Neama Abdalla

Selenium and nano-selenium in agroecosystems

Selenium (Se) is an essential health element becoming rare in food as a result of intensive plant production. Indeed, several enzymes contain selenium in the form of the unusual selenocysteine amino acid. Selenium was found an essential nutrient in the late 1950s, when selenium was found to replace vitamin E in the diets of rats and chicks for the prevention of vascular, muscular, and hepatic lesions. At that time, selenium was considered solely as a toxic element in the northern Great Plains of the USA, because selenium was associated with the ‘alkali disease’ of grazing livestock. The major source of Se in soils is the weathering of Se-containing rocks. Secondary sources are volcanic activities, dusts such as in the vicinity of coal burning, Se-containing fertilizers, and some waters. Se cycles through the food system; Se is first removed from soils by plants and soil microorganisms, which can take up Se into their proteins and produce volatile forms such as dimethylselenide. Dimethylselenide enters the atmosphere to be brought down with precipitation and airborne particulates. Here, we review Se in agroecosystems. We focus on the production, biological effects, and use of nano-selenium particles.

Selenium and nano-selenium in plant nutrition

Abstract Selenium (Se) is a naturally occurring metalloid element which occurs nearly in all environments. Se is considered as a finite and non-renewable resource on the Earth. The common sources of Se in earth’s crust occur in association with sulfide minerals such as metal selenide, whereas it is rarely found in elemental form (Se0). While there is no evidence of Se need for higher plants, several reports show that when Se added at low concentrations, Se exerts beneficial effects on plant growth. Se may act as quasi-essential micronutrient through altering different physiological and biochemical traits. Thus, plants vary considerably in their physiological and biochemical response to Se. This review focusses on the physiological importance of Se forms as well as different Se fertilizers for higher plants, especially plant growth, uptake, transport, and metabolism.

Postharvest Management of Fruits and Vegetables Storage

Sustainable agriculture is a core part of the concept of sustainable development. Given the forecast in population increase, sustainable agriculture has to achieve food security in combination with economic viability, social responsibility and have as little effect on biodiversity and natural ecosystems as possible. Based on Agenda 21, signed at the world summit in Rio de Janeiro 1992, sustainable agriculture takes a truly global perspective. This concept requires a thorough understanding of agro-ecosystem functions. The protection of soil and water is one necessary prerequisite as well as the efficient use of mineral and organic fertilizers. This might be achieved by means of improved technology and better understanding of the basic processes in soils. Solving the persistent hunger problem is not simply a matter of developing new agricultural technologies and practices. Most poor producers cannot afford expensive technologies. They will have to find new types of solutions based on locally-available and cheap technologies combined with making the best of natural and human resources. Sustainable intensification is the use of the best available technologies and inputs such as best genotypes, best agronomic management practices and best postharvest technologies to maximize yields, while at the same time minimizing or eliminating harm to the environment. Clearly, over the next 50 years we will need to learn to do just this. Therefore, this review will be focused on the postharvest physiology and management including harvesting, handling, packing, storage and hygiene of fruits and vegetables to enhance using of new postharvest biotechnology. The postharvest biology including biochemical parameters of horticultural crops quality, postharvest handling under extreme weather conditions, potential impacts of climate changes on vegetable postharvest and postharvest biotechnology will be also highlighted.

Selenium and its Role in Higher Plants

Selenium (Se) is a naturally occurring metalloid element which occurs nearly in all environments in the universe. The common sources of Se in earth crust occurs in association with sulfide minerals as metal selenide whereas, it is rarely seen in elemental form (Se0). Furthermore, Se is considered a finite and non-renewable resource on earth, and has been found to be an essential element for humans, animals, micro-organisms and some other eukaryotes; but as yet its essentiality to plants is in dispute. Thus, plants vary considerably in their physiological and biochemical response to Se. Therefore, this review focuses on of the physiological importance of Se for higher plants, especially plant growth, uptake, transport, metabolism and interaction of selenium with other minerals. Biogeochemistry of Se, its relationship with S, application of Se-containing fertilizers, Se in edible plants and finally, red elemental Se nanoparticles in higher plants will be highlighted.

