Plant nutrition is the study of the chemical elements and compounds necessary for plant growth, plant metabolism and their external supply. In 1972, Emanuel Epstein defined two criteria for an element to be essential for plant growth:
This is in accordance with Justus von Liebig's law of the minimum. The essential plant nutrients include carbon, oxygen and hydrogen which are absorbed from the air, whereas other nutrients including nitrogen are typically obtained from the soil (exceptions include some parasitic or carnivorous plants).
There are seventeen most important nutrients for plants. Plants must obtain the following mineral nutrients from their growing medium:-
These elements stay beneath soil as salts, so plants consume these elements as ions. The macronutrients are consumed in larger quantities; hydrogen, oxygen, nitrogen and carbon contribute to over 95% of a plants' entire biomass on a dry matter weight basis. Micronutrients are present in plant tissue in quantities measured in parts per million, ranging from 0.1 to 200 ppm, or less than 0.02% dry weight.
Most soil conditions across the world can provide plants adapted to that climate and soil with sufficient nutrition for a complete life cycle, without the addition of nutrients as fertilizer. However, if the soil is cropped it is necessary to artificially modify soil fertility through the addition of fertilizer to promote vigorous growth and increase or sustain yield. This is done because, even with adequate water and light, nutrient deficiency can limit growth and crop yield.
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.
The root, especially the root hair, is the essential organ for the uptake of nutrients. The structure and architecture 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 conducting tissues, xylem and phloem. The Casparian strip, a cell wall outside the stele but within the root, prevents passive flow of water and nutrients, helping to regulate the uptake of nutrients and water. Xylem moves water and mineral ions within the plant and phloem accounts for organic molecule transportation. Water potential plays a key role in a plant's 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:
Nutrients can be moved within plants 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 within the plant, 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
Though nitrogen is plentiful in the Earth's atmosphere, relatively few plants harbour nitrogen-fixing bacteria, so most plants rely on nitrogen compounds present in the soil to support their growth. These can be supplied by mineralization of soil organic matter or added plant residues, nitrogen fixing bacteria, animal waste, through the breaking of triple bonded N2 molecules by lightning strikes or through the application of fertilizers.
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 sulfur; 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. An abundance of one nutrient may cause a deficiency of another nutrient. For example, K+ uptake can be influenced by the amount of NH+
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.
Carbon forms the backbone of most plant biomolecules, including proteins, starches and cellulose. Carbon is fixed through photosynthesis; this converts carbon dioxide from the air into carbohydrates which are used to store and transport energy within 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.
Oxygen is a component of many organic and inorganic molecules within the plant, and is acquired in many forms. These include: O2 and CO2 (mainly from the air via leaves) and H2O, NO−
4 and SO2−
4 (mainly from the soil water via roots). Plants produce oxygen gas (O2) along with glucose during photosynthesis but then require O2 to undergo aerobic cellular respiration and break down this glucose to produce ATP.
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. It is also an essential constituent of chlorophyll. 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. Most of the nitrogen taken up by plants is from the soil in the forms of NO−
3, although in acid environments such as boreal forests where nitrification is less likely to occur, ammonium NH+
4 is more likely to be the dominating source of nitrogen. Amino acids and proteins can only be built from NH+
4, so NO−
3 must be reduced. In many agricultural settings, nitrogen is the limiting nutrient for rapid growth. Nitrogen is transported via the xylem from the roots to the leaf canopy as nitrate ions, or in an organic form, such as amino acids or amides. Nitrogen can also be transported in the phloem sap as amides, amino acids and ureides; it is therefore mobile within the plant, and the older leaves exhibit chlorosis and necrosis earlier than the younger leaves.
There is an abundant supply of nitrogen in the earth's atmosphere — N2 gas comprises nearly 79% of air. However, N2 is unavailable for use by most organisms because there is a triple bond between the two nitrogen atoms in the molecule, making it almost inert. In order for nitrogen to be used for growth it must be “fixed” (combined) in the form of ammonium (NH+
4) or nitrate (NO−
3) 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 a suitable climate and availability of water to support life.
