Significant Decrease In Chlorophyll Research Articles

A novel transcription factor FnMYB4 regulates pigments metabolism of yellow leaf mutants in Fragaria nilgerrensis

The strawberry species Fragaria nilgerrensis Schlechtendal ex J. Gay, renowned for its distinctive white, fragrant peach-like fruits and strong disease resistance, is an exceptional research material. In a previous study, an ethyl methane sulfonate (EMS) mutant library was established for this species, resulting in various yellow leaf mutants. Leaf yellowing materials are not only the ideal materials for basic studies on photosynthesis mechanism, chloroplast development, and molecular regulation of various pigments, but also have important utilization value in ornamental plants breeding. The present study focused on four distinct yellow leaf mutants: mottled yellow leaf (MO), yellow green leaf (YG), light green leaf (LG), and buddha light leaf (BU). The results revealed that the flavonoid content and carotenoid-to-chlorophyll ratio exhibited a significant increase among these mutants, while experiencing a significant decrease in chlorophyll and carotenoid contents compared to the wild type (WT). To clarify the regulatory mechanisms and network relationships underlying these mutants, the RNA-seq and weighted gene co-expression network (WGCNA) analyses were employed. The results showed flavonoid metabolism pathway was enriched both in MO and YG mutants, while the chlorophyll biosynthesis pathway and carotenoid degradation pathway were only enriched in MO and YG mutants, respectively. Subsequently, key structural genes and transcription factors were identified on metabolic pathways of three pigments through correlation analyses and quantitative experiments. Furthermore, a R2R3-MYB transcription factor, FnMYB4, was confirmed to be positively correlated with flavonoid synthesis through transient overexpression, virus-induced gene silencing (VIGS), and RNA interference (RNAi), accompanying by reoccurrence and attenuation of mutant phenotype. Finally, dual-luciferase (LUC) and yeast one-hybrid assays confirmed the binding of FnMYB4 to the FnFLS and FnF3H promoters, indicating that FnMYB4 positively regulates flavonoid synthesis. In addition, correlation analyses suggested that FnMYB4 also might be involved in chlorophyll and carotenoid metabolisms. These findings demonstrated the pivotal regulatory role of FnMYB4 in strawberry leaf coloration.

Physiological and Transcriptomic Analysis of ‘Candidatus Phytoplasma pruni’ Infection in Prunus persica

‘ Candidatus Phytoplasma pruni’ is the causative agent of X-disease on peach ( Prunus persica) trees. Infected trees exhibit premature yellowing, leaf necrosis causing a shot-hole appearance, limb dieback, and eventual death. How pathogen infection leads to these symptoms is unknown. This study undertook a modern characterization of the disease by assessing the physiological and transcriptomic consequences of phytoplasma infection. Phytoplasma titer was high in the symptomatic tissues and undetected or low in asymptomatic tissues. Symptomatic leaves had a significant decrease in chlorophyll a, chlorophyll b, and carotenoids. Transcriptomic analysis showed alterations in genes related to phytohormone synthesis and signaling, circadian rhythms, lignification, and sugar synthesis and transport. Several transcripts that might be related to symptom development were identified. Collectively, these data give a much clearer picture of symptom development in ‘ Ca. P. pruni’-infected P. persica and provide several avenues for further research in determining how ‘ Ca. P. pruni’ interacts with its host to elicit the observed symptoms. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Effects of Salinity Stress on Growth and Physiological Parameters and Related Gene Expression in Different Ecotypes of Sesuvium portulacastrum on Hainan Island.

