and roots regenerate from the leaf base. To investigate the endogenous hormonal regulation of plant regeneration in G. paraguayense, we evaluated the effects of applying gibberellin (GA), abscisic acid (ABA), and phytohormone biosynthesis inhibitors to leaves detached from the mother plant. GA3 and paclobutrazol did not affect plant regeneration of G. paraguayense, whereas ABA treatment significantly suppressed plant regeneration. When leaves were treated with the ABA biosynthesis inhibitor fluridone at 10 μM, the frequency of shoot regeneration was more than twice that of the control on the 6th day after leaf detachment. In addition, when both fluridone and ABA were applied at the same time, the frequency of plant regeneration decreased to control levels or below. Endogenous ABA in leaves was approximately 1.3 ng gFW−1 just after leaf detachment, decreased to 0.3 ng gFW−1 by the 1st day after leaf detachment, and increased to 3.0 ng gFW−1 by the 9th day after leaf detachment. These findings indicate that ABA plays an important role in suppression of plant regeneration in G. paraguayense. Although plant regeneration during storage and transportation currently reduces the economic value of G. paraguayense, our findings may provide a method to delay unwanted plant formation at the leaf base. [ABSTRACT FROM AUTHOR]

Moss paraphyllia, the trichome-like or foliose structures on moss stem surfaces, are usually treated as epidermal outgrowths. However, in some taxa of the moss families Leskeaceae, Neckeraceae, and Amblystegiaceae their distribution along the stem is consistently correlated with parts of the stem surface near branch primordia. In other moss families, Climaciaceae, Hylocomiaceae, and Pseudoleskeaceae the specific paraphyllia-generating epidermal layer produces paraphyllia evenly all along the stem. These results suggest that there are at least two different types of regulation of paraphyllia development; however, both of them may be involved in the morphogenesis of paraphyllia in some families, for example in the Thuidiaceae. Exogenous abscisic acid treatment consistently increases the number of paraphyllia of the Leskea -type, and it also induces the development of proximal branch leaves that normally do not develop a lamina above the stem surface. This fact supports conclusions regarding the homology of the Leskea -type of paraphyllia with leaves. [ABSTRACT FROM AUTHOR]

Main conclusion: ABA and GA metabolism during incubation rather than hormone contents in dry seeds is the key to understanding secondary dormancy and germination of Syngonanthus verticillatus seeds. The mechanism of seed dormancy cycle, although very important for preventing germination during unfavorable periods for seedling establishment, is poorly understood in tropical species. Here, we used a perennial tropical species of the Brazilian campo rupestre, Syngonanthus verticillatus (Eriocaulaceae), to investigate the involvement of ABA and GA in modulating secondary dormancy of seeds buried in situ over time and the dynamic of these hormones during the incubation of dormant and non-dormant seeds. Hormone analyses were carried out with freshly harvested seeds and on buried seeds exhumed after 3, 6 and 9 months. Dynamics of ABA and GAs in dormant and non-dormant seeds during incubation (0, 12, 24 and 36 h) under favorable conditions for germination (at 20 °C in the presence of light) were also investigated. In addition, the effects of GA4 and fluridone were evaluated for overcoming secondary dormancy. Our results showed that changes in the contents of both ABA and GA4 occurred after burial, suggesting they may be related to the modulation of secondary dormancy/germination of S. verticillatus seeds. The application of fluridone was more effective than GA4 at overcoming secondary dormancy. We conclude that during incubation, de novo ABA synthesis and its consequent maintenance at high contents regulate the inhibition of germination in dormant seeds, while GA4 synthesis and ABA catabolism modulate the germination of non-dormant seeds. ABA and GA metabolism during incubation of both dormant and non-dormant seeds rather than hormone contents of dry seeds in the field is thought to be the key to understanding secondary dormancy and germination. [ABSTRACT FROM AUTHOR]

