Plant nutrition

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It is the study of the chemical elements and compoundsthat are necessary for plant growth, and also of their ex-ternal supply and internal metabolism. In 1972, E. Ep-stein defined two criteria for an element to be essentialfor plant growth:

1. in its absence the plant is unable to complete a nor-mal life cycle; or

2. that the element is part of some essential plant con-stituent or metabolite.

This is in accordance with Liebig’s law of the mini-mum.[1] There are 14 essential plant nutrients. Carbonand oxygen are absorbed from the air, while other nutri-ents including water are typically obtained from the soil(exceptions include some parasitic or carnivorous plants).Plants must obtain the following mineral nutrients fromthe growing media:[2]

• the primary macronutrients: nitrogen (N), phospho-rus (P), potassium (K)

• the three secondary macronutrients: calcium (Ca),sulfur (S), magnesium (Mg)

• the micronutrients/trace minerals: boron (B), chlo-rine (Cl), manganese (Mn), iron (Fe), zinc (Zn),copper (Cu), molybdenum (Mo), nickel (Ni)

The macronutrients are consumed in larger quantities andare present in plant tissue in quantities from 0.2% to4.0% (on a dry matter weight basis). Micro nutrients arepresent in plant tissue in quantities measured in parts permillion, ranging from 5 to 200 ppm, or less than 0.02%dry weight.[3]

Most soil conditions across the world can provide plantswith adequate nutrition and do not require fertilizer fora complete life cycle. However, humans can artificiallymodify soil through the addition of fertilizer to promotevigorous growth and increase yield. The plants are ableto obtain their required nutrients from the fertilizer addedto the soil. A colloidal carbonaceous residue, known ashumus, can serve as a nutrient reservoir.[4] Even with ad-equate water and sunshine, nutrient deficiency can limitgrowth.Nutrient uptake from the soil is achieved by cation ex-change, where root hairs pump hydrogen ions (H+) intothe soil through proton pumps. These hydrogen ions dis-place cations attached to negatively charged soil particlesso that the cations are available for uptake by the root.Plant nutrition is a difficult subject to understand com-pletely, partly because of the variation between differ-ent plants and even between different species or indi-viduals of a given clone. An element present at a lowlevel may cause deficiency symptoms, while the same el-ement at a higher level may cause toxicity. Further, defi-ciency of one element may present as symptoms of toxic-ity from another element. An abundance of one nutrientmay cause a deficiency of another nutrient. For exam-ple, lower availability of a given nutrient such as SO4

2−

can affect the uptake of another nutrient, such as NO3−.

As another example, K+ uptake can be influenced by theamount of NH4

+ available.[4]

The root, especially the root hair, is the most essential or-gan for the uptake of nutrients. The structure and archi-tecture of the root can alter the rate of nutrient uptake.Nutrient ions are transported to the center of the root,the stele in order for the nutrients to reach the conduct-ing tissues, xylem and phloem.[4] The Casparian strip, acell wall outside the stele but within the root, preventspassive flow of water and nutrients, helping to regulatethe uptake of nutrients and water.[4] Xylem moves wa-ter and inorganic molecules within the plant and phloemaccounts for organic molecule transportation. Water po-

1

2 2 FUNCTIONS OF NUTRIENTS

tential plays a key role in a plants nutrient uptake. If thewater potential is more negative within the plant than thesurrounding soils, the nutrients will move from the regionof higher solute concentration—in the soil—to the area oflower solute concentration: in the plant.There are three fundamental ways plants uptake nutrientsthrough the root:

1. simple diffusion, occurs when a nonpolar molecule,such as O2, CO2, and NH3 follows a concentrationgradient, moving passively through the cell lipid bi-layer membrane without the use of transport pro-teins.

2. facilitated diffusion, is the rapid movement of so-lutes or ions following a concentration gradient, fa-cilitated by transport proteins.

3. Active transport, is the uptake by cells of ions ormolecules against a concentration gradient; this re-quires an energy source, usually ATP, to powermolecular pumps that move the ions or moleculesthrough the membrane.[4]

• Nutrients are moved inside a plant to where they aremost needed. For example, a plant will try to sup-ply more nutrients to its younger leaves than to itsolder ones. When nutrients are mobile, symptomsof any deficiency become apparent first on the olderleaves. However, not all nutrients are equally mo-bile. Nitrogen, phosphorus, and potassium are mo-bile nutrients, while the others have varying degreesof mobility. When a less mobile nutrient is deficient,the younger leaves suffer because the nutrient doesnot move up to them but stays in the older leaves.This phenomenon is helpful in determining whichnutrients a plant may be lacking.

