Reduced Chlorophyll Content Research Articles

Toxicological effects and mechanisms of lithium on growth, photosynthesis and antioxidant system in the freshwater microalga Chromochloris zofingiensis

The growing prevalence of lithium (Li) batteries has drawn public attention to Li as an emerging pollutant. The present study investigates the toxicity of Li+ on Chromochloris zofingiensis, examining physiological, biochemical and omics aspects. Results reveal hormesis effects of Li+ on C. zofingiensis growth. At Li+ concentrations below 5 mg L−1, Li+ can enhance chlorophyll content, mitochondrial activity, and antioxidant capacity, leading to increased dry cell weight and cell number. Conversely, when it exceeded 10 mg L−1, Li+ can reduce chlorophyll content, induce oxidative stress, and disrupt chloroplast and mitochondria structure and function, ultimately impeding cell growth. In addition, under 50 mg L−1 Li+ stress, microalgae optimize absorbed light energy use (increasing Fv/Fm and E TR ) and respond to stress by up-regulating genes in starch and lipid biosynthesis pathways, promoting the accumulation of storage components. Weighted gene co-expression network analysis indicates that peptidylprolyl cis/trans isomerase, GTPase and L-ascorbate oxidase might be the key regulators in response to Li+ stress. This research marks the toxic effects and molecular mechanisms of Li+ on freshwater microalga, which would improve our understanding of Li’s toxicology and contributing to the establishment of Li pollution standards.

Pollen Viability, and the Photosynthetic and Enzymatic Responses of Cowpea (Vigna unguiculata (L.) Walp., Fabaceae) in the Face of Rising Air Temperature: A Problem for Food Safety

Rising temperature affects agricultural production, causing food insecurity. Thus, the objective of this study was to evaluate how increased temperature influences pollen viability, photosynthetic and enzymatic responses, and their consequences on the final yield of cowpea cultivars. The cultivars BRS Acauã, BRS Guariba, BRS Gurguéia, and BRS Pajeú were used, kept in growth chambers under two temperature regimes: 24.8–30.8–37.8 °C and 20–26–33 °C. The cultivars BRS Acauã, BRS Guariba, and BRS Pajeú showed prolonged flowering and greater flower abortion, at 23.58%, 34.71%, and 25.55%, respectively, under an increase of 4.8 °C in temperature. This increase also reduced the viability of BRS Acauã and BRS Pajeú pollen by 34 and 7%, respectively. Heating increased stomatal opening and transpiration but reduced chlorophyll content. The enzymatic response varied according to cultivars and temperature. Changes in photosynthetic and enzymatic activities contribute to reducing pollen viability and productivity. BRS Acauã was the most affected, with an 82% reduction in the number of seeds and a 70% reduction in production. BRS Gurguéia maintained its production, even with an increase of 4.8 °C, and can be selected as a cultivar with the potential to tolerate high temperatures as it maintained pollen viability, with less flower abortion, with the synchrony of physiological and biochemical responses and, consequently, greater production.

Photosynthetic Responses of Racomitrium japonicum L. to Strontium Stress Evaluated through Chlorophyll a Fluorescence OJIP Transient Analysis.

Nuclides pollution and its biological effects are of great concern, especially for bryophytes during their terrestrial adaptation. Understanding PSII activity and electron transport response is vital for comprehending moss abiotic stress reactions. However, little is known about the photosynthetic performance of moss under nuclide treatment. Therefore, this study aimed to evaluate the chlorophyll fluorescence of Racomitrium japonicum L. The moss was subjected to Sr2+ solutions at concentrations of 5, 50, and 500 mg/L to evaluate chlorophyll a fluorescence using the OJIP test. Moderate and high Sr2+ stress led to inner cell membrane dissolution and reduced chlorophyll content, indicating impaired light energy absorption. At 5 mg/L Sr2+, fluorescence kinetics showed increased light energy capture, energy dissipation, and total photosynthetic driving force, thus stimulating transient photosynthetic activity of PSII and improving PSI reduction. Linear electron transfer and PSII stability significantly decreased under moderate and high Sr2+ stress, indicating potential photosynthetic center damage. Cyclic electron transfer (CEF) alleviated photosynthetic stress at 5 mg/L Sr2+. Thus, low Sr2+ levels stimulated CEF, adjusting energy flux and partitioning to protect the photosynthetic apparatus. Nevertheless, significant damage occurred due to inefficient protection under high Sr2+ stress.