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An improved understanding of seed quality and germination control can contribute effectively to the use and conservation of neglected native species with ecological and economic value, such as Trichocline catharinensis, an endemic Asteraceae species from southern Brazil. We investigated the effects of applying gibberellin (GA3), abscisic acid (ABA) and their biosynthesis inhibitors, paclobutrazol (PAC) and fluridone (FLU), respectively, on T. catharinensis seed germination, and on polyamine (PA) content and antioxidant enzyme activities in germinating seeds. FLU and GA3 increased seed germination speed compared to treatment with H2O only. ABA inhibited both germination speed index and percentage, while PAC severely inhibited seed germination. The stimulatory effect of GA3 and FLU was associated with increased contents of putrescine (PUT) and spermidine (SPD) relative to spermine (SPM). As a result, high ratio (PUT + SPD/SPM) as well as superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) enzyme activities were observed when seed germination occurs. In contrast, in low or no seed germination treatment (ABA and PAC), low ratio (PUT + SPD/SPM) was observed, while the antioxidant enzymes, mainly SOD activity, tended to increase. Application of PAs at 200 μM stimulated germination through improving the speed and uniformity, and this effect was associated with antioxidant enzyme activity. Our results suggest a relationship between PA and the antioxidant system with the physiological mechanism of seed germination. These results improve the physiological knowledge of seed germination control in Asteraceae and contribute to the biological groundwork for future studies on the use and conservation of native species. [ABSTRACT FROM AUTHOR]

THE NOVEL branching regulators fluridone and imazalil (IMA) were examined for micropropagation of Paco (Zantedeschia sprengeri). IMA concentrations were 0, 4.5, 13.5 and 45µM in combination with 5µM benzylaminopurine (BAP). The shoots were transferred after 8 weeks to standard MS medium without IMA but with 5µM BAP. IMA resulted in a strong increase of new shoots from which the outgrowth was inhibited when IMA was present but that did grow out when IMA had been removed. Fluridone inhibits the biosynthesis of the endogenous regulator strigolactone. Increasing concentrations of fluridone were applied in combination with 13.5µM IMA for 8 weeks. Then the shoots were subcultured on standard medium without IMA and fluridone but with 5µM BAP for 8 weeks. Again a strong increase of new shoots occurred from which outgrowth was inhibited when IMA and fluridone were present but that did grow out when these regulators had been removed. [ABSTRACT FROM AUTHOR]

The herbicides glyphosate, imazamox and fluridone are herbicides, with low toxicity towards fish and invertebrates, which are applied to waterways to control invasive aquatic weeds. However, the effects of these herbicides on natural isolates of phytoplankton and cyanobacteria are unknown. Three species of microalgae found in the San Francisco Estuary (SFE)/Sacramento-San Joaquin River Delta (Delta) (Microcystis aeruginosa, Chlamydomonas debaryana, and Thalassiosira pseudonana) were exposed to the three herbicides at a range of concentrations in 96-well plates for 5–8 days. All three algal species were the most sensitive to fluridone, with IC50 of 46.9, 21, and 109 µg L−1 for M. aeruginosa, T. pseudonana and C. debaryana, respectively. Imazamox inhibited M. aeruginosa and T. pseudonana growth at 3.6 × 104 µg L−1 or higher, and inhibited C. debaryana growth at 1.0 × 105 µg L−1 or higher. Glyphosate inhibited growth in all species at ca. 7.0 × 104 µg L−1 or higher. Fluridone was the only herbicide that inhibited the microalgae at environmentally relevant concentrations in this study and susceptibility to the herbicide depended on the species. Thus, the application of fluridone may affect cyanobacteria and phytoplankton community composition in water bodies where it is applied. [ABSTRACT FROM AUTHOR]

We examined the response of maturing tomato fruit exposed for 7 days to fluridone (1-methyl-3-phenyl-5-[3-trifluoromethyl(phenyl)]-4(1H)-pyridinone). Fluridone was applied in lanolin paste in the form of a 2–3 mm wide strip from the top to the base of the fruit. As a control, a similar stripe of lanolin was applied in the same way on the opposite side of the same fruit. The content of major carotenoids, as well as flavonoids, and free and bound phenolic acids were determined using a HPLC and HPLC-MS-MS methods. Fluridone almost completely blocked the biosynthesis of lycopene and substantial declined content of ß-carotene and lutein in the tomato fruit. The fluridone caused a decreased content of quercetin, rutin and naringenin, and increased level of epicatechin. The herbicide did not affect the content of p-coumaric acid, but reduced the level of caffeic acid, both free and ester form, and declined the content of free ferulic and chlorogenic acids. Changes in phenolics composition observed for the first time indicate that fluridone interferes with the biosynthesis of further products of the metabolism of p-coumaric acid, both flavonoids and phenolic acids.

