Content Of Seedlings Research Articles

Assessment of the Potential Phytotoxicity of Chlorpyrifos in the Wetland Macrophyte Bidens laevis (L.).

Chlorpyrifos (CPF) has been used worldwide, but its possible negative effects on macrophytes have been scarcely studied. The main goal of the present work was to assess the potential phytotoxic effects of CPF on different stages (seed and seedling) of the wetland macrophyte Bidens laevis. During the germination of seeds, stimulation of radicle growth at low concentrations of CPF (10µg/L) and inhibition of its elongation at 80µg/L CPF were observed. In seedlings, concentrations ≤ 160µg/L CPF did not exhibit adverse effects on growth after 7 days of exposure, despite the decrease of photosynthetic pigments and carotenoids observed at 40µg/L CPF compared to the control. Environmentally relevant concentrations of CPF altered neither oxidative stress biomarkers nor pigment contents in seedlings exposed for 48h, suggesting CPF would be non-toxic to B. laevis in natural scenarios.

Synthesis of calcium-based nanofertilizer and its efficacy towards reduction of oxidative stress and fluoride uptake in rice (Oryza sativa L.)

The phytotoxicity of fluoride and its build-up in agricultural plants and subsequently the entry into the food chain is a serious threat to human health. The present study highlighted the green synthesis of calcium oxide nanoparticles (CaO NPs) and characterization using UV-Vis spectrophotometer, TEM, SEM, EDX, XRD, and FTIR. Further, synthesized CaO NPs (0, 10, and 50 mg/L) were applied on fluoride-stressed (10 mg/L) rice seedlings to check its possible ameliorative effects towards growth and fluoride accumulation in different parts of rice seedlings. Characterization revealed that nanoparticles were crystalline (46.72 %) and spherical in shape, with an average diameter of 20–25 nm. Results of the seedling growth analysis revealed that CaO NPs inhibited the translocation of fluoride in rice plants, which in turn decreased the phytotoxicity caused by fluoride, including lipid peroxidation and chlorosis, and enhanced the overall growth of seedlings. The co-exposure of CaO NPs with fluoride also showed a reduction in the fluoride-induced oxidative stress, as demonstrated by lower MDA, O2•- contents, and activity of antioxidant enzymes (CAT, SOD, and POD) as compared to fluoride treatment alone. The application of CaO NPs also restored potassium content in seedlings grown under fluoride stress. Furthermore, the highest reduction of fluoride accumulation by 65 and 76 % in roots and shoots was recorded at 50 mg/L of CaO NPs treatment, respectively. Therefore, the present study clearly indicated the ameliorative potential of CaO NPs towards fluoride stress in rice. However, a field study is needed to establish the social acceptance of this valuable nanofertilizer in fluoride-contaminated areas.

Mutual intercropping affects the growth and selenium content of cherry tomato seedlings

Intercropping can increase the utilization rate of light and water and can also improve plant growth. The objective of this study was to investigate the growth and selenium (Se) content in seedlings of three genotypes of cherry tomato under intercropping while applying Se. The pot experiment was conducted in a greenhouse. The monoculture of red, yellow and purple cherry tomato; among the three genotypes of cherry tomatoes, intercropping of two genotypes with each other, at the same time intercropping of three genotypes. These results show that the biomass increased under intercropping compared with monoculture. The chlorophyll b content of purple cherry tomato increased in different intercropping combinations. Furthermore, the net photosynthetic rate, stomatal conductance, and transpiration rate of purple were increased by intercropping with red and purple cherry tomatoes. The soluble protein and soluble sugar contents in yellow and purple cherry tomato increased by 49.13% and 8.37%, respectively, under mutual intercropping. Similarly, soluble sugar increased in purple cherry tomato by intercropping with yellow and red. The activities of superoxide and peroxidase in red and yellow cherry tomato seedlings were higher in all intercropping combinations than in monoculture, whereas free proline content and relative conductivity in all cherry tomatoes decreased. The Se content of roots, stem, and leaves in seedlings increased with intercropping. Therefore, intercropping can improve the growth and Se content of cherry tomatoes, and the combination of red, yellow and purple is better, which can be used to cultivate strong seedlings.