Impact of Climate Change on Vegetable Production and Management Strategies

Vegetables are an important component of human nutrition that encompasses great species diversity and are very sensitive to unpredictable climatic changes. In recent decades, there has been an increase in the frequency of events like drought, flooding, high-temperature, low temperature, salinity and changes of atmospheric CO2 or ozone level which considerably affect morphological, physiological and biochemical changes in the plants. The occurrences of these types of abiotic stresses lead to membrane damage, oxidative burst, reduction of chlorophyll content and photosynthesis rate which ultimately affect the yield and quality of vegetable crops. The adoption of appropriate crop management practices and climate-resilient cultivars would help immensely in dealing with the adverse impacts of abiotic stresses. Alteration in planting dates, advanced irrigation technology, moisture-saving methods, use of plant growth regulators, use of plant growth promoting rhizobacteria, grafting technology, use of climate resilient cultivars and protected cultivation-like management practices can reduce the impact and intensity of abiotic stress enhance the production as well. Overall in this review, we have summarized the adverse effects of abiotic stresses that are induced by climate change and management strategies that enable to overcome the ill effects and sustain the production of vegetable crops.

Effects of Exogenous Zinc on Growth and Root Architecture Classification of Maize Seedlings Under Cadmium Stress

To explore the effects of different concentrations of zinc （Zn） on the growth and root architecture classification of maize seedlings under cadmium （Cd） stress， a hydroponic experiment was conducted to study the effects of different concentrations of Zn （0， 10， 25， 50， 100， 200， and 400 μmol·L-1） on the growth， root architecture and classification characteristics， Cd content， root Cd uptake capacity， and photosynthetic system of maize seedlings under Cd stress （50 μmol·L-1） by using Zhengdan 958 as the experimental material. Principal component analysis and the membership function method were used for comprehensive evaluation. The results showed that the 50 μmol·L-1 Cd stress had a significant toxic effect on maize seedlings， which significantly reduced chlorophyll content and photosynthetic parameters. The main root length， plant height， biomass， root forks， and root tips， including the root length and root surface area of the grade Ⅰ-Ⅲ diameter range and the root volume of the grade Ⅰ-Ⅱ diameter range， decreased significantly， which hindered the normal growth and development of maize seedlings. Compared with that under no Zn application， 100 μmol·L-1 and 200 μmol·L-1 Zn application reduced the uptake of Cd by maize seedlings， significantly reduced the Cd content in shoots and roots and the Cd uptake efficiency. The toxic effect on maize seedlings was alleviated， and the fresh weight， dry weight， tolerance index， and root forks of shoots and roots were significantly increased. The photosynthesis of maize seedlings was significantly enhanced， and the photosynthetic rate and the total chlorophyll content was significantly increased. The RL， SA， and RV in the Ⅰ-Ⅱ diameter range reached the maximum at 100 μmol·L-1 Zn， and the RL， SA， and RV in the Ⅲ diameter range reached the maximum at 200 μmol·L-1 Zn， which were significantly higher than those without Zn treatment. The comprehensive evaluation of the growth tolerance of maize seedlings showed that 100 μmol·L-1 and 200 μmol·L-1 Zn had better effects on alleviating Cd toxicity. Comprehensive analysis showed that the application of appropriate concentration of Zn could reduce the Cd content in maize seedlings， the Cd uptake capacity， and Cd uptake efficiency of roots； increase the biomass accumulation of maize seedlings； reduce the effect of Cd toxicity on root architecture； reduce the effect on the light and system； and improve the tolerance of maize seedlings to Cd.

Boosting cadmium tolerance in Phoebe zhennan: the synergistic effects of exogenous nitrogen and phosphorus treatments promoting antioxidant defense and root development.