We examined the response of maturing tomato fruit exposed for 7 days to fluridone (1-methyl-3-phenyl-5--[3-trifluoromethyl(phenyl)]-4(1H)-pyridinone). Fluridone was applied in lanolin paste in the form of a 2-3 mm wide strip from the top to the base of the fruit. As a control, a similar stripe of lanolin was applied in the same way on the opposite side of the same fruit. The content of major carotenoids, as well as flavonoids, and free and bound phenolic acids were determined using a HPLC and HPLC-MS-MS methods. Fluridone almost completely blocked the biosynthesis of lycopene and substantial declined content of ß-carotene and lutein in the tomato fruit. The fluridone caused a decreased content of quercetin, rutin and naringenin, and increased level of epicatechin. The herbicide did not affect the content of p-coumaric acid, but reduced the level of caffeic acid, both free and ester form, and declined the content of free ferulic and chlorogenic acids. Changes in phenolics composition observed for the first time indicate that fluridone interferes with the biosynthesis of further products of the metabolism of p-coumaric acid, both flavonoids and phenolic acids. [ABSTRACT FROM AUTHOR]

Main conclusion: A novel method for culturing ovules of Gossypium barbadense allowed in vitro comparisons with Gossypium hirsutum and revealed variable roles of microtubules in controlling cotton fiber cell expansion. Cotton fibers undergo extensive elongation and secondary wall thickening as they develop into our most important renewable textile material. These single cells elongate at the apex as well as elongating and expanding in diameter behind the apex. These multiple growth modes represent an interesting difference compared to classical tip-growing cells that needs to be explored further. In vitro ovule culture enables experimental analysis of the controls of cotton fiber development in commonly grown Gossypium hirsutum cotton, but, previously, there was no equivalent system for G. barbadense, which produces higher quality cotton fiber. Here, we describe: (a) how to culture the ovules of G. barbadense successfully, and (b) the results of an in vitro experiment comparing the role of microtubules in controlling cell expansion in different zones near the apex of three types of cotton fiber tips. Adding the common herbicide fluridone, 1-Methyl-3-phenyl-5-[3-(trifluoromethyl)phenyl]-4(1H)-pyridinone, to the medium supported G. barbadense ovule culture, with positive impacts on the number of useful ovules and fiber length. The effect is potentially mediated through inhibited synthesis of abscisic acid, which antagonized the positive effects of fluridone. Fiber development was perturbed by adding colchicine, a microtubule antagonist, to ovules of G. barbadense and G. hirsutum cultured 2 days after flowering. The results supported the zonal control of cell expansion in one type of G. hirsutum fiber tip and highlighted differences in the role of microtubules in modulating cell expansion between three types of cotton fiber tips. [ABSTRACT FROM AUTHOR]

