Amandeep Rattan

Redox homeostasis in plants under abiotic stress: role of electron carriers, energy metabolism mediators and proteinaceous thiols

Contemporaneous presence of both oxidized and reduced forms of electron carriers is mandatory in efficient flux by plant electron transport cascades. This requirement is considered as redox poising that involves the movement of electron from multiple sites in respiratory and photosynthetic electron transport chains to molecular oxygen. This flux triggers the formation of superoxide, consequently give rise to other reactive oxygen species (ROS) under adverse environmental conditions like drought, high or low temperature, heavy metal stress etc. that plants owing during their life span. Plant cells synthesize ascorbate, an additional hydrophilic redox buffer, which protect the plants against oxidative challenge. Large pools of antioxidants also preside over the redox homeostasis. Besides, tocopherol is a liposoluble redox buffer, which efficiently scavenges the ROS like singlet oxygen. In addition, proteinaceous thiol members such as thioredoxin, peroxiredoxin and glutaredoxin, electron carriers and energy metabolism mediators phosphorylated (NADP) and non-phosphorylated (NAD+) coenzyme forms interact with ROS, metabolize and maintain redox homeostasis.

Selenium: An Antioxidative Protectant in Plants Under Stress

Abstract Selenium (Se), the sister element of sulfur, has gained importance recently as an essential trace element in the plant systems. It uses the transporters of sulfur for its uptake and similar biochemical pathways for its metabolism, which leads to its incorporation in various biomolecules. The wide range of beneficial effects of Se on plants has been established. Low concentrations of Se have been proven to enhance seed germination, growth, photosynthesis, respiratory potential, yield, etc. Its role in protecting the plants against various types of biotic and abiotic stresses has become an area of active research. Various studies have revealed its direct effect on antioxidative defense system thereby increasing the potential of the plants to combat the stressful conditions. Despite of its well documented positive effects, Se still is an intermediate between being beneficial or harmful because of its toxic effects at higher concentrations. Therefore, concentration of Se to be used, is still a matter of contemplation and research.

Alleviation of Cadmium and Mercury Stress by Supplementation of Steroid Hormone to Raphanus sativus Seedlings

The present work was undertaken to study the effects of 24-epibrassinolide (24-EBL) on percent germination, growth (root length, shoot length, fresh weight and dry weight), lipid peroxidation, sodium and potassium ion concentrations, proline content, total osmolyte content, level of antioxidants (ascorbic acid, tocopherol and glutathione) in 7-day old seedlings of Raphanus sativus exposed to cadmium and mercury toxicity. Results of present study revealed that growth of seedlings was enhanced with the treatment of 24-EBL. In addition, 24-EBL was proved effective to overcome cadmium and mercury stress by altering the level of ions, osmoprotectants and antioxidants of plant.

Cd-Metal Stress Protection in B. juncea triggered by the Synthesis of Osmolytes, Plant Growth Regulators and Antioxidants

The present piece of work was undertaken to determine the influence of cadmium (Cd) metal on H2O2, level of antioxidants (ascorbic acid and tocopherol), antioxidant assays (DPPH and ABTS), antioxidative enzyme activities (POD, APOX and GR), total osmolytes content, photosynthetic pigments (carotenoid and flavonoid contents), gaseous exchange parameters (photosynthetic rate and water use efficiency), level of Na+ and K+ ions and hormone profiling of 60 days old plants of Brassica juncea. This study demonstrated that Cd metal led to increase in the level of hydrogen peroxide. There was a reduction in the level of photosynthetic pigments, photosynthetic rate and water use efficiency due to Cd toxicity. However, enhancement in the antioxidant potential and level of osmolytes had been noticed in Cd treated plants. In addition, Cd toxicity caused the alteration in the content of ions and hormones.

Gene Silencing: A Novel Cellular Defense Mechanism Improving Plant Productivity under Environmental Stresses

Pests and pathogens have become tolerant to the use of conventional methods to improve agricultural production. This has resulted in low yields of crops worldwide. Currently, genetic engineering is being employed to enhance yields both quantitatively and qualitatively. RNA interference is one such novel cellular process in functional genomics. It is triggered by short double-stranded RNA molecules referred to as small interfering RNAs that target and degrade complementary mRNAs and are controlled by an RNA-induced silencing complex. RNAi is rapidly becoming an important methodology for analyzing sequence functions in eukaryotes and even holds promise for the development of therapeutic gene silencing. Therefore, in this chapter, an endeavor has been made to concisely consolidate the available information on RNAi, its mode of action, and its utilization in crop improvement under changing climatic conditions.