Photosynthetic Pigment Content Research Articles

Effects of paclobutrazol seed priming on seedling quality, photosynthesis, and physiological characteristics of fragrant rice

BackgroundPaclobutrazol is widely used in the agricultural field. This study investigated the effects of seed priming with different concentrations of paclobutrazol on seedling quality, 2-acetyl-1-pyrroline (2-AP, a key aroma component of fragrant rice) biosynthesis, and related physiological and biochemical indicators in fragrant rice seedlings.ResultsThe experiment is being conducted at the College of Agriculture, South China Agricultural University. In the experiment, three concentrations of paclobutrazol (Pac 1: 20 mg·L−1; Pac 2: 40 mg·L−1; Pac 3: 80 mg·L−1) were used to initiate the treatment of fragrant rice seeds, while water treatment was used as a control (CK). The results showed that compared with CK, paclobutrazol treatment reduced plant height, increased stem diameter, and increased fresh and dry weight of aromatic rice seedlings. Moreover, paclobutrazol treatment also increased the seedlings’ photosynthetic pigment content and net photosynthetic rate.ConclusionsThis study demonstrates that paclobutrazol primarily increases the content of proline by reducing the content of glutamate and down-regulating the expression of P5CS2, thereby promoting the conversion of proline to the aromatic substance 2-AP. Under the appropriate concentration of paclobutrazol (40 mg·L−1~80 mg·L−1), the seedling quality, stress resistance, and aroma of fragrant rice can be improved.

Effects of Extended Light/Dark Cycles on Solanaceae Plants.

The absence of an externally-imposed 24 h light/dark cycle in closed plant production systems allows setting the light environmental parameters in unconventional ways. Innovative lighting modes for energy-saving, high-quality, and yield production are widely discussed. This study aimed to evaluate the effects of the light/dark cycles of 16/8 h (control) and 24/12 h, 48/24 h, 96/48 h, 120/60 h (unconventional cycles) based on the same total light amount, and continuous lighting (360/0 h) on plant performance of some Solanaceae species. Responses of eggplant (Solanum melongena L.), sweet pepper (Capsicum annuum L.), tobacco (Nicotiana tabacum L.), and tomato (Solanum lycopersicum L.) plants to extended light/dark cycles and continuous lighting were studied under controlled climate conditions. Plants with two true leaves were exposed to different light/dark cycles for 15 days. Light intensity was 250 µmol m-2 s-1 PPFD, provided by light-emitting diodes (LEDs). After the experiment, tomato, sweet pepper, and eggplant transplants were planted in a greenhouse and grown under identical conditions of natural photoperiod for the estimation of the after-effect of light treatments on fruit yield. Extended light/dark cycles of 24/12 h, 48/24 h, 96/48 h, 120/60 h, and 360/0 h affected growth, development, photosynthetic pigment content, anthocyanin and flavonoid content, and redox state of plants. Effects varied with plant species and length of light/dark cycles. In some cases, measured parameters improved with increasing light/dark periods despite the same total sum of illumination received by plants. Treatments of tomato and pepper transplants with 48/24 h, 96/48 h, and 120/60 h resulted in higher fruit yield compared to conventional 16/8 h photoperiod. The conclusion was made that extended light/dark cycles can result in increased light use efficiency compared to conventional photoperiod and, therefore, reduced product cost, but for practical application, the effects need to be further explored for individual plant species or even cultivars.

Leather bergenia as an alternative to synthetic colorants for food systems

The topicality of studying synthetic colorants and a possibility of their strictly regulated application is linked with an increasing producers’ interest in natural food colorants due to the attempt to grant the status of natural products to foods. New data on the content of photosynthetic pigments in leaves of leather bergenia (Вergenia crassifolia (L.) Fitsch) of different periods of vegetation growing in the Republic of Buryatia were obtained in this work. It is shown that it is one of the few plants, which leaves contain a significant amount of carotenoids. Their maximum total content (1257.9 ± 33.1 mmol/mol chlorophyll) was noticed in red leaves of bergenia. Seasonal changes in the complex of photosynthetic pigments in leaves were revealed. For example, the content of chlorophylls in black leaves reduced by four times compared to the amount of pigments in green leaves. Insignificant losses of the pool of green pigments were also observed in red leaves. About 18% of chlorophylls remained in black leaves. During the period after plants’ appearance from under the snow, the content of chlorophyll α increased by 3 times and chlorophyll β by 1.8 times. In leaves of bergenia, β- carotene was found in the composition of carotenoids (30% of the sum of carotenoids). Among xanthophyllic pigments, lutein was found in the prevailing quantity; its proportion accounted for 51% of the sum of carotenoids.

