chlorophyll-a and pyrene

Photosynthesis mediated by chlorophyll metabolism is the basis for plant growth, and also the important regulatory mechanism of carbon pool in cropland ecosystems. Soil organic pollutants induced growth inhibition in crop plants, herein, we conducted an in-depth investigation on the effects of three representative polycyclic aromatic hydrocarbons (PAHs), including phenanthrene (PHE), pyrene (PYR), and benzo[a]pyrene (BaP) on rice (Oryza sativa) growth and photosynthesis. PAHs were absorbed via root uptake and accumulated in leaves, causing the swelling of thylakoids and the increase of osmiophilic granules in chloroplasts. The actual quantum efficiency of PSII was significantly decreased under the stress of PHE, PYR, and BaP by 29.9%, 11.9%, and 24.1% respectively, indicating the inhibition in photon absorption and transfer, which was consistent with the decrease of chlorophyll a (22.3%-32.2% compared to the control) in rice leaves. Twenty-two encoding genes involved in chlorophyll metabolism were determined and the results indicated that the expression of chlorophyll synthetases was downregulated by over 50% whereas the degradation process was promoted. Consequently, the production of carbohydrates and the carbon fixation were inhibited, which revealed by the downregulation of intermediate metabolites in Calvin cycle and the declined carboxylation rate. The disturbed photosynthesis resulted in the decrease of the biomasses of both roots (21.0%-42.7%) and leaves (6.4%-22.1%) under the tested PAH stresses. The findings of this study implied that the photosynthetic inhibition was possibly attributed to the disorder of chlorophyll metabolism, thus providing novel insights into the mechanism of growth inhibition induced by organic pollutants and theoretical basis for the estimation of cropland carbon sequestration potential.

Topics: Chlorophyll; Chlorophyll A; Ecosystem; Environmental Pollutants; Oryza; Photosynthesis; Polycyclic Aromatic Hydrocarbons

Syagrus coronata, a native palm tree of the Brazilian semi-arid region, exhibits low germinability due to seed dormancy. This study aimed to increase the germinability, analyze the morphology of seedlings and evaluate the performance of young plants under a water deficit. We used immersion in water and gibberellic acid (GA3) as pyrene (seed with endocarp) pre-germination treatments, and we analyzed the water relations, gas exchange, chlorophyll fluorescence and carbon balance components of young plants under drought and rehydration conditions. The immersion of pyrenes in 0.3 mM GA3 solution for 24 h enhanced the emergence and survival of plants and the emergence rate index. The germination of S. coronata is of the remote tubular type, and seedling growth originates with the protrusion of the cotyledon petiole, followed by the subsequent emergence of the root, leaf sheaths and eophyll. The plants exhibited high tolerance to no irrigation for 37 days, which was attributed to strong stomatal control, a higher proportion of energy dissipation and a higher content of photoprotective pigments. Despite the reduced stomatal conductance (regardless of soil water availability), the photosynthetic rate remained high throughout the day, which indicated a low correlation between these two parameters. After rehydration, we observed that both the leaf water content and photosynthesis recovered, which showed an absence of irreversible damage of the photosynthetic apparatus. The use of 0.3 mM GA3 is recommended as a treatment for overcoming seed dormancy in this species. Young S. coronata plants showed high tolerance during drought and resilience after rehydration by adjusting their leaf metabolism, which could explain the endemism of this species in semi-arid regions and its ability to remain evergreen throughout the year. Furthermore, with high photosynthetic rate in the most favorable time of day, even under drought stress.

Topics: Arecaceae; Carbohydrates; Chlorophyll; Droughts; Fluorescence; Gases; Germination; Gibberellins; Plant Dormancy; Pyrenes; Seedlings; Seeds; Solubility; Stress, Physiological; Vapor Pressure; Water

In order to investigate the effects of soil microorganisms on biochemical and physiological response of plants to PAHs, PAH-degrading bacteria (Acinetobacter sp.) and/or arbuscular mycorrhizal fungus (Glomus mosseae) were inoculated with ryegrass (Lolium multiflorum) under four different concentrations of phenanthrene and pyrene (0, 50 + 50, 100 + 100, 200 + 200 mg kg(-1)) in soils. Acinetobacter sp. played limited roles on the growth of ryegrass, chlorophyll content, water soluble carbohydrate content, malondialdehyde (MDA) content, activities of superoxide dismutase (SOD) and peroxidase (POD) in shoot. By contrast, G. mosseae significantly (P < 0.01) increased ryegrass growth, partially by improving the photosynthetic activity through increasing the chlorophyll content in shoot. G. mosseae also significantly decreased MDA content in shoot. However, G. mosseae significantly increased SOD activity in shoot, which seemed to be resulted from significantly higher pyrene concentrations in shoot. The present study suggested that AM fungi could reduce the damage of cell membranes caused by free radicals, which may be one of the mechanisms involved in mycorrhizal alleviation of plant stress under PAHs. The present study indicated that the dual inoculation was superior to single inoculation in remediating PAHs contaminated soils.