Highlights • The inhibitory effects of FLU and INA against B. gibsoni were assessed in vitro. • The IC 50 value of FLU against B. gibsoni was 60.6 ± 3.4 μM. • The IC 50 value of INA against B. gibsoni was 4.3 ± 0.3 μM. • Parasitemia and viability observed in the treated groups were significantly lower than control. • Both FLU and INA showed low toxicity to the MDCK cells. Abstract Pharmacological options to treat canine babesiosis caused by Babesia gibsoni , are limited. To address this challenge, screening for novel drug candidates and drug targets against B. gibsoni is urgently needed. In this study, we explored the inhibitory effects of two phytohormone inhibitors, fluridone (FLU) and inabenfide (INA), against B. gibsoni in vitro. The half-maximal inhibitory concentration (IC 50) values of FLU and INA against B. gibsoni were 60.6 ± 3.4 and 4.3 ± 0.3 μM, respectively. Parasitemia and viability at 24, 48, and 72 h after FLU and INA treatments were significantly lower than those in the control group. The cytotoxicity of FLU and INA was evaluated using the dog-derived Madin-Darby canine kidney (MDCK) cell line; both FLU and INA were less toxic to the MDCK cells than to the control cells. The selectivity index of FLU and INA were higher than 16.5 and 232.6, respectively. In summary, the present study demonstrated that FLU and INA were effective against B. gibsoni infection in vitro and that these compounds might have potential as candidate drugs for the treatment of B. gibsoni. [ABSTRACT FROM AUTHOR]

Myriophyllum spicatum or Eurasian watermilfoil (hereafter, milfoil) is among the most problematic invasive aquatic plant species throughout much of North America. M. spicatum infestations can result in reduced diversity and abundance of native plant populations. Control of the invader is essential to promoting healthy ecosystems. Several treatment alternatives are available for milfoil control, although cost and efficacy vary significantly, with some treatments resulting in more harm to the native population than no treatment at all. A series of field-based microcosms containing actively growing milfoil were constructed in order to directly compare the impact of two herbicides (2,4-dichlorophenoxyacetic acid and fluridone) and the milfoil weevil (Euhrychiopsis lecontei) on weed control and plant biochemistry. Herbicide concentrations in water, plants, and sediments were monitored, as were weevil population dynamics and resulting invertebrate damage to milfoil stems. The impact of the different treatments on levels of polyphenols, carbohydrates, ash, and overall carbon and nitrogen levels in the milfoil were determined. Total biomass of the untreated milfoil increased by more than 2.7-fold during the 53-day experimental period. Conversely, the biomass of milfoil subjected to chemical or biological treatment either remained constant or decreased significantly during the experiment. The herbicide 2,4-D resulted in nearly 100% milfoil mortality by day 20, whereas fluridone toxicity was significantly slower but reached 75% by the end of the trial. Similarly, milfoil growth in the weevil-amended tanks was somewhat erratic but by the end of the trial, the total plant biomass was 71% less than that of un-amended controls. Although the total biomass remaining at the end of the fluridone and weevil treatments was similar, the carbohydrate and starch content of the shoots in the insect treatment were nearly 4.6- and 4.8-fold greater, respectively, than that of the herbicide treated plants. The higher starch content in insect-treated plants could lead to increased autofragmentation and spread of M. spicatum. However, herbicide treatments are frequently required for several years. Therefore, integrated pest management, which combines the long-term benefits of biological controls with the short-term benefits of herbicides may provide the best solution to the control of M. spicatum and the conservation of native plants.

Myriophyllum spicatum or Eurasian watermilfoil (hereafter, milfoil) is among the most problematic invasive aquatic plant species throughout much of North America. M. spicatum infestations can result in reduced diversity and abundance of native plant populations. Control of the invader is essential to promoting healthy ecosystems. Several treatment alternatives are available for milfoil control, although cost and efficacy vary significantly, with some treatments resulting in more harm to the native population than no treatment at all. A series of field-based microcosms containing actively growing milfoil were constructed in order to directly compare the impact of two herbicides (2,4-dichlorophenoxyacetic acid and fluridone) and the milfoil weevil (Euhrychiopsis lecontei) on weed control and plant biochemistry. Herbicide concentrations in water, plants, and sediments were monitored, as were weevil population dynamics and resulting invertebrate damage to milfoil stems. The impact of the different treatments on levels of polyphenols, carbohydrates, ash, and overall carbon and nitrogen levels in the milfoil were determined. Total biomass of the untreated milfoil increased by more than 2.7-fold during the 53-day experimental period. Conversely, the biomass of milfoil subjected to chemical or biological treatment either remained constant or decreased significantly during the experiment. The herbicide 2,4-D resulted in nearly 100% milfoil mortality by day 20, whereas fluridone toxicity was significantly slower but reached 75% by the end of the trial. Similarly, milfoil growth in the weevil-amended tanks was somewhat erratic but by the end of the trial, the total plant biomass was 71% less than that of un-amended controls. Although the total biomass remaining at the end of the fluridone and weevil treatments was similar, the carbohydrate and starch content of the shoots in the insect treatment were nearly 4.6- and 4.8-fold greater, respectively, than that of the herbicide treated plants. The higher starch content in insect-treated plants could lead to increased autofragmentation and spread of M. spicatum. However, herbicide treatments are frequently required for several years. Therefore, integrated pest management, which combines the long-term benefits of biological controls with the short-term benefits of herbicides may provide the best solution to the control of M. spicatum and the conservation of native plants. [ABSTRACT FROM AUTHOR]