Effects of polystyrene nanoplastics (PSNPs) on the physiology of Allium sativum L.: Photosynthetic pigments, antioxidant enzymes, phytohormones, and nutritional quality

Nanoplastics (NPs) arouse increasing attention recently. Many studies have shown possible negative effects on plants exposed to NPs, but more data are needed on various species of plants to elucidate the potential phytotoxicity mechanisms of NPs. In this work, a pot experiment was conducted to analyze toxicity induced by polystyrene nanoplastics (PSNPs; particle size, 75.10 nm) at diverse doses (0.05, 0.1, 0.25, 0.5, 1.0 mg/g dry soil weight) to seedlings of garlic (Allium sativum L.). The photosynthetic pigments, antioxidant enzyme activities, common phytohormones and styrene contents, and nutritional quality of leaves of A. sativum seedlings were determined. Results showed that the toxic effects of PSNPs on plants at 42 days after exposure were stronger than those at 28 days. Chlorophyll a, chlorophyll b, as well as carotenoids levels within A. sativum leaves treated with PSNPs for 42 days decreased, with the highest decreasing rates of 40.22%, 41.29%, and 27.38%, respectively. The malondialdehyde (MDA) level within A. sativum leaves was noticeably up-regulated at 0.5 and 1.0 mg/g of PSNPs. Furthermore, the guaiacol peroxidase (POD) and catalase (CAT) activities and the abscisic acid (ABA) contents increased significantly with increasing the concentrations of PSNPs. After exposure for 42 days, allicin, soluble sugar and soluble protein levels decreased with increasing the concentration of PSNPs. The highest styrene content in leaves of A. sativum was obtained for the treatment group of the 0.5 mg/g PSNPs, showing an increase of 23.73% relative to control. Collectively, PSNPs were translocated into the leaves of A. sativum from roots, significantly affected the photosynthetic pigments contents, and significantly induced oxidative stress in A. sativum. Furthermore, high doses of PSNPs exposure impaired the A. sativum’s nutritive quality. These research results can provide basic data for accurately evaluating the ecological toxicity of NPs on crops.

Differential capacity of phragmites ecotypes in remediation of inorganic contaminants in coastal ecosystems: Implications for climate change

Remediating inorganic pollutants is an important part of protecting coastal ecosystems, which are especially at risk from the effects of climate change. Different Phragmites karka (Retz) Trin. ex Steud ecotypes were gathered from a variety of environments, and their abilities to remove inorganic contaminants from coastal wetlands were assessed. The goal is to learn how these ecotypes process innovation might help reduce the negative impacts of climate change on coastal environments. The Phragmites karka ecotype E1, found in a coastal environment in Ichkera that was impacted by residential wastewater, has higher biomass production and photosynthetic pigment content than the Phragmites karka ecotypes E2 (Kalsh) and E3 (Gatwala). Osmoprotectant accumulation was similar across ecotypes, suggesting that all were able to successfully adapt to polluted marine environments. The levels of both total soluble sugars and proteins were highest in E2. The amount of glycine betaine (GB) rose across the board, with the highest levels being found in the E3 ecotype. The study also demonstrated that differing coastal habitats significantly influenced the antioxidant activity of all ecotypes, with E1 displaying the lowest superoxide dismutase (SOD) activity, while E2 exhibited the lowest peroxidase (POD) and catalase (CAT) activities. Significant morphological changes were evident in E3, such as an expansion of the phloem, vascular bundle, and metaxylem cell areas. When compared to the E3 ecotype, the E1 and E2 ecotypes showed striking improvements across the board in leaf anatomy. Mechanistic links between architectural and physio-biochemical alterations are crucial to the ecological survival of different ecotypes of Phragmites karka in coastal environments affected by climate change. Their robustness and capacity to reduce pollution can help coastal ecosystems endure in the face of persistent climate change.

