Nanoscience and Nano-Technology

Nano-science coupled with nano-technology has emerged as possible cost-cutting measure to prodigal farming and environmental clean-up operations. It has ushered as a new interdisciplinary field by converging various science disciplines, and is highly relevant to agricultural and food systems. Environmental Protection Agency of USA defined nanotechnology as the understanding and control of matter at dimensions of roughly 1-100 nm, where unique physical properties make novel applications possible. By this definition all soil-clays, many chemicals derived from soil organic matter (SOM), several soil microorganisms fall into this category. Apart from native soil-materials, many new nanotech products are entering into soil system, some of which are used for agricultural production and some others for many other purposes.

Nano-science (also nanotechnology) has found applications in controlling release of nitrogen, characterization of soil minerals, studies of weathering of soil minerals and soil development, micro-morphology of soils, nature of soil rhizosphere, nutrient ion transport in soil-plant system, emission of dusts and aerosols from agricultural soil and their nature, zeoponics, and precision water farming. In its stride, nanotechnology converges soil mineralogy with imaging techniques, artificial intelligence, and encompass bio molecules and polymers with microscopic atoms and molecules, and macroscopic properties (thermodynamics) with microscopic properties (kinetics, wave theory, uncertainty principles, etc.), to name a few.

Some of the examples include clinoloptolite and other zeolite based substrates, and Fe-, Mn-, and Cu- substituted synthetic hydroxyapatites that have made it possible to grow crops in space stations and at Antarctica. This has eliminated costs of repeated launching of space crafts. A disturbing fact is that the fertilizer use efficiency is 20-50 percent for nitrogen, and 10-25 percent for phosphorus (<1% for rock phosphate in alkaline calcareous soils). With nano-fertilizers emerging as alternatives to conventional fertilizers, build ups of nutrients in soils and thereby eutrophication and drinking water contamination may be eliminated. In fact, nano-technology has opened up new opportunities to improve nutrient use efficiency and minimize costs of environmental protection. It has helped to divulge to recent findings that plant roots and microorganisms can directly lift nutrient ions from solid phase of minerals (that includes so-called susceptible (i.e., easily weatherable, as well as non-susceptible minerals).

Source: Mukhopadhyay et al. 2009. Nanoscience and Nano-Technology: Cracking Prodigal Farming.

Securing a future for soil science

The soil‐science community needs to continue to redefine its disciplinary context and  expand its core activities. These measures are critical, not only to meet contemporary societal challenges and the needs and interests of students, but also to respond effectively and engage actively in central issues addressed by the scientific community (environment, climate change, food security, etc.). We think that perceived constraints on “soil science” as a discipline (i.e., that we are narrowly focused scientifically) limit the prospects of fully applying our knowledge and understanding of soil processes to address emerging societal challenges. Because the structure and image of the Soil Science Society of America (SSSA) have appeared inflexible, we believe this has limited broad integration of soil science into emerging transdisciplinary science topics. We are hopeful that the current strategy and proposed SSSA activities (e.g., enhanced outreach, reorganization task force, etc.) will broaden the association and improve dialog with the wider scientific community. Nonetheless, the perception of soil science as a dynamic and rewarding professional career for established and younger scientists is in decline, the reputation of the discipline among peers in neighboring fields and by some funding agencies is alarmingly low. Image problems may contribute to the persistent decline in soil science student and faculty numbers (Baveye et al., 2006; Hopmans, 2007; Havlin et al., 2010). The rapidly shifting emphases of many early‐career soil scientists toward environmental issues confound the problem. It is therefore imperative that the SSSA take action to quickly reverse the persistent decline in key metrics—from attendance at annual meetings, to student populations and faculty in soil departments, to overall professional viability. Ironically this decrease in status is occurring when soil as a biogeochemical‐hydrological element of the biosphere is gaining prominence in the context of many societal challenges: climate and land‐use change, environmental protection, ecosystem services, food security and energy production, all while soil is undergoing profound change from human activities (Richter, 2007). Hence, in addition to building a stronger society internally, the SSSA must expand its efforts to build professional relationships with sister organizations in related environmental sciences. This white paper originated from members of the Soil Physics Division. More than 30 individuals (see Appendix I) across SSSA responded to an earlier draft; their suggestions are incorporated in this final version. We seek to chart a path forward—from the ground up—and to complement the agenda of other task forces/committees.

