IT may occasion some surprise to those men of science who are ill-acquainted with India, and who so frequently express the view that Governments are unappreciative of the importance of science to learn that as far back as 1886 the Government of India arranged for Dr. George (later Sir George) Watt, professor of botany in the Presidency College, Calcutta, to prepare a "Dictionary of the Economic Products of India". The six volumes of this standard work were published during the years 1889-99. In 1908 Sir George Watt published a condensed version, "The Commercial Products of India". Whatever the defects of these 'dictionaries', they have been of inestimable value to all interested in Indian natural products. The Wealth of India A Dictionary of Indian Raw Materials and Industrial Products. Raw Materials, Vol. 1. Pp. xxvii+254+39 plates. 15 rupees ; 24s. Industrial Products, Part 1. Pp. xii+182+8 plates. 8 rupees ; 12s. (New Delhi : Council of Scientific and Industrial Research, 1948.)

The Wealth of India

Abiotic stresses hamper plant growth and productivity. Climate change and agricultural malpractices like excessive use of fertilizers and pesticides have aggravated the effects of abiotic stresses on crop productivity, and degraded the ecosystem. There is an urgent need for environment-friendly management techniques such as the use of arbuscular mycorrhizal fungi (AMF) for enhancing crop productivity. AMF are commonly known as bio-fertilizers. Moreover, it is widely believed that the inoculation of AMF provides tolerance to host plants against various stressful situations like heat, salinity, drought, metals and extremes of temperature. AMF may both assist host plants in up-regulation of tolerance mechanisms, and prevent the down-regulation of key metabolic pathways. AMF, being natural root symbionts, provide essential plant inorganic nutrients to host plants, thereby improving growth and yield under unstressed and stressed regimes. The role of AMF as a bio-fertilizer can potentially strengthen plants’ adaptability to changing environment. Thus, further research focusing on the AMF-mediated promotion of crop quality and productivity is needed. The present review provides a comprehensive up-to-date knowledge on AMF and their influence on host plants at various growth stages, their advantages and applications, and consequently the importance of the relationships of different plant nutrients with AMF.

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Role of Arbuscular Mycorrhizal Fungi in Plant Growth Regulation: Implications in Abiotic Stress Tolerance.

Among the plant nutrients, potassium (K) is one of the vital elements required for plant growth and physiology. Potassium is not only a constituent of the plant structure but it also has a regulatory function in several biochemical processes related to protein synthesis, carbohydrate metabolism, and enzyme activation. Several physiological processes depend on K, such as stomatal regulation and photosynthesis. In recent decades, K was found to provide abiotic stress tolerance. Under salt stress, K helps to maintain ion homeostasis and to regulate the osmotic balance. Under drought stress conditions, K regulates stomatal opening and helps plants adapt to water deficits. Many reports support the notion that K enhances antioxidant defense in plants and therefore protects them from oxidative stress under various environmental adversities. In addition, this element provides some cellular signaling alone or in association with other signaling molecules and phytohormones. Although considerable progress has been made in understanding K-induced abiotic stress tolerance in plants, the exact molecular mechanisms of these protections are still under investigation. In this review, we summarized the recent literature on the biological functions of K, its uptake, its translocation, and its role in plant abiotic stress tolerance.

Potassium: A Vital Regulator of Plant Responses and Tolerance to Abiotic Stresses

Plants face a combination of different abiotic stresses under field conditions which are lethal to plant growth and production. Simultaneous occurrence of chilling and drought stresses in plants due to the drastic and rapid global climate changes, can alter the morphological, physiological and molecular responses. Both these stresses adversely affect the plant growth and yields due to physical damages, physiological and biochemical disruptions, and molecular changes. In general, the co-occurrence of chilling and drought combination is even worse for crop production rather than an individual stress condition. Plants attain various common and different physiological and molecular protective approaches for tolerance under chilling and drought stresses. Nevertheless, plant responses to a combination of chilling and drought stresses are unique from those to individual stress. In the present review, we summarized the recent evidence on plant responses to chilling and drought stresses on shared as well as unique basis and tried to find a common thread potentially underlying these responses. We addressed the possible cross talk between plant responses to these stresses and discussed the potential management strategies for regulating the mechanisms of plant tolerance to drought and/or chilling stresses. To date, various novel approaches have been tested in minimizing the negative effects of combine stresses. Despite of the main improvements there is still a big room for improvement in combination of drought and chilling tolerance. Thus, future researches particularly using biotechnological and molecular approaches should be carried out to develop genetically engineered plants with enhanced tolerance against these stress factors.