Toxicity of ZnFe-SO4 layered double hydroxide in Tetradesmus obliquus and evaluation of some physiological responses of the microalgae for stress management

Layered double hydroxides (LDHs), regarding their physical and structural properties, have different and wide applications industry and their increasing use may raise ecological and human health concerns. However, the potential toxicity mechanisms of LDHs in different organisms are still unclear. In the present work, after synthesizing of ZnFe-SO4 LDH and studying of its characterization by XRD, FT-IR, SEM, EDX-mapping, TEM and Raman, its toxicity in Tetradesmus obliquus was evaluated. According to experimental results, the growth of the algae and content of photosynthetic pigments were significantly decreased after treatment with 100 mg/L of ZnFe-SO4 LDH. The high dose exposure to the LDH also inhibited the activity of SOD and POD enzymes, possibly due to the LDH- catalyzed reactive oxygen species production. In addition, lipid peroxidation and the content of phenolic compounds, as no-enzymatic antioxidants were increased by enhancement of the LDH concentration. The rise of phenol, flavonoids and MDA contents could be regarded as some manifestations and responses to the toxic effects of the contaminant in the algae cells. The results provided a better understanding of the undesirable effects and toxicity of LDHs in aquatic organisms.

Exogenous γ‐aminobutyric acid (GABA) improves the cadmium phytoremediation capacity of Solanum nigrum var. humile under cadmium stress

Abstractγ‐aminobutyric acid (GABA) has shown promise in enhancing crop tolerance to heavy metal stress. To improve the cadmium (Cd) phytoremediation capacity of hyperaccumulator Solanum nigrum var. humile, the effects of exogenous GABA on the growth and Cd accumulation of S. nigrum var. humile were studied. When exposed to Cd stress (0.1 mg/L) through irrigation, S. nigrum var. humile exhibited inhibited growth, characterized by decreased biomass and contents of photosynthetic pigments (chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid). However, the application of exogenous GABA at 1 and 2 g/L increased various organs biomass and photosynthetic pigment content of S. nigrum var. humile to certain degree under Cd stress. Compared with the Cd treatment, the concentrations of 1 and 2 g/L GABA increased the shoot biomass by 8.24% and 16.62%, respectively. GABA also increased the Cd contents, bioconcentration factors, and Cd extractions in various organs of S. nigrum var. humile. Compared with the Cd treatment, the concentrations of 1 and 2 g/L GABA increased the shoot Cd extraction by 17.66% and 24.47%, respectively. Moreover, correlation and gray relational analyses showed that the shoot biomass, chlorophyll b content, and total chlorophyll content were the top three parameters closely related to shoot Cd extraction. These findings suggest that GABA can alleviate Cd‐induced stress in S. nigrum var. humile, thus enhancing its phytoremediation capacity for Cd‐contaminated soils.

Physiological response and phytoremediation potential of dioecious Hippophae rhamnoides inoculated with arbuscular mycorrhizal fungi to Pb and Zn pollution.

Plant-microorganism combined remediation of heavy metal pollution has been reported, but little attention has been paid to the effect of arbuscular mycorrhizal (AM) fungi on phytoremediation of dioecious plants under heavy metal pollution. In this study, the growth, physiological responses and phytoremediation traits of Hippophae rhamnoides were determined to evaluate whether sex-specific ecophysiological responses and phytoremediation capacities of females and males are affected by additional AM fungi (Glomus mosseae) under heavy metal treatments. The results showed that excess Pb and Zn stresses inhibited photosynthetic capacities of both sexes. However, inoculated AM fungi treatment increased the activity of photosynthesis, content of photosynthetic pigment, activity of superoxide dismutase, the content of proline and root Pb content and enrichment coefficient of males while decreased root Pb content of females under Pb stress. On the other hand, inoculated AM fungi treatment increased the photosynthetic activities and Pro accumulation of females, and activity of superoxide dismutase and transport coefficient of males under Zn stress. These results demonstrate that H. rhamnoides inoculated AM fungi showed significant sex-specific responses on the growth, physiological traits and phytoremediation potential to Pb and Zn stress. AM fungi significantly improved the tolerance of males to Pb stress and both sexes to Zn stress, which indicates H. rhamnoides and AM fungi can be used as a plant-microbial combined remediation method for Pb and Zn contaminated soil. More attention should be paid on sexual-specific responses and phytoremediation of dioecious plants to heavy metals in the future.

