Plant macronutrients

Calcium is a macronutrient essential for all organisms. Chlorine is a micronutrient essential for higher (ie, seed) plants but not considered essential for mammals. Above certain levels chloride is toxic to plants and animals, thus when considering calcium chloride, potentially large concentrations of calcium ion can be tolerated, but at these concentrations the chloride ion becomes toxic. 

Macronutrient An element required in large proportion by plants and other life forms for survival and growth. Macronutrients include Nitrogen (N), Potassium (K), and Phosphorous (P). 

The level of plant mineral nutrients available to trees is known to affect fruit quality, but its relative effect is often overestimated compared to other factors such as fruit load and light (and associated assimilate supply to fruit) (see sections above) (for review see Neilsen and Neilsen, 2003). The mineral nutrition of trees and fruits is complex. Uptake of the macronutrients nitrogen... 

Plant nutrients are interesting not only in connection with the yields and the fertilisation, but also with regard to environmental effects of energy conversion processes. Thus, they are regulated in various standards. Nitrogen (N), phosphorous (P) and potassium (K), as well as sulphur (S) and chlorine (Cl) are the most important environmentally relevant macronutrient and micronutrient elements. 

The increased growth response documented in almost all the solarization studies is mainly due to the above-cited higher levels of macronutrients or the improved uptake of micronutrients solubilized by humic substances (Chen and Aviad 1990 Chen et al. 1991). As a consequence of the enhancing effect of solarization on soil nutrients, Flores et al. (2007) suggested the application of low rates of mineral fertilizers before heating soil, in order to avoid an increased vegetative growth of the plants at the expense of crop yield. 

The different metal uptake by plants is accompanied by a different involvement of these trace metals and macronutrients in the biogeochemical cycles. A comparison of... 

The largest and most complex carbohydrates are the polysaccharides. They are polymers, long chains of repeating chemical units. Each individual unit is called a monomer. The monomer unit of polysaccharides is the monosaccharide, normally glucose. A typical polysaccharide contains several hundred individual monomers. Examples of common polysaccharides are starches, plant products that are major macronutrients in the human diet, and cellulose, found in plant cell walls. In the human diet, cellulose is referred to as fiber, indigestible but beneficial for normal intestinal motility. More than half of the Earth s total carbon is stored in these two polysaccharides. 

Humic substances have been shown to stimulate plant growth and nutrient accumulation (for reviews, see Vaughan and Malcolm, 1985 Chen and Aviad, 1990). Various studies performed on excised roots or whole plants show that the uptake of cationic and anionic macronutrients is usually greater when roots are in contact with appropriate concentrations of humic substances (Varanini and Pinton, 1995). 

As rocks are transformed to soil so a proportion of each element is usually converted to a form which plant roots can absorb. Consequently, most of the elements in the Periodic Table would probably be detected in any plant sample if sufficiently sensitive analytical methods were used. Uptake of an element is no evidence that it plays any role in the development of the plant since a root has no power to reject any soluble element entirely. One must therefore differentiate between those elements which are needed, the essential nutrients, and the rest. The conventional criteria by which the presence of an element is regarded as essential rather than adventitious are these the plant cannot complete its life cycle in the absence of the element the action of the element must be specific in that no other element can wholly substitute for it nor is the element simply involved in beneficially altering the plants root environment the element must be shown to be a constituent of an essential metabolite, or required for the proper functioning of an essential enzyme system or be uniquely involved in maintaining the overall ionic composition of tissue. Table 1-2 lists the elements which are generally accepted as being essential for plants. Major or macronutrients are separated from micronutrients, the latter being present in tissue concentration < 0.1 %. 

Table 1-2. The essential plant nutrients. The major or macronutrients are divided into (a) the major structural elements and (b) the other macronutrients.

Plant micronutrients are those required in plant tissue at concentrations which are equal to or less than 100 mg kg-1 dry weight. Macronutrients or major elements are those which are needed in concentrations of 1000 mg kg-1 or more in dry weight of the plant. Typical concentrations of elements in plants are given by Bowen (1966), Kabata-Pendias and Pendias (1984) and Markert (1992) Angelone and Bini (1992) have detailed elemental concentrations for plants and soils of western Europe. 

P and, to some extent, N, K, and S are higher in the tubers, whereas Ca and Mn concentrations are much lower than in other plant parts, the selectivity of which is thought to be associated with the mobility of each element and its physiological function in the plant. Macronutrient harvest indices range from only 16% for Ca to 94% for P (Table 10.6). Among the micronutrients, only Cu, Fe, Na, and Zn harvest indices were above 50%. The concentration of the other mineral elements (Ba, Co, Cr, Mo, Ni, Pb, Si, and Sr) in the tubers is low. 

FIGURE 10.13 General distribution of macronutrients within the Jerusalem artichoke throughout the production cycle grown at 30°57 N. (After Somda, Z.C. et al., J. Plant Nu.tr, 22, 1315-1334, 1999.)... 

Ekblad, A., Wallander, H., Carlsson, R. Huss-Danell, K. (1995). Fungal biomass in roots and extramatrical mycelium in relation to macronutrients and plant biomass of ectomycorrhizal Pinus sylvestris and Alnus incana. New Phytologist, 131, 443-51. 

The initial assumption might be that a photobiological H2 process would not require any raw materials. However, any biological process requires water and an adequate supply of macronutrients (i.e., nitrogen and phosphorus) and possibly some supplemental micronutrients, depending upon what nutrients and minerals are already present in the water supply to the process. One method to reduce raw material costs would be to utilize the waste stream from another process. For example, effluent streams from wastewater treatment anaerobic digesters are nitrogen rich, and blowdown streams from power plants are relatively pure. 

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