Abstract The methionine residues of proteins are the preferred targets of oxidation by reactive oxygen species resulting in the formation of methionine sulfoxide (MetSO), which impairs protein function. Methionine sulfoxide reductase A and B (MSR) catalyze the reduction of the MetSO S and R epimers back to Met residues, respectively. The roles of abscisic acid (ABA) and nitric oxide (NO) on the transcript levels of methionine sulfoxide reductase (MSR; EC 1.8.4.6) in the roots of 2-d-old etiolated rice (Oryza sativa L.) seedlings exposed to NaCl were examined. The OsMSR transcript levels increased upon exposure to NaCl, which increased as the NaCl concentrations increased. Fluridone (Flu) pretreatment inhibited the increases in ABA and NO contents and the OsMSRA4 , OsMSRA5 , OsMSRB1.1 , OsMSRB3 and OsMSRB5 transcripts by NaCl, while ABA application reversed the effects of Flu. Flu did not affect the OsMSRA2 and OsMSRB1.2 transcripts. The application of the NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5,-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), to NaCl-treated roots inhibited the increase in all of the OsMSR s transcripts with the exception of OsMSRB1.2. Treatment with the NO donor sodium nitroprusside (SNP) increased all the OsMSRs transcripts. The inhibitory effect of Flu on the increase of the OsMSRA4 , OsMSRA5 , OsMSR1.1 , OsMSRB 3 , and OsMSRB5 transcripts in the NaCl-treated roots was reversed by SNP. cPTIO inhibited the expression of all the OsMSR genes. The OsMSRA2.1 and OsMSRB1.2 transcripts can be increased by SNP. The Flu-inhibited internal ABA contents cannot be recovered by treatment with cPTIO or SNP. In addition, NaCl-induced NO production can be divided into ABA-dependent and ABA-independent routes. Therefore, the ABA-dependent NO route regulated the expression of OsMSRA4 , OsMSRA5 , OsMSRB1.1 , OsMSRB 3 , and OsMSRB5 in the NaCl-treated rice roots, while the ABA-independent NO pathway modulated OsMSRA2.1 , and the ABA-independent and NO-independent pathway modulated OsMSRB1.2 expression in response to NaCl treatment. [ABSTRACT FROM AUTHOR]

Fluridone (FLU) is widely used as a herbicide and interferes with photosynthesis via induction of leaf bleaching. However, the mechanism of FLU-induced leaf bleaching remains elusive. In this study, the effects of FLU on the metabolism of leaf pigments, including chlorophyll and carotenoids, were investigated. Our results demonstrate that FLU induced rice leaf bleaching in a dose-dependent manner. Treatment with 5 µM FLU strongly induced leaf bleaching by decreasing pigment content, with carotenoids and chlorophyll decreased by 98 and 95%, respectively, in the second leaves of rice seedlings. Our results indicate that the transcription levels of leaf pigment biosynthetic and catabolic genes were significantly downregulated by 5 µM FLU treatment. These results suggest that FLU induces leaf bleaching by decreasing leaf pigment content via downregulation of the transcription levels of leaf pigment biosynthetic genes, and that the downregulation of transcription levels of leaf pigment catabolic genes is a result of feedback inhibition mediated by FLU-decreased leaf pigment content. In addition, to test whether FLU-induced leaf bleaching is due to FLU-induced abscisic acid (ABA) deficiency, the effect of FLU treatment on endogenous ABA content and the recovery effect of ABA on FLU-induced leaf bleaching were investigated. Application of FLU significantly decreased endogenous ABA content, but FLU-induced leaf bleaching was not rescued by ABA application, thus FLU-induced leaf bleaching is not due to FLU-induced ABA deficiency. [ABSTRACT FROM AUTHOR]