The fungal endophyte Metarhizium anisopliae (MetA1) coordinates salt tolerance mechanisms of rice to enhance growth and yield

The implementation of salt stress mitigation strategies aided by microorganisms has the potential to improve crop growth and yield. The endophytic fungus Metarhizium anisopliae shows the ability to enhance plant growth and mitigate diverse forms of abiotic stress. We examined the functions of M. anisopliae isolate MetA1 (MA) in promoting salinity resistance by investigating several morphological, physiological, biochemical, and yield features in rice plants. In vitro evaluation demonstrated that rice seeds primed with MA enhanced the growth features of rice plants exposed to 4, 8, and 12 dS/m of salinity for 15 days in an agar medium. A pot experiment was carried out to evaluate the growth and development of MA-primed rice seeds after exposing them to similar levels of salinity. Results indicated MA priming in rice improved shoot and root biomass, photosynthetic pigment contents, leaf succulence, and leaf relative water content. It also significantly decreased Na+/K+ ratios in both shoots and roots and the levels of electrolyte leakage, malondialdehyde, and hydrogen peroxide, while significantly increasing proline content in the leaves. The antioxidant enzymes catalase, glutathione S-transferase, ascorbate peroxidase, and peroxidase, as well as the non-enzymatic antioxidants phenol and flavonoids, were significantly enhanced in MA-colonized plants when compared with MA-unprimed plants under salt stress. The MA-mediated restriction of salt accumulation and improvement in physiological and biochemical mechanisms ultimately contributed to the yield improvement in salt-exposed rice plants. Our findings suggest the potential use of the MA seed priming strategy to improve salt tolerance in rice and perhaps in other crop plants.

Foliar application of plant growth regulators for enhancing heavy metal phytoextraction efficiency by Sedum alfredii Hance in contaminated soils: Lab to field experiments

The phytoremediation efficiency of plants in removing the heavy metals (HMs) might be influenced by their growth status and accumulation capacity of plants. Herein, we conducted a lab-scale experiment and a field try out to assess the optimal plant growth regulators (PGRs) including indole-3-acetic acid (IAA)/brassinolide (BR)/abscisic acid (ABA) in improving the phytoextraction potential of Sedum alfredii Hance (S. alfredii). The results of pot experiment revealed that application of IAA at 0.2 mg/L, BR at 0.4 mg/L, and ABA at 0.2 mg/L demonstrated notable potential as optimal dosage for Cd/Pb/Zn phytoextraction in S. alfredii. The findings of subcellular level of Cd/Pb/Zn in leaves showed that IAA (0.2 mg/L), BR (0.4 mg/L) or ABA (0.2 mg/L) promoted the HMs storage in the soluble and cell wall fraction, therefore contributing HMs subcellular compartmentation. In addition, application of PGRs notably enhanced the antioxidant system (SOD, CAT, POD, APX activities) while reducing lipid peroxidation (MDA content) in S. alfredii, consequently improving HMs tolerance and growth of S. alfredii. Moreover, the results of field trial showed that application of BR, IAA, or ABA+BR substantially improved the growth of S. alfredii by inducing plants biomass and augmenting the levels of photosynthetic pigment contents. Notably, ABA+BR noticed the highest theoretical biomass by 42.9 %, followed by IAA (41.6 %), and BR (36.4 %), as compared with CK. Additionally, ABA+BR treatment showed effectiveness in removing the Cd by 103.4 %, while BR and IAA led to a significant increase of Pb and Zn removal by 239 % and 116 %, respectively, when compared with CK. Overall, the results of this study highlights that the foliar application of IAA, BR, or ABA+BR can serve as viable strategy to boosting phytoremediation efficiency of S. alfredii in contaminated soil by improving the biomass and metal accumulation in harvestable parts.