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Source: Dani et al. 2011. Securing a future for soil science – A white paper

Amino Acids in Agricultural Soil and their Uptake by Plants

Barley plants in a solution uptake study

Therefore, in the investigations this thesis is based upon, key aspects of the uptake of amino acids by agricultural plants were explored in field studies (to ensure ecological relevance) and laboratory analyses (to ensure precision). Small tension lysimeters were used to collect soil solution from several agricultural soils with minimal disturbance. Concentrations of free amino acids were found to be low (0-12.7 ìM). However, they may be continuously replenished from bound amino acid pools and were found to be sufficiently high (generally) for uptake by hydroponically grown barley, Hordeum vulgare L., and Arabidopsis, Arabidopsis thaliana L. Hence, the effective minimum concentrations for uptake by these species do not seem to exceed most of the field-measured concentrations.

The uptake affinity in both barley and Arabidopsis was found to be comparable to reported
values for nitrate at corresponding concentrations and for uptake of amino acids by soil micro-organisms. The amino acid transporters lysine histidine transporter 1 (LHT1) and amino acid permease 5 (AAP5) were found to be largely responsible for amino acid uptake in Arabidopsis at these concentrations. These transporters have complementary affinities for amino acids with differing properties; LHT1 transporting acidic and neutral amino acids, and AAP5 basic amino acids.
Furthermore, the gene expression of LHT1 and AAP5 clearly increased after roots were exposed to amino acids, even in the presence of inorganic nitrogen, resulting in up to 15-fold increases in the rate of amino acid uptake. The induced amino acid uptake rates were up to 10-fold higher than nitrate uptake rates in Arabidopsis. According to standard textbooks, nitrate and ammonium are the major nitrogen sources for plants. However, the results of these studies indicate that plants have the capacity to take up amino acids at field concentrations in presence of nitrate and ammonium. This capacity requires gene expression, synthesis and regulation of amino acid transporters, and the ability of plants to sense and respond to amino acid concentrations at ambient concentrations. There is, therefore, little doubt that plants can take up amino acids in their natural environment. Thus, it is time to reconsider traditional views of the nitrogen compounds used by agricultural plants.

Ref. Sandra Jämtgård. 2010. The Occurrence of Amino Acids in Agricultural Soil and their Uptake by Plants. Doctoral Thesis Swedish University of Agricultural Sciences Umeå.

Uptake of Multiple Amino Acids by Wheat

Schematic representation of the experimental setup, showing roots of wheat seedlings penetrating the glass media and the sampling procedure using 2 ml syringe.

Recent research has proven that higher plants can utilize amino acids as nitrogen (N) and carbon (C) sources. Most studies have focused on single amino acids with or without inorganicN, but a range of amino acids may be expected under conditions where the main N input derives from turnover of organic N sources. This study investigated the uptake of multiple amino acids by plant roots and further the active versus passive uptake was determined. Under minimum microbial activity conditions, seedlings of wheat (Triticum aestivum L. cv. ‘Baldus’) were exposed to a series of different concentrations of seven mixed amino acids solutions. Samples of the depleted solutions were periodically collected over a period of ten hours to measure the concentration of amino acids. For all tested amino acids passive uptake was a minor contribution compared to the total uptake. The uptake rates of the amino acids were well described by single Michaelis- Menten kinetic equations with R2 ranging from 0.87 to 0.96. All of the tested amino acids showed a similar uptake pattern.Wheat plants had the highest affinity (lowest Km values) for glutamine followed by tryptophan, alanine, arginine, glycine, and serine. The Vmax values for amino acids uptake by wheat ranged from 2.26 for tryptophan to 16.6 ìmol g.1 root FW h.1 in case of serine.

This study reports, for the first time the simultaneous uptake of multiple amino acids in important agricultural crops. The simultaneous uptake of the six mixed amino acids was dependent on the outer concentration and not on the amino acid type .  The uptake kinetics for the six amino acids showed similar trends, a results that agrees with the conclusion of Fischer et al. (1998) that plants contain multiple sets of amino acid transport proteins and that there are also a large number of general amino acid transporters, which can transport many different amino acids. The finding of multiple amino acids uptake also agrees with the expectations of Okumoto et al. (2002) that multiple transporters with differing kinetic characteristics are responsible for import of amino acids into seeds since this action could allow the growing seed to adapt to varying N-supply and alteration in amino acids available.

Ref: A. El-Naggar, A. de Neergaard, A. El-Araby & H. Hogh-Jensen (2009): Simultaneous Uptake of Multiple Amino Acids by Wheat, Journal of Plant Nutrition, 32:5, 725-740