We conducted a study to examine the growth and physiological changes in 12 different ecotypes of Sesuvium portulacastrum collected from Hainan Island in China. These ecotypes were subjected to different concentrations (0, 200, 400, and 600 mmol/L) of sodium chloride (NaCl) salt stress for 14 days. We also analyzed the expression of metabolic genes related to stress response. Under low salt stress, indicators such as plant height in region K (0 mmol/L: 45% and highest at 200 mmol/L: 80%), internode length (0 mmol/L: 0.38, 200 mmol/L: 0.87, 400 mmol/L: 0.25, and 600 mmol/L: 1.35), as well as leaf area, relative water content, fresh weight, and dry weight exhibited an overall increasing trend with the increase in salt concentration. However, as the salt concentration increased, these indicators showed a decreasing trend. Proline and malondialdehyde contents increased with higher salt concentrations. When the NaCl concentration was 400 mmol/L, MDA content in the leaves was highest in the regions E (196.23%), F (94.28%), J (170.10%), and K (136.08%) as compared to the control group, respectively. Most materials demonstrated a significant decrease in chlorophyll a, chlorophyll b, and total chlorophyll content compared to the control group. Furthermore, the ratio of chlorophyll a to chlorophyll b (Rab) varied among different materials. Using principal component analysis, we identified three ecotypes (L from Xinglong Village, Danzhou City; B from Shuigoupo Village, Lingshui County; and J from Haidongfang Park, Dongfang City) that represented high, medium, and low salt tolerance levels, respectively, based on the above growth and physiological indexes. To further investigate the expression changes of related genes at the transcriptional level, we employed qRT-PCR. The results showed that the relative expression of SpP5CS1, SpLOX1, and SpLOX1 genes increased with higher salt concentrations, which corresponded to the accumulation of proline and malondialdehyde content, respectively. However, the relative expression of SpCHL1a and SpCHL1b did not exhibit a consistent pattern. This study contributes to our understanding of the salt tolerance mechanism in the true halophyte S. portulacastrum, providing a solid theoretical foundation for further research in this field.

Evaluation of nano-silicon efficiency on compatible solutes and nutrient status of Damask rose affected by in vitro simulated drought stress

BackgroundDrought stress is a critical environmental factor that disturbs plant performance. However, some non-essential elements such as silicon can improve water deficit tolerance by modulating photosynthesis assimilates and compatible solutes production. Therefore, the present work was conducted to modulate polyethylene glycol (PEG)-induced water deficiency under in vitro culture in Damask rose genotypes (Maragheh and Kashan) by nano-silicon (SiO2-NPs) treatment. A completely randomized factorial experiment was used as three concentrations of SiO2-NPs (0, 50, and 100 mg L−1) and five concentrations of PEG (0, 25, 50, 75, and 100 g L−1). Then, the comparative effects of water deficiency on vegetative traits, metabolites, and nutrients were studied.ResultsThe drought promoted a significant decrease in chlorophyll, fresh/dry weight, biomass, and an increase in electrolyte leakage. The amount of micro- and macronutrients were affected by drought stress and decreased in both genotypes. In contrast, the activity of polyphenol oxidase (PPO) and total phenolic compounds (TPC) along with biochemical traits was increased. Treatment with SiO2-NPs improved the leaf area index (LAI), chlorophyll, and biomass under severe water deficiency. The concentration of compatible solutes such as carbohydrates, total flavonoid content (TFC), TPC, anthocyanin, and antioxidative capacity enhanced by the application of SiO2-NPs by about twofolded. As well as an increase in PEG concentration, the absorption of nutritional elements such as P, K, Mn, Fe, Zn, and Cu was decreased. However, SiO2-NPs application especially at 100 mg L−1 increased the amount of nutrient absorption.ConclusionsIn general, the drought tolerance in Damask rose was associated mainly with its suitable manipulation of antioxidant production and orderly enhancement of nutrient adsorption, so that the effect of SiO2-NPs in improving the qualitative and quantitative characteristics of ʻKashanʼ was more than that of ʻMaraghehʼ. These results briefly highlight that the SiO2-NPs may provide greater tolerance to drought stress in Damask rose.Graphical

Phytochemical Profile and Antioxidant Capacity of Viscum album L. Subsp. album and Effects on Its Host Trees.