Efeito do cloreto de cálcio e do ácido salicílico em algumas propriedades morfológicas, bioquímicas e pós-colheita de flores cortadas de Alstroemeria ‘Orange Queen’

Abstract This study investigated the impact of varying calcium chloride (CaCl2) and salicylic acid (SA) concentrations on the growth, biochemical, and postharvest quality of Alstroemeria ‘Orange Queen’ flowers. A completely randomized factorial design (CRD) with two factors and three replications was employed. The first factor involved foliar application of 0, 75, 150, or 225 mg L-1 CaCl2, while the second factor consisted of 0, 150, 300, or 450 mg L-1 SA. Morphological characteristics (number of leaves, leaf fresh and dry weight, number of florets) and biochemical parameters (photosynthetic pigment content, soluble sugar content) were evaluated. Additionally, postharvest traits (relative fresh weight, relative solution uptake, malondialdehyde content, catalase and ascorbate peroxidase activity) were assessed. The highest fresh and dry weights and the greatest number of florets were observed in Alstroemeria treated with 225 mg L-1 CaCl2 and 450 mg L-1 SA. This combination also improved the flowers' postharvest quality. Photosynthetic pigment content was significantly enhanced by both CaCl2 and SA, while malondialdehyde content was reduced compared to the control. Antioxidant enzyme activity was significantly increased following the application of CaCl2 and SA. Foliar application of 225 mg L-1 CaCl2 and 450 mg L-1 SA promoted the growth, biochemical composition, and postharvest quality of Alstroemeria ‘Orange Queen’ flowers. This treatment improved flower size, number, and enhanced their resistance to stress, suggesting its potential for enhancing the commercial value of this cultivar.

Impact of anionic synthetic surfactants of lead ions and their combinations on the pigment profile of freshwater plant organisms Ceratophyllum demersum and Egeria densa

The development of human civilization inevitably leads to the development of production with increasing emissions of many chemicals into the environment. This is especially noticeable in relation to surface waters of fresh water bodies. A very alarming point is that the amount of toxic anthropogenic substances, including heavy metals, is growing every year and is increasingly disturbing the existing ecological balance. Plant organisms of water bodies are among the first to experience the effects of any anthropogenic pollutants and especially heavy metals and surfactants, the amount of which increases in the water of rivers and lakes. Very important in this is the complex of morpho-physiological adaptations associated with restructuring in the structure of chloroplasts. Changes in the content of photosynthetic pigments in plants of two species (Ceratophyllum demersum and Egeria densa) were assessed when they were exposed to very common technogenic substances (lead ions and a solution of anionic synthetic surfactants). In plants, there is a decrease in the activity of molecular transport, inhibition of H+-ATPase, leading to a decrease in the pH of the cytoplasm and activation of hydrolases, which enhance the breakdown of biopolymers. This leads to changes in the expression of individual genes and increased synthesis of a number of stress proteins. Under these conditions, the assembly of cytoskeletal elements is activated, the structures of membrane proteins and lipids change, the level of ATP decreases, free radical processes are activated and the intensity of photosynthesis is inhibited.

Characteristics of vegetation and soil in Caragana korshinskii plantations in the hilly and sandy areas of northwestern Shanxi Province, China

We investigated the changes of soil nutrients and plant communities in the artificial sand fixation forests of Caragana korshinskii with different ages. The results showed that soil organic carbon and soil total nitrogen contents increased with the stand ages, and were significantly higher in 40 and 50 year-old than other ages. Soil organic carbon and total nitrogen contents recovered much faster in the surface layer (0-10 cm) than in others. Soil nutrient stoichiometric ratios (C:P, N:P) in the 0-10 cm soil layer differed significantly among different stand ages. With the increases of stand age, C and N contents in C. korshinskii leaves increased significantly, and reached the maximum at 50 year-old. Leaf P content increased first and then decreased, being maximum at 18 year-old. Leaf C:N first increased and then decreased, being maximum at 12 year-old. The contents of photosynthetic pigments and leaf C:P and N:P decreased first and then increased, being minimum at 18 year-old. C. korshinskii was mainly influenced by N availability before 40 year-old, but mainly limited by P after. The species number, density, and vegetation cover of annual and perennial herbaceous plants increased with stand ages, and the community shifted from a simple shrub plant community to a complex shrub-herb community. The biomass of C. korshinskii and herbaceous plants increased significantly with stand age, and had a significant positive correlation with the contents of soil organic carbon, total nitrogen and N:P.