Giant reed for selenium phytoremediation under changing climate

At very low concentrations selenium is an essential micronutrient for humans, animals and some lower plants including algae and bacteria, whereas Se is extremely toxic at higher doses. Living organisms can be exposed to high selenium concentrations from both natural and anthropogenic sources. Climate is a major factor governing the biogeochemistry of Se. Climate change can indeed modify Se uptake by plants and the rhizosphere and the volatilization of Se by plants. High precipitation rates and low temperatures can reduce Se accumulation by plants. Se-hyperaccumulator plants such as giant reed thus appear as a means to regulate Se flow in ecosystems. Se-hyperaccumulator plants can indeed be used to clean Se-contaminated agricultural soils and wastewaters and as a source of dietary Se. Those plants are also converting mineral soil Se into volatile organic Se that is released in the atmosphere.

Nanoparticles, Soils, Plants and Sustainable Agriculture

Humanity faces major challenges involving energy, water, food, environment, poverty, diseases, education, democracy and population. Green nanotechnology could be a solution for providing sustainable energy, clean water and a better environment. Various nanomaterials can sustain the agricultural sectors. Here we review the applications of nanoparticles for soil security and plant nutrition.

Selenium Phytoremediation by Giant Reed

Selenium (Se) is an essential micronutrient for humans, animals and some lower plants at very low concentrations, whereas it is extremely toxic at higher doses. Furthermore, living organisms become exposed to high Se concentrations via both anthropogenic and natural releases of Se to the environment. Thus, Se may be released naturally into soils formed from Se-bearing shales. Hence, this in turn can lead to the production of large quantities of Se-contaminated irrigation and drainage water. About the anthropogenic sources of Se, they include coal ash leachates or mining production, aqueous discharges from electric power plants, industrial wastewater and oil refinery industry. In general, Se levels in most soils are very low (0.44 mg kg−1) and naturally Se occurs in certain Cretaceous shale sediments. Furthermore, seleniferous soils contain up to 100 mg kg−1 Se, and when fossil fuels derived from these soils are used, or when these soils are cultivated, toxic levels of Se may accumulate in the environment. Hence, using of Se hyperaccumulator plants can be thrived on seleniferous soils, providing another portal for Se into the agroecosystem. These plants could be alleviated both of these problems, either as a source of dietary Se or for phytoremediation of excess Se from the environment. On the other hand, these plants also have the ability to clean up agricultural soils and industrial wastewaters, due to their capacity to not only take up and then accumulate Se but also convert inorganic Se into volatilized forms that are released into the atmosphere.

Nanoremediation for Sustainable Crop Production

Nanoremediation is a promising strategy to controlling pollution. Nanoremediation involves the use of nanomaterials and plants, named phyto-nanoremediation, animals, named zoo-nanoremediation and microbes, named microbial nanoremediation. Here we review environmental pollution, crop protection and nanoremediation.

The Rhizosphere and Plant Nutrition Under Climate Change

The plant root–soil interfaces could be considered the rhizosphere area, which is the most important active zone in the soils for different microbial activities, biodegradation of pollutants and plant nutrition. Polluted soils are characterized by low organic matter content, limiting their microbial activity, nutrient availability and degradation of pollutants. Soil phyto- and/or bioremediation is mainly based on the use of plant roots and their associated soil microorganisms, whereas conventional approaches are based on physico-chemical methods in soil remediation. Plant root exudates are the most important compounds in the rhizosphere, which play a crucial role in the interactions between plant roots and soil microbes. It is worthy to mention that several plant species and soil microbes have been used in soil remediation for different pollutants. The role of rhizosphere and its significance in plant nutrition are mainly controlled by the change in climatic attributes including temperature, moisture content, precipitation, etc. Therefore, global warming and climate changes do have a great and serious effect on the agricultural production through their effects on the rhizosphere and in turn plant nutrition. Hence, the aim of this review is to evaluate the significance of rhizosphere in plant nutrition under the changing climate. Soil biological activity and its security will be also highlighted.

Soils and Humans

Soil has a great and holy position worldwide. This position has been acquired from the importance of soil in saving food, feed, fuel, and fibre for animals and humans. Egypt was and still one of the most important countries, which soils played a crucial role in the Egyptian civilization. Therefore, very strong link between soils and humans has been reported based on the great roles of soils in plant and human nutrition. On the other hand, there are several anthropogenic activities, which cause many problems for soils such as pollution, degradation, and erosion. There are direct and/or indirect effects of soils on human health as well as plants. Therefore, this chapter is an attempt to emphasize the great roles of soils in plant and human health as well as the security of soils under pollution conditions.