Viscum album L. subsp. album is a hemiparasitic plant that is recognized as a medicinal plant due to its beneficial effects, including anti-tumor activity, antioxidant, anti-inflammatory, anti-hepatotoxic, hypoglycemic, and antimicrobial properties as well as for lowering blood pressure. On the other hand, mistletoe is a biotic stressor for both deciduous trees and conifers. Our main aim was to evidence the influence of mistletoe on the content of chlorophylls, proline, total phenols, flavonoids, and antioxidant capacity of leaves from tree host trees (Malus domestica, Prunus domestica, and Populus alba) that grow on the northwest of Romania. In addition, HPLC-DAD-MS-ESI+ was used to analyze the phenolic acid and flavonoid profiles of V. album L. subsp. album leaves according to their parasitized hosts. A significant decrease in chlorophyll a level of approximately 32% was detected in poplars infested with mistletoe, followed by infested apples and plums with pigment reductions of 29.25% and 9.65%, respectively. The content of total phenols and flavonoids in the parasitized trees was higher compared to the non-parasitized ones. In the case of poplar, which presented the highest incidence of mistletoe infestation (70.37%), the content of total phenols in the leaves was two times higher compared to non-infested leaves. Based on HPLC chromatographic analysis, leaves of mistletoe growing on apple (VAM) had the highest content of phenolic acids (7.833 mg/g dw), followed by mistletoe leaves on poplar (VAO) and plum (VAP) (7.033 mg/g dw and, respectively, 5.559 mg/g dw). Among the flavonols, the predominant component was Rhamnazin glucosides in the amount of 1.025 ± 0.08 mg/g dw in VAO, followed by VAP and VAM (0.514 ± 0.04 and 0.478 ± 0.04 mg/g dw, respectively). Although our results show that mistletoe negatively influences the host trees, it is still a valuable plant that must be exploited to bring benefits to human health.

Titanium dioxide nanoparticles mitigate cadmium toxicity in Coriandrum sativum L. through modulating antioxidant system, stress markers and reducing cadmium uptake

Anthropogenic activities are the foremost reason of metal pollution in soils of the cultivated areas, resulting abnormal physiochemical processes in plants. Among metals contaminants, cadmium (Cd) is one of the most injurious contaminants that deleteriously affect physiological activities, growth and yield of the crop plants. Keeping in view the stress mitigation potential of titanium dioxide (TiO2), the existing research work was premeditated to inspect the beneficial role of seed priming with titanium dioxide nanoparticles (TiO2-NPs) on biochemical, morphological and physiological characteristics of Coriandrum sativum L. (coriander) plants under Cd stress. For this purpose, C. sativum seeds were primed with 0, 40, 80 and 160 mg L−1 TiO2-NPs. Cadmium stress triggered a significant decrease in chlorophyll a content (49%), chlorophyll b content (44%), photosynthetic rate (62%) and plant growth (51%) as compared with control. Tanium dioxide nanoparticles treated seedlings exhibited reduced Cd contents besides improved agronomic traits (seedlings biomass, number of seeds and yield). The TiO2-NPs treatment declined the magnitude of EL and MDA by 1.5 fold and 1.71 fold, respectively. Furthermore, TiO2-NPs diminished oxidative injuries in plants exposed to Cd stress. Additionally, TiO2-NPs enhanced the biosynthesis of osmatic regulators (proline) by 47% which helped in the mitigation of Cd persuaded toxicity in plants. Briefly, treatment of 80 mg L−1 TiO2-NPs perhaps ameliorates the deleterious influence of Cd stress and enhance the yield of coriander.

Titanium Dioxide Nanoparticles Mitigate Cadmium Toxicity in <i>Coriandrum Sativum</i> L. Through Modulating Antioxidant System, Stress Markers and Reducing Cadmium Uptake

Among metals contaminants, cadmium (Cd) is one of the most injurious contaminants that deleteriously affect physiological activities and growth of the plants. Cadmium declines growth of plants through impelling the photosynthetic activity and antioxidant enzymatic activities. Cadmium induced toxicity enriches the synthesis of reactive oxygen species causing membranous injuries and reduction of photosynthesis in plants. Cadmium toxicity results poor growth and yield of crop plants. Keeping in view the stress mitigation potential of titanium dioxide (TiO2), the existing research work was premeditated to inspect the beneficial role of seed priming with titanium dioxide nanoparticles (TiO2-NPs) on biochemical, morphological and physiological characteristics of Coriandrum Sativum L. (coriander) plants under Cd stress. For this purpose, C. sativum seeds were primed with 0, 40, 80 and 160 mg L −1 TiO2-NPs. Cadmium stress triggered a significant decrease in chlorophyll a content (49 %), chlorophyll b content (44 %), photosynthetic rate (62 %) and plant growth (51 %) as compared with control. TiO2-NPs treated seedlings exhibited reduced Cd contents besides improved agronomic traits (seedlings biomass, number of seeds and yield). The 2-NPs treatment declined the magnitude of EL and MDA by 1.5 fold and 1.71 fold respectively. Additionally, TiO2-NPs diminished oxidative injuries in plants exposed to Cd stress. Additionally, TiO2-NPs enhanced the biosynthesis of osmatic regulators (proline) by 47 % which helped in mitigation of Cd persuaded toxicity in plants. Furthermore, the maximum amount of essential oil production (37 %) and carbohydrate content (47 %) was attained in 80 mg L−1 TiO2-NPs supplemented plants under control circumstances. Briefly, treatment of 80 mg L −1 TiO2-NPs perhaps ameliorate the deleterious influence of Cd stress and enhance the yield of coriander.