Silicon attenuates nutritional disorder of phosphorus in seedlings of Eucalyptus grandis × Eucalyptus urophylla

BackgroundNutritional disorders of phosphorus (P), due to deficiency or toxicity, reduce the development of Eucalyptus spp. seedlings. Phosphorus deficiency often results in stunted growth and reduced vigor, while phosphorus toxicity can lead to nutrient imbalances and decreased physiological function. These sensitivities highlight the need for precise management of P levels in cultivation practices. The use of the beneficial element silicon (Si) has shown promising results under nutritional stress; nevertheless, comprehensive studies on its effects on Eucalyptus spp. seedlings are still emerging. To further elucidate the role of Si under varying P conditions, an experiment was conducted with clonal seedlings of a hybrid Eucalyptus spp. (Eucalyptus grandis × Eucalyptus urophylla, A207) in a soilless cultivation system. Seedlings were propagated using the minicutting method in vermiculite-filled tubes, followed by treatment with a nutrient solution at three P concentrations: a deficient dose (0.1 mM), an adequate dose (1.0 mM) and an excessive dose (10 mM), with and without the addition of Si (2mM). This study assessed P and Si concentration, nutritional efficiency, oxidative metabolism, photosynthetic parameters, and dry matter production.ResultsSi supply increased phenolic compounds production and reduced electrolyte leakage in seedlings provided with 0.1 mM of P. On the other hand, Si favored quantum efficiency of photosystem II as well as chlorophyll a content in seedlings supplemented with 10 mM of P. In general, Si attenuates P nutritional disorder by reducing the oxidative stress, favoring the non-enzymatic antioxidant system and photosynthetic parameters in seedlings of Eucalyptus grandis × Eucalyptus urophylla.ConclusionThe results of this study indicate that Eucalyptus grandis × Eucalyptus urophylla seedlings are sensitive to P deficiency and toxicity and Si has shown a beneficial effect, attenuating P nutritional disorder by reducing the oxidative stress, favoring the non-enzymatic antioxidant system and photosynthetic parameters.

Enhancing iron content and growth of cucumber seedlings with MgFe-LDHs under low-temperature stress.

The development of cost-effective and eco-friendly fertilizers is crucial for enhancing iron (Fe) uptake in crops and can help alleviate dietary Fe deficiencies, especially in populations with limited access to meat. This study focused on the application of MgFe-layered double hydroxide nanoparticles (MgFe-LDHs) as a potential solution. We successfully synthesized and characterized MgFe-LDHs and observed that 1-10mg/L MgFe-LDHs improved cucumber seed germination and water uptake. Notably, the application of 10mg/L MgFe-LDHs to roots significantly increased the seedling emergence rate and growth under low-temperature stress. The application of 10mg/L MgFe-LDHs during sowing increased the root length, lateral root number, root fresh weight, aboveground fresh weight, and hypocotyl length under low-temperature stress. A comprehensive analysis integrating plant physiology, nutrition, and transcriptomics suggested that MgFe-LDHs improve cold tolerance by upregulating SA to stimulate CsFAD3 expression, elevating GA3 levels for enhanced nitrogen metabolism and protein synthesis, and reducing levels of ABA and JA to support seedling emergence rate and growth, along with increasing the expression and activity of peroxidase genes. SEM and FTIR further confirmed the adsorption of MgFe-LDHs onto the root hairs in the mature zone of the root apex. Remarkably, MgFe-LDHs application led to a 46% increase (p < 0.05) in the Fe content within cucumber seedlings, a phenomenon not observed with comparable iron salt solutions, suggesting that the nanocrystalline nature of MgFe-LDHs enhances their absorption efficiency in plants. Additionally, MgFe-LDHs significantly increased the nitrogen (N) content of the seedlings by 12% (p < 0.05), promoting nitrogen fixation in the cucumber seedlings. These results pave the way for the development and use of LDH-based Fe fertilizers.