Topics: Acinetobacter; Antioxidants; Biodegradation, Environmental; Carbohydrates; Chlorophyll; Glomeromycota; Lolium; Malondialdehyde; Mycorrhizae; Phenanthrenes; Plant Roots; Plant Shoots; Polycyclic Aromatic Hydrocarbons; Pyrenes; Soil; Stress, Physiological; Water

The present study was carried out to investigate the effects of exogenously applied 24-epibrassinolide (BR) on growth, gas exchange, chlorophyll fluorescence characteristics, lipid peroxidation and antioxidant systems of tomato seedlings grown under different levels (0, 10, 30, 100 and 300μM) of phenanthrene (PHE) and pyrene (PYR) in hydroponics. A concentration-dependent decrease in growth, photosynthetic pigment contents, net photosynthetic rate (Pn), stomatal conductance (Gs), maximal quantum yield of PSII (Fv/Fm), effective quantum yield of PSII (Φ(PSII)), photochemical quenching coefficient (qP) has been observed following PHE and PYR exposure. By contrast, non-photochemical quenching coefficient (NPQ) was increased. PHE was found to induce higher stress than PYR. However, foliar or root application of BR (50nM and 5nM, respectively) alleviated all those depressions with a sharp improvement in the activity of photosynthetic machinery. The activities of guaicol peroxidase (GPOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) as well as content of malondialdehyde (MDA) were increased in a dose-dependent manner under PHE or PYR treatments. Compared with control the highest increments of GPOD, CAT, APX, GR and MDA by PHE/PYR alone treatments were observed following 300μM concentration, which were 67%, 87%, 53%, 95% and 74% by PHE and 42%, 53%, 30%, 86% and 62% by PYR, respectively. In addition, both reduced glutathione (GSH) and oxidized glutathione (GSSG) were induced by PHE or PYR. Interestingly, BR application in either form further increased enzymatic and non enzymatic antioxidants in tomato roots treated with PHE or PYR. Our results suggest that BR has an anti-stress effect on tomato seedlings contaminated with PHE or PYR and this effect is mainly attributed by increased detoxification activity.

Topics: Ascorbate Peroxidases; Brassinosteroids; Catalase; Chlorophyll; Glutathione Reductase; Malondialdehyde; Phenanthrenes; Photosynthesis; Plant Growth Regulators; Pyrenes; Soil Pollutants; Solanum lycopersicum; Steroids, Heterocyclic

The effects of polycyclic aromatic hydrocarbon (PAH) (pyrene) on superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase, peroxidase, malondialdehyde (MDA) and proline were studied in leaves, stems and roots of Bruguiera gymnorrhiza. The results showed that the responses of enzymatic and non-enzymatic antioxidants varied significantly among the three tissues studied. The activities of antioxidant enzymes in PAH-treated stems and roots fluctuated in different stress levels compared to the controls, while the antioxidant enzymes such as SOD, APX in leaves increased when stressed by PAH with a significant positive relation between PAH and leaf SOD or APX activity. Low PAH treatments could also stimulate proline in leaves and stems. MDA content was obviously accumulated in stems and roots under PAH stress while decreased in leaves, indicating that the increased antioxidant enzymes in leaves may partly alleviate lipid peroxidation. For pollution monitoring purpose, SOD and APX in leaves may be potential biomarkers of PAH pollution in intertidal estuaries.

Topics: Antioxidants; Ascorbate Peroxidases; Chlorophyll; Environmental Monitoring; Lipid Peroxidation; Malondialdehyde; Plant Leaves; Plant Roots; Proline; Pyrenes; Rhizophoraceae; Superoxide Dismutase

With indoor static stimulation test, this paper studied the effects of different concentrations (0.01, 0.02, 0.05, 0.07 and 0.1 mg x L(-1)) pyrene on the pyrene accumulation, free radical, antioxidant defenses, and the contents of chlorophyll and soluble sugar in Vallisneria spiralis. The results showed that after 10 days exposure to pyrene, V. spiralis leaf could accumulate large amount of pyrene. The free radical generation, peroxidase (POD) activity and malondialdehyde (MDA) content had a persistent increase, but the increment decreased when exposed to higher concentrations (> 0.05 mg x L(-1) pyrene. Glutathione S-transferase (GST) activity and oxidized glutathione (GSSG) and soluble sugar contents increased with increasing concentration of pyrene, while reduced glutathione (GSH) and chlorophyll contents were in adverse. It was concluded that V. spiralis was sensitive to pyrene, and the stress effect would happen at 0.01 mg x L(-1) of pyrene.

Topics: Carbohydrates; Chlorophyll; Glutathione Transferase; Hydrocharitaceae; Malondialdehyde; Peroxidase; Plant Leaves; Pyrenes; Water Pollutants