Elucidating growth and biochemical characteristics of rice seedlings under stress from chromium VI salt and nanoparticles.

Plants are usually provoked by a variety of heavy metal (HM) stressors that have adverse effects on their growth and other biochemical characterizations. Among the HMs, chromium has been considered the most toxic for both plants and animals. The present study was conducted to compare the phytotoxic effects of increasing chromium (VI) salt and nanoparticles (NPs) concentrations on various growth indexes of rice (Oryza sativa L. var. swat 1) seedlings grown in a hydroponic system. The 7-day rice seedlings were exposed to Cr (VI) salt and NPs hydroponic suspensions which were adjusted to the concentration of 0, 50, 100, 150, 200 and 250 mg/L. Both the Cr (VI) salt and NPs with lower concentrations (up to 100mg/L) exerted minimum inhibitory effects on the growth performance of rice seedlings. However, a significant decrease in shoot and root length and their fresh and dry weight was recorded at higher doses of Cr (VI) salt (200 mg/L) and NPs (250 mg/L). The stress induced by Cr (VI) salt has drastically affected the roots, whereas, Cr (VI) NPs significantly affected the shoot tissues. Photosynthetic pigments decreased significantly in a dose-dependent manner, and the reduction was more pronounced in rice seedlings exposed to Cr (VI) NPs compared to Cr (VI) salt. Cr (VI) NPs enhanced the membrane permeability in shoots and roots as compared to that of Cr (VI) salt, which resulted in higher concentration of reactive oxygen species (ROS) and increased lipid peroxidation. The activities of antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) increased significantly in shoot/root tissue following exposure to higher doses of Cr (VI) salt (200 mg/L) and NPs stress (250 mg/L), while minor changes in CAT and APX activities were observed in root and shoot tissues after exposure to higher concentration of Cr (VI) NP. Furthermore, the increasing concentrations of Cr (VI) NPs increased the length of stomatal guard cells. Conclusively, Cr (VI) salt and NPs in higher concentrations have higher potential to damage the growth and induce oxidative stress in rice plants.

Responses of morphological, physiological, and biochemical characteristics of maize (Zea mays L.) seedlings to atrazine stress.

Atrazine is a synthetic herbicide applied to control broadleaf weeds in different crops. In many parts of the world, atrazine is mainly applied for controlling weeds in maize fields. However, studies on the possible adverse effects of atrazine on maize crop can hardly be found in literature. The present study was therefore conducted to evaluate the effect of atrazine on different characteristics of maize seedlings including germination, growth, chlorophyll contents, soluble sugars, proteins and proline levels, ions accumulation, cell viability, and cell injury. In addition, the effects of atrazine on reactive oxygen species (ROS) accumulation and antioxidant enzymes activities in maize seedlings were estimated. It was found that at high concentration, atrazine slightly but significantly inhibited seed germination and growth of maize seedlings. Light-harvesting pigments (chlorophylls a and b, and total carotenoids) exhibited a higher sensitivity to atrazine and were negatively impacted by atrazine at doses above 50 ppm. Atrazine caused an increase in soluble sugars at all tested doses and decrease in soluble proteins at the highest tested dose. Exposure of maize seedlings to atrazine resulted in an increased cell injury and decreased cell viability. Atrazine did not affect the concentration of Na+, K+, and Ca2+ ions in maize seedlings to any greater extent; however, some minor changes were observed in some cases. An increase in the stress marker, proline, was found upon exposure to atrazine. The observed effects of atrazine in maize seedlings can be attributed to oxidative stress as revealed by an increase in H2O2 content and higher activities of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) enzymes in atrazine-treated seedlings. The present investigation concludes that atrazine has the potential to adversely affect germination and growth of maize seedlings by inducing oxidative stress that causes increased cell injury and decreased cell viability as well as impairs the concentration of light-harvesting pigments.

Phytotoxic effects of two commonly used laundry detergents on germination, growth, and biochemical characteristics of maize (Zea mays L.) seedlings.

