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Plant nutrition

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Title: Plant nutrition  
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Plant nutrition

Plant nutrition is the study of the chemical elements and compounds necessary for plant growth, plant metabolism and their external supply. In 1972, E. Epstein defined two criteria for an element to be essential for plant growth:University of Wah

  1. in its absence the plant is unable to complete a normal life cycle;
  1. or that the element is part of some essential plant constituent or metabolite.

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

The macronutrients are consumed in larger quantities and are present in plant tissue in quantities from 0.2% to 4.0% (on a dry matter weight basis). Micro nutrients are present in plant tissue in quantities measured in parts per million, ranging from 5 to 200 ppm, or less than 0.02% dry weight.[3]

Most soil conditions across the world can provide plants with adequate nutrition and do not require fertilizer for a complete life cycle. However, humans can artificially modify soil through the addition of fertilizer to promote vigorous growth and increase yield. The plants are able to obtain their required nutrients from the fertilizer added to the soil. A colloidal carbonaceous residue, known as humus, can serve as a nutrient reservoir.[4] Even with adequate water and sunshine, nutrient deficiency can limit growth.

Nutrient uptake from the soil is achieved by cation exchange, where root hairs pump hydrogen ions (H+) into the soil through proton pumps. These hydrogen ions displace cations attached to negatively charged soil particles so that the cations are available for uptake by the root.

Plant nutrition is a difficult subject to understand completely, partly because of the variation between different plants and even between different species or individuals of a given clone. An element present at a low level may cause deficiency symptoms, while the same element at a higher level may cause toxicity. Further, deficiency of one element may present as symptoms of toxicity from another element. An abundance of one nutrient may cause a deficiency of another nutrient. For example, lower availability of a given nutrient such as SO42− can affect the uptake of another nutrient, such as NO3. As another example, K+ uptake can be influenced by the amount of NH4+ available.[4]

The Water potential plays a key role in a plants nutrient uptake. If the water potential is more negative within the plant than the surrounding soils, the nutrients will move from the region of higher solute concentration—in the soil—to the area of lower solute concentration: in the plant.

There are three fundamental ways plants uptake nutrients through the root:

  1. simple diffusion, occurs when a nonpolar molecule, such as O2, CO2, and NH3 follows a concentration gradient, moving passively through the cell lipid bilayer membrane without the use of transport proteins.
  2. facilitated diffusion, is the rapid movement of solutes or ions following a concentration gradient, facilitated by transport proteins.
  3. Active transport, is the uptake by cells of ions or molecules against a concentration gradient; this requires an energy source, usually ATP, to power molecular pumps that move the ions or molecules through the membrane.[4]
  • Nutrients are moved inside a plant to where they are most needed. For example, a plant will try to supply more nutrients to its younger leaves than to its older ones. When nutrients are mobile, symptoms of any deficiency become apparent first on the older leaves. However, not all nutrients are equally mobile. Nitrogen, phosphorus, and potassium are mobile nutrients, while the others have varying degrees of mobility. When a less mobile nutrient is deficient, the younger leaves suffer because the nutrient does not move up to them but stays in the older leaves. This phenomenon is helpful in determining which nutrients 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 out biological nitrogen fixation, in which atmospheric nitrogen (N2) is converted into ammonium (NH4); and
  2. with mycorrhizal fungi, which through their association with the plant roots help to create a larger effective root surface area. Both of these mutualistic relationships 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 in the soil to support their growth. These can be supplied by 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 their plants in a controlled environment. The most common solution, is the Hoagland solution, developed by D. R. Hoagland in 1933, the solution consists of all the essential nutrients in the correct proportions necessary for most plant growth.[4] An aerator is used to prevent an anoxic event or hypoxia. Hypoxia can affect nutrient uptake of a plant because without oxygen present, respiration becomes inhibited within the root cells. The Nutrient film technique is a variation of hydroponic technique. The roots are not fully submerged, which allows for adequate aeration of the roots, while a "film" thin layer of nutrient rich water is pumped through the system to provide nutrients and water to the plant.


  • Processes 1
  • Functions of nutrients 2
    • Macronutrients (derived from air and water) 2.1
      • Carbon 2.1.1
      • Hydrogen 2.1.2
      • Oxygen 2.1.3
    • Macronutrients (primary) 2.2
      • Nitrogen 2.2.1
      • Phosphorus 2.2.2
      • Potassium 2.2.3
    • Macronutrients (secondary and tertiary) 2.3
      • Sulphur 2.3.1
      • Calcium 2.3.2
      • Magnesium 2.3.3
    • Micro-nutrients 2.4
      • Iron 2.4.1
      • Molybdenum 2.4.2
      • Boron 2.4.3
      • Copper 2.4.4
      • Manganese 2.4.5
      • Sodium 2.4.6
      • Zinc 2.4.7
      • Nickel 2.4.8
      • Chlorine 2.4.9
      • Cobalt 2.4.10
      • Aluminium 2.4.11
      • Silicon 2.4.12
    • Nutrient deficiency 2.5
    • Nutrient status of plants 2.6
  • See also 3
  • References 4
    • Notes 4.1
    • Sources 4.2
  • External links 5


Plants take up essential elements from the soil through their roots and from the air (mainly consisting of nitrogen and oxygen) through their leaves. Nutrient uptake in the soil is achieved by cation exchange, wherein root hairs pump hydrogen ions (H+) into the soil through proton pumps. These hydrogen ions displace cations attached to negatively charged soil particles so that the cations are available for uptake by the root. In the leaves, stomata open to take in carbon dioxide and expel oxygen. The carbon dioxide molecules are used as the carbon source in photosynthesis.

Functions of nutrients

At least 17 elements are known to be essential nutrients for plants. In relatively large amounts, the soil supplies nitrogen, phosphorus, potassium, calcium, magnesium, and sulphur; these are often called the macronutrients. In relatively small amounts, the soil supplies iron, manganese, boron, molybdenum, copper, zinc, chlorine, and cobalt, the so-called micronutrients. Nutrients must be available not only in sufficient amounts but also in appropriate ratios.

Plant nutrition is a difficult subject to understand completely, partially because of the variation between different plants and even between different species or individuals of a given clone. Elements present at low levels may cause deficiency symptoms, and toxicity is possible at levels that are too high. Furthermore, deficiency of one element may present as symptoms of toxicity from another element, and vice versa.

Although nitrogen is plentiful in the Earth's atmosphere, relatively few plants engage in nitrogen fixation (conversion of atmospheric nitrogen to a biologically useful form). Most plants therefore require nitrogen compounds to be present in the soil in which they grow.

Carbon and oxygen are absorbed from the air, while other nutrients are absorbed from the soil. Green plants obtain their carbohydrate supply from the carbon dioxide in the air by the process of photosynthesis. Each of these nutrients is used in a different place for a different essential function.[5]

Macronutrients (derived from air and water)


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


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


Oxygen by itself or in the molecules of H2O or CO2 are necessary for plant cellular respiration. Cellular respiration is the process of generating energy-rich adenosine triphosphate (ATP) via the consumption of sugars made in photosynthesis. Plants produce oxygen gas during photosynthesis to produce glucose but then require oxygen to undergo aerobic cellular respiration and break down this glucose and produce ATP.

Macronutrients (primary)


Nitrogen is a major constituent of several of the most important plant substances. For example, nitrogen compounds comprise 40% to 50% of the dry matter of protoplasm, and it is a constituent of amino acids, the building blocks of proteins (Swan 1971a).[6] Nitrogen deficiency most often results in stunted growth, slow growth, and chlorosis. Nitrogen deficient plants will also exhibit a purple appearance on the stems, petioles and underside of leaves from an accumulation of anthocyanin pigments.[4] Most of the nitrogen taken up by plants is from the soil in the forms of NO3, although in acid environments such as boreal forests where nitrification is less likely to occur, ammonium NH4+ is more likely to be the dominating source of nitrogen.[7] Amino acids and proteins can only be built from NH4+ so NO3 must be reduced. Under many agricultural settings, nitrogen is the limiting nutrient of high growth. Some plants require more nitrogen than others, such as corn (Zea mays). Because nitrogen is mobile, the older leaves exhibit chlorosis and necrosis earlier than the younger leaves. Soluble forms of nitrogen are transported as amines and amides.[4]

The growth of all organisms depends on the availability of mineral nutrients, and none is more important than ammonium (NH4) or nitrate (NO3) ions. The weathering of rocks releases these ions so slowly that it has a negligible effect on the availability of fixed nitrogen. Therefore, nitrogen is often the limiting factor for growth and biomass production in all environments where there is suitable climate and availability of water to support life.

Nitrogen enters the plant largely through the Konrad, Mengel; Kirkby, Ernest; Kosegarten and Appel (2001). Principles of Plant Nutrition (5th ed.). Kluwer Academic Publishers.

  • Journal of Plant Nutrition
  • International Fertilizer Industry Association
  • Principles of Plant Nutrition

External links



  1. ^ Emanuel Epstein. Mineral Nutrition of Plants: Principles and Perspectives. 
  2. ^ a b Allen V. Barker; D. J. Pilbeam (2007). Handbook of plant nutrition. CRC Press. pp. 4–.  
  3. ^ Retrieved Jan. 2010
  4. ^ a b c d e f g h i j k l m n Norman P. A. Huner; William Hopkins. "3 & 4". Introduction to Plant Physiology 4th Edition. John Wiley & Sons, Inc.  
  5. ^ Pages 68 and 69 Taiz and Zeiger Plant Physiology 3rd Edition 2002 ISBN 0-87893-823-0
  6. ^ a b Swan, H.S.D. 1971a. Relationships between nutrient supply, growth and nutrient concentrations in the foliage of white and red spruce. Pulp Pap. Res. Inst. Can., Woodlands Pap. WR/34. 27 p.
  7. ^ Lowenfels, Lewis, Jeff, Wayne (2011). Teaming with microbes. pp. 49, 110.  
  8. ^ Krasowski, M.J.; Owens, J.N. 1999. Tracheids in white spruce seedling’s long lateral roots in response to nitrogen availability. Plant and Soil 217(1/2):215–228.
  9. ^ Black, C.A. 1957. Soil-plant relationships. New York, Wiley and Sons. 332 p.
  10. ^ a b c Russell, E.W. 1961. Soil Conditions and Plant Growth, 9th ed. Longmans Green, London, U.K.. 688 p.
  11. ^ Benzian, B. 1965. Experiments on nutrition problems in forest nurseries. U.K. Forestry Commission, London, U.K., Bull. 37. 251 p. (Vol. I) and 265 p. (Vol II).
  12. ^ Swan, H.S.D. 1960b. The mineral nutrition of Canadian pulpwood species. Phase II. Fertilizer pellet field trials. Progress Rep. 1. Pulp Pap. Res. Instit. Can., Montreal QC, Woodlands Res. Index No. 115, Inst. Project IR-W133, Res. Note No. 10. 6 p.
  13. ^ Swan, H.S.D. 1962. The scientific use of fertilizers in forestry. p. 13-24 in La Fertilisation Forestière au Canada. Fonds de Recherches Forestières, Laval Univ., Quebec QC, Bull. 5
  14. ^ Heiberg, S.O.; White, D.P. 1951. Potassium deficiency of reforested pine and spruce stands in northern New York. Soil Sci. Soc. Amer. Proc. 15:369–376.
  15. ^ Sato, Y.; Muto, K. 1951. (Factors affecting cold resistance of tree seedlings. II. On the effect of potassium salts.) Hokkaido Univ., Coll. Agric., Coll. Exp. Forests, Res. Bull. 15:81–96.
  16. ^ a b University of Zurich (2011). Blossom end rot: Transport protein identified.
  17. ^ a b (2012). New Light Shined on Photosynthesis. University of Arizona
  18. ^ a b Chapman, H.D. (Ed.) 1966. Diagnostic Criteria for Plants and Soils. Univ. California, Office of Agric. Publ. 794 p.
  19. ^ a b Dunn, C.E. 1991. Assessment of biogeochemical mapping at low sample density. Trans. Instit. Mining Metall., Vol. 100:B130–B133.
  20. ^ (2012). "Nutrient and toxin all at once: How plants absorb the perfect quantity of minerals". Ruhr-Universität
  21. ^ a b "Silicon nutrition in plants" (PDF). Plant Health Care,Inc.: 1. 12 December 2000. Retrieved 1 July 2011. 
  22. ^ Prakash, Dr. N. B. (2007). "Evaluation of the calcium silicate as a source of silicon in aerobic and wet rice". University of Agricultural Science Bangalore. p. 1. 
  23. ^ "AAPFCO Board of Directors 2006 Mid-Year Meeting" (PDF). Association of American Plant Food Control Officials. Retrieved 18 July 2011. 
  24. ^ Miranda, Stephen R.; Barker, Bruce (August 4, 2009). "Silicon: Summary of Extraction Methods". Harsco Minerals. Retrieved 18 July 2011. 
  25. ^ Ronco, F. 1970. Chlorosis of planted Engelmann spruce seedlings unrelated to nitrogen content. Can. J. Bot. 48(5):851–853.
  26. ^ a b c Parent, S.-E. et al. 2013. The plant ionome revisited by the nutrient balance concept. Front. Plant Sci. 4. doi:10.3389/fpls.2013.00039
  27. ^ a b Baxter, I. 2015. Should we treat the ionome as a combination of individual elements, or should we be deriving novel combined traits? J. Exp. Bot. 66, 2127–2131. doi:10.1093/jxb/erv040
  28. ^ a b Bittsanszky, A. et al. 2015. Overcoming ammonium toxicity. Plant Sci. Int. J. Exp. Plant Biol. 231C, 184–190. doi:10.1016/j.plantsci.2014.12.005



See also

[27] [28] [28]

Nutrient status (mineral nutrient and trace element composition, also called ionome and nutrient profile) of plants are commonly portrayed by tissue elementary analysis. Interpretation of the results of such studies, however, has been controversial.[26] During the last decades the nearly two-century-old “law of minimum” or “Liebig's law” (that states that plant growth is controlled not by the total amount of resources available, but by the scarcest resource) has been replaced by several mathematical approaches that use different models in order to take the interactions between the individual nutrients into account. The latest developments in this field are based on the fact that the nutrient elements (and compounds) do not act independently from each other;[26] Baxter, 2015,[27] because there may be direct chemical interactions between them or they may influence each other’s uptake, translocation, and biological action via a number of mechanisms as exemplified for the case of ammonia.[26]

Nutrient status of plants

Chlorosis of foliage is not always due to mineral nutrient deficiency. Solarization can produce superficially similar effects, though mineral deficiency tends to cause premature defoliation, whereas solarization does not, nor does solarization depress nitrogen concentration.[25]

The effect of a nutrient deficiency can vary from a subtle depression of growth rate to obvious stunting, deformity, discoloration, distress, and even death. Visual symptoms distinctive enough to be useful in identifying a deficiency are rare. Most deficiencies are multiple and moderate. However, while a deficiency is seldom that of a single nutrient, nitrogen is commonly the nutrient in shortest supply.

Nutrient deficiency

  • Wetland graminae-wetland rice, horsetail (10–15%)
  • Dryland graminae-sugar cane, most of the cereal species and few dicotyledons species (1–3%)
  • Most of dicotyledons especially legumes (<0.5%)
  • The long distance transport of Si in plants is confined to the xylem. Its distribution within the shoot organ is therefore determined by transpiration rate in the organs
  • The epidermal cell walls are impregnated with a film layer of silicon and effective barrier against water loss, cuticular transpiration rate in the organs.

Higher plants differ characteristically in their capacity to take up silicon. Depending on their SiO2 content they can be divided into three major groups:

In plants, silicon has been shown in experiments to strengthen cell walls, improve plant strength, health, and productivity.[21] There have been studies showing evidence of silicon improving drought and frost resistance, decreasing lodging potential and boosting the plant's natural pest and disease fighting systems.[22] Silicon has also been shown to improve plant vigor and physiology by improving root mass and density, and increasing above ground plant biomass and crop yields.[21] Silicon is currently under consideration by the Association of American Plant Food Control Officials (AAPFCO) for elevation to the status of a "plant beneficial substance".[23][24]

Silicon is not considered an essential element for plant growth and development. It is always found in abundance in the environment and hence if needed it is available. It is found in the structures of plants and improves the health of plants.


  • Tea has a high tolerance for aluminum (Al) toxicity and the growth is stimulated by Al application. The possible reason is the prevention of Cu, Mn or P toxicity effects.
  • There have been reports that Al may serve as fungicide against certain types of root rot.


  1. The requirement of Co for N2 fixation in legumes and non-legumes have been documented clearly
  2. Protein synthesis of Rhizobium is impaired due to Co deficiency
  3. It is still not clear whether Co has direct effect on higher plant

Cobalt has proven to be beneficial to at least some plants, but is essential in others, such as legumes where it is required for nitrogen fixation for the symbiotic relationship it has with nitrogen-fixing bacteria. Vanadium may be required by some plants, but at very low concentrations. It may also be substituting for molybdenum. Selenium and sodium may also be beneficial.