Many plants engage in symbiosis with microorganisms.Two important types of these relationship are

1. with bacteria such as rhizobia, that carry outbiological nitrogen fixation, in which atmosphericnitrogen (N2) is converted into ammonium (NH4);and

2. with mycorrhizal fungi, which through their associ-ation with the plant roots help to create a larger ef-fective root surface area. Both of these mutualisticrelationships enhance nutrient uptake.[4]

Though nitrogen is plentiful in the Earth’s atmosphere,relatively few plants harbor nitrogen fixing bacteria,so most plants rely on nitrogen compounds present inthe soil to support their growth. These can be sup-plied by mineralization of soil organic matter or addedplant residues, nitrogen fixing bacteria, animal waste, orthrough the application of fertilizers.

Hydroponics, is a method for growing plants in a water-nutrient solution without the use of nutrient-rich soil.It allows researchers and home gardeners to grow theirplants in a controlled environment. The most commonsolution, is the Hoagland solution, developed by D. R.Hoagland in 1933, the solution consists of all the essen-tial nutrients in the correct proportions necessary for mostplant growth.[4] An aerator is used to prevent an anoxicevent or hypoxia. Hypoxia can affect nutrient uptake ofa plant because without oxygen present, respiration be-comes inhibited within the root cells. The Nutrient filmtechnique is a variation of hydroponic technique. Theroots are not fully submerged, which allows for adequateaeration of the roots, while a “film” thin layer of nutri-ent rich water is pumped through the system to providenutrients and water to the plant.

1 Processes

Plants take up essential elements from the soil throughtheir roots and from the air (mainly consisting of nitro-gen and oxygen) through their leaves. Nutrient uptake inthe soil is achieved by cation exchange, wherein root hairspump hydrogen ions (H+) into the soil through protonpumps. These hydrogen ions displace cations attachedto negatively charged soil particles so that the cations areavailable for uptake by the root. In the leaves, stomataopen to take in carbon dioxide and expel oxygen. Thecarbon dioxide molecules are used as the carbon sourcein photosynthesis.

2 Functions of nutrients

Further information: Soil § Nutrients

At least 17 elements are known to be essential nutrientsfor plants. In relatively large amounts, the soil supplies ni-trogen, phosphorus, potassium, calcium, magnesium, andsulphur; these are often called the macronutrients. In rel-atively small amounts, the soil supplies iron, manganese,boron, molybdenum, copper, zinc, chlorine, and cobalt,the so-called micronutrients. Nutrients must be availablenot only in sufficient amounts but also in appropriate ra-tios.Plant nutrition is a difficult subject to understand com-pletely, partially because of the variation between differ-ent plants and even between different species or individ-uals of a given clone. Elements present at low levels maycause deficiency symptoms, and toxicity is possible at lev-els that are too high. Furthermore, deficiency of one ele-ment may present as symptoms of toxicity from anotherelement, and vice versa.Although nitrogen is plentiful in the Earth’s atmosphere,relatively few plants engage in nitrogen fixation (con-

2.2 Macronutrients (primary) 3

version of atmospheric nitrogen to a biologically usefulform). Most plants therefore require nitrogen compoundsto be present in the soil in which they grow.Carbon and oxygen are absorbed from the air, while othernutrients are absorbed from the soil. Green plants obtaintheir carbohydrate supply from the carbon dioxide in theair by the process of photosynthesis. Each of these nutri-ents is used in a different place for a different essentialfunction.[5]

2.1 Macronutrients (derived from air andwater)

2.1.1 Carbon

Carbon forms the backbone of many plants biomolecules,including starches and cellulose. Carbon is fixed throughphotosynthesis from the carbon dioxide in the air and is apart of the carbohydrates that store energy in the plant.

2.1.2 Hydrogen

Hydrogen also is necessary for building sugars and build-ing the plant. It is obtained almost entirely from water.Hydrogen ions are imperative for a proton gradient tohelp drive the electron transport chain in photosynthesisand for respiration.[4]

2.1.3 Oxygen

Oxygen by itself or in the molecules of H2O or CO2 arenecessary for plant cellular respiration. Cellular respira-tion is the process of generating energy-rich adenosinetriphosphate (ATP) via the consumption of sugars madein photosynthesis. Plants produce oxygen gas during pho-tosynthesis to produce glucose but then require oxygen toundergo aerobic cellular respiration and break down thisglucose and produce ATP.