Effects of Cadmium Stress on Seed Germination and Physiology and Biochemistry during Early Seedling Growth of Masson Pine (Pinus massoniana Lamb.)

Abstract This study evaluated the effects of cadmium (Cd) on seed germination and the physiological and biochemical characteristics of Pinus massoniana, which was used as the experimental material; culture dishes and germination boxes were used as testing devices. Seed germination and seedling growth in the presence of various Cd concentrations (0.4, 0.8, 1.2, 2, and 0 mg/L) were explored. The germination indexes of Pinus massoniana seeds used were germination percentage (GP), germination energy (GE), germination index (GI), vigor index (VI). and embryo length. The indexes of early growth of seedlings used were soluble sugar and soluble protein content, antioxidant enzyme activity, Cd content, and Cd enrichment. We found that Pinus massoniana presented reduced GP, GE, GI, VI, and embryo length with increasing Cd concentrations, and the VI and embryo length significantly decreased (P &amp;lt; .05). The physiological and biochemical indexes of Pinus massoniana seedlings were promoted at low Cd concentrations and inhibited at high Cd concentrations; each index peaked under 0.4 mg/L Cd. The Cd content in seedlings and the degree of enrichment decreased and then increased with increasing Cd concentration. Grey correlation analysis results showed that the effects of Cd stress were the strongest on embryo length in seeds (correlation degree: 0.769). Study Implications The effect of heavy metal pollution on seed germination and growth is closely related to phytoremediation of heavy metal soil. Pinus massoniana is the most widely distributed pine species in China. It is an economically important industrial timber with important ecological value. This study found that under the stress of different cadmium concentrations, heavy metal Cd stress inhibited the germination of Pinus massoniana seeds, and moderate Cd concentration promoted the physiological and biochemical of Pinus massoniana seedlings. Pinus massoniana seedlings have the ability to enrich heavy metal Cd.

Hydrogen Sulfide Alleviates Oxidative Damage under Chilling Stress through Mitogen-Activated Protein Kinase in Tomato.

Tomato is the vegetable with the largest greenhouse area in China, and low temperature is one of the main factors affecting tomato growth, yield, and quality. Hydrogen sulfide (H2S) plays an important role in regulating plant chilling tolerance, but its downstream cascade reaction and mechanism remain unclear. Mitogen-activated protein kinases (MAPK/MPKs) are closely related to a variety of signaling substances in stress signal transmission. However, whether H2S is related to the MPK cascade pathway in response to low-temperature stress is rarely reported. In this study, NaHS treatment significantly decreased the electrolyte leakage (EL), superoxide anion (O2-) production rate, and hydrogen peroxide (H2O2) content of seedlings at low temperatures. In addition, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were obviously increased; and the photochemical efficiency of PSII (Fv/Fm) was enhanced with treatment with NaHS, indicating that NaHS improved the seedlings' cold tolerance by alleviating the degree of membrane lipid peroxidation and oxidative damage. However, H2S scavenger hypotaurine (HT) treatment showed the opposite effect. We found that H2S content, L-cysteine desulfhydrase (LCD) activity, and mRNA expression were increased by chilling stress but reduced by MPK inhibitor PD98059; PD98059 reversed the alleviating effect of H2S via increasing the EL and H2O2 contents. The expression levels of MPK1-MPK7 at low temperatures showed that SlMPK4 was significantly induced by exogenous NaHS and showed a trend of first increasing and then decreasing, while the expression level of SlMPK4 in HT-treated seedlings was lower than that of the control. After SlMPK4 was silenced by virus-induced gene silencing, the H2S-induced upregulation of C-repeat-Binding Factor (CBF1), inducer of CBF expression 1 (ICE1), respiratory burst oxidase homologs (RBOH1, RBOH2) at low temperatures disappeared, and tomato cold tolerance decreased. In conclusion, H2S improves the cold tolerance of tomato plants by increasing the activity of antioxidant enzymes and reducing reactive oxygen species (ROS) accumulation and membrane lipid peroxidation. MPK4 may act as a downstream signaling molecule in this process.