Epiphyton Pigment Indices in the River Section of the Kaniv Reservoir (Ukraine)

The content of photosynthetic pigments (chlorophyll <i>a, b, c</i> and carotenoids) was studied in algal epiphyton of nine species of higher aquatic plants of various ecological groups occurring in the river section of the Kaniv Reservoir. It has been found that these indices varied over a wide range. Thus, in the fouling of emergent plants, the content of chlorophyll <i>a</i> was 0.9 μg/g of the dry mass of plant substratum, in epiphyton of submerged plants it varied from 15.4 to 62.4 μg/g, and in that of plants with floating leaves-from 3.1 to 11.0 μg/g. The content of chlorophyll <i>b</i> and <i>c</i> in epiphyton of submerged plants accounted for 1.0 and 8.5 μg/g, respectively, in that of plants with floating leaves - 0.5 and 2.1 μg/g, and in the fouling of emergent plants - 0.1 and 0.2 μg/g. The concentration of carotenoids in the fouling of emergent plants was 0.7 μgSPU/g of the dry mass of plant substratum, in epiphyton of submerged plants it varied from 13.2 to 49.3 μgSPU/g, and in that of plants with floating leaves it was within 2.5-9.5 μgSPU/g. It has been found that the content of chlorophyll <i>a</i> and carotenoids in algal epiphyton of higher aquatic plants correlates with its biomass.

Effect of PGPR Arthrobacter sp. CTF1 and foliar iodine spraying on pea microgreens growth in hydroponic culture

The use of plant growth-promoting rhizobacteria (PGPR) along with additional biofortification of agricultural plants with scarce essential elements, such as iodine, is a promising area of agricultural biotechnology. The seeds of Pisum sativum L. (var. Madras) pre-inoculated for two hours with PGPR Arthrobacter sp. strain CTF1 (108 CFU/mL) were grown for 14 days in a hydroponic culture at foliar spraying with iodine solution (0.01% KI or KIO3) on the 7th day of the vegetation. Growth parameters such as the length of shoot, fresh and dry biomass of seedlings were studied, the germination percentage and vigor index were calculated, and the content of photosynthetic pigments in pea leaves was assessed. The results showed inoculation of pea seeds with PGPR strain CTF1 had a positive effect on the biomass of two-week-old pea microgreens and their vigor index. At the same time, a significant increase in photosynthetic pigments was also observed in the leaves of pea seedlings, especially chlorophyll a (by almost 25%) and carotenoids (by almost 40%). Additionally, application of iodine via foliar spraying, irrespective of its form (KI or KIO3), resulted in nearly a 26-fold surge in amount of microgreens. However, the significant effect of such iodine treatment had a positive effect only on the content of carotenoids.

Polystyrene nanoplastics alter the ecotoxicological effects of diclofenac on freshwater microalgae Scenedesmus obliquus.