2.2 Macronutrients (primary)

Further information: Microbial inoculant

2.2.1 Phosphorus

Further information: Phosphorus cycle

Like nitrogen, phosphorus is closely concerned withmany vital plant processes. It is present mainly as a struc-tural component of the nucleic acids, deoxyribonucleicnucleic acid (DNA) and ribose nucleic acid (RNA), andas a constituent of fatty phospholipids, of importance inmembrane development and function. It is present in

both organic and inorganic forms, both of which are read-ily translocated. All energy transfers in the cell are criti-cally dependent on phosphorus. As a component of ATP,phosphorus is needed for the conversion of light energyto chemical energy (ATP) during photosynthesis. Phos-phorus can also be used to modify the activity of vari-ous enzymes by phosphorylation, and can be used for cellsignaling. Since ATP can be used for the biosynthesisof many plant biomolecules, phosphorus is important forplant growth and flower/seed formation. Phosphate es-ters make up DNA, RNA, and phospholipids. Most com-mon in the form of polyprotic phosphoric acid (H3PO4)in soil, but it is taken up most readily in the form ofH2PO4. Phosphorus is limited in most soils because itis released very slowly from insoluble phosphates. Undermost environmental conditions it is the limiting elementbecause of its small concentration in soil and high de-mand by plants and microorganisms. Plants can increasephosphorus uptake by a mutualism with mycorrhiza.[4] APhosphorus deficiency in plants is characterized by an in-tense green coloration in leaves. If the plant is experi-encing high phosphorus deficiencies the leaves may be-come denatured and show signs of necrosis. Occasion-ally the leaves may appear purple from an accumulationof anthocyanin. Because phosphorus is a mobile nutrient,older leaves will show the first signs of deficiency.On some soils, the phosphorus nutrition of someconifers, including the spruces, depends on the abilityof mycorrhizae to take up, and make soil phosphorusavailable to the tree, hitherto unobtainable to the non-mycorrhizal root. Seedling white spruce, greenhouse-grown in sand testing negative for phosphorus, were verysmall and purple for many months until spontaneous my-corrhizal inoculation, the effect of which was manifestedby greening of foliage and the development of vigorousshoot growth.Phosphorus deficiency can produce symptoms similar tothose of nitrogen deficiency (Black 1957),[6] but, as notedby Russell (1961):[7] “Phosphate deficiency differs fromnitrogen deficiency in being extremely difficult to diag-nose, and crops can be suffering from extreme starva-tion without there being any obvious signs that lack ofphosphate is the cause”. Russell’s observation applies toat least some coniferous seedlings, for Benzian (1965)[8]found that although response to phosphorus in very acidforest tree nurseries in England was consistently high, nospecies (including Sitka spruce) showed any visible symp-tom of deficiency other than a slight lack of lustre. Phos-phorus levels have to be exceedingly low before visiblesymptoms appear in such seedlings. In sand culture at 0ppm phosphorus, white spruce seedlings were very smalland tinted deep purple; at 0.62 ppm, only the smallestseedlings were deep purple; and at 6.2 ppm, the “lowphosphorus” treatment, seedlings were of good size andcolor (Swan 1960b).[9] Swan (1962)[10]

It is useful to apply a high phosphorus content fertilizer,such as bone meal, to perennials to help with successful

4 2 FUNCTIONS OF NUTRIENTS

root formation.[4]

2.2.2 Potassium

Unlike other major elements, potassium does not enterinto the composition of any of the important plant con-stituents involved in metabolism (Swan 1971a),[11] but itdoes occur in all parts of plants in substantial amounts.It seems to be of particular importance in leaves and atgrowing points. Potassium is outstanding among the nu-trient elements for its mobility and solubility within planttissues. Processes involving potassium include the forma-tion of carbohydrates and proteins, the regulation of inter-nal plant moisture, as a catalyst and condensing agent ofcomplex substances, as an accelerator of enzyme action,and as contributor to photosynthesis, especially under lowlight intensity.When soil potassium levels are high, plants take up morepotassium than needed for healthy growth. The term lux-ury consumption has been applied to this. When potas-sium is moderately deficient, the effects first appear inthe older tissues, and from there progress towards thegrowing points. Acute deficiency severely affects grow-ing points, and die-back commonly occurs. Symptomsof potassium deficiency in white spruce include: brown-ing and death of needles (chlorosis); reduced growth inheight and diameter; impaired retention of needles; andreduced needle length (Heiberg and White 1951).[12] Arelationship between potassium nutrition and cold resis-tance has been found in several tree species, including 2species of spruce (Sato and Muto 1951).[13]

