Said A. Shehata

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.

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.

Plant Nutrition: From Liquid Medium to Micro-farm

Soil fertility and plant nutrition have played an important role in the agricultural science during the twentieth century in increasing crop yields. In the twenty-first century, importance of this field is still expanding due to the limitations of natural land and water resources, sustainable agriculture, and concern about environmental pollution. Under these conditions, improving food supply worldwide with adequate quantity and quality is fundamental. Supply of adequate mineral nutrients in adequate amount and proportion to higher plants will certainly determine such accomplishments. Further, in developing crop production technologies, research work under field and controlled conditions is necessary to generate basic and applied information. In addition, research is very dynamic and complex due to variation in climatic, soil, and plant factors and their interactions. This demands that basic research information can only be obtained under controlled conditions to avoid or reduce effects of environmental factors on treatments. Hence, the objective of this review article is to discuss basic principles of research in soil fertility and plant nutrition under different conditions from to liquid or solid media, micro-farm, green house and field experiments. These information will be included the management of different tools of plant nutrition even on the small or large scale i.e., Petri dishes (in case of medium) or hectare unit (in case of fields). Topics discussed are soil and solution culture experimental techniques including, fertilizer application and planting, experimental duration and observations, considerations of pot or field experimentations.

Plant Nano-nutrition: Perspectives and Challenges

The global agriculture is facing many challenges including sustainable use and conservation of natural resources, climate change, urbanization, and pollution resulting from agrochemicals (e.g., fertilizers and pesticides). So, the sustainable agriculture is an urgent issue and hence the suitable agro-technological interventions are essential (e.g., nano- and bio-technology) for ensuring the safety and sustainability of relevant production system. Biotechnology and nanotechnology also can be considered emerging solutions to resolve the global food crisis. Nanoparticles or nanomaterials can be used in delivering different nutrients for plant growth. These nanoparticles as nanofertilizers have positive and negative effects on soils, soil-biota and plants. These effects mainly depend on multiple factors including nanofertilizer properties, plant species, soil fate and dynamics as well as soil microbial communities. Nanofertilizers could improve the nutrient use efficiencies through releasing of nutrients slowly and steadily for more than 30 days as well as reducing the loss of nutrients in agroecosystems and sustaining farm productivity. Here we review the plant nano-nutrition including the response of plants and soils to nanonutrients and their fate, dynamic, bioavailability, phytotoxicity, etc. Concerning the effects of nanonutrients on terrestrial environments are still an ongoing processes and it demands further researches as well as a knowledge gap towards different changes in shape, texture, color, taste and nutritional aspects on nanonutrients exposed plants as a major component in the food chain. Moreover, the interaction between nanonutrients and plants, soils, soil biota and the entire agroecosystem will be also highlighted.

Postharvest quality and nutrient contents of long sweet pepper enhanced by supplementary potassium foliar application

ABSTRACT Inadequate amounts of potassium uptake by plant roots, even if it is available in soil, can be due to soil pH, plant type, and plant growth stage. Quality and shelf-life of long sweet pepper (Capsicum annuum L.) are affected by plant nutrition. To determine the suitable potassium source for foliar fertilization during plant growth, effects of supplementary foliar K sources (K-humate, KCl, and K2SO4) were evaluated on fruit quality, chemical composition, and postharvest behavior of long sweet pepper. Pepper fruit were stored for 28 days at 10°C. Fruit weight loss and decay were reduced, and total soluble solids were increased by supplementary K application; K2SO4 and KCl were the most effective sources. The L* and chrome values, as indicator for surface color, were enhanced by K foliar fertilizer. Chlorophyll a and b were increased by K treatments compared to control. Carotenoids were increased by KCl treatment; K2SO4 was the most effective source for enhanced total phenols. Total sugar and vitamin C were increased by K application, especially when K was added as KCl. Nitrogen and phosphorous contents in fruit were enhanced by K-humate and KCl treatments while potassium content was enhanced by all K treatments. The K2SO4 and KCl could be suitable K sources for foliar fertilizer during plant growth to enhance growth, yield, and quality of pepper fruit.

Quality and Shelf-Life of Onion Bulbs Influenced by Biostimulants

ABSTRACT Onion (Allium cepa L) yield and postharvest shelf-life have not been meeting their potentials even when recommended amounts of mineral fertilizers are applied during production. Biostimulants have been proposed as alternatives to mineral fertilizers to improve crop production within sustainable agriculture systems. The objective of this study was to assess the effects of the commercially available biostimulants Humic Total, Amino Total, Seamino Pro, CaBoron, and Elga 600 on yield, bulb quality, and storage ability of onion, cv. Giza 20, during the cropping seasons in 2014 and 2015. The biostimulants significantly increased total yield and bulb weight and decreased cull yield compared to the control. The best treatments were Humic Total, Amino Total, and CaBoron. Control plants had bulb total soluble solids and firmness that were not different from other treatments. The lowest decay rates were from plants receiving Amino Total and CaBoron and the control had the highest bulb weight loss. Onion growth, yield, quality, and storage ability may be improved with application of biostimulants.