Nitric oxide acts upstream of indole-3-acetic acid in ameliorating arsenate stress in tomato seedlings

After their discovery, nitric oxide (NO) and indole-3-acetic acid (IAA) have been reported as game-changing cellular messengers for reducing abiotic stresses in plants. But, information regarding their shared signaling in regulating metal stress is still unclear. Herein, we have investigated about the joint role of NO and IAA in mitigation of arsenate [As(V)] toxicity in tomato seedlings. Arsenate being a toxic metalloid increases the NPQ level and cell death while decreasing the biomass accumulation, photosynthetic pigments, chlorophyll a fluorescence, endogenous NO content in tomato seedlings. However, application of IAA or SNP to the As(V) stressed seedlings improved growth together with less accumulation of arsenic and thus, preventing cell death. Interestingly, addition of c-PTIO, {2-(4-carboxyphenyl)-4, 4, 5, 5-tetramethylimidazoline-1-oxyl-3-oxide, a scavenger of NO} and 2, 3, 5-triidobenzoic acid (TIBA, an inhibitor of polar auxin transport) further increased cell death and inhibited activity of GST, leading to As(V) toxicity. However, addition of IAA to SNP and TIBA treated seedlings reversed the effect of TIBA resulting into decreased As(V) toxicity. These findings demonstrate that IAA plays a crucial and advantageous function in NO-mediated reduction of As(V) toxicity in seedlings of tomato. Overall, this study concluded that IAA might be acting as a downstream signal for NO-mediated reduction of As(V) toxicity in tomato seedlings.

Biochar reduces the cadmium content of Panax quinquefolium L. by improving rhizosphere microecology

Cadmium (Cd) accumulation in American ginseng (Panax quinquefolium L.) can negatively impact its yield and safety. Our previous study found that biochar could reduce cadmium content of P. quinquefolius, however, the mechanism was yet to be elucidated. In the present study, we tested four treatments in order to reveal the mechanism by which this phenomenon occurs: control, Cd, Cd + biochar and biochar. The results showed that the following responses were induced by the addition of biochar under Cd stress. Firstly, the soil physicochemical properties were improved, this is especially true for the soil pH value and soil organic matter content, which were increased by 20.42 % and 15.57 %, respectively. Secondly, the relative abundances of several beneficial microorganism phyla; such as Proteobacteria, Bacteroidota and Actinobacteria; were increased by 10.69 %, 20.11 % and 60.86 %, respectively. Thirdly, treatment with biochar reduced the Cd content by increasing cadmium-chelated metabolites within the soil (e.g., naringenin, caffeic acid, and valine) and increasing detoxification substances in plants (e.g., malic acid, flavonoids, and fumaric acid). Changes in these metabolites were significantly correlated with rhizosphere microecology. In summary, biochar treatment reduced the Cd content in seedlings by improving the soil properties, rhizosphere community, soil metabolites, and plant metabolites.

The Effects of Cadmium Concentrations on Germination and Physiological Parameters in Tomato (Solanum lycopersicum Lam.)

Cadmium (Cd) is omnipresent trace element in environmental that is unessential in plants. Cd levels rise because of anthropogenic activity such as the combustion of fossil fuels, phosphate fertilizer manufacturing, mineral fertilizers, batteries technology. It is extremely toxic metal and reduces plant growth. In this context, the aim of this study was to investigate the effect of different concentrations (5/10/20/40 ppm) of Cd on germination of seeds and physiological effects in early developmental stage of tomato Solanum lycopersicum Lam. seedlings. 20 ppm (80%) and 40 ppm (83.3%) Cd concentrations caused significantly decrease in germination percentage. All Cd treatments were resulted with decrease in Vigor Index, especially in 20 ppm (42% decrease compared to control). Application of 5 ppm Cd caused decreases in chlorophyll and carotenoid contents in seedlings. Finally, significant decrease in protein content of 5 ppm, 10 ppm and 20 ppm treated seedlings were determined compared to control. As a conclusion, Cd negatively affected germination and physiological parameters of tomato in early developmental stage. Overall, these results indicate that Cd affects different physiologic processes and pathways according to concentration.