Concerns regarding non-target toxicity of new herbicides used to control invasive aquatic weeds in the San Francisco Estuary led us to compare sub-lethal toxicity of four herbicides (penoxsulam, imazamox, fluridone, and glyphosate) on an endangered fish species Delta Smelt ( Hypomesus transpacificus ). We measured 17β-estradiol (E2) and glutathione (GSH) concentrations in liver, and acetylcholinesterase (AChE) activity in brain of female and male fish after 6 h of exposure to each of the four herbicides. Our results indicate that fluridone and glyphosate disrupted the E2 concentration and decreased glutathione concentration in liver, whereas penoxsulam, imazamox, and fluridone inhibited brain AChE activity. E2 concentrations were significantly increased in female and male fish exposed to 0.21 μM of fluridone and in male fish exposed to 0.46, 4.2, and 5300 μM of glyphosate. GSH concentrations decreased in males exposed to fluridone at 2.8 μM and higher, and glyphosate at 4.2 μM. AChE activity was significantly inhibited in both sexes exposed to penoxsulam, imazamox, and fluridone, and more pronounced inhibition was observed in females. The present study demonstrates the potential detrimental effects of these commonly used herbicides on Delta Smelt. [ABSTRACT FROM AUTHOR]

Summary: Wound‐induced suberin deposition involves the temporal and spatial coordination of phenolic and fatty acid metabolism. Phenolic metabolism leads to both soluble metabolites that accumulate as defense compounds as well as hydroxycinnamoyl derivatives that form the basis of the poly(phenolic) domain found in suberized tissue. Fatty acid metabolism involves the biosynthesis of very‐long‐chain fatty acids, 1‐alkanols, ω‐hydroxy fatty acids and α,ω‐dioic acids that form a poly(aliphatic) domain, commonly referred to as suberin. Using the abscisic acid (ABA) biosynthesis inhibitor fluridone (FD), we reduced wound‐induced de novo biosynthesis of ABA in potato tubers, and measured the impact on the expression of genes involved in phenolic metabolism (StPAL1, StC4H, StCCR, StTHT), aliphatic metabolism (StCYP86A33, StCYP86B12, StFAR3, StKCS6), metabolism linking phenolics and aliphatics (StFHT) or acyl chains and glycerol (StGPAT5, StGPAT6), and in the delivery of aliphatic monomers to the site of suberization (StABCG1). In FD‐treated tissue, both aliphatic gene expression and accumulation of aliphatic suberin monomers were delayed. Exogenous ABA restored normal aliphatic suberin deposition in FD‐treated tissue, and enhanced aliphatic gene expression and poly(aliphatic) domain deposition when applied alone. By contrast, phenolic metabolism genes were not affected by FD treatment, while FD + ABA and ABA treatments slightly enhanced the accumulation of polar metabolites. These data support a role for ABA in the differential induction of phenolic and aliphatic metabolism during wound‐induced suberization in potato. [ABSTRACT FROM AUTHOR]