Due to the escalating risk of plastic pollution, nanoplastics have attracted considerable attention in the recent past. They can co-exist and interact with other contaminants like pharmaceuticals in the aquatic environment. Therefore, it is pertinent to understand how these pollutants interact with one another in the ecosystem. The current study examined the individual and combined effects of fluorescent polystyrene nanoplastics (FNPs) and diclofenac (DCF) on Scenedesmus obliquus using a full factorial design. The toxicity of S. obliquus significantly increased in a dose-dependent manner upon exposure to pristine forms of DCF and FNPs. The major cause of individual toxicity of DCF and FNPs in S. obliquus was oxidative stress. In the combined toxicity tests when FNPs (0.01, 0.1, and 1 mg L-1) and DCF (1 mg L-1) were mixed, a synergistic effect was noted compared to the respective pristine FNPs. However, when the DCF concentration in the mixture was decreased to 0.25 mg L-1, the combined toxicity with FNPs (0.01, 0.1, and 1 mg L-1) reduced indicating an antagonistic effect. The independent action model also showed an antagonistic effect for low-dose combinations of DCF and a synergistic effect for high-dose combinations. The estimation of oxidative stress parameters, antioxidant enzyme activity, and photosynthetic pigment content in the algae further validated the cytotoxicity data. The mean hydrodynamic diameter and surface charge analyses further indicated that the colloidal stability of the FNPs in the medium was affected when they were combined with DCF. The key reason for differences in the cytotoxicity of combinations could be observed variations in the aggregation of FNPs and differential adsorption patterns of DCF on the FNPs. These factors efficiently altered cell-particle interactions in the mixture demonstrating a hormesis effect. Thus, this current study highlighted the hazardous nature of the nanoplastics and their co-exposure risks with pharmaceuticals on microalgae in freshwater environments.

Functional ecological traits in young and adult thalli of canopy-forming brown macroalga Gongolaria barbata (Phaeophyta) from a transitional water system.

Gongolaria barbata is a canopy-forming brown macroalga that thrives in the intertidal and subtidal habitats of the warm-temperate Mediterranean Sea, which is particularly exposed to environmental changes due to its peculiar geographical location and exposure to both global and local stressors. Testing whether this species is featured by specific functional, eco-physiological and biochemical traits allowing an efficient use of habitat resources and adaptation to environmental stress, and whether this potential might change with population growth, is essential for predicting the performance of the algae under different environmental abiotic variables (e.g., temperature, nutrient availability, light) and biotic interactions (such as grazing). Young (juveniles) and adult thalli of G. barbata were sampled in the winter season from the Venice Lagoon, Italy, featured by high environmental changes (temperature, salinity) and analyzed for thallus dry matter content (TDMC), photosynthetic activity, photosynthetic pigment and protein content, and antioxidant capacity to assess if thallus age may be considered a significant driver in determining the ecological responses of this species to environmental changes. Our results showed that TDMC was higher in adults than juveniles. At the functional level, rapid light curves indicated an elevated photosynthetic efficiency in juveniles compared to adults highlighted by the higher quantum yield of PSII electron transport, electron transport rate, and Rubisco content observed in juveniles. On the contrary, adults exhibited a higher non-photochemical quenching and total pigment concentration. No difference in maximum PSII photochemical efficiency and D1 protein content between the two thalli groups was found. Along with better photosynthesis, juveniles also displayed a higher amount of total polyphenols, flavonoids, and tannins, and a stronger antioxidant capacity compared to adults. Our findings revealed significant differences in the eco-physiological characteristics of G. barbata at different growth stages. It was observed that young thalli, allocate more energy to photosynthesis and chemical defenses by increasing the production of antioxidant compounds, such as polyphenols, flavonoids, and tannins. With growth, thalli likely adopt a more conservative strategy, reducing photosynthesis and promoting structural biomass accumulation to mitigate the potential risks associated with prolonged exposure to environmental stressors, such as the wavy way. Although our study focused on a single phase of G. barbata life cycle under winter settings, it offers preliminary insights into this species eco-physiological traits and auto-ecology. Future research could explore the potential implications of these findings, evaluating the species' resilience to environmental changes at the population level.