Exogenous γ-Aminobutyric Acid Can Improve Seed Germination and Seedling Growth of Two Cotton Cultivars under Salt Stress.

Excessive salt content in soil has adverse effects on cotton production, especially during the germination and seedling stages. γ-aminobutyric acid (GABA) is an important active substance that is expected to improve the resistance of plants to abiotic stresses. This study focused on two cotton cultivars (Gossypium hirsutum L.: Tahe 2 and Xinluzhong 62) and investigated the impact of exogenous GABA (0, 1, 2, 3, and 4 mM) on seed germination, seedling growth, and related morphological, physiological, and biochemical indicators under salt stress (150 mM NaCl). The results showed that salt stress significantly reduced the germination rate and germination index of cotton seeds (decreased by 20.34% and 32.14% for Tahe 2 and Xinluzhong 62, respectively), leading to decreased seedling height and biomass and causing leaf yellowing. Salt stress induced osmotic stress in seedlings, resulting in ion imbalance (marked reduction in K+/Na+ ratio) and oxidative damage. Under salt stress conditions, exogenous GABA increased the germination rate (increased by 10.64~23.40% and 2.63~31.58% for Tahe 2 and Xinluzhong 62, respectively) and germination index of cotton seeds, as well as plant height and biomass. GABA treatment improved leaf yellowing. Exogenous GABA treatment increased the content of proline and soluble sugars, with varying effects on betaine. Exogenous GABA treatment reduced the Na+ content in seedlings, increased the K+ content, and increased the K+/Na+ ratio (increased by 20.44~28.08% and 29.54~76.33% for Tahe 2 and Xinluzhong 62, respectively). Exogenous GABA treatment enhanced the activities of superoxide dismutase and peroxidase, and reduced the accumulation of hydrogen peroxide and malondialdehyde, but had a negative impact on catalase activity. In conclusion, exogenous GABA effectively improved cotton seed germination. By regulating osmoprotectant levels, maintaining ion homeostasis, and alleviating oxidative stress, GABA mitigated the adverse effects of salt stress on cotton seedling growth.

Photosynthetic and Physiological Responses to Combined Drought and Low–Temperature Stress in Poa annua Seedlings from Different Provenances

Combined drought and low–temperature stress is a crucial factor affecting turfgrass establishment and limiting the sustainability of the turfgrass industry in drought– and cold–prone regions. In this context, we evaluated the effects of regular watering (the soil water content was 80% of the maximum water–holding capacity of the field) at room temperature (25 °C) and combined drought (the soil water content was 30% of the maximum water–holding capacity of the field) and low–temperature (0 °C) stress on the morphology, photosynthesis, and physiology of wild Poa annua seedlings from different provenances (‘PA’, ‘WY’, ‘NX’ and ‘YC’). Results indicated that the combined drought and low–temperature stress changed the morphological and growth indicators of seedlings in four provenances to different extents. Moreover, combined drought and low–temperature stress reduced the net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), water use efficiency (WUE), and chlorophyll content in seedlings from four provenances. However, intertemporal CO2 concentration (Ci), relative electrical conductivity (REC), the contents of malondialdehyde (MDA), proline (Pro), soluble sugars (SS), the superoxide anion (O2•−) production rate, the contents of hydrogen peroxide (H2O2) and hydroxyl radical (·OH), the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) were all increased. The increase in ‘PA’ was much greater than that in ‘NX.’ The comprehensive evaluation results showed that the order of combined drought and low–temperature resistance of seedlings from the four provenances was ‘PA’ &gt; ‘YC’ &gt; ‘WY’ &gt; ‘NX’, which corresponded to the order of the morphological damage symptoms. In conclusion, ‘PA’ may maintain stronger combined drought and low–temperature resistance by improving the cellular water absorption and retention capacity, enhancing the function of the antioxidant defense system, and maintaining the integrity of the cell membrane, which is a crucial germplasm resource for breeding combined drought and low–temperature resistance in Poa annua.

