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Among the various abiotic stresses, low temperature is one of the major environmental constraints that limit the plant development and crop productivity. Plants are able to adapt to low-temperature stress through the changes in membrane composition and activation of reactive oxygen scavenging systems. The genetic pathway induced due to temperature downshift is based on C-repeat-binding factors (CBF) which activate promoters through the C-repeat (CRT) cis-element. Calcium entry is a major signalling event occurring immediately after a downshift in temperature. The increase in the level of cytosolic calcium activates many enzymes, such as phospholipases and calcium dependent-protein kinases. MAP-kinase module has been shown to be involved in the cold response. Ultimately, the activation of these signalling pathways leads to changes in the transcriptome. Several phytohormones, such as abscisic acid, brassinosteroids, auxin, salicylic acid, gibberellic acid, cytokinins and jasmonic acid, have been shown to play key roles in regulating the plant development under low-temperature stress. These phytohormones modulate important events involved in tolerance to low-temperature stress in plants. Better understanding of these events and genes controlling these could open new strategies for improving tolerance mediated by phytohormones.

In plants, hydrogen peroxide (H 2 O 2) acts as a signalling molecule that facilitates various biochemical and physiological processes. H 2 O 2 is a versatile molecule, involved in several cellular processes both under stress and stress-free conditions. In regulating plant metabolism under stress conditions, exogenous application of H 2 O 2 also plays a pivotal role which is manifested in improved growth, photosynthetic capacity, and antioxidant protection. Abiotic stress is an inevitable environmental factor that extensively affects and reduces growth, quality, yield, and productivity of plants. Several signalling pathways involved in H 2 O 2-mediated stress and defense responses have been extensively studied and there is ample scope of additional research that could further clarify the mechanism and modulating factors which regulate these pathways. An attempt has been made to dissect the role of H 2 O 2 under low temperature stress and how it affects plant growth and development, photosynthetic capacity, regulation of antioxidant system, and signalling.

Environmental degradation and unethical human intervention in the natural system has increased the concern for the betterment of healthy living. The deterioration of aquatic system is commonplace in the developing world. The present paper shows the trace elements (Ni, Zn, Fe, Pb, Cd, Co, Cu and Mn) concentrations in the drinking water of Aligarh city and their possible effect on the health of the inhabitants. The higher concentration of some elements in the drinking water and the poor health of inhabitants are found correlated. The statistical analysis of the data shows positive correlation between some elements. The principal component analysis of the data gives four factors with significance level of 42%, 29%, 15% and 12% respectively.