Nitrogen enters the plant largely through the roots. A “pool” of soluble nitrogen accumulates. Its composition within a species varies widely depending on several factors, including day length, time of day, night temperatures, nutrient deficiencies, and nutrient imbalance. Short day length promotes asparagine formation, whereas glutamine is produced under long day regimes. Darkness favors protein breakdown accompanied by high asparagine accumulation. Night temperature modifies the effects due to night length, and soluble nitrogen tends to accumulate owing to retarded synthesis and breakdown of proteins. Low night temperature conserves glutamine; high night temperature increases accumulation of asparagine because of breakdown. Deficiency of K accentuates 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 of nitrate and further reduction and conversion of N to organic forms is restricted more than is protein synthesis. Deficiencies of Ca, K, and S affect the conversion of organic N to protein more than uptake and reduction. The size of 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 be a useful ratio in this regard. Nitrogen availability in the rooting medium also affects the size and structure of tracheids formed in the long lateral roots of white spruce (Krasowski and Owens 1999).
Microorganisms have a central role in almost all aspects of nitrogen availability, and therefore for life support on earth. Some bacteria can convert N2 into ammonia by the process termed nitrogen fixation; these bacteria are either free-living or form symbiotic associations with plants or other organisms (e.g., termites, protozoa), while other bacteria bring about transformations of ammonia to nitrate, and of nitrate to N2 or other nitrogen gases. Many bacteria and fungi degrade organic matter, releasing fixed nitrogen for reuse by other organisms. All these processes contribute to the nitrogen cycle.
Like nitrogen, phosphorus is involved with many vital plant processes. Within a plant, it is present mainly as a structural component of the nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), as well as a constituent of fatty phospholipids, that are important in membrane development and function. It is present in both organic and inorganic forms, both of which are readily translocated within the plant. All energy transfers in the cell are critically dependent on phosphorus. As with all living things, phosphorus is part of the Adenosine triphosphate (ATP), which is of immediate use in all processes that require energy with the cells. Phosphorus can also be used to modify the activity of various enzymes by phosphorylation, and is used for cell signaling. Phosphorus is concentrated at the most actively growing points of a plant and stored within seeds in anticipation of their germination. Phosphorus is most commonly found in the soil in the form of polyprotic phosphoric acid (H3PO4), but is taken up most readily in the form of H2PO−
4. Phosphorus is available to plants in limited quantities in most soils because it is released very slowly from insoluble phosphates and is rapidly fixed once again. Under most environmental conditions it is the element that limits growth because of this constriction and due to its high demand by plants and microorganisms. Plants can increase phosphorus uptake by a mutualism with mycorrhiza. A Phosphorus deficiency 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 anthocyanin. Because phosphorus is a mobile nutrient, older leaves will show the first signs of deficiency.
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 a greening of foliage and the development of vigorous shoot growth.
Phosphorus deficiency can produce symptoms similar to those of nitrogen deficiency, but as noted by Russel: “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 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; at 6.2 ppm, the seedlings were of good size and color.
It is useful to apply a high phosphorus content fertilizer, such as bone meal, to perennials to help with successful root formation.
Unlike other major elements, potassium does not enter into the composition of any of the important plant constituents involved in metabolism, 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.
Potassium regulates the opening and closing of the stomata by a potassium ion pump. Since stomata are important in water regulation, potassium regulates water loss from the leaves and increases drought tolerance. Potassium deficiency may cause necrosis or interveinal chlorosis. The potassium ion (K+) is highly mobile and can aid in balancing the anion (negative) charges within the plant. Potassium helps in fruit coloration, shape and also increases its brix. Hence, quality fruits are produced in potassium-rich soils. Potassium serves as an activator of enzymes used in photosynthesis and respiration. 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. A relationship between potassium nutrition and cold resistance has been found in several tree species, including two species of spruce.