Laundry detergents, a mixture of different compounds, are used as washing agents in houses and cleaning agents in institutions and industries. As a result, industrial and domestic wastewater usually contains detergent contamination in variable amount. In many developing countries, untreated municipal and industrial wastewater is used for irrigation of crops. There is a possibility that laundry detergents and their ingredients present in irrigation water may affect plant growth as reported in several plant species. However, studies on the effects of laundry detergents on important cereal crops like maize can rarely be found in literature. Therefore, the present study was conducted to evaluate the effects of two commonly used commercial laundry detergents on germination, root-shoot length, fresh biomass, leaf number, leaf width, cell viability, cell injury, light-harvesting pigments, protein contents, and ion concentration in maize (Zea mays L.) seedlings. The obtained results revealed that both the detergents in the tested concentration range (1-500 mg L-1) did not significantly affect seed germination in maize. Similarly, shoot growth, leaf number, and leaf width were not significantly affected by detergents, while in the case of root, one detergent promoted root growth while the other one inhibited it. Both the detergents caused a slight increase in total soluble proteins, and this effect was significant at the highest tested one or two concentrations of detergents (100 and 500 mg L-1). Chlorophylls a and b and total carotenoids were very sensitive to detergent stress and significantly reduced at detergent concentration above 1 or 10 mg L-1. Both the detergents caused an increased cell leakage and reduced cell viability, and in most cases, this effect was statistically significant at detergent doses above 10 mg L-1. Exposure to detergents caused an increased accumulation of Na+, K+, and Ca2+ in maize seedlings. It can be concluded that detergents present in irrigation water at higher concentrations can adversely affect maize by impairing light-harvesting pigments and cell viability.

Ecotoxicological evaluation of two anti-dandruff hair shampoos using Lemna minor.

Hair shampoos, a mixture of various organic and organic compounds, are commonly used personnel care products. Since shampoos are used in almost every household and beauty shop, their ingredients are common components of domestic and municipal wastewater. However, studies on the effect of shampoos to aquatic plants can hardly be found in literature. Therefore, the present study was conducted to investigate the phytotoxic effects of two commonly used anti-dandruff shampoos (named here AD 1 and AD 2) using Lemna minor as a biotest organism. For toxicity assessment, frond number, fresh and dry biomass, and light-harvesting pigments (chlorophyll a, b and total carotenoids) of Lemna were used as end points. Five different concentrations (0.001, 0.01, 0.1, 1, and 5%) of each shampoo were tested in comparison to the control. At lower concentrations of shampoos, some minor and non-significant stimulatory effects were observed in some parameters, but at concentrations above 0.01% both the shampoos significantly inhibited almost all parameters in Lemna. The EC50 values obtained for frond number were 0.034 and 0.11% for AD 1 and AD 2, respectively. The fresh biomass gave EC50 values of 0.07 and 0.066% for AD 1 and AD 2, respectively. Based on the preset study, it can be speculated that shampoo contamination at higher concentrations in water bodies can be a threat to aquatic organisms. This study can be used as a baseline to further investigate shampoo toxicity using other species and to explore the mechanism of shampoo toxicity in aquatic plants.

Pesticide-induced oxidative stress and antioxidant responses in tomato (Solanum lycopersicum) seedlings.

Excessive use of pesticides can adversely affect the growth of non-target host plants in different ways. Pesticide-induced stress can affect non-target plants through elevated levels of reactive oxygen species (ROS) responsible for detrimental effects on cell metabolism, biochemical and other physiological activities. In response to oxidative stress, plant activates antioxidant defense system consisting of both enzymatic and non-enzymatic components. In the present investigation, three commonly used pesticides, emamectin benzoate, alpha-cypermethrin and imidacloprid, were assessed for causing oxidative stress in tomato. The oxidative damage induced by these pesticides at five different concentrations i.e. 1/4X, 1/2X, recommended application dose (X), 2X and 4X in the root and shoot tissues of tomato plant/seedlings were evaluated. Following pesticide exposure for 35 days, cell viability, cell injury, total soluble sugar (TSS) and total soluble proteins (TSP) were measured. Antioxidant activities were estimated by measuring activity levels of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) peroxidase (POD), ascorbate peroxidase (APX) and proline. Hydrogen peroxide (H2O2) levels were analysed as ROS, lipid peroxidation was measured in term of thiobarbituric acid reactive substances (TBARS) as membrane damage caused by ROS was also assessed. Analysis of the data revealed that pesticides application at higher concentrations significantly elevated ROS levels and caused membrane damage by the formation of TBARS, increased cell injury and reduced cell viability both in root and shoot tissues compared with non-treated plants. Moreover, a gradual decrease in the levels of TSS and TSP was observed in plants subjected to increasing doses of pesticides. To cope with pesticide-induced oxidative stress, a significant increase in levels of antioxidants was observed in the plants exposed to higher doses of pesticides. Shoot tissues responded more drastically by producing higher levels of antioxidants as compared to root tissues indicating the direct exposure of shoots to foliar application of pesticides. Taken together, these results strongly suggested that the application of pesticides above the recommended dose can provoke the state of oxidative stress and can cause oxidative damages in non-target host plants.