Spermine alleviates heat-induced senescence in creeping bentgrass by regulating water and oxidative balance, photosynthesis, and heat shock proteins

Spermine (SPM) is involved in response to abiotic stress in plants, but the potential role of SPM in regulating senescence has not been well documented. Objectives of this study were to examine the effect of changes in endogenous polyamines (PAs) by SPM application on improving heat tolerance of creeping bentgrass (Agrostis stolonifera) and explore the SPM-regulated senescence associated with alterations of water and oxidative balance, photosynthesis, and heat shock proteins under heat stress. The results showed that persistent high temperature caused severe oxidative damage and significant decreases in chlorophyll (Chl) content, photosynthetic efficiency, and leaf water content leading to premature senescence in creeping bentgrass, as reflected by a significant upregulation of transcriptions of senescence-associated genes (AsSAG39, Ash36, and Asl20). The improvement of endogenous spermidine (SPD) and SPM content induced by SPM application could significantly alleviate heat stress damage to creeping bentgrass through maintaining higher Chl content, net photosynthetic rate, photochemical efficiency, and performance index on absorption basis, promoting osmotic adjustment ability and antioxidant enzyme (superoxid dismutase, catalase, peroxidase, and ascorbate peroxidase) activities to enhance the scavenging capacity of reactive oxygen species, and upregulating transcriptions of heat shock protein (HSP) genes (HSP90-5, HSP90.1-b1, HSP82, HSP70, HSP26.7, HSP17.8, and HSP12) helping to maintain normal synthesis and functions of proteins under high temperature stress, thereby delaying heat-induced leaf senescence. These findings reveal an important role of PAs in regulating senescence in perennial plants exposed to a high temperature environment.

The influence of laser beam and high light intensity on lentil (Lens culinaris) and wheat (Triticum aestivum) seedlings growth and metabolism

Light is considered as an environmental signal that controls plants growth and development. Sufficient duration, quality and wavelength are mainly responsible for switching on/off many physiological processes. The aim of this study was to examine the role of gamma aminobutyric acid (GABA) shunt pathway specific response in wheat (Triticum aestivum) and lentil (Lens culinaris) seedlings to blue LED laser (intensity= 1.48 W/cm2) and high intensity invisible ultraviolet light (intensity= 3.99 W/cm2) treatments separately, with respect to: seed germination, seedling growth, oxidative damage in term of reactive oxygen substances accumulation, GABA accumulation level, total proteins and total carbohydrates level and glutamate decarboxylase gene (GAD) expression. Data showed a remarkable changes in proteins content, carbohydrates content, chlorophyll level, dry and fresh weight, GABA accumulation, MDA level, and GAD m-RNA level under blue LED laser and high intensity invisible ultraviolet light treatments; separately in the both wheat and lentil cultivars. There were no significant differences of root emergence in all cultivars under all treatments. The concentrations of MDA increased in all cultivars under blue LED laser and high intensity invisible ultraviolet light treatments with increasing exposure durations. GABA levels increased and correlated significantly in all cultivars as the exposure duration of blue LED laser and high light intensity increased. Significant decrease in chlorophyll a and b contents in Um Qayes, Jordan1 and Jordan2 cultivars under all laser and high intensity invisible ultraviolet light treatments. A significant difference was found in proteins content in all cultivars in response to laser and high intensity invisible ultraviolet light treatments. Carbohydrates content in all cultivars used in this study were significantly decreased under laser treatments. The transcription level of GAD increased significantly under blue LED laser and high intensity invisible ultraviolet light in all cultivars used in this study. GAD expression was high in Hurani75 cultivar in agreement with the low level of GABA accumulation under high intensity invisible ultraviolet light at 60 min which strongly suggested that GABA was catabolized to enter another pathways (C:N balance) that was confirmed by increase in higher level of carbohydrates and proteins beside reduction in MDA content at the same exposure duration. On other hand, GAD expression in Jordan 2 was lower in response to laser treatment under the same exposure duration. The high increase of GAD gene expression explains the high accumulation of GABA level under both treatments. Results indicated that GABA shunt is a key metabolic pathway that allows wheat and lentil to adapt blue LED laser and high intensity invisible ultraviolet light stressful treatments.