Potassium regulates the opening and closing of thestomata by a potassium ion pump. Since stomata areimportant in water regulation, potassium reduces wa-ter loss from the leaves and increases drought tolerance.Potassium deficiency may cause necrosis or interveinalchlorosis. K+ is highly mobile and can aid in balancingthe anion charges within the plant. Potassium helps infruit colouration, shape and also increases its brix. Hence,quality fruits are produced in Potassium rich soils. Italso has high solubility in water and leaches out of rockyor sandy soils. This water solubility can result in potas-sium deficiency. Potassium serves as an activator of en-zymes used in photosynthesis and respiration[4] Potas-sium is used to build cellulose and aids in photosynthesisby the formation of a chlorophyll precursor. Potassiumdeficiency may result in higher risk of pathogens, wilting,chlorosis, brown spotting, and higher chances of damagefrom frost and heat.

2.2.3 Nitrogen

Further information: Nitrogen cycle

Nitrogen is a major constituent of several of the mostimportant plant substances. For example, nitrogen com-

pounds comprise 40% to 50% of the dry matter ofprotoplasm, and it is a constituent of amino acids, thebuilding blocks of proteins (Swan 1971a).[11] Nitrogendeficiency most often results in stunted growth, slowgrowth, and chlorosis. Nitrogen deficient plants will alsoexhibit a purple appearance on the stems, petioles andunderside of leaves from an accumulation of anthocyaninpigments.[4] Most of the nitrogen taken up by plants isfrom the soil in the forms of NO3

−, although in acid en-vironments such as boreal forests where nitrification isless likely to occur, ammonium NH4

+ is more likely to bethe dominating source of nitrogen.[14] Amino acids andproteins can only be built from NH4

+ so NO3− must be

reduced. Under many agricultural settings, nitrogen isthe limiting nutrient of high growth. Some plants requiremore nitrogen than others, such as corn (Zea mays). Be-cause nitrogen is mobile, the older leaves exhibit chloro-sis and necrosis earlier than the younger leaves. Sol-uble forms of nitrogen are transported as amines andamides.[4]

The growth of all organisms depends on the availabil-ity of mineral nutrients, and none is more importantthan nitrogen, which is required in large amounts asan essential component of proteins, nucleic acids, andother cellular constituents, including enzymes. Nitro-gen is an essential constituent of chlorophyll, but it influ-ences growth and utilization of sugars more than it influ-ences photosynthesis through a reduction in chlorophyll.There is an abundant supply of nitrogen in the earth’satmosphere—nearly 79% in the form of N2 gas. How-ever, N2 is unavailable for use by most organisms becausethere is a triple bond between the 2 nitrogen atoms, mak-ing the molecule almost inert. In order for nitrogen tobe used for growth it must be “fixed” (combined) in theform of ammonium (NH4) or nitrate (NO3) ions. Theweathering of rocks releases these ions so slowly that ithas a negligible effect on the availability of fixed nitrogen.Therefore, nitrogen is often the limiting factor for growthand biomass production in all environments where thereis suitable climate and availability of water to support life.Nitrogen enters the plant largely through the roots. A“pool” of soluble nitrogen accumulates. Its composi-tion within a species varies widely depending on severalfactors, including day length, time of day, night tem-peratures, nutrient deficiencies, and nutrient imbalance.Short day length promotes asparagine formation, whereasglutamine is produced under long day regimes. Dark-ness favours protein breakdown accompanied by highasparagine accumulation. Night temperaturemodifies theeffects due to night length, and soluble nitrogen tends toaccumulate owing to retarded synthesis and breakdownof proteins. Low night temperature conserves glutamine;high night temperature increases accumulation of as-paragine because of breakdown. Deficiency of K ac-centuates differences between long- and short-day plants.The pool of soluble nitrogen is much smaller than in well-nourished plants when N and P are deficient, since uptake