Plants possess intricate defense mechanisms to resist cadmium (Cd) stress, including strategies like metal exclusion, chelation, osmoprotection, and the regulation of photosynthesis, with antioxidants playing a pivotal role. The application of nitrogen (N) and phosphorus (P) fertilizers are reported to bolster these defenses against Cd stress. Several studies investigated the effects of N or P on Cd stress in non-woody plants and crops. However, the relationship between N, P application, and Cd stress resistance in valuable timber trees remains largely unexplored. This study delves into the Cd tolerance mechanisms of Phoebe zhennan, a forest tree species, under various treatments: Cd exposure alone, combined Cd stress with either N or P and Cd stress with both N and P application. Our results revealed that the P application enhanced root biomass and facilitated the translocation of essential nutrients like K, Mn, and Zn. Conversely, N application, especially under Cd stress, significantly inhibited plant growth, with marked reductions in leaf and stem biomass. Additionally, while the application of P resulted in reduced antioxidant enzyme levels, the combined application of N and P markedly amplified the activities of peroxidase by 266.36%, superoxide dismutase by 168.44%, and ascorbate peroxidase by 26.58% under Cd stress. This indicates an amplified capacity of the plant to neutralize reactive oxygen species. The combined treatment also led to effective regulation of nutrient and Cd distribution in roots, shoots, and leaves, illustrating a synergistic effect in mitigating toxic impact of N. The study also highlights a significant alteration in photosynthetic activities under different treatments. The N addition generally reduced chlorophyll content by over 50%, while P and NP treatments enhanced transpiration rates by up to 58.02%. Our findings suggest P and NP fertilization can manage Cd toxicity by facilitating antioxidant production, osmoprotectant, and root development, thus enhancing Cd tolerance processes, and providing novel strategies for managing Cd contamination in the environment.

Fate of pharmaceuticals and personal care products like metronidazole, naproxen, and methylparaben and their effect on the physiological characteristics of two wetland plants

Plants play a vital role in the phytoremediation process, attenuating various pollutants. However, the dynamic root uptake and fate of emerging pollutants in plants, along with their effects on plant characteristics, have received limited research attention. This study explores the potential of Chrysopogon zizanioides (Vetiver) and Colocasia esculenta (Taro) in mitigating pharmaceutical and personal care products (PPCPs) - metronidazole (MNZ), naproxen (NAP), and methylparaben (MeP), under hydroponic conditions. Both plants demonstrated similar specific uptake potentials for the target pollutants (5.23 to 5.76 mg/g of biomass dry weight), with pollutant accumulation in plants remaining very low (<10 %). Notably, a substantial fraction of pollutants (66.27 % to 78.42 %) underwent metabolism. Qualitative analysis identified five MNZ and NAP metabolites and six MeP metabolites in plant tissues. Over a 28-day PPCPs exposure, accumulation of reactive oxygen species (ROS) resulted in reduced chlorophyll content, root activity, protein, and carbohydrates, alongside increased oxidative stress levels. The study highlighted distinct accumulation patterns, with NAP (anion) primarily in roots and MeP (cation) and MNZ (neutral) predominantly in aerial parts. Phloroglucinol staining confirmed the intact endodermis (Casparian Strips) in Vetiver roots, indicating symplastic transport of PPCPs to aerial parts. Moreover, significant morphological alterations were observed in plant roots exposed to target pollutants. During recuperation, a decrease in accumulated ROS indicates partial self-recovery from oxidative damage. In conclusion, both Vetiver and Taro emerge as promising candidates for removing specified PPCPs, emphasizing the critical role of addressing emerging contaminants for sustainable development and preserving the environment and human wellbeing.

Melatonin priming manipulates antioxidant regulation and secondary metabolites production in favour of drought tolerance in Chenopodium quinoa Willd.