Physiological and biochemical responses of selected cowpea (Vigna unguiculata (L.) Walp.) accessions to iron toxicity

This study aimed to investigate the effect of iron toxicity in cowpea using physiological and biochemical responses of selected accessions. Fifteen accessions of cowpea were exposed to two treatments of iron using FeSO4 solution (100 mg l-1 and 400 mg l-1) and distilled water at pH 6.2 as control. The results showed that there was a general reduction in germination morphology; germination percentage among the 400 mg l-1 Fe-treated accessions. Seed mortality rates were significantly higher among the 400 mg l-1Fe-treated accessions (> 35 %). Water imbibition capacity and relative mass gained were higher for Fe-treated accessions. Furthermore, significant increase in the total sugar and percentage utilization of sugars was accompanied by an insignificant decrease in chlorophyll a, a significant decrease in chlorophyll b contents and the persistence of foliar chlorosis, among the 400 mg l-1 Fe-treated accessions. MDA levels were significantly increased while proline remained unchanged, mean SOD activity was insignificantly increased, whereas Cat decreased among the 400 mg l-1 Fe-treated accessions. Documentation of these observable changes in physiological and biochemical parameters will be useful in understanding the impact of elevated iron concentrations on the cultivation of cowpea accessions in soils associated with ferruginous ultisols.

Effect of putrescine application on some growth, biochemical and anatomical characteristics of Thymus vulgaris L. under drought stress

This study investigated the effect of foliar application of putrescine on growth, biochemical, essential oil percent and morpho-anatomical characteristics of Thymus vulgaris L. under water deficit conditions. In pot experiments, plants were grown under two different irrigation levels 70–80% and 30–40% of water holding capacity and foliar sprayed with putrescine at 0, 0.1 and 0.2 mM twice at 10 and 50 days after transplanting. The results indicated that water stress caused significant reductions in the shoot, root fresh and dry weights whereas there was a significant increase in shoot/root dry matter ratio. Moreover, water stress led to multiple significant decreases in chlorophyll a, b concentration and chlorophyll a/b ratio. Whereas significant increases in the total soluble phenolic compounds and the activities of phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO) enzymes and the essential oil percent were detected in plants exposed to drought stress. Stressed plants induced some morph-anatomical changes in roots, stems, and leaves to avoid tissue dehydration. Otherwise, putrescine reduce the impacts of drought by changing anatomical features, keeping chlorophyll concentrations, accumulation of total soluble phenolic compounds and activities some related enzymes. Consequently putrescine has the ability to improve growth and oil yield hence allowing thyme plants to grow better under water stress condition.

Impacts of warming and water deficit on antioxidant responses in Panicum maximum Jacq.

Agricultural activities are affected by many biotic and abiotic stresses associated with global climate change. Predicting the response of plants to abiotic stress under future climate scenarios requires an understanding of plant biochemical performance in simulated stress conditions. In this study, the antioxidant response of Panicum maximum Jacq. cv. Mombaça exposed to warming (+2°C above ambient temperature) (eT), water deficit (wS) and the combination eT + wS was analysed under field conditions using a temperature free-air-controlled enhancement facility. Warming was applied during the entire growth period. Data were collected at 13, 19 and 37 days after the start of the water deficit treatment (DAT) and at two sampling times (6:00 and 12:00 h). A significant decrease in chlorophyll was observed under the wS treatment, but an increment in total chlorophyll was observed in eT + wS, particularly at 19 DAT. Significant increase in H2 O2 content, malondialdehyde and protein oxidation was observed in the wS treatment at noon of the third sampling. In the combined wS + eT stress treatment, the activity of the enzymatic antioxidant system increased, particularly of superoxide dismutase (SOD; EC 1.15.1.1) and ascorbate peroxidase (APX; EC 1.11.1.11). The chlorophyll fluorescence images showed that the photochemical performance was not significantly affected by the treatments. In conclusion, under simulated future warming and water stress conditions, the photosystem II (PSII) activity of P. maximum acclimated to moderate warming and a water-stressed environment associated with a relatively favourable antioxidant response, particularly in the activity of APX and SOD.