2.3 Macronutrients (secondary and tertiary) 5

of nitrate and further reduction and conversion of N toorganic forms is restricted more than is protein synthesis.Deficiencies of Ca, K, and S affect conversion of organicN to protein more than uptake and reduction. The sizeof the pool of soluble N is no guide per se to growth rate,but the size of the pool in relation to total N might bea useful ratio in this regard. Nitrogen availability in therooting medium also affects the size and structure of tra-cheids formed in the long lateral roots of white spruce(Krasowski and Owens 1999).[15]

Microorganisms have a central role in almost all aspectsof nitrogen availability, and therefore for life supporton earth. Some bacteria can convert N2 into ammoniaby the process termed nitrogen fixation; these bacteriaare either free-living or form symbiotic associations withplants or other organisms (e.g., termites, protozoa), whileother bacteria bring about transformations of ammonia tonitrate, and of nitrate to N2 or other nitrogen gases. Manybacteria and fungi degrade organic matter, releasing fixednitrogen for reuse by other organisms. All these processescontribute to the nitrogen cycle.

2.3 Macronutrients (secondary and ter-tiary)

2.3.1 Sulphur

Sulphur is a structural component of some amino acidsand vitamins, and is essential in the manufacturing ofchloroplasts. Sulphur is also found in the Iron Sulphurcomplexes of the electron transport chains in photosyn-thesis. It is immobile and deficiency therefore affectsyounger tissues first. Symptoms of deficiency include yel-lowing of leaves and stunted growth.

2.3.2 Calcium

Calcium regulates transport of other nutrients into theplant and is also involved in the activation of certainplant enzymes. Calcium deficiency results in stunting.This nutrient is involved in photosynthesis and plantstructure.[16][17] Blossom end rot is also a result of inade-quate calcium.[16]

Calcium in plants occurs chiefly in the leaves, with lowerconcentrations in seeds, fruits, and roots. A main func-tion is as a constituent of cell walls. When coupled withcertain acidic compounds of the jelly-like pectins of themiddle lamella, calcium forms an insoluble salt. It is alsointimately involved in meristems, and is particularly im-portant in root development, with roles in cell division,cell elongation, and the detoxification of hydrogen ions.Other functions attributed to calcium are: the neutral-ization of organic acids; inhibition of some potassium-activated ions; and a role in nitrogen absorption. A no-table feature of calcium-deficient plants is a defective rootsystem. Calcium deficiency causes stunting of root sys-

tems (Russell 1961).[7] Roots are usually affected beforeabove-ground parts (Chapman 1966).[18]

Calcium deficiency appears to have 2 main effects onplants: (1) stunting of the root system, and (2) a“fairly characteristic” effect on the visual appearance ofleaves (Russell 1961).[7] Roots are usually affected beforeabove-ground parts (Chapman 1966).[18]

2.3.3 Magnesium

Main article: Magnesium in biological systems

The outstanding role of magnesium in plant nutrition isas a constituent of the chlorophyll molecule. As a carrier,it is also concerned in numerous enzyme reactions as aneffective activator, in which it is closely associated withenergy-supplying phosphorus compounds. Magnesium isvery mobile in plants, and, like potassium, when deficientis translocated from older to younger tissues, so that signsof deficiency appear first on the oldest needles and thenspread progressively to younger and younger tissues andis also a very important part of our body.

2.3.4 Silicon

Silicon is not considered an essential element for plantgrowth and development.In plants, silicon has been shown in experiments tostrengthen cell walls, improve plant strength, health, andproductivity.[19] There have been studies showing evi-dence of silicon improving drought and frost resistance,decreasing lodging potential and boosting the plant’s nat-ural pest and disease fighting systems.[20] Silicon has alsobeen shown to improve plant vigor and physiology byimproving root mass and density, and increasing aboveground plant biomass and crop yields.[19] Silicon is cur-rently under consideration by the Association of Amer-ican Plant Food Control Officials (AAPFCO) for eleva-tion to the status of a “plant beneficial substance”.[21][22]

Silicon is the second most abundant element in earth’scrust. Higher plants differ characteristically in their ca-pacity to take up silicon. Depending on their SiO2 con-tent they can be divided into three major groups:

• Wetland graminae-wetland rice, horsetail (10–15%)

• Dryland graminae-sugar cane, most of the cerealspecies and few dicotyledons species (1–3%)

• Most of dicotyledons especially legumes (<0.5%)

• The long distance transport of Si in plants is confinedto the xylem. Its distribution within the shoot organis therefore determined by transpiration rate in theorgans

6 2 FUNCTIONS OF NUTRIENTS

• The epidermal cell walls are impregnated with a filmlayer of silicon and effective barrier against waterloss, cuticular transpiration rate in the organs.