Sulfur is a structural component of some amino acids (including cystein and methionine) and vitamins, and is essential for chloroplast growth and function; it is found in the iron-sulfur complexes of the electron transport chains in photosynthesis. It is needed for N2 fixation by legumes, and the conversion of nitrate into amino acids and then into protein.
In plants, sulfur cannot be mobilized from older leaves for new growth, so deficiency symptoms are seen in the youngest tissues first. Symptoms of deficiency include yellowing of leaves and stunted growth.
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. Blossom end rot is also a result of inadequate calcium.
Another common symptom of calcium deficiency in leaves is the curling of the leaf towards the veins or center of the leaf. Many times this can also have a blackened appearance Calcium has been found to have a positive effect in combating salinity in soils. It has been shown to ameliorate the negative effects that salinity has such as reduced water usage of plants. Calcium in plants occurs chiefly in the leaves, with lower concentrations in seeds, fruits, and roots. A major function is as a constituent of cell walls. When coupled with certain acidic compounds of the jelly-like pectins of the middle lamella, calcium forms an insoluble salt. It is also intimately involved in meristems, and is particularly important in root development, with roles in cell division, cell elongation, and the detoxification of hydrogen ions. Other functions attributed to calcium are; the neutralization of organic acids; inhibition of some potassium-activated ions; and a role in nitrogen absorption. A notable feature of calcium-deficient plants is a defective root system. Roots are usually affected before above-ground parts.
The outstanding role of magnesium in plant nutrition is as a constituent of the chlorophyll molecule. As a carrier, it is also involved 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 tissues and then spread progressively to younger tissues.
Plants are able sufficiently to accumulate most trace elements. Some plants are sensitive indicators of the chemical environment in which they grow (Dunn 1991), 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). 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.
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. It helps in the electron transport of plant.
Molybdenum is a cofactor to enzymes important in building amino acids and is involved in nitrogen metabolism. Molybdenum is part of the nitrate reductase enzyme (needed for the reduction of nitrate) and the nitrogenase enzyme (required for biological nitrogen fixation). Reduced productivity as a result of molybdenum deficiency is usually associated with the reduced activity of one or more of these enzymes.
Boron is absorbed by plants in the form of the anion BO3−
3. It is available to plants in moderately soluble mineral forms of Ca, Mg and Na borates and the highly soluble form of organic compounds. It is available to plants over a range of pH, from 5.0 to 7.5. It is mobile in the soil, hence, it is prone to leaching. Leaching removes substantial amounts of boron in sandy soil, but little in fine silt or clay soil. Boron's fixation to those minerals at high pH can render boron unavailable, while low pH frees the fixed boron, leaving it prone to leaching in wet climates. It precipitates with other minerals in the form of borax in which form it was first used over 400 years ago as a soil supplement. Decomposition of organic material causes boron to be deposited in the topmost soil layer. When soil dries it can cause a precipitous drop in the availability of boron to plants as the plants cannot draw nutrients from that desiccated layer. Hence, boron deficiency diseases appear in dry weather.
Boron has many functions within a plant: it affects flowering and fruiting, pollen germination, cell division, and active salt absorption. The metabolism of amino acids and proteins, carbohydrates, calcium, and water are strongly affected by boron. Many of those listed functions may be embodied by its function in moving the highly polar sugars through cell membranes by reducing their polarity and hence the energy needed to pass the sugar. If sugar cannot pass to the fastest growing parts rapidly enough, those parts die.
Boron is not relocatable in the plant via the phloem. It must be supplied to the growing parts via the xylem. Foliar sprays affect only those parts sprayed, which may be insufficient for the fastest growing parts, and is very temporary.