Melatonin can be considered a physiological protective agent against environmental stress because of its natural antioxidant ability. The main goal of this study was to investigate the possible melatonin-positive effects on the growth enhancement and drought tolerance of quinoa (Chenopodium quinoa Willd) cultivars. To accomplish this objective, we compared the effects drought stress (100 % field capacity as control and 40 % field capacity), priming (melatonin priming (MP), hydro priming (HP), non-priming (NP), and cultivars (Titicaca, Giza1). Thus, the obtained results indicated higher oxidative damage, lipid peroxidation, and reduced chlorophyll content, which decreased the seed yield more in Giza1 than in Titicaca in comparison with the control. MP remarkably enhanced endogenous melatonin content, superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) activity in Titicaca (1.57, 2.50, 1.40, 1.90, and 2 times, respectively) and Giza1 (1.68, 4.50, 4, 2 and 2.6 times, respectively), compared with NP, under drought stress. MP effectively protected Titicaca and Giza1 chlorophylls and carotenoids, while decreasing the malondialdehyde (MDA) content through antioxidant enzyme activation, facilitation of soluble protein, as well as sugar synthesis and osmolyte accumulation. Therefore, MP improved photosynthesis in Titicaca and Giza1 under drought stress compared with NP. Overall, Titicaca showed a relatively higher drought stress tolerance. Furthermore, MP ameliorated the adverse consequences of drought stress and facilitated the recovery of susceptible cultivars such as Giza1 through the enhancement of photosynthetic pigments, antioxidant systems, osmotic adjustment, and secondary metabolite production. The main novelty of the current study is the elucidation of the role of melatonin priming in the induction of drought tolerance in quinoa.

YGL3 Encoding an IPP and DMAPP Synthase Interacts with OsPIL11 to Regulate Chloroplast Development in Rice

As the source of isoprenoid precursors, the plastidial methylerythritol phosphate (MEP) pathway plays an essential role in plant development. Here, we report a novel rice (Oryza sativa L.) mutant ygl3 (yellow-green leaf3) that exhibits yellow-green leaves and lower photosynthetic efficiency compared to the wild type due to abnormal chloroplast ultrastructure and reduced chlorophyll content. Map-based cloning showed that YGL3, one of the major genes involved in the MEP pathway, encodes 4-hydroxy-3-methylbut-2-enyl diphosphate reductase, which is localized in the thylakoid membrane. A single base substitution in ygl3 plants resulted in lower 4-hydroxy-3-methylbut-2-enyl diphosphate reductase activity and lower contents of isopentenyl diphosphate (IPP) compared to the wild type. The transcript levels of genes involved in the syntheses of chlorophyll and thylakoid membrane proteins were significantly reduced in the ygl3 mutant compared to the wild type. The phytochrome interacting factor-like gene OsPIL11 regulated chlorophyll synthesis during the de-etiolation process by directly binding to the promoter of YGL3 to activate its expression. The findings provides a theoretical basis for understanding the molecular mechanisms by which the MEP pathway regulate chloroplast development in rice.

Effects of Exogenous Melatonin on the Growth and Physiological Characteristics of Ginkgo biloba L. under Salinity Stress Conditions

Ginkgo (Ginkgo biloba L.) is a cherished relic among plants, commonly planted as a street tree. However, it faces cultivation challenges due to escalating soil salinization and widespread snowmelt application. Therefore, this study used 4-year-old Ginkgo seedlings to investigate how exogenous melatonin at varying concentrations affects seedling growth and physiology under salinity stress. The results revealed that appropriate melatonin concentrations (0.02, 0.1 mmol·L−1) significantly mitigated leaf yellowing under different NaCl stress levels. Furthermore, they increased ground diameter, current-year branch growth, relative water concentration, free proline, and soluble sugars in leaves. Melatonin also reduced electrolyte exudation rates, flavonoids, and malonic dialdehyde concentration, while enhancing peroxidase and superoxide dismutase activities. This led to reduced chlorophyll content, photosynthetic rate, stomatal conductance, and transpiration rate, stabilizing intercellular CO2 concentration, preserving photosynthetic structures, and enhancing photosynthetic rates. Additionally, the decline in the photosynthetic electron transport rate, the effective photochemical quantum yield of PSII, and the potential efficiency of primary conversion of light energy of PSII was alleviated. Minimal fluorescence and the non-photochemical quenching coefficient also improved. However, high melatonin concentration (0.5 mmol·L−1) exacerbated salinity stress. After analyzing composite scores, the 0.02 mmol·L−1 melatonin treatment was most effective in alleviating NaCl stress, while the 0.5 mmol·L−1 treatment intensified physiological stress under 200 mmol·L−1 NaCl stress. Principal component analysis and correlation analysis identified seven physiological indicators (photosynthetic rate, transpiration rate, photosynthetic electron transport rate, minimal fluorescence, superoxide dismutase, free proline, and chlorophyll a) and three growth indicators (ground diameter, branch length, and current-year branch thickness) as key markers for rapid salinity stress assessment in Ginkgo. These findings are crucial for addressing challenges associated with snowmelt’s impact on roadside Ginkgo trees, expanding planting areas, and breeding exceptional salt-tolerant Ginkgo varieties.