2.4 Micro-nutrients

Some elements are directly involved in plant metabolism(Arnon and Stout, 1939). However, this principle doesnot account for the so-called beneficial elements, whosepresence, while not required, has clear positive effectson plant growth. Mineral elements that either stimulategrowth but are not essential, or that are essential only forcertain plant species, or under given conditions, are usu-ally defined as beneficial elements.Plants are able sufficiently to accumulate most trace ele-ments. Some plants are sensitive indicators of the chemi-cal environment in which they grow (Dunn 1991),[23] andsome plants have barrier mechanisms that exclude or limitthe uptake of a particular element or ion species, e.g.,alder twigs commonly accumulate molybdenum but notarsenic, whereas the reverse is true of spruce bark (Dunn1991).[23] Otherwise, a plant can integrate the geochem-ical signature of the soil mass permeated by its root sys-tem together with the contained groundwaters. Samplingis facilitated by the tendency of many elements to accu-mulate in tissues at the plant’s extremities.

2.4.1 Iron

Iron is necessary for photosynthesis and is present as anenzyme cofactor in plants. Iron deficiency can result ininterveinal chlorosis and necrosis. Iron is not a structuralpart of chlorophyll but very much essential for its synthe-sis. Copper deficiency can be responsible for promotingan iron deficiency.[24]

2.4.2 Molybdenum

Molybdenum is a cofactor to enzymes important in build-ing amino acids. Involved in Nitrogen metabolism. Mois part of Nitrate reductase enzyme.

2.4.3 Boron

Boron is important for binding of pectins in the RGII re-gion of the primary cell wall, secondary roles may be insugar transport, cell division, and synthesizing certain en-zymes. Boron deficiency causes necrosis in young leavesand stunting. Boron is required for the uptake and utiliza-tion of calcium, membrane functioning, pollen germina-tion, cell elongation, cell differentiation and carbohydratemetabolism.

2.4.4 Copper

Copper is important for photosynthesis. Symptoms forcopper deficiency include chlorosis. Involved in many en-zyme processes. Necessary for proper photosythesis. In-volved in the manufacture of lignin (cell walls). Involvedin grain production. It is also hard to find in some condi-tions.

2.4.5 Manganese

Manganese is necessary for photosynthesis,[17] includingthe building of chloroplasts. Manganese deficiency mayresult in coloration abnormalities, such as discolored spotson the foliage.

2.4.6 Sodium

Sodium is involved in the regeneration ofphosphoenolpyruvate in CAM and C4 plants. Sodiumcan potentially replace potassium’s regulation of stomatalopening and closing.[4]

Essentiality

• Essential for C4 plants rather C3

• Substitution of K byNa: Plants can be classified intofour groups:

1. Group A—a high proportion of K can be replacedby Na and stimulate the growth, which cannot beachieved by the application of K

2. Group B—specific growth responses to Na are ob-served but they are much less distinct

3. Group C—Only minor substitution is possible andNa has no effect

4. Group D—No substitution is occurred

• Stimulate the growth—increase leaf area, stomata,improve the water balance

• Na functions in metabolism

1. C4 metabolism

2. Impair the conversion of pyruvate to phosphoenol-pyruva

3. Reduce the photosystem II activity and ultrastruc-tural changes in mesophyll chloroplast

• Replacing K functions

1. Internal osmoticum

2.5 Nutrient deficiency 7

2. Stomatal function

3. Photosynthesis

4. Counteraction in long distance transport

5. Enzyme activation

• Improves the crop quality e.g. improve the taste ofcarrots by increasing sucrose

2.4.7 Zinc

Zinc is required in a large number of enzymes and playsan essential role in DNA transcription. A typical symp-tom of zinc deficiency is the stunted growth of leaves,commonly known as “little leaf” and is caused by the ox-idative degradation of the growth hormone auxin.

