Plants are confronted with a variety of environmenmtal stresses resulting in enhanced production of ROS. Plants require a threshold level of ROS for vital functions and any change in their concentration alters the entire physiology of plant. Delicate balance of ROS is maintained by an efficient functioning of intriguing indigenous defence system called antioxidant system comprising enzymatic and non enzymatic components. Down regulation of antioxidant system leads to ROS induced oxidative stress causing damage to important cellular structures and hence anomalies in metabolism. Proper mineral nutrition, in addition to other agricultural practices, forms an important part for growth and hence the yield. Potassium (K) is a key macro-element regulating growth and development through alterations in physiological and biochemical attributes. K has been reported to result into accumulation of osmolytes and augmentation of antioxidant components in the plants exposed to water and salt stress. In the present review an effort has been made to revisit the old findings and the current advances in research regarding the role of optimal, suboptimal and deficient K soil status on growth under normal and stressful conditions. Effect of K deficiency and sufficiency is discussed and the information about the K mediated antioxidant regulation and plant response is highlighted.

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Marigold (Tagetes erecta L.), a popular ornamental plant of the family Asteraceae, is commonly cultivated in many countries, including India, for its decorative flowers. The plants grow easily in a variety of soil and climatic conditions and have been reported to damage the nematode population of soil and control indirectly harmful microbes. High-performance thin-layer chromatography (HPTLC) was utilized in the present study, with a view to identify some important biologically active compounds in the flowers and leaves of two cultivars of marigold, Pusa Narangi Gainda (PNG) and Pusa Basanti Gainda (PBG). Quantitative analyses were carried out using silica gel thin-layer chromatography (TLC) plates and toluene–ethyl acetate–formic acid (T-E-F) (13:11:2 v/v/v) as the mobile phase used. Bands of gallic acid, caffeic acid, quercetin, p-coumaric acid, and kaempferol were observed. The results revealed a greater number of compounds in leaves than in flowers, and that the cultivar PNG accumulated a greater number of compounds than PBG. Gallic acid was found in leaves and flowers of both cultivars; however, it was found maximum in the flowers of cultivar PBG. Caffeic acid and quercetin were detected in the leaves of both cultivars, whereas p-coumaric acid was detected only in the leaves and kaempferol only in the flowers of cultivar PNG. The information generated in this report may be meaningfully used for the furtherance of research on marigolds as a natural source of antioxidants, insecticides, herbicides, etc.

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