Muhammad Rizwan Ashraf

Effect of water management and silicon on germination, growth, phosphorus and arsenic uptake in rice

Silicon (Si) is the 2nd most abundant element in soil which is known to enhance stress tolerance in wide variety of crops. Arsenic (As), a toxic metalloid enters into the human food chain through contaminated water and food or feed. To alleviate the deleterious effect of As on human health, it is a need of time to find out an effective strategy to reduce the As accumulation in the food chain. The experiments were conducted during September-December 2014, and 2016 to optimize Si concentration for rice (Oryza sativa L.) exposed to As stress. Further experiment were carried out to evaluate the effect of optimum Si on rice seed germination, seedling growth, phosphorus and As uptake in rice plant. During laboratory experiment, rice seeds were exposed to 150 and 300µM As with and without 3mM Si supplementation. Results revealed that As application, decreased the germination up to 40-50% as compared to control treatment. Arsenic stress also significantly (P < 0.05) reduced the seedling length but Si supplementation enhanced the seedlings length. Maximum seedling length (4.94cm) was recorded for 3mM Si treatment while, minimum seedling length (0.60cm) was observed at day7 by the application of 300µM As. Silicon application resulted in 10% higher seedling length than the control treatment. In soil culture experiment, plants were exposed to same concentrations of As and Si under aerobic and anaerobic conditions. Irrigation water management, significantly (P˂0.05) affected the plant growth, Si and As concentrations in the plant. Arsenic uptake was relatively less under aerobic conditions. The maximum As concentration (9.34 and 27.70mgkg DW-1 in shoot and root, respectively) was found in plant treated with 300µM As in absence of Si under anaerobic condition. Similarly, anaerobic condition resulted in higher As uptake in the plants. The study demonstrated that aerobic cultivation is suitable to decrease the As uptake and in rice exogenous Si supply is beneficial to decrease As uptake under both anaerobic and aerobic conditions.

Pesticides Pollution in Agricultural Soils of Pakistan

Pesticides are widely used worldwide to control a range of pests infesting the agricultural crops. Increased use of pesticides has threaten human and enviroenmnetal health. In this book chapter, we have compiled data regarding pesticide use, soil and water contamination, and human poining in Pakistan. Pesticide utilization in Pakistan started in 1954 and is currently on the rise. Of the total pesticides used in Pakistan, insecticides shared major portion, followed by herbicides, acaricides, and fumigants. High percentage of pesticides is being applied in the Punjab province, followed by Sindh, Khyber Pakhtoonkhaw and Balochistan. In Pakistan, the pesticide uses are mostly focused on cotton crop (almost 70–85 % of total pesticides use) and other crops such as wheat, sugarcane, maize, rice and tobacco as well as for vegetables and fruits. Different groups of pesticides, especially the residues of organochlorine, have been reported in soils and waters in different areas of Pakistan. The fate and charactiristics of pesticides in soils and percolation to deep soil depends vary with soil physico-chemical properties. Over 500,000 Pakistanis suffered annually from poisoning due to agro-chemicals, out of which 10,000 died. Regulations have also been developed for safe use of pesticides in Pakistan such as Farmer Field School led Integrated Pest Management model.

The Role of Hydrophobicity in Bio-Accessibilityof Environmental PollutantsAmong Different Organisms

This study concerns the relationship between hydrophobicity and bio-accessibility of environmental pollutants among the protozoan Tetrahymena pyriformis, the water flea Daphnia magna, and the fish Poecilia reticulata. The toxicological data of 55 chemicals in terms of 50% effect concentration was selected toward these three biological objects along with their hydrophobic potential (octanol-water partition coefficients (log Kow)). Overall, a significant correlation was achieved among all test systems, with the highest between Tetrahymena pyriformis and Poecilia reticulata (R = 0.93). The acute toxicity results revealed substantial differences in the sensitivity of the three test systems, but at a certain level of hydrophobicity (log Kow values 0.5 to 2.5), where all environmental pollutants have the utmost ability to reach biological compartments as cytosole and target sites within the membranes, to interfere with normal cell functioning by effecting normal enzymatic activity and directly to biological macromolecules.