2.4.8 Nickel

In higher plants, Nickel is absorbed by plants in the formof Ni2+ ion. Nickel is essential for activation of urease,an enzyme involved with nitrogen metabolism that is re-quired to process urea. Without Nickel, toxic levels ofurea accumulate, leading to the formation of necrotic le-sions. In lower plants, Nickel activates several enzymesinvolved in a variety of processes, and can substitute forZinc and Iron as a cofactor in some enzymes.[2]

2.4.9 Chlorine

Chlorine, as compounded chloride, is necessary forosmosis and ionic balance; it also plays a role inphotosynthesis.

2.4.10 Cobalt

Cobalt has proven to be beneficial to at least some plants,but is essential in others, such as legumes where it is re-quired for nitrogen fixation for the symbiotic relationshipit has with nitrogen-fixing bacteria. Vanadiummay be re-quired by some plants, but at very low concentrations. Itmay also be substituting for molybdenum. Selenium andsodium may also be beneficial.

1. The requirement of Co for N2 fixation in legumesand non-legumes have been documented clearly

2. Protein synthesis of Rhizobium is impaired due toCo deficiency

3. It is still not clear whether Co has direct effect onhigher plant

2.4.11 Aluminium

• Tea has a high tolerance for Al toxicity and thegrowth is stimulated by Al application. The possi-ble reason is the prevention of Cu, Mn or P toxicityeffects.

• There have been reports that Al may serve as fungi-cide against certain types of root rot.

2.5 Nutrient deficiency

The effect of a nutrient deficiency can vary from a subtledepression of growth rate to obvious stunting, deformity,discoloration, distress, and even death. Visual symptomsdistinctive enough to be useful in identifying a deficiencyare rare. Most deficiencies are multiple and moderate.However, while a deficiency is seldom that of a single nu-trient, nitrogen is commonly the nutrient in shortest sup-ply.Chlorosis of foliage is not always due to mineral nutrientdeficiency. Solarization can produce superficially simi-lar effects, though mineral deficiency tends to cause pre-mature defoliation, whereas solarization does not, nordoes solarization depress nitrogen concentration (Ronco1970).[25]

2.6 Nutrient status of plants

Nutrient status (mineral nutrient and trace element com-position, also called ionome and nutrient profile) of plantsare commonly portrayed by tissue elementary analysis.Interpretation of the results of such studies, however, hasbeen controversial (for a recent overview see Parent et al.2013).[26] During the last decades the nearly two-century-old “law of minimum” or “Liebig’s law” (that states thatplant growth is controlled not by the total amount of re-sources available, but by the scarcest resource) has beenreplaced by several mathematical approaches that use dif-ferent models in order to take the interactions betweenthe individual nutrients into account. The latest devel-opments in this field are based on the fact that the nutri-ent elements (and compounds) do not act independentlyfrom each other (Parent et al., 2013;[26] Baxter, 2015[27]), because 1) there may be direct chemical interac-tions between them or 2) they may influence each other’suptake, translocation, and biological action via a numberof mechanisms as exemplified for the case of ammoniaby Bittsanszky et al. (2015).[26][27] [28] [28]

3 See also

• Horticulture

8 4 REFERENCES

• Photosynthesis

• Plant physiology

• Phytochemistry

• Soil pH

4 References

4.1 Notes[1] Emanuel Epstein. Mineral Nutrition of Plants: Principles

and Perspectives.

[2] Allen V. Barker; D. J. Pilbeam (2007). Handbook of plantnutrition. CRC Press. pp. 4–. ISBN 978-0-8247-5904-9.Retrieved 17 August 2010.

[3] http://aesl.ces.uga.edu/publications/plant/Nutrient.htmRetrieved Jan. 2010

[4] Norman P. A. Huner; William Hopkins. “3 & 4”. In-troduction to Plant Physiology 4th Edition. John Wiley &Sons, Inc. ISBN 978-0-470-24766-2.

[5] Pages 68 and 69 Taiz and Zeiger Plant Physiology 3rd Edi-tion 2002 ISBN 0-87893-823-0

[6] Black, C.A. 1957. Soil-plant relationships. New York,Wiley and Sons. 332 p.

[7] Russell, E.W. 1961. Soil Conditions and Plant Growth,9th ed. Longmans Green, London, U.K.. 688 p.

[8] Benzian, B. 1965. Experiments on nutrition problemsin forest nurseries. U.K. Forestry Commission, London,U.K., Bull. 37. 251 p. (Vol. I) and 265 p. (Vol II).

