حدود التفسير الموضوعي

This study deals with the limitations of thematic exegesis of the Qur’ān. The main place where exegesis of the Qur’ān can be found remains the commentaries. In the majority of cases such commentaries start from the beginning of the first sūrah. In order to acknowledge the inputs and outputs in the Qur’ānic studies; explanation of the literary aspects of the verse, an account of its background and occasionally an interpretation of it with the help of another verse will be reviewed in this paper. In order to achieve the objectives of this study, scientists’ quotes will be critically examined.

Enzyme Expression Studies in Plants under Exposure to Some Abiotic Stresses

Abiotic stress is a natural part of every ecosystem that adversely affects the population‘s performance or individual physiology of the organism in a significant way. It is essentially unavoidable. Abiotic stressors are most harmful when combined with other stresses. These stresses alter morphological, physiological, biochemical, metabolic and molecular parameters. Plants, in general, have the ability to cope with these stressful conditions. They do so by triggering a complex set of defense system to survive and maintain growth. Mechanisms of these events are however, not yet clearly understood. To explore intricacies of stress tolerance processes we need to examine natural phenomenon of plant survival under harsh environments such as arid and semi-arid locals. NaCl or salinity stress is just one among abiotic stresses present around. The project being presented has been conceived with the idea of investigating salinity stress tolerance in Vetiveria zizanioide, a hardy grass, which grows abundantly under the harsh environmental conditions of a nearby arid landmass, the Cholistan desert. During the present study two ecotypes (E1 & E2) of Vetiver grass were exposed to varying levels of NaCl stress (0 to 350 mM). Various morphological features including plant health, plant height, shoot length, total number of tillers, no. of nodes on main stem, no. of internodes on main stem, average leaf area, root health and root length were examined. It was seen that on exposure to salt stress most of the E2 plants exhibited better health as compared to E1 plants. However, in both ecotypes 71% of the plants were of green color indicating healthy status of plants. Rest of the plants was either yellowish green (14.29 %) or pale yellow color (14.29 %) due to adverse effects of high salt concentrations. Better health status of E2 plants was also depicted by higher plant height, shoot length and root length observed in case of E2 plants as compared to E1 plants when treated with 200 mM NaCl. Overall morphological results indicated that E1 is more susceptible while E2 is more tolerant ecotype. Morphological analysis was followed by physico-chemical analysis that included measurement of moisture contents (%), dry mass (%), Electrical conductivity (EC), pH, sodium contents and chloride contents. In both ecotypes of hydroponically grown Vetiver plants, at higher salt concentrations % dry mass was higher in shoots followed by leaves and roots. It is obvious that EC of the nutrient solution increases with the increasing levels of NaCl. A gradual increase in EC was seen with increasing NaCl concentration from T1 to T6 as compared to control. Our results of Na and Cl estimation of plant tissues showed that almost all tissues (leaves stem and root) showed a gradual increase in Na and Cl contents as NaCl concentration increased. This verified that under salt stress all tissues had accumulated a considerable amount of Na and Cl contents. We then documented expression profile of three enzymes guaiacol peroxidase, amylase and catalase and their isozymes, , through native PAGE using enzyme specific staining methods. Level of enzymatic activity was accessed by performing enzyme specific quantitative assays. All morphological and biochemical data were analyzed by ANOVA (one-way analysis of variance) employing Post Hoc multiple comparisons test and Independent samples T-test. Moreover, the average leaf area, plant height, shoot length, root length, sodium contents, chloride contents, and specific activity of three studied enzymes were initially increased under low salt concentration (25 mM to 150 mM NaCl) then at high saline conditions beyond 150 mM NaCl, a sharp declined was observed and both ecotypes exhibited statistically significant variations in almost all parameters (P< 0.0005 or 0.005). Variations in expression of these enzymes in different tissues indicated that these tissues sense and hence are exposed to different levels of NaCl stress. They probably adopt different strategies to generate an effective and beneficial response. It is known that these strategies may include comprised of ‘switching on’ or ‘switching off’ the corresponding genes, enhancing or decreasing their levels of expression, generating a variety of isoforms, and coordinated and sequential expression of the related genes. Vetiver plants were analysed to document expression profile of three enzymes (Guaiacol peroxidase, amylase and catalase) and their isoforms in both ecotypes. Densitometric analysis was done by gel image analyzer software. The result of densitometric analysis depicted that 8 isoforms of guaiacol peroxidase (GPX), seven isoforms of amylase and seven isoforms of catalase (CAT) were identified in roots, shoots and leaves of both E1 and E2 when exposed to NaCl salt stress. In almost all cases the expression pattern of isoforms was dependent on salt concentration. Different isoforms were expressed at different salt concentrations. Thus each ecotype develops a unique pattern of response and hence the related genetic variations. This research has provided insight in the stress tolerance process. The information thus obtained demands exploring these responses at molecular and gene levels. Once delineated these genetic components could help to develop transgenic commercial varieties for cultivation in arid land masses such as Cholistan.