Effect of Endophytic Bacteria Bacillus subtilis on Seedling Growth and Root Lignification of Pisum sativum L. under Normal and Sodium Chloride Salt Conditions

The influence of endophytic bacteria Bacillus subtilis (strain 10-4) was studied on the parameters of growth and tolerance as well as the intensity of lignin deposition in the roots of Pisum sativum L. seedlings under conditions of sodium chloride salinity (1% NaCl). It was found that the impact of salinity reduced the germination energy, viability, length of the roots and shoots of seedlings, their wet and dry weight, and also increased the content of proline and the level of lipid peroxidation (LPO). Pretreatment with strain 10-4 had a stimulating effect on seedlings in normal conditions and a protective effect on salinity, which was reflected in the improvement of germination energy and seed viability, root length, and accumulation of their dry mass under saline conditions; however, in terms of shoot growth under stress, there was no significant difference from the control (nonbacterized) variants. At the same time, strain 10-4 promoted earlier formation of lateral roots as well as a decrease in stress-induced LPO and proline content in seedlings, which indicates that cells are protected from oxidative and osmotic damage under saline conditions. Priority data were obtained on the important role of endophytic B. subtilis strain 10-4 in the process of lignification and strengthening of the barrier properties of the cell walls of the roots, which contributes to the reduction of the toxic effect of sodium chloride salinity and the implementation of the protective effect of these bacteria on pea plants.

Effect of Trichoderma viride on insoluble phosphorus absorption ability and growth of Melilotus officinalis

Phosphorus (Pi) deficiency is a major factor of limiting plant growth. Using Phosphate-solubilizing microorganism (PSM) in synergy with plant root system which supply soluble Pi to plants is an environmentally friendly and efficient way to utilize Pi. Trichoderma viride (T. viride) is a biocontrol agent which able to solubilize soil nutrients, but little is known about its Pi solubilizing properties. The study used T. viride to inoculate Melilotus officinalis (M. officinalis) under different Pi levels and in order to investigate the effect on Pi absorption and growth of seedlings. The results found that T. viride could not only solubilizate insoluble inorganic Pi but also mineralize insoluble organic Pi. In addition, the ability of mineralization to insoluble organic Pi is more stronger. Under different Pi levels, inoculation of T. viride showed that promoted the growth of aboveground parts of seedlings and regulated the morphology of roots, thus increasing the dry weight of seedlings. The effect of T. viride on seedling growth was also reflected the increasing of chlorophyll fluorescence parameters and photosynthetic pigment content. Moreover, compared to the uninoculated treatments, inoculation of T. viride also enhanced Pi content in seedlings. Thus, the T. viride was a beneficial fungus for synergistic the plant Pi uptake and growth.

Effects of Selenium on Growth and Biochemical Characters of Tissue Culture Seedlings of Sophora tonkinensis

Background Selenium (Se) plays a key role in controlling several processes in plant development, such as root growth and regulation of enzyme activity. However, research on the effects of Se in Sophora tonkinensis, a medicinal plant, has not been reported. To elucidate the effect of Se on the accumulation of secondary metabolites in tissue-cultured seedlings of S. tonkinensis. Materials and Methods Tissue culture seedlings of S. tonkinensis was treated with different concentrations of Se in the rooting medium. Agronomic traits of roots and concentrations of hormones and some secondary metabolites were measured from seedlings. Results The results show that (1) root growth of tissue culture seedlings were stimulated by Se; (2) a specific amount of Se enhanced the activities of peroxidase (POD) and superoxide dismutase (SOD), as well as the production and storage of soluble proteins and chlorophyll; and (3) Se treatment lowered brassinolide (BR) content, and 15 mg/L Se minimized abscisic acid (ABA) content, while 60 mg/L Se enhanced ABA content. The gibberellin (GA3) content in seedlings increased significantly compared with the control under the treatment of 60 mg/L Se. Conclusion Se concentration of 30 mg/L facilitated matrine and oxymatrine production and accumulation in stem/leaf tissues.