[9] Swan, H.S.D. 1960b. The mineral nutrition of Canadianpulpwood species. Phase II. Fertilizer pellet field trials.Progress Rep. 1. Pulp Pap. Res. Instit. Can., MontrealQC, Woodlands Res. Index No. 115, Inst. Project IR-W133, Res. Note No. 10. 6 p.

[10] Swan, H.S.D. 1962. The scientific use of fertilizersin forestry. p. 13-24 in La Fertilisation Forestière auCanada. Fonds de Recherches Forestières, Laval Univ.,Quebec QC, Bull. 5

[11] Swan, H.S.D. 1971a. Relationships between nutrient sup-ply, growth and nutrient concentrations in the foliage ofwhite and red spruce. Pulp Pap. Res. Inst. Can., Wood-lands Pap. WR/34. 27 p.

[12] Heiberg, S.O.; White, D.P. 1951. Potassium deficiency ofreforested pine and spruce stands in northern New York.Soil Sci. Soc. Amer. Proc. 15:369–376.

[13] Sato, Y.; Muto, K. 1951. (Factors affecting cold resis-tance of tree seedlings. II. On the effect of potassiumsalts.) Hokkaido Univ., Coll. Agric., Coll. Exp. Forests,Res. Bull. 15:81–96.

[14] Lowenfels, Lewis, Jeff, Wayne (2011). Teaming with mi-crobes. pp. 49, 110. ISBN 978-1-60469-113-9.

[15] Krasowski, M.J.; Owens, J.N. 1999. Tracheids in whitespruce seedling’s long lateral roots in response to nitrogenavailability. Plant and Soil 217(1/2):215–228.

[16] University of Zurich (2011). Blossom end rot:Transport protein identified. http://phys.org/news/2011-11-blossom-protein.html

[17] (2012). New Light Shined on Photosyn-thesis. http://www.newswise.com/articles/new-light-shined-on-photosynthesis University ofArizona

[18] Chapman, H.D. (Ed.) 1966. Diagnostic Criteria forPlants and Soils. Univ. California, Office of Agric. Publ.794 p.

[19] “Silicon nutrition in plants” (PDF). Plant Health Care,Inc.:1. 12 December 2000. Retrieved 1 July 2011.

[20] Prakash, Dr. N. B. (2007). “Evaluation of the calcium sil-icate as a source of silicon in aerobic and wet rice”. Uni-versity of Agricultural Science Bangalore. p. 1.

[21] “AAPFCO Board of Directors 2006 Mid-Year Meeting”(PDF). Association of American Plant Food Control Of-ficials. Retrieved 18 July 2011.

[22] Miranda, Stephen R.; Barker, Bruce (August 4, 2009).“Silicon: Summary of Extraction Methods”. HarscoMin-erals. Retrieved 18 July 2011.

[23] Dunn, C.E. 1991. Assessment of biogeochemical map-ping at low sample density. Trans. Instit. Mining Metall.,Vol. 100:B130–B133.

[24] (2012). “Nutrient and toxin all at once: How plants absorbthe perfect quantity of minerals”. http://esciencenews.com/articles/2012/04/13/nutrient.and.toxin.all.once.how.plants.absorb.perfect.quantity.minerals Ruhr-Universität

[25] Ronco, F. 1970. Chlorosis of planted Engelmann spruceseedlings unrelated to nitrogen content. Can. J. Bot.48(5):851–853.

[26] Parent, S.-E. et al. 2013. The plant ionome revisited bythe nutrient balance concept. Front. Plant Sci. 4. doi:10.3389/fpls.2013.00039

[27] Baxter, I. 2015. Should we treat the ionome as a com-bination of individual elements, or should we be deriv-ing novel combined traits? J. Exp. Bot. 66, 2127–2131.doi:10.1093/jxb/erv040

[28] Bittsanszky, A. et al. 2015. Overcoming ammonium tox-icity. Plant Sci. Int. J. Exp. Plant Biol. 231C, 184–190.doi:10.1016/j.plantsci.2014.12.005

4.2 Sources

Konrad, Mengel; Kirkby, Ernest; Kosegarten and Appel(2001). Principles of Plant Nutrition (5th ed.). KluwerAcademic Publishers. ISBN 1-4020-0008-1.

9

5 External links• Journal of Plant Nutrition

• International Fertilizer Industry Association

• Principles of Plant Nutrition

• Soil and Plant Nutrients

10 6 TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

6 Text and image sources, contributors, and licenses

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