CHANGES IN CHLOROPHYLL a FLUORESCENCE AND PIGMENTS COMPOSITION IN OAK LEAVES WITH GALLS OF TWO CYNIPID SPECIES (Hymenoptera, Cynipidae)

Gall-inducing insects may cause multiple physiological changes in host plants, such as the loss of photosynthetic pigments and reduced photosynthetic capacity. However, the direction of these changes is usually insect species-dependent. Therefore, the objective of this research was to characterize the indirect effects of galls induced by asexual generation of Neuroterus numismalis (Fourc.) and N. quercusbaccarum L. on photosynthesis by comparing changes in photosynthetic and photoprotective pigments and chlorophyll a fluorescence in foliar tissue with and without galls in naturally growing pedunculate oak trees (Quercus robur L.). The presence of galls of both Cynipidae species caused a significant decrease of chlorophyll a, b and carotenoids contents. Moreover, photosynthetic parameters (F0, Fm, Fv/Fm, Y, qP, qN) were significantly decreased. These results provide valuable information for diagnosing the oak infections using a non-invasive method, such as chlorophyll a fluorescence and predicting the effect of infections on photosynthetic productivity.

Impacts of ultraviolet radiation on certain physiological and biochemical processes in cyanobacteria inhabiting diverse habitats

Certain physiological and biochemical processes of Fischerella sp. strain HKAR-13 and Nostoc sp. strain HKAR-2 isolated from paddy field and hot spring respectively were studied in response to ultraviolet radiation (UVR). Cultures were irradiated under varying combinations of UV-B, UV-A and photosynthetically active radiation (PAR). Significant decrease in chlorophyll a content was observed in Nostoc sp. strain HKAR-2 (19.31 to 4.08 μg/gfw) and Fischerella sp. strain HKAR-13 (13.55 to 3.40 μg/gfw) after 72 h of PAR + UV-A + UV-B (PAB) treatment. Total carotene content increased upto 36 h where as phycocyanin content decreased as exposure time increased in both the cyanobacteria. Photosystem II (PSII) activity decreased to about 88% and 93% in Nostoc sp. strain HKAR-2 and Fischerella sp. strain HKAR-13 respectively. Antioxidative activities of superoxide dismutase and catalase increased to 1.8–6.0 fold after 48 h of UVR exposure as compared to non-irradiated cultures. Additionally, Fischerella sp. strain HKAR-13 was also able to synthesize scytonemin that carry out UV-screening but its synthesis was not observed in Nostoc sp. strain HKAR-2. UVR also resulted in 3–5 fold increase in reactive oxygen species in Fischerella sp. strain HKAR-13 and 2.0–4.5 fold increase in Nostoc sp. strain HKAR-2. Significant decrease in ds DNA content and increase in malondialdehyde content was observed in both cyanobacterial strains. These results revealed that combined effects of UV-A + UV-B was more deleterious than UV-A and UV-B alone and Fischerella sp. strain HKAR-13 was more prone to UVR as compared to Nostoc sp. strain HKAR-2, a hot spring isolate. The more resistant cyanobacterium Nostoc sp. strain HKAR-2 can be used as inoculant in desert soil and production of various value added products.

Effect of some osmoregulators on photosynthesis, lipid peroxidation, antioxidative capacity, and productivity of barley (Hordeum vulgare L.) under water deficit stress.