Can corn straw and its pyrolytic biochar be used to mitigate the toxicity of CuO NPs to wheat seedlings?

In order to understand whether corn straw (CS) and straw-derived biochar (CB) can be used as soil amendments to alleviate soil contaminated with metal oxide nanoparticles, CS and CB prepared by pyrolysis at 300 °C (with a weight ratio of 2% and 5%) were added to two types of soil contaminated with copper oxide nanoparticles (CuO NPs) to study the effects of CS and CB application on soil properties, wheat seedling growth, and metal transport. Our results showed that both 2% and 5% additions of CS and CB enhanced the nitrogen, phosphorus, and potassium fertility of both soils. In red earth (acidic), the addition of 2% and 5% of CB significantly increased soil pH (9.24% ~ 18.4%), wheat growth (12.2% ~ 14.9%), chlorophyll content (significantly increased by 32.3% for 2% CB treatment), and decreased antioxidant enzyme activity and membrane lipid peroxidation. In fluvo-aquic soil (alkaline), CS and CB did not increase soil pH, only 5% of CB significantly promoted wheat growth (by 11.0%), and decreased antioxidant enzyme activity, whereas 2% of CB reduced chlorophyll content (by 22.2%). Furthermore, 2% and 5% of CS and CB affected the transport of Cu in wheat, decreasing the translocation factor in red earth but increasing it in fluvo-aquic soil. Principal component analysis showed that 5% of CB had the best alleviating effect on CuO NPs toxicity in red earth, compared to CS. Taken together, CB obtained by pyrolysis at 300 °C appears to be an effective soil amendment specifically for red earth.Highlights• Corn straw (CS) and straw-derived biochar (CB) were used to mitigate CuO NP toxicity• 5% of CB showed the best mitigation effect on CuO NP toxicity in red earth• CS and CB had no significant mitigation on CuO NP toxicity in fluvo-aquic soilGraphical

Gene Mapping of a Yellow-to-Lethal Mutation Based on Bulked-Segregant Analysis-Seq in Soybean

Plant photosynthesis is mainly dependent on leaf color, and this has an impact on yield. Mutants lacking in chlorophyll have been analyzed to gain insight into the genetic processes involved in photosynthesis, chloroplast development, and chlorophyll metabolism. A yellow-to-lethal mutant, ytl, was selected from the M6 generation of the 60Coγ ray irradiation-treated soybean cultivar Nannong 1138-2. The mutant exhibited reduced chlorophyll content, with the thylakoid structure disrupted. Segregation of the cross between Williams 82 (W82) and ytl indicated that a recessive allele controlled yellow-to-lethal traits. The bulked-segregant analysis (BSA)-Seq method performed preliminary mapping, followed by simple sequence repeat (SSR) marker validation and further mapping. The candidate gene was mapped to a 418 Kb region containing 53 genes. High-throughput sequencing and first-generation sequencing results showed a two bp deletion in the second exon of Glyma.08g106500, leading to a frameshift mutation in ytl. As a promising candidate gene, Glyma.08g106500 encoded a chloroplast-localized pentatricopeptide repeat (PPR) domain-containing protein involved in the assembly of chloroplast proteins. These results will contribute to cloning the mutant ytl gene and provide insight into the regulatory processes controlling photosynthesis and chloroplast development and growth in soybean.

Chloroplast C-to-U editing, regulated by a PPR protein BoYgl-2, is important for chlorophyll biosynthesis in cabbage.