Effects of Magnetic Field and Ultrasound Applications on Endogenous Melatonin Content and Drought Stress Tolerance of Pepper Seedlings

Uncertainty about climate change exposes agriculture to high risks. Magnetic field (MF) applications are one of the methods that can be used to reduce the effects of environmental stress conditions. Melatonin (MEL) acts as a broad-spectrum antioxidant in eliminating the effects of damage caused in plants exposed to stress. This study aims to examine the effect of MF and ultrasound (US) applications on endogenous MEL levels in peppers and investigate the usability of treated seeds against drought stress. Pre-sowing pepper seeds, 0, 0.3, 0.9, 1.1 T MF and 0, 15, 30 min 40 Hz US were applied. The results show that the highest increase in MEL content was detected at 0.3 T MF with 82% and with 30 min of US application at 98%. MF and US treatments decreased the malondialdehyde (MDA) (19% and 35%, respectively) and hydrogen peroxide (H2O2) (52% and 58%, respectively) contents in seedlings. An increase of 24% and 22% (MF-US, respectively) was observed in catalase (CAT) enzyme activity with these applications. As a result, it was observed that MF and US treatments increased the endogenous MEL content and provided tolerance against drought stress. MF and US applications could be suggested as methods to increase drought tolerance in peppers by increasing the endogenous MEL content.

Effect of far-red light on the production and diversity of ginsenosides in leaves of Panax ginseng Meyer

Ginsenosides are the most valuable and pharmacologically active triterpenoid saponins found in Panax ginseng. Although light quality affects ginsenoside content, little is known about the underlying genetic and regulatory mechanisms. Additionally, the correlation between the adaptability of ginseng to shade and ginsenoside biosynthesis remains poorly understood. In the present study, transcriptome analysis of ginseng seedlings using RNA sequencing revealed that the expression of ginsenoside biosynthesis genes, including PgHMGR, PgFPS, PgSS, and PgUGT, was enhanced in shade conditions but downregulated by red light, indicating that far-red light might play an essential role in ginsenoside production. Further, gene expression analysis in adventitious roots and 2-year-old plants using qRT-PCR showed that the light quality-mediated expression patterns of ginsenoside genes varied with tissue and age. However, unlike the transcriptome, there was no difference in the total ginsenoside content in seedlings among various light conditions. Nevertheless, the amount of major protopanaxadiol-type ginsenosides increased under shade and red light conditions. Unlike seedlings and adventitious roots, there was a decrease in the expression of PgHMGR, PgFPS, PgSS, and PgDDS in 2-year-old plants, along with an increase in the ginsenoside content, under far-red light. Taken together, our findings suggest that far-red light is an important environmental factor for ginsenoside biosynthesis and diversification and provide information that can improve the quality of ginseng produced for medicinal purposes.

Effect of Heavy Metal Stress on Phenolic Compounds Accumulation in Winter Wheat Plants.