Water deficit stress is an abiotic stress that causes reductions in growth and yield of many field crops around the world. The present research was aimed to elucidate the mitigating efficiency of exogenous application of select osmoregulators and biostimulants, i.e., potassium dihydrogen phosphate, actosol® (humic acid), Amino more (amino acids), and Compound fertilizer, applied as a spray that reached both foliage and the soil, on growth characteristics, antioxidant capacity, and productivity of barley (Hordeum vulgare L. Giza123) under water deficit stress during two successive growing seasons of field experiments in Egypt. Water deficit resulted in stress as estimated by stress indicators and decreased growth and poor health and development as reflected in statistically significant decreases in chlorophyll a and b and major nutrient (NPK) levels in tissues, stem length, number of leaves, and fresh and dry mass as well as yield components such as spike length, grains per spike, biological yield, grain yield, and 1000-grain weight. As a response to water deficit stress, reactive oxygen species (ROS, i.e., superoxide and hydrogen peroxide) levels increased significantly resulting in lipid peroxidation and decreased membrane integrity and significant increases in antioxidant enzymes such as catalase (CAT), polyphenol oxidase (PPO), and peroxidase (POX). All four treatments alleviated the detrimental impacts of water deficit stress as evidenced by statistically significantly increased photosynthetic pigment concentration, tissue NPK levels, growth, and yield parameters compared to the water deficit-stressed control, while the stress responses were significantly reduced. The osmoregulators used either partially restored the growth and yield of osmotic-stressed barley plants or certain treatments enhanced them. All osmoregulators tested mitigated the adverse impacts of water deficit stress on barley plants, but the highest induction was found when plants were treated with actosol®. The beneficial effects of the osmoregulators tested were the strongest overall in the order actosol® ˃ potassium dihydrogen phosphate ˃ Amino more ˃ Compound fertilizer.

COMPARATIVE STUDIES ON GROWTH, METABOLISM AND YIELD OF SESAME PLANT BY USING SEAWEED, PLANT EXTRACTS AND SOME GROWTH REGULATORS

A field experiments were carried out in season of 2016/2017 at Botanical garden, Botany and Microbiology Department, Faculty of Science, Al- Azhar University, Nasr City, Cairo, to study the role of bio stimulant (seaweed and plant leaves extracts as a liquid fertilizer) and some growth regulators (indole acetic acid and benzyl adenine) as comparative studies to select the better for improving the growth, biochemical constituents and yield of sesame plants. The results revealed that application leaves extracts of Punica granatum showed significant improvement effects on shoot length, number of pods/plant, weight of seeds / plant, contents of chlorophyll a; b; total chlorophyll (a+ b), carotenoids, total lipids, amylases and peroxidase activities of sesame plants as compared to the other treatments. Fresh and dry weight of shoot was significant increases by using Olea europaea leave and Sargassum latifolium water extracts. Carotenoids content was significant increase in response to all of bio stimulant growth regulators. Olea europaea, Carolina elongata leaves water extracts (5g/L) and benzyl adenine (50 ppm) caused significant decrease of chlorophyll a, b and a+b. Total soluble carbohydrates of shoots of sesame plants significantly decreased in response to Psidium guajava leaves extract compared to the control and other treatments. However, Olea europaea and benzyl adenine caused significant increase in total soluble carbohydrates at yield stage. All treatments caused significant increase of total lipids of sesame plants. Data cleared that, amylase and peroxidase activities significantly increased by all treatments.

Nano-fumed silica as a novel pollutant that inhibits the algicidal effect of p-hydroxybenzoic acid on Microcystis aeruginosa

ABSTRACTNanomaterials and/or contaminants are becoming more common in the developing world, but their effects on interspecific interactions are rarely reported, particularly in aquatic ecosystems. Thus, the present study determined the effects of the novel pollutant nano-fumed silica (NFS) on algal control by a macrophyte via the allelochemical p-hydroxybenzoic acid in a microcosm test. The allelochemical p-hydroxybenzoic acid caused significant decreases in chlorophyll a, but increased the amount of superoxide anion radicals () and the electric conductivity in Microcystis aeruginosa. The 50% inhibitory concentration (IC50) for p-hydroxybenzoic acid was 0.919 mmol/L in microalga during the exponential phase. Interestingly, NFS at 100–1600 mg/L had clear stimulatory effects on M. aeruginosa. When NFS at 800 mg/L was combined with different concentrations of p-hydroxybenzoic acid, the IC50 for p-hydroxybenzoic acid was 1.045 mmol/L. Thus, NFS significantly reduced the algicidal effect exhibited by p-hydroxybenzoic acid on M. aeruginosa. Furthermore, NFS might act as a silicon nutrient and enhance allelopathic resistance in M. aeruginosa to inhibit the algicidal effects of macrophytes via allelopathy. These findings suggest that before algal control is considered using macrophyte allelopathy, it is essential to remove the pollutant NFS from polluted lakes.