Chlorine, as compounded chloride, is necessary for osmosis and ionic balance; it also plays a role in photosynthesis.


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


Zinc is required in a large number of enzymes and plays an essential role in DNA transcription. A typical symptom of zinc deficiency is the stunted growth of leaves, commonly known as "little leaf" and is caused by the oxidative degradation of the growth hormone auxin.


  • Improves the crop quality e.g. improve the taste of carrots by increasing sucrose
  1. Internal osmoticum
  2. Stomatal function
  3. Photosynthesis
  4. Counteraction in long distance transport
  5. Enzyme activation
  • Replacing K functions
  1. C4 metabolism
  2. Impair the conversion of pyruvate to phosphoenol-pyruva
  3. Reduce the photosystem II activity and ultrastructural changes in mesophyll chloroplast
  • Stimulate the growth—increase leaf area, stomata, improve the water balance
  • Na functions in metabolism
  1. Group A—a high proportion of K can be replaced by Na and stimulate the growth, which cannot be achieved by the application of K
  2. Group B—specific growth responses to Na are observed but they are much less distinct
  3. Group C—Only minor substitution is possible and Na has no effect
  4. Group D—No substitution is occurred
  • Essential for C4 plants rather C3
  • Substitution of K by Na: Plants can be classified into four groups:

Essentiality of sodium:

Sodium is involved in the regeneration of phosphoenolpyruvate in CAM and C4 plants. Sodium can potentially replace potassium's regulation of stomatal opening and closing.[4]


Manganese is necessary for photosynthesis,[17] including the building of chloroplasts. Manganese deficiency may result in coloration abnormalities, such as discolored spots on the foliage.


Copper is important for photosynthesis. Symptoms for copper deficiency include chlorosis. Involved in many enzyme processes. Necessary for proper photosythesis. Involved in the manufacture of lignin (cell walls). Involved in grain production. It is also hard to find in some conditions.


Boron is important for binding of pectins in the RGII region of the primary cell wall, secondary roles may be in sugar transport, cell division, and synthesizing certain enzymes. Boron deficiency causes necrosis in young leaves and stunting. Boron is required for the uptake and utilization of calcium, membrane functioning, pollen germination, cell elongation, cell differentiation and carbohydrate metabolism.


Molybdenum is a cofactor to enzymes important in building amino acids. Involved in Nitrogen metabolism. Mo is part of Nitrate reductase enzyme.


Iron is necessary for photosynthesis and is present as an enzyme cofactor in plants. Iron deficiency can result in interveinal chlorosis and necrosis. Iron is not a structural part of chlorophyll but very much essential for its synthesis. Copper deficiency can be responsible for promoting an iron deficiency.[20]


Plants are able sufficiently to accumulate most trace elements. Some plants are sensitive indicators of the chemical environment in which they grow (Dunn 1991),[19] and some plants have barrier mechanisms that exclude or limit the uptake of a particular element or ion species, e.g., alder twigs commonly accumulate molybdenum but not arsenic, whereas the reverse is true of spruce bark (Dunn 1991).[19] Otherwise, a plant can integrate the geochemical signature of the soil mass permeated by its root system together with the contained groundwaters. Sampling is facilitated by the tendency of many elements to accumulate in tissues at the plant’s extremities.

Some elements are directly involved in plant metabolism (Arnon and Stout, 1939). However, this principle does not account for the so-called beneficial elements, whose presence, while not required, has clear positive effects on plant growth. Mineral elements that either stimulate growth but are not essential, or that are essential only for certain plant species, or under given conditions, are usually defined as beneficial elements.


The outstanding role of magnesium in plant nutrition is as a constituent of the chlorophyll molecule. As a carrier, it is also concerned in numerous enzyme reactions as an effective activator, in which it is closely associated with energy-supplying phosphorus compounds. Magnesium is very mobile in plants, and, like potassium, when deficient is translocated from older to younger tissues, so that signs of deficiency appear first on the oldest needles and then spread progressively to younger and younger tissues and is also a very important part of our body.