Inhibition of lettuce plant growth under increased planting density was accompanied by accumulation of abscisic acid (ABA) in the shoots of competing plants. To check causal relationship between these responses we studied the effect of decreased synthesis of ABA on growth indexes and hormonal balance of lettuce plants under elevated density of their planting (one (single) or three (competing) plants per pot). Herbicide fluridone was used to inhibit ABA synthesis. Preliminary experiments with single plants showed that presence of fluridone in the soil solution at rather low concentration (0.001 mg/L) did not affect either chlorophyll content or growth rate of shoots and roots during at least one week. Treatment of competing (grouped) plants with this concentration of fluridone prevented both accumulation of ABA and competition induced growth inhibition. These results confirm important role of this hormone in the growth inhibiting effect of increased planting density. Furthermore, as in the case of ABA, fluridone prevented allocation of indoleacetic acid (IAA) to the shoots of competing plants likely contributing to leveling off the increase in the ratio of leaf area to their mass that is characteristic effect of shading in the dense plant populations. The results suggest involvement of ABA in allocation of IAA in competing plants. Application of fluridone did not influence the concentration of cytokinins in the shoots, whose level was decreased by competition either in fluridone treated or control (untreated with fluridone) plants. Accumulation of ABA in the shoots of competing plants accompanied by inhibition of their growth and the absence of either accumulation of ABA or inhibition of their growth in fluridone treated grouped plants confirms importance of ABA synthesis for growth response to competition. [ABSTRACT FROM AUTHOR]

Carotenoids are lipophilic pigments found in plants and algae, as well as some bacteria, archaea, and fungi that serve two functions—(1) as light harvesting molecules—primary carotenoids, and (2) as antioxidants, acting against reactive oxygen species–secondary carotenoids. Because of their strong antioxidant properties, they are also valuable for the development of anti-aging and photo-protective cosmetic applications. Of particular interest is the carotenoid phytoene, for its colorless and UV absorption characteristics. In this study, we targeted a reduction of phytoene desaturase (PDS) activity with the pigment-inhibiting herbicide 1-methyl-3-phenyl-5-[3-(trifluoromethyl)phenyl]pyridin-4-one (fluridone), which leads to the over-accumulation of phytoene in the recently characterized microalgal strain Chlorococcum sp. (UTEX B 3056). After post-incubation with fluridone, phytoene levels were measured at ~33 ug/mg cell tissue, as opposed to non-detectable levels in control cultures. Hence, the novel microalga Chlorococcum sp. is a viable candidate for the production of the high-value carotenoid phytoene and subsequent applications in cosmeceuticals, as well as more obvious nutraceutical and pharmaceutical applications.

Fluridone (FLU) was a pyrrolidone herbicide that was used for selective weeding in wheat, rice, corn and pasture and was also a biosynthesis inhibitor of abscisic acid (ABA), a significant plant hormone. ABA-promoted callose deposition facilitates rice resistance to pests but whether FLU had the opposite influence was unknown. The effects of FLU on the feeding behavior of the brown planthopper (Nilaparvata lugens Stål; BPH), after feeding with rice plants treated with FLU, were studied, using an electrical penetration graph (EPG). For susceptible rice cultivar (TN1), the duration for which BPH sucked phloem sap (N4 wave duration) after 15 μmol/L of FLU treatment was longer than that of the control but decreased after 30 and 60 μmol/L FLU treatments. Fecundity of BPH treated with 15 μmol/L FLU had no significant change, while the deposition area of callose was significantly decreased. For moderately-resistant rice cultivar (IR42), no differences in BPH feeding behavior and fecundity were observed but the deposition area of callose declined after treated with 15 μmol/L of FLU. These findings suggested that a low concentration of FLU (15 μmol/L) promoted BPH feeding behavior in TN1 but not in IR42 and the response in IR42 appeared to be more complicated, which provided supplementary evidence that ABA promoted plant resistance to BPH.

Genetic engineering for heat stress tolerance can promote crop growth and improve yield. One wheat (Triticum aestivum L.) line Y16 (wild type) and two transgenic plants (Y16-3 and Y16-46) that express Hpa1, a functional fragment of harpin protein, were used in this study to investigate their possible abiotic stress tolerance under heat stress. Results showed that enhanced thermotolerance was observed in the Y16-3 and Y16-46 lines over the control wheat under stress conditions. However, this increased stress tolerance was significantly abolished by specific inhibitors such as fluridone or sodium tungstate (i.e., arrests abscisic acid (ABA) biosynthesis) and EGTA or La (i.e., arrests Ca signaling pathway) under heat exposure. By contrast, high activities of antioxidant enzymes such as superoxide dismutase, catalase, and ascorbate peroxidase (but not peroxidase) and low levels of oxidative damage (thiobarbituric acid reactive substance (TBARS) and chlorophyll) were detected in transgenic wheat lines compared with the control plant under stress exposure. However, this significant difference diminished after the addition of these specific inhibitors. Furthermore, a slight increase of HO was observed in the transgenic plant, instead of the control, without the addition of chemicals under heat stress. These results suggested that antioxidant enzymes, calcium, and ABA signaling pathways were involved in this Hpa1-mediated thermotolerance of transgenic wheat plants under stress exposure. Finally, a hypothetical model based on HO signaling was proposed to illustrate the possible mechanism of this enhanced heat stress tolerance. [ABSTRACT FROM AUTHOR]

P. aegyptiaca is one of the most destructive root parasitic plants worldwide, causing serious damage to many crop species. Under natural conditions P. aegyptiaca seeds must be conditioned and then stimulated by host root exudates before germinating. However, preliminary experiments indicated that TIS108 (a triazole-type inhibitor of strigolactone) and fluridone (FL, an inhibitor of carotenoid-biosynthesis) both stimulated the germination of P. aegyptiaca seeds without a water preconditioning step (i.e. unconditioned seeds). The objective of this study was to use deep RNA sequencing to learn more about the mechanisms by which TIS108 and FL stimulate the germination of unconditioned P. aegyptiaca seeds. Deep RNA sequencing was performed to compare the mechanisms of germination in the following treatments: (i) unconditioned P. aegyptiaca seeds with no other treatment, (ii) unconditioned seeds treated with 100 mg/L TIS108, (iii) unconditioned seeds treated with 100 mg/L FL + 100 mg/L GA3, (iv) conditioned seeds treated with sterile water, and (v) conditioned seeds treated with 0.03 mg/L GR24. The de novo assembled transcriptome was used to analyze transcriptional dynamics during seed germination. The key gene categories involved in germination were also identified. The results showed that only 119 differentially expressed genes were identified in the conditioned treatment vs TIS108 treatment. This indicated that the vast majority of conditions for germination were met during the conditioning stage. Abscisic acid (ABA) and gibberellic acid (GA) played important roles during P. aegyptiaca germination. The common pathway of TIS108, FL+GA3, and GR24 in stimulating P. aegyptiaca germination was the simultaneous reduction in ABA concentrations and increase GA concentrations. These results could potentially aid the identification of more compounds that are capable of stimulating P. aegyptiaca germination. Some potential target sites of TIS108 were also identified in our transcriptome data. The results of this experiment suggest that TIS108 and FL+GA3 could be used to control P. aegyptiaca through suicidal germination. [ABSTRACT FROM AUTHOR]

The remoteness of subarctic and arctic ecosystems no longer protects against invasive species introductions. Rather, the mix of urban hubs surrounded by undeveloped expanses creates a ratchet process whereby anthropogenic activity is sufficient to introduce and spread invaders, but for which the costs of monitoring and managing remote ecosystems is prohibitive. Elodea spp. is the first aquatic invasive plant to become established in Alaska and has potential for widespread deleterious ecological and economic impacts. A rapid eradication response with herbicides has been identified as a priority invasion control strategy. We conducted a multi-lake monitoring effort to assess collateral impacts from herbicide treatment for Elodea in high latitude systems. Variability in data was driven by seasonal dynamics and natural lake-to-lake differences typical of high latitude waterbodies, indicating lack of evidence for systematic impacts to water quality or plankton communities associated with herbicide treatment of Elodea . Impacts on native macrophytes were benign with the exception of some evidence for earlier onset of leaf senescence for lily pads ( Nuphar spp.) in treated lakes. We observed a substantial increase in detected native flora richness after Elodea was eradicated from the most heavily infested lake, indicating potential for retention of native macrophyte communities if infestations are addressed quickly. While avoiding introductions through prevention may be the most desirable outcome, these applications indicated low risks of non-target impacts associated with herbicide treatment as a rapid response option for Elodea in high latitude systems. [ABSTRACT FROM AUTHOR]