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Chilling and Drought Stresses in Crop Plants: Implications, Cross Talk, and Potential Management Opportunities

At the end of the class, students will be able to answer the following questions: • What is organic agriculture? • Where do I go to get certification in organic agriculture? • How can I get more information about organic agriculture? What is organic? • The term " organic " is not synonymous to the terms " natural " or " eco-friendly. " • The label " natural " on foodstuff does not guarantee complete adherence to organic practices as defined by a law. • Produce food of high quality in sufficient quantity • Maintain biological diversity within the farming system • Maintain long-term soil fertility • Rely on renewable resources in locally organized agricultural systems • Minimize pollution and protect the environment What is allowed in organic crop production? • New varieties of crops and agricultural technologies • Crop rotations, cover crops and natural-based products that maintain soil fertility • Biological, cultural and physical methods to limit pest expansion and increase population of beneficial insects

英国有机农业（Organic farming）的新举措

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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Plant growth under water/salt stress: ROS production; antioxidants and significance of added potassium under such conditions.

Salinity stress induced alterations in antioxidant metabolism and nitrogen assimilation in wheat (Triticum aestivum L) as influenced by potassium supplementation.

Pot experiments were conducted to find out the effectivity of K on Triticum aestivum L cultivars. Polyethylene glycol 6000 (PEG 6000) was used as an osmoticum to induce osmotic stress under sand culture setting up the water potential of external solution at −3 and −5 bars. In pots, plants were raised under restricted and normal irrigation and K was applied in varying doses (0, 20, 40, 60 kg ha−1) and estimation of different physiological and biochemical parameters was done at two developmental stages, i.e., preflowering and flowering. Supplementation of K resulted in obvious increase in growth and activity of antioxidant enzymes in both normal and stressed plants. Added potassium increased total phenols and tannins thereby strengthening the components of both the enzymatic as well as non-enzymatic antioxidant system. Under both normal and stressed conditions, K-fed plants experienced significant increase in the synthesis of osmolytes like free proline, amino acids, and sugars which assumes special significance in growth under water stress conditions. Wheat plants accumulating greater K were able to counteract the water stress-induced changes by maintaining lower Na/K ratio.

Potassium up-regulates antioxidant metabolism and alleviates growth inhibition under water and osmotic stress in wheat (Triticum aestivum L)

Potassium is actively involved in many functions such as enzyme activation, osmotic adjustment and uptake of deleterious ions like Na. Present report analyses the effectivity of different potassium salts on growth and certain components of nitrogen metabolism and antioxidant system in oat and their possible role in amelioration of water stress. Potassium induced enhancement in the activities of nitrate reductase and aminotransferases was evident indicating a positive role of potassium in nitrogen metabolism. Potassium supplementation enhanced activities of antioxidant enzymes (superoxide dismutase, catalase and ascorbate peroxidase) and contents of total phenols and tannins, probably strengthening both the enzymatic as well as non enzymatic antioxidant system. Free amino acids, proline and free sugars also exhibited the same trend in treated plants ensuring better plant growth.

https://www.tandfonline.com/doi/pdf/10.1080/17429145.2015.1056260

Potassium induces positive changes in nitrogen metabolism and antioxidant system of oat (Avena sativa L cultivar Kent)

Present communication reports laboratory and pot experiments conducted to study the influence of water and osmotic stress on nitrogen uptake and metabolism in two wheat (Triticum aestivum L) cultivars with and without potassium supplementation. Polyethylene glycol 6000-induced osmotic stress/restricted irrigation caused a considerable decline in the activity of nitrate reductase, glutamate synthase, alanine and aspartate aminotransferases, and glutamate dehydrogenase. Potassium considerably improved nitrogen metabolism under normal water supply conditions and also resulted in amelioration of the negative impact of water and osmotic stresses indicating that potassium supplementation can be used as a potential tool for enhancing the nitrogen use efficiency in wheat for exploiting its genetic potential.

R. M. Agarwal

Papers

Plant growth under water/salt stress: ROS production; antioxidants and significance of added potassium under such conditions.

Salinity stress induced alterations in antioxidant metabolism and nitrogen assimilation in wheat (Triticum aestivum L) as influenced by potassium supplementation.

Potassium up-regulates antioxidant metabolism and alleviates growth inhibition under water and osmotic stress in wheat (Triticum aestivum L)

Potassium induces positive changes in nitrogen metabolism and antioxidant system of oat (Avena sativa L cultivar Kent)

Alleviation of water and osmotic stress-induced changes in nitrogen metabolizing enzymes in Triticum aestivum L. cultivars by potassium.