Ethylene mediates dichromate‐induced inhibition of primary root growth by altering AUX1 expression and auxin accumulation in Arabidopsis thaliana

The hexavalent form of chromium [Cr(VI)] causes a major reduction in yield and quality of crops worldwide. The root is the first plant organ that interacts with Cr(VI) toxicity, which inhibits primary root elongation, but the underlying mechanisms of this inhibition remain elusive. In this study, we investigate the possibility that Cr(VI) reduces primary root growth of Arabidopsis by modulating the cell cycle‐related genes and that ethylene signalling contributes to this process. We show that Cr(VI)‐mediated inhibition of primary root elongation was alleviated by the ethylene perception and biosynthesis antagonists silver and cobalt, respectively. Furthermore, the ethylene signalling defective mutants (ein2‐1 and etr1‐3) were insensitive, whereas the overproducer mutant (eto1‐1) was hypersensitive to Cr(VI). We also report that high levels of Cr(VI) significantly induce the distribution and accumulation of auxin in the primary root tips, but this increase was significantly suppressed in seedlings exposed to silver or cobalt. In addition, genetic and physiological investigations show that AUXIN‐RESISTANT1 (AUX1) participates in Cr(VI)‐induced inhibition of primary root growth. Taken together, our results indicate that ethylene mediates Cr(VI)‐induced inhibition of primary root elongation by increasing auxin accumulation and polar transport by stimulating the expression of AUX1.     

Responses of morphological, physiological, and biochemical parameters in Euglena gracilis to 7-days exposure to two commonly used fertilizers DAP and urea

Diammonium phosphate (DAP) and urea are commonly used fertilizers throughout the world. The effects of these fertilizers on the freshwater flagellate Euglena gracilis was studied after 7 days of growth using morphological, physiological and biochemical parameters as end points. NOEC and EC₅₀ values for various parameters like cell density, motility, velocity, cell shape, gravitaxis, chlorophyll a, b and total carotenoids were calculated. NOEC and EC₅₀ values of DAP varied from 0.5 to 2.5 g L⁻¹ and 3.14 to 5.96 g L⁻¹, respectively, for different parameters. NOEC and EC₅₀ values for urea ranged from 5 to 25 g L⁻¹ and 28 to 44.05 g L⁻¹, respectively, for various parameters. Photosynthetic pigments were found to be more sensitive to both fertilizers as compared to other measured end points. The NOEC and EC₅₀ values obtained for DAP were much lower than those for urea; i.e., DAP showed a stronger inhibitory effect as compared to urea. Application of DAP resulted in an increased concentration of ammonia in Euglena cultures but urea did not. The stronger inhibitory effect of DAP is attributed to release of free ammonia in the culture due to DAP decompostion. No release of ammonia by urea occurred due to the absence of the enzyme urease in E. gracilis.     

Fast bioassessment of wastewater and surface water quality using freshwater flagellate Euglena gracilis—a case study from Pakistan

Wastewater is a big source of water pollution in the world. Selected wastewater samples from Dera Ismail Khan (D.I. Khan), a city in Pakistan, were analyzed for physicochemical and ecotoxicological properties. Samples from the Indus River before and after the municipal wastewater is discharged into it were tested to determine the effects of municipal wastewaters from D.I. Khan on the river Indus. Different parameters of the freshwater flagellate Euglena gracilis such as motility, swimming velocity, gravitactic orientation, cell shape, and photosynthetic efficiency were used as end points. Gravitactic orientation and cell shape were found to be significantly impaired by the wastewater samples. Swimming velocity and relative electron transport rate of cells were positively affected by all water samples. Quantum yield of photosystem II (F _v/F _m) was not affected, except by ghee (oil) industry effluent where it was significantly increased. Comparison of upstream and downstream samples from the Indus River showed that waste effluents from D.I. Khan affect the physicochemical and ecological properties of the river Indus.     

Ethnobotanical assessment of plant resources of Banda Daud Shah,District Karak,Pakistan

Background

The Indigenous knowledge of plants is scientifically and culturally very significant. This paper elucidates the empirical findings of an ethnobotanical survey of Banda Daud Shah, District Karak, Pakistan.

Methods

Data collection was carried out from October 2011 to September 2012. Total twelve survey trips were made, three in each season. About 100 respondents were interviewed; most of them were aged people between 60–70 years. Interviews were conducted using structured questionnaire composed of variety of questions regarding ethnomedicinal uses of plants of the study area. Direct matrix ranking (DMR), informant citations and market survey of multipurpose plants were also carried out.

Results

The local community was using 58 plant species belonging to 52 genera and 34 families for different purposes. A total of 25 plant species were herbs followed by 18 shrubs. Leaf (45%) was the most commonly used plant part followed by the whole plants (23%). In total, 40 plant species were medicinally used to treat variety of diseases, of which highest number of species being used for gastro-intestinal problems (19 spp.), expectorant (3 spp.) and antipyretic (3 spp.). Beside medicinal values, 25 species were used for fuel and 18 for fodder purposes. Informant consensus showed that gastrointestinal and respiratory infections were ranked highest (F_IC?=?0.75) among all ailments. According to DMR output, Dalbergia sisso ranked first due to high multipurpose uses among all species and was found most threatened with higher market value.

Conclusion

The investigated area is rural in nature and the inhabitants are highly dependent on the native plants for their health care needs and other requirements like fuel wood and fodder due to financial constraints and unavailability of resources. Medicinal plants for high ranked diseases may be phtyochemicaly and pharmacologically investigated to prove their efficacy. The local medicinal flora is facing overexploitation, overgrazing and improper way of collection. Proper conservation strategies such as controlled grazing, reforestation and rangeland management among many others may be adopted to promote the sustainable use of medicinal plants.

     

Sensitivity of various parameters in Euglena gracilis to short-term exposure to industrial wastewaters

Due to the presence of various potential pollutants industrial wastewaters pose considerable threats to natural waters and make it unfit for the aquatic biota. Analysis of wastewaters by chemical methods is a common practice; however, it does not reflect the toxic effects on living organism. Therefore, bioassessment is necessary for monitoring of wastewater quality. In the present study, the toxic effects of wastewater samples from different industries were evaluated using Euglena gracilis as a biotest organism. Various parameters of the freshwater flagellate E. gracilis like motility, swimming velocity, cell shape, gravitactic orientation (using the automatic biotest ECOTOX) and photosynthetic efficiency (using a pulse amplitude modulated fluorometer) were used as end points for toxicity assessment. In addition, the samples were analysed for some ecologically important physicochemical properties. With some exceptions, most of the physicochemical properties of the tested samples were within the acceptable range of national environmental quality standards for municipal and industrial effluents. However, all the water samples adversely affected different parameters in E. gracilis. This study led to the conclusion that different toxic substances present in wastewater, even at low concentrations, can be a possible threat to aquatic biota. The results of this study prove that ECOTOX is a sensitive, easy, and fast bioassay for monitoring of water and wastewater quality. Gravitactic orientation and cell compactness of E. gracilis were the most sensitive parameters to wastewater toxicity.