Calcium deficiency appears to have 2 main effects on plants: (1) stunting of the root system, and (2) a “fairly characteristic” effect on the visual appearance of leaves (Russell 1961).[10] Roots are usually affected before above-ground parts (Chapman 1966).[18]

Calcium in plants occurs chiefly in the Calcium deficiency causes stunting of root systems (Russell 1961).[10] Roots are usually affected before above-ground parts (Chapman 1966).[18]

Calcium regulates transport of other nutrients into the plant and is also involved in the activation of certain plant enzymes. Calcium deficiency results in stunting. This nutrient is involved in photosynthesis and plant structure.[16][17] Blossom end rot is also a result of inadequate calcium.[16]


Sulphur is a structural component of some amino acids and vitamins, and is essential in the manufacturing of chloroplasts. Sulphur is also found in the Iron Sulphur complexes of the electron transport chains in photosynthesis. It is immobile and deficiency therefore affects younger tissues first. Symptoms of deficiency include yellowing of leaves and stunted growth.


Macronutrients (secondary and tertiary)

Potassium regulates the opening and closing of the stomata by a potassium ion pump. Since stomata are important in water regulation, potassium reduces water loss from the leaves and increases drought tolerance. Potassium deficiency may cause necrosis or interveinal chlorosis. K+ is highly mobile and can aid in balancing the anion charges within the plant. Potassium helps in fruit colouration, shape and also increases its brix. Hence, quality fruits are produced in Potassium rich soils. It also has high solubility in water and leaches out of rocky or sandy soils. This water solubility can result in potassium deficiency. Potassium serves as an activator of enzymes used in photosynthesis and respiration[4] Potassium is used to build cellulose and aids in photosynthesis by the formation of a chlorophyll precursor. Potassium deficiency may result in higher risk of pathogens, wilting, chlorosis, brown spotting, and higher chances of damage from frost and heat.

When soil potassium levels are high, plants take up more potassium than needed for healthy growth. The term luxury consumption has been applied to this. When potassium is moderately deficient, the effects first appear in the older tissues, and from there progress towards the growing points. Acute deficiency severely affects growing points, and die-back commonly occurs. Symptoms of potassium deficiency in white spruce include: browning and death of needles (chlorosis); reduced growth in height and diameter; impaired retention of needles; and reduced needle length (Heiberg and White 1951).[14] A relationship between potassium nutrition and cold resistance has been found in several tree species, including 2 species of spruce (Sato and Muto 1951).[15]

Unlike other major elements, potassium does not enter into the composition of any of the important plant constituents involved in metabolism,[6] but it does occur in all parts of plants in substantial amounts. It seems to be of particular importance in leaves and at growing points. Potassium is outstanding among the nutrient elements for its mobility and solubility within plant tissues. Processes involving potassium include the formation of carbohydrates and proteins, the regulation of internal plant moisture, as a catalyst and condensing agent of complex substances, as an accelerator of enzyme action, and as contributor to photosynthesis, especially under low light intensity.


It is useful to apply a high phosphorus content fertilizer, such as bone meal, to perennials to help with successful root formation.[4]

Phosphorus deficiency can produce symptoms similar to those of nitrogen deficiency,[9] but as noted by Russel:[10] “Phosphate deficiency differs from nitrogen deficiency in being extremely difficult to diagnose, and crops can be suffering from extreme starvation without there being any obvious signs that lack of phosphate is the cause”. Russell’s observation applies to at least some coniferous seedlings, but Benzian[11] found that although response to phosphorus in very acid forest tree nurseries in England was consistently high, no species (including Sitka spruce) showed any visible symptom of deficiency other than a slight lack of lustre. Phosphorus levels have to be exceedingly low before visible symptoms appear in such seedlings. In sand culture at 0 ppm phosphorus, white spruce seedlings were very small and tinted deep purple; at 0.62 ppm, only the smallest seedlings were deep purple; an attitional 6.2 ppm, the seedlings were of good size and color.[12][13]

On some soils, the phosphorus nutrition of some conifers, including the spruces, depends on the ability of mycorrhizae to take up, and make soil phosphorus available to the tree, hitherto unobtainable to the non-mycorrhizal root. Seedling white spruce, greenhouse-grown in sand testing negative for phosphorus, were very small and purple for many months until spontaneous mycorrhizal inoculation, the effect of which was manifested by greening of foliage and the development of vigorous shoot growth.

. Because phosphorus is a mobile nutrient, older leaves will show the first signs of deficiency. anthocyanin in plants is characterized by an intense green coloration or reddening in leaves due to lack of chlorophyll. If the plant is experiencing high phosphorus deficiencies the leaves may become denatured and show signs of death. Occasionally the leaves may appear purple from an accumulation of Phosphorus deficiency A [4] Like nitrogen,


nitrogen cycle.


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