Leaf color is an important agronomic trait in cabbage (Brassica oleracea L. var. capitata), but the detailed mechanism underlying leaf color formation remains unclear. In this study, we characterized a Brassica oleracea yellow-green leaf 2 (BoYgl-2) mutant 4036Y, which has significantly reduced chlorophyll content and abnormal chloroplasts during early leaf development. Genetic analysis revealed that the yellow-green leaf trait is controlled by a single recessive gene. Map-based cloning revealed that BoYgl-2 encodes a novel nuclear-targeted P-type PPR protein, which is absent in the 4036Y mutant. Functional complementation showed that BoYgl-2 from the normal-green leaf 4036G can rescue the yellow-green leaf phenotype of 4036Y. The C-to-U editing efficiency and expression levels of atpF, rps14, petL and ndhD were significantly reduced in 4036Y than that in 4036G, and significantly increased in BoYgl-2 overexpression lines than that in 4036Y. The expression levels of many plastid- and nuclear-encoded genes associated with chloroplast development in BoYgl-2 mutant were also significantly altered. These results suggest that BoYgl-2 participates in chloroplast C-to-U editing and development, which provides rare insight into the molecular mechanism underlying leaf color formation in cabbage.

Evaluation of Morpho-Physiological Traits of Oat (Avena sativa L.) under Drought Stress

The increase in intensity and frequency of drought due to global climate change has increased the urgency of developing crop cultivars suitable for dry environments. Drought tolerance is a complex trait that involves numerous physiological, biochemical, and morphological responses. A better understanding of those mechanisms is critical to develop drought tolerant cultivars. In this study, we aimed to understand the morphophysiological changes at the shoot and root levels in response to drought stress of ten oat genotypes with diverse root morphological characteristics. Twenty-one-day old plants were subjected to drought stress in a greenhouse by withholding water for two weeks. Several characteristics including chlorophyll content, relative water content (RWC), stomatal conductance, stomata number, shoot dry weight (SDW), root dry weight (RDW), root-to-shoot biomass ratio (RSR), root length, root area, and root volume were measured on well-watered, and drought-stressed plants. Grain yield was evaluated by continuing the drought treatment with a drying and rewatering cycle every 15 days until physiological maturity. The water regime had a significant impact on all traits evaluated. A significant interaction between genotype and water treatment was observed for RWC, chlorophyll content, stomatal conductance, stomata number, and grain yield but not for root traits, suggesting that the root system of all genotypes responded similarly to drought stress. Hayden, the cultivar with the lowest reduction in grain yield from the drought treatment, was among the genotypes with the lowest reduction in RWC and chlorophyll content but with a sharp decrease in stomata number, thus indicating that regulating the plant water status and maintaining the photosynthesis level are important for oat plants to maintain grain yield under drought stress. The size of the root system was not correlated with grain yield under drought, but the RWC and grain yield were significantly correlated under drought, thus suggesting that maintaining the RWC is an important characteristic for oat plants to maintain yield under drought stress.

Supplementary Low Far-Red Light Promotes Proliferation and Photosynthetic Capacity of Blueberry In Vitro Plantlets.

Far-red light exerts an important regulatory influence on plant growth and development. However, the mechanisms underlying far-red light regulation of morphogenesis and photosynthetic characteristics in blueberry plantlets in vitro have remained elusive. Here, physiological and transcriptomic analyses were conducted on blueberry plantlets in vitro supplemented with far-red light. The results indicated that supplementation with low far-red light, such as 6 μmol m-2 s-1 and 14 μmol m-2 s-1 far-red (6FR and 14FR) light treatments, significantly increased proliferation-related indicators, including shoot length, shoot number, gibberellin A3, and trans-zeatin riboside content. It was found that 6FR and 14 FR significantly reduced chlorophyll content in blueberry plantlets but enhanced electron transport rates. Weighted correlation network analysis (WGCNA) showed the enrichment of iron ion-related genes in modules associated with photosynthesis. Genes such as NAC, ABCG11, GASA1, and Erf74 were significantly enriched within the proliferation-related module. Taken together, we conclude that low far-red light can promote the proliferative capacity of blueberry plantlets in vitro by affecting hormone pathways and the formation of secondary cell walls, concurrently regulating chlorophyll content and iron ion homeostasis to affect photosynthetic capacity.

Screening and identification of heat tolerance in Indian wheat genotypes using generalized regression neural network (GRNN) model

The present study using a generalized regression neural network (GRNN) model was carried out to check the effect of high temperature on five Indian bread wheat genotypes, namely, C306, K7903, CBW12, HD2329, and HD2428, and to develop an algorithm for the screening and identification of heat tolerance in wheat. A highly significant differential survivability in response to the temperature induction response technique with germinating seeds was observed for the five wheat genotypes. Maximum survivability was observed for C306 and K7903, whereas HD2329 and HD2428 showed minimum survival in response to lethal temperature stress. Similarly, at the mature plant stage, in response to heat treatment of 34°C/26°C (day/night), all five wheat genotypes showed a significant difference in chlorophyll a fluorescence, total chlorophyll content, and the reduction of 1,1- diphenyl-2-picryl-hydrazyl (DPPH) in response to heat treatment. The genotypes, C306, K7903, and CBW12 showed better performance for all the chlorophyll a fluorescence parameters under study including Fo, Fv/Fm, qL, qP, NPQ, θPSII, ETR, along with the total chlorophyll content and DPPH reduction, in contrast, the genotypes, HD2329 and HD2428 performed poorly for all parameters including chlorophyll a fluorescence parameters, total chlorophyll, and DPPH reduction. Higher inflection temperature and peak temperature were observed in C306 and K7903, in contrast, HD2329 and HD2428 showed significantly lower inflection temperature and peak temperature. Higher expression of the selected genes involved in photosynthesis and ROS scavenging was observed in C306 and K7903 relative to HD2329 and HD2428. On the basis of the different chlorophyll a fluorescence parameters, the algorithm was developed for the calculation of the heat susceptibility index. The algorithm was independently checked for the identification and segregation of all the five wheat genotypes taken in this study as tolerant, moderate, and susceptible. For all the genotypes, the algorithm was able to predict the heat susceptibility of the genotypes with high accuracy. Hence, the algorithm in combination with chlorophyll a fluorescence can be used for the screening of wheat and other plant species in response to abiotic stress, especially heat stress.

Salinity tolerance in tomato genotypes at an early plant growth stage: Morphological and physiological responses

Salinity is a significant factor restricting plant development at various stages, resulting in lower yield and productivity. The current study was carried out to investigate and assess the tolerance of several tomato genotypes to salty conditions. Thirty (30) tomato genotypes were cultivated in pots and tested for salinity at three levels: 5 ds/m NaCl, 10 ds/m NaCl, and 15 ds/m NaCl, in comparison to the control (0 mM NaCl). Two weeks after treatment, several morphological and physiological parameters were measured. The effects of salt stress on tomato genotypes included a considerable reduction in leaf area, chlorophyll content, shoot and root length, shoot and root biomass, and relative water content. Different tomato genotypes responded differently to salinity severity score (SSS). Reduction of shoot dry weight (0.27 to 0.44) and leaf area (0.33 to 0.45) were positively correlated with SSS at moderate (10 ds/m) to higher (15 ds/m) salinity levels, respectively. Based on the experiment results, the genotypes BARI Tomato 4, BARI Tomato 14, BARI Tomato 15, SAU Tomato 2, AV0T0 1228, and NS 501 were found to be more salinity tolerant than other genotypes. The results showed that measuring shoot length, leaf area, and shoot fresh and dry weight was better for evaluating salinity stress and screening salt-tolerant tomato genotypes.

Photons at the ultraviolet-visible interface: Effects on leaf expansion and photoinhibition