Can a low concentration of an organophosphate insecticide cause negative effects on an aquatic macrophyte? Exposure of Potamogeton pusillus at environmentally relevant chlorpyrifos concentrations

The contamination of the aquatic environments with organophosphorus pesticides may affect non-target organisms. The aim of this study was to evaluate the toxic effects of the insecticide chlorpyrifos (CPF) at environmental concentrations on the freshwater macrophyte Potamogeton pusillus belonging to a genus of worldwide distribution. For this purpose, individuals were exposed from 3.5 to 94.5ng of CPF L−1 for 96h. A battery of biochemical responses including bioaccumulation, defense and damage biomarkers were measured in leaf, stem and root. Even when CPF was not detected in the macrophyte tissues, our results showed that this insecticide promotes oxidative stress and biomolecule damages in P. pusillus after acute exposure. Significant response of biomarkers was observed from the lowest tested concentration (3.5ng CPF L−1). Oxidative stress was evidenced by increased lipid peroxidation and antioxidant enzymatic activation, including changes in superoxide dismutase, guaiacol peroxidase and glutathione peroxidase activities, especially in leaf. Also, a significant decrease in chlorophyll a and b contents was observed mainly in leaf. Finally, with some selected biomarkers, an Integrated Biomarker Response index was calculated showing a dose–response relationship with CPF exposure. Previous studies reported that herbicides and organophosphorus pesticides are responsible for several effects on photosynthetic systems but at higher exposure concentrations than the tested in this study. These results draw attention to the need for more studies in toxic effects of insecticides on aquatic macrophytes, at low concentrations and different biological levels, since the protection guidelines would not be preserving these species.

Effect of NaCl stress on chlorophyll content of isabgol (Plantago ovata Forsk.) genotypes

Chlorophyll content in leaves of isabgol (Plantago ovata Forsk.) genotypes viz., GI2, HI-96, PB-80 and HI-5 was studied under salt stress at different EC levels viz., control (without salt), 5 and 10 d/Sm of nutrient supplemented NaCl salt solutions in sand filled polythene bags. The results revealed a significant decrease in chlorophyll ‘a’ and chlorophyll ‘b’ contents with increasing EC levels. Reduction in chlorophyll ‘a’ and chlorophyll ‘b’ contents was maximum in the genotype PB-80 and minimum in the genotype GI-2 indicating the higher tolerance of genotype GI-2 and higher sensitivity of the genotype PB-80 to salt stress among all genotypes studied.

Leaf miner-induced morphological, physiological and molecular changes in mangrove plantAvicennia marina(Forsk.) Vierh

Avicennia marina (Forsk.) Vierh is a widespread mangrove species along the southeast coasts of China. Recently, the outbreak of herbivorous insect, Phyllocnistis citrella Stainton, a leaf miner, have impacted on the growth of A. marina. Little is reported about the responses of A. marina to leaf miner infection at the biochemical, physiological and molecular levels. Here, we reported the responses of A. marina to leaf miner infection from the aspects of leaf structure, photosynthesis, and antioxidant system and miner responsive genes expression. A. marina leaves attacked by the leaf miner exhibited significant decreases in chlorophyll, carbon and nitrogen contents, as well as a decreased photosynthetic rate. Scanning and transmission electron microscopic observations revealed that the leaf miner only invaded the upper epidermis and destroyed the epidermal cell, which lead to the exposure of salt glands. In addition, the chloroplasts of mined leaves (ML) were swollen and the thylakoids degraded. The maximal net photosynthetic rate, stomatal conductance (Gs), carboxylation efficiency (CE), dark respiration (Rd), light respiration (Rp) and quantum yields (AQE) significantly decreased in the ML, whereas the light saturation point (Lsp), light compensation point (Lcp), water loss and CO2 compensation point (Г) increased in the ML. Moreover, chlorophyll fluorescence features also had been changed by leaf miner attacks. Interestingly, higher generation rate of O2ˉ· and lower antioxidant enzyme expression in the mined portion (MP) were found; on the contrary, higher H2O2 level and higher antioxidant enzyme expression in the non-mined portion (NMP) were revealed, implying that the NMP may be able to sense that the leaf miner attacks had happened in the MP of the A. marina leaf via H2O2 signaling. Besides, the protein expression of glutathione S-transferase (GST) and the glutathione (GSH) content were increased in the ML. In addition, insect resistance-related gene expression such as chitinase 3, RAR1, topless and PIF3 had significantly increased in the ML. Taken together, our data suggest that leaf miners could significantly affect leaf structure, photosynthesis, the antioxidant system and miner responsive gene expression in A. marina leaves.