Heavy metal stress can lead to many adverse effects that inhibit cellular processes at various levels of metabolism, causing a decrease in plant productivity. In response to environmental stressors, phenolic compounds fulfill significant molecular and biochemical functions in plants. Increasing the biosynthesis of phenolic compounds in plants subjected to heavy metal stress helps protect plants from oxidative stress. A pot experiment was carried out to determine the effect of the accumulation of copper (Cu) and lead (Pb) salts at concentrations of 200, 500, and 1000 ppm on seed germination, the activity of enzymes in the phenylalanine ammonia-lyase pathway (PAL) and tyrosine ammonia-lyase (TAL), along with the total phenol and flavonoid contents in seedlings of hybrid Triticum aestivum L. (winter wheat) cultivars. The accumulation of heavy metals, especially Cu, had a negative impact on the seed germination process. The cultivar "Hyacinth" reacted most strongly to heavy metal stress, which was confirmed by obtaining the lowest values of the germination parameters. Heavy metal stress caused an increase in the activity of PAL and TAL enzymes and an increase in the accumulation of phenolic compounds. Under the influence of Cu, the highest activity was shown in cv. "Hyvento" (especially at 200 ppm) and, due to the accumulation of Pb, in cv. "Hyacinth" (1000 ppm) and cv. "Hyking" (200 ppm). The cultivar "Hyking" had the highest content of phenolic compounds, which did not increase with the application of higher concentrations of metals. In other cultivars, the highest content of total phenols and flavonoids was usually observed at the lowest concentration (200 ppm) of the tested heavy metals, Cu and Pb.

Potassium transporter KUP9 participates in K+ distribution in roots and leaves under low K+ stress

Potassium (K) is a major essential element in plant cells, and KUP/HAK/KT-type K+ transporters participate in the absorption of K+ into roots and in the long-distance transport to above-ground parts. In Arabidopsis thaliana, KUP9 is involved in the transport of K+ and Cs+ in roots. In this study, we investigated KUP9 function in relation to the K+ status of the plant. The expression of KUP9 was upregulated in older leaves on K+-depleted medium, compared to the expression of the other 12 KUP genes in the KUP/HAK/KT family in Arabidopsis. When grown on low K+ medium, the kup9 mutant had reduced chlorophyll content in seedlings and chlorosis in older rosette leaves. Tissue-specific expression of KUP9 determined by KUP9 promoter:GUS assay depended on the K+ status of the plants: In K+ sufficient medium, KUP9 was expressed in the leaf blade towards the leaf tip, whereas in K+ depleted medium expression was mainly found in the petioles. In accordance with this, K+ accumulated in the roots of kup9 plants. The short-term 43K+ tracer measurement showed that 43K was transferred at a lower rate in roots and shoots of kup9, compared to the wild type. These data show that KUP9 participates in the distribution of K+ in leaves and K+ absorption in roots under low K+ conditions.

The Roles of the Moss Layer in Mediating Tree Seedling Environmental Stress, Mercury Exposure, and Regeneration in High-Elevation Conifer Forests

The persistence of future forests depends on the success of tree seedlings which are experiencing increasing physiological stress from changing climate and air pollution. Although the moss layer can serve as an important substrate for tree seedlings, its potential for reducing environmental stress and enhancing the establishment of seedlings remains poorly understood. We tested if the moss layer decreased environmental stress and increased the abundance of balsam fir seedlings dominant in high-elevation forests of northeastern United States that are sensitive to changing climate and mercury deposition. We surveyed balsam fir seedling density by substrate (moss, litter, other) on 120 quadrats (1 × 1 m) in two contrasting canopy environments (in gaps and under canopies), measured seedling stress, and quantified mercury content in seedlings and substrates. We observed that, in both canopy environments, tree seedlings established on moss exhibited (i) increased density, (ii) decreased physiological stress, and (iii) higher potential to recruit into larger size classes, compared to seedlings established in litter. Regardless of canopy environment, seedling foliar mercury levels did not correspond to substrate mercury despite large differences in substrate mercury concentrations (relative to moss, litter concentrations were ~ 4-times greater and soil concentrations were ~ 6-times greater), likely reflecting the dominance of foliar over root uptake of mercury. Because the moss layer appeared to mitigate seedling drought stress, and to increase seedling establishment and recruitment compared to other substrates, these microsite effects should be considered in models predicting forest regeneration and dynamics under increased drought stress associated with the ongoing climate warming.