High energy ultraviolet-A (UV-A) and violet photons are at the edge of photosynthetically active radiation and may induce damage to sensitive metabolic pathways. The increasing use of light emitting diodes (LEDs) that provide these photons makes it important to better understand their effects on horticultural crops. We compared the effects of UV-A/violet photons to blue photons on short-term photosynthetic efficiency and long-term growth and morphological responses of lettuce ‘Rex’ and cucumber ‘Straight Eight’ under high and low photon flux densities (PFD). All plants received 67 % of the total PFD from white LEDs with the remaining 33 % of the photons from either blue (peak at 442 nm) or UV-A/violet LEDs (peak at 404 nm). Under a high PFD (500 μmol m−2 s−1; 16 hr photoperiod), the UV-A/violet photon treatment increased leaf area (by 24 %) and dry mass (by 17 %) in cucumber. In contrast, ‘Rex’ lettuce plants grown with UV-A/violet photons had significantly reduced chlorophyll content, leaf area, leaf photosynthetic rate, Fv/Fm ratio (indication of photoinhibition) and dry mass. The photoinhibition induced by UV-A/violet photons was reversible. Chlorophyll concentration of ‘Rex’ lettuce dramatically increased 2 days after being transferred from the UV-A/violet + white treatment to the blue + white light treatment, and plants regained full photosynthetic capacity after one week. The photoinhibition was also dose-dependent and did not occur when the photon flux density of UV-A/violet photons was reduced by 50 % at a lower daily light integral. We further evaluated the effects of UV-A/violet photons on three additional lettuce cultivars. Contrary to the detrimental effects in ‘Rex’ lettuce, UV-A/violet photons significantly increased leaf area and dry mass of ‘Marshall’ and tended to improve growth of ‘Parris Island’ and ‘Red Salad Bowl’ (although not statistically significant). Our analysis revealed that ‘Rex’ lettuce contained much lower levels of photoprotective pigments carotenoids and anthocyanins than other cultivars. We conclude that differences in photoprotective pigments are likely responsible for the contrasting responses to UV-A/violet photons.

The double heterostructure photocatalyst MoS2@ZIF-67/TiO2: Triumphant modification of TiO2 and efficient removal of Karenia mikimotoi

Water eutrophication led to the occurrence of harmful algal blooms (HABs) with the increase of urban sewage and industrial wastewater. As a periodic ecological disaster, it caused serious harm to the ecological environment (including the destruction of the food chain and the death of animals, etc.) and human health. Karenia mikimotoi (K. mikimotoi) was a kind of common algae that caused red tides, and it could produce harmful toxins. Therefore, a composite photocatalyst MoS2@ZIF-67/TiO2 (MZ/T) for the inactivation of K. mikimotoi was synthesized by a simple and easy-to-operate hydrothermal synthesis method. The MoS2@ZIF-67 nanoflowers were attached by the grainy TiO2. The composite photocatalyst MZ/T showed excellent photocatalytic performance, and the inactivation efficiency of MZ/T was up to 97.2 % in 4 h and 99.45 % in 12 h. The composite photocatalyst MZ/T could inactivate algal cells by destroying cell membrane structure, reducing chlorophyll content, soluble protein content. This study would provide a novel photocatalyst for water treatment of HABs.

Light quality regulates plant biomass and fruit quality through a photoreceptor-dependent HY5-LHC/CYCB module in tomato

Abstract Increasing photosynthesis and light capture offers possibilities for improving crop yield and provides a sustainable way to meet the increasing global demand for food. However, the poor light transmittance of transparent plastic films and shade avoidance at high planting density seriously reduce photosynthesis and alter fruit quality in vegetable crops, and therefore it is important to investigate the mechanisms of light signaling regulation of photosynthesis and metabolism in tomato (Solanum lycopersicum). Here, a combination of red, blue, and white (R1W1B0.5) light promoted the accumulation of chlorophyll, carotenoid, and anthocyanin, and enhanced photosynthesis and electron transport rates by increasing the density of active reaction centers and the expression of the genes LIGHT-HARVESTING COMPLEX B (SlLHCB) and A (SlLHCA), resulting in increased plant biomass. In addition, R1W1B0.5 light induced carotenoid accumulation and fruit ripening by decreasing the expression of LYCOPENE β-CYCLASE (SlCYCB). Disruption of SlCYCB largely induced fruit lycopene accumulation, and reduced chlorophyll content and photosynthesis in leaves under red, blue, and white light. Molecular studies showed that ELONGATED HYPOCOTYL 5 (SlHY5) directly activated SlCYCB, SlLHCB, and SlLHCA expression to enhance chlorophyll accumulation and photosynthesis. Furthermore, R1W1B0.5 light-induced chlorophyll accumulation, photosynthesis, and SlHY5 expression were largely decreased in the slphyb1cry1 mutant. Collectively, R1W1B0.5 light noticeably promoted photosynthesis, biomass, and fruit quality through the photoreceptor (SlPHYB1 and SlCRY1)-SlHY5-SlLHCA/B/SlCYCB module in tomato. Thus, the manipulation of light environments in protected agriculture is a crucial tool to regulate the two vital agronomic traits related to crop production efficiency and fruit nutritional quality in tomato.