Response of tomatoes to inactivated endophyte LSE01 under combined stress of high-temperature and drought

Endophytes can assist crops in adapting to high temperatures and drought conditions, thereby reducing agricultural losses. However, the mechanism through which endophytes regulate crop resistance to high temperatures and drought stress remains unclear, and concerns regarding safety and stability exist with active endophytes. Thus, heat-treated endophytic bacteria LSE01 (HTB) were employed as a novel microbial fertilizer to investigate their effects on plant adaptation to high temperatures and drought conditions. The results indicated that the diameter and weight of tomatoes treated with HTB under stress conditions increased by 23.04% and 71.15%, respectively, compared to the control. Tomato yield did not significantly decrease compared to non-stress conditions. Additionally, the contents of vitamin C, soluble sugars, and proteins treated with HTB increased by 18.81%, 11.54%, and 99.75%, respectively. Mechanistic research revealed that HTB treatment enhances tomato's stress resistance by elevating photosynthetic pigment and proline contents, enhancing antioxidant enzyme activities, and reducing the accumulation of MDA. Molecular biology research demonstrates that HTB treatment upregulates the expression of drought-resistant genes (GA2ox7, USP1, SlNAC3, SlNAC4), leading to modifications in stomatal conductance, plant morphology, photosynthetic intensity, and antioxidant enzyme synthesis to facilitate adaptation to dry conditions. Furthermore, the upregulation of the heat-resistant gene (SlCathB2-2) can increases the thickness of tomato cell walls, rendering them less vulnerable to heat stress. In summary, HTB endows tomatoes with the ability to adapt to high temperatures and drought conditions, providing new opportunities for sustainable agriculture.

Integrated physiological and metabolomic responses reveal mechanisms of Cd tolerance and detoxification in kenaf (Hibiscus cannabinus L.) under Cd stress.

Cadmium (Cd) is a highly toxic trace element that occurs in large quantities in agricultural soils. The cultivation of industrial crops with high phytoremediation potential, such as kenaf, could effectively reduce soil Cd contamination, but the mechanisms of toxicity, tolerance, and detoxification remain unclear. In this study, the effects of different Cd concentrations (0, 100, 250, and 400 µM) on growth, biomass, Cd uptake, physiological parameters, metabolites and gene expression response of kenaf were investigated in a hydroponic experiment. The results showed that Cd stress significantly altered the ability of kenaf to accumulate and transport Cd; increased the activity of hydrogen peroxide (H2O2), superoxide anion (O2 -), and malondialdehyde (MDA); reduced the activities of superoxide dismutase (SOD) and catalase (CAT); and decreased the content of photosynthetic pigments, resulting in significant changes in growth and biomass production. Exposure to Cd was found to have a detrimental effect on the ascorbate-glutathione (AsA-GSH) cycle in the roots, whereas it resulted in an elevation in AsA levels and a reduction in GSH levels in the leaves. The increased content of cell wall polysaccharides under Cd stress could contribute to Cd retention in roots and limited Cd transport to above-ground plant tissues. Metabolomic analyses revealed that alanine, aspartate, and glutamate metabolism, oxidative phosphorylation, ABC transporter, and carbon metabolism were the major metabolic pathways associated with Cd stress tolerance. Cd stress increased gene expression of IRT1 and MTP1 in roots, which resulted in kenaf roots accumulating high Cd concentrations. This study extends our knowledge of the factors regulating the response of kenaf to Cd stress. This work provided a physiological and metabolomic perspective on the mechanism controlling the response of kenaf to Cd stress.

Efeitos do Fe e Zn no crescimento, bioforticação e qualidade de alface cultivado em hidroponia

ABSTRACT Iron (Fe) and zinc (Zn) are essential elements for human health and their deficiencies cause reduced work capacity, physiological and immune system disorders, anemia and even death, being considered primary global public health problems. Agronomic biofortification aims to increase the concentration of these nutrients in the edible part of the plant and, consequently, increase human intake of these nutrients. The aim of this study was to evaluate the effects of Fe and Zn concentrations on the growth, biofortification and quality of lettuce grown in hydroponics. Six treatments corresponding to the combinations of Zn (0.06 and 0.24 mg L-1) and Fe (2, 4 and 8 mg L-1) concentrations were evaluated. Increase of Zn in the nutrient solution positively influenced only leaf Zn contents at 18 days after transplanting the seedlings and ascorbic acid at harvest. On the other hand, the increase in Fe concentration positively influenced the contents of photosynthetic pigments, ascorbic acid and Fe; however, it negatively affected the leaf Zn content, leaf area and leaf dry mass of lettuce. Greater biofortification of lettuce for Fe was observed with the Fe concentration of 8 mg L-1 in the solution.