Boron is essential for the proper forming and strengthening of cell walls. Lack of boron results in short thick cells producing stunted fruiting bodies and roots. Calcium to boron ratio must be maintained in a narrow range for normal plant growth. For alfalfa, that calcium to boron ratio must be from 80:1 to 600:1. Boron deficiency appears at 800:1 and higher. Boron levels within plants differ with plant species and range from 2.3 mg/kg for barley to 94.7 mg/kg for poppy. Lack of boron causes failure of calcium metabolism which produces hollow heart in beets and peanuts.
Inadequate amounts of boron affect many agricultural crops, legume forage crops most strongly. Of the micronutrients, boron deficiencies are second most common after zinc. Deficiency results in the death of the terminal growing points and stunted growth.
Boron supplements derive from dry lake bed deposits such as those in Death Valley, USA, in the form of sodium tetraborate (borax), from which less soluble calcium borate is made. Foliar sprays are used on fruit crop trees in soils of high alkalinity. Boron is often applied to fields as a contaminant in other soil amendments but is not generally adequate to make up the rate of loss by cropping. The rates of application of borate to produce an adequate alfalfa crop range from 15 pounds per acre for a sandy-silt, acidic soil of low organic matter, to 60 pounds per acre for a soil with high organic matter, high cation exchange capacity and high pH.
Boron concentration in soil water solution higher than one ppm is toxic to most plants. Toxic concentrations within plants are 10 to 50 ppm for small grains and 200 ppm in boron-tolerant crops such as sugar beets, rutabaga, cucumbers, and conifers. Toxic soil conditions are generally limited to arid regions or can be caused by underground borax deposits in contact with water or volcanic gases dissolved in percolating water. Application rates should be limited to a few pounds per acre in a test plot to determine if boron is needed generally. Otherwise, testing for boron levels in plant material is required to determine remedies. Excess boron can be removed by irrigation and assisted by application of elemental sulfur to lower the pH and increase boron solubility.
Boron deficiencies can be detected by analysis of plant material to apply a correction before the obvious symptoms appear, after which it is too late to prevent crop loss. Strawberries deficient in boron will produce lumpy fruit; apricots will not blossom or, if they do, will not fruit or will drop their fruit depending on the level of boron deficit. Broadcast of boron supplements is effective and long term; a foliar spray is immediate but must be repeated.
Copper is important for photosynthesis. Symptoms for copper deficiency include chlorosis.It is involved in many enzyme processes; necessary for proper photosynthesis; involved in the manufacture of lignin (cell walls) and involved in grain production. It is also hard to find in some soil conditions.
Essentiality of sodium:
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.
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.
Cobalt has proven to be beneficial to at least some plants although it does not appear to be essential for most species. It has, however, been shown to be essential for nitrogen fixation by the nitrogen-fixing bacteria associated with legumes and other plants.
Aluminum is one of the few elements capable of making soil more acidic. This is achieved by aluminum taking hydroxide ions out of water, leaving hydrogen ions behind. As a result, the soil is more acidic, which makes it unlivable for many plants. Another consequence of aluminum in soils is aluminum toxicity, which inhibits root growth.
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.
In plants, silicon has been shown in experiments to strengthen cell walls, improve plant strength, health, and productivity. 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. 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. 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".
Selenium is probably not essential for flowering plants, but it can be beneficial; it can stimulate plant growth, improve tolerance of oxidative stress, and increase resistance to pathogens and herbivory.
Selenium is, however, an essential mineral element for animal (including human) nutrition and selenium deficiencies are known to occur when food or animal feed is grown on selenium-deficient soils. The use of inorganic selenium fertilizers can increase selenium concentrations in edible crops and animal diets thereby improving animal health.
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.
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.
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. 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; Baxter, 2015, 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.
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. 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 hydroponic technique in which the roots are not fully submerged. This 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.
Agrobiology is the science of plant nutrition and growth in relation to soil conditions, especially to determine ways to increase crop yields.
Agrