الأثر المباشر للمحاكاة في النقد الثقافي

يعد النقد الثقافي من الظواهر الادبية ما بعد نصية والذي يبحث في الأنساق المضمرة وبذلك أصبح هو وما انطوى تحت مظلته من نقد نسوي وهوية محاكاة وانعكاس للواقع. وهدفت الدراسة للتعرف على الأثر المباشر للمحاكاة في النقد الثقافي، وخلصت الدراسة الى أن النقد الثقافي وما انطوى تحت عباءته من نقد نسوي أو هوية يعد من المناهج ما بعد نصية التي تجاوزت النص لتبحث في مرجعياته الفكرية غير متجاهل للعلوم الانسانية من تاريخ واجتماع ونفس للكشف عن أنساقه المضمرة أو ابراز هوية ما، وهنا تكمن العلاقة بين تلك المناهج والمحاكاة وانعكاسها المباشر على الواقع

Growth and Physiological Responses of Rice to Pb and Amendments in Normal and Salt-Affected Soils

Contamination of soils by heavy metals is of widespread occurrence as a result of human activities. Among heavy metals, lead (Pb) is a potential pollutant that accumulates in soils, water, crops and atmosphere. Lead is not required for any known biological function but it is absorbed by crop plants and gets way into human food chain. There are few examples of genetic differences being exploited to produce low Pb containing rice through decreased metal uptake in Pb-contaminated areas. In normal and salt-affected soils, a very few efforts had been previously done to explore the growth and physiological responses of rice to Pb and inorganic amendments including calcium (Ca), sulphur (S) or phosphorous (P) based compounds. For these reasons, a research project with a series of experiments was carried out at University of Agriculture, Faisalabad, Pakistan and at Ghent University, Belgium. The first study was carried out to evaluate the variations among fourteen rice genotypes for Pb tolerance, accumulation and translocation in hydroponics, at different applied Pb salts i.e., PbCl2, PbSO4 and Pb(NO3)2 with their increasing application rates (0, 100 and 200 μM). The results showed that the Pb bioavailability/phyto-toxicity to rice was greater when Pb was applied as Pb(NO3)2 followed by PbCl2 and PbSO4. It was evident that Shaheen basmati and KS-282 rice varieties can be a wise choice in low to moderately Pbcontaminated areas for safe rice production. The second study was undertaken to investigate the effect of foliar applied Pb at 25 mg L-1 as PbCl2 and Pb(NO3)2 along with an uncontaminated control, for Pb tolerance, accumulation and translocation of rice genotypes. The results showed that the rice varieties had significant variations for Pb tolerance, absorption and translocation. Shaheen basmati and KS-282 rice varieties were proved to be Pb-tolerant. The foliar application of Pb(NO3)2 had more devastating effect than PbCl2. Salinity and heavy metals (e.g., Pb) can occur simultaneously in soil and water. Therefore, the differential growth and physiological responses of two rice varieties (Shaheen basmati and KS-282) were evaluated in normal and salt-affected Pb-contaminated soils in a pot study. The results showed that growth, yield and physiological indices of rice decreased with increasing rates of Pb (0, 50, 100 and 150 mg kg-1 soil) in both rice varieties in normal and salt-affected soils. The Pb concentration, uptake and translocation in rice increased with a gradual increase in soil applied Pb. At a certain defined rate of Pb (0, 50, 100 or 150 mg kgxxiii 1 soil), the concentration, uptake and translocation of Pb in rice straw and paddy was found significantly (p ≤ 0.05) higher in salt-affected soil than normal soil. The higher growth, yield, physiological features, lower Pb concentration, uptake and translocation were found in Shaheen basmati than KS-282, at all rates of applied Pb, in both types of soils. Chemical immobilization of Pb with soil-applied inorganic amendments seems very important for Pb-contaminated soils. A pot study was conducted to evaluate the effectiveness of inorganic amendments at different rates of application for the immobilization/remediation of Pb in normal and salt-affected soils. There were three amendments with different rates viz. gypsum (3, 6 and 9 me Ca 100g-1 soil), rock phosphate i.e., RP (3, 6 and 9 me Ca/P 100g-1 soil) and di-ammonium phosphate i.e., DAP (20 and 40 % higher P than the recommended P as DAP fertilizer). Shaheen basmati was grown in spiked soil with Pb at 100 mg kg-1. The results showed that the reduction in rice growth, yield and physiological attributes were more pronounced in salt-affected Pb-contaminated soil than normal Pb-contaminated soil. The decrease in rice growth, yield and physiological features were counteracted by the applied gypsum, RP and DAP amendments. Gypsum application at 9 me Ca 100g-1 soil was proved the most efficient in improving rice growth and yield, and reducing Pb concentration, accumulation and translocation in the normal and salt-affected Pb-contaminated soils. Total heavy metal contents provide little information on the bioavailability of the heavy metals. Understanding the mobility of Pb in the soil and its chemical speciation in the soil solution is of great importance for accurately assessing environmental risks posed by Pb. Therefore, an incubation study was conducted to explore the effect of amendments (gypsum, RP and DAP) under different soil moisture regimes i.e., flooding regime (FR) and 75 % field capacity (FC) and incubation time on Pb mobility and chemical speciation in normal and saltaffected Pb-contaminated paddy soils. The results showed that after 110 days of incubation, the concentration of Pb in pore water was more in soils at 75 % FC than FR. Gypsum remained more effective in reducing Pb bioavailability followed by DAP and RP. After 2 and 30 days of applied treatments, Pb species were estimated by using geochemical modeling software Visual MINTEQ version 3.0. Among these species, free Pb2+ was found more in Pb-contaminated soils, while PbCl+ was pronounced in salt-affected soils. Whereas, gypsum increased Pb(SO4)2 2-, while DAP and RP enhanced the PbH2PO4 + species formation and decreased free Pb2+ in pore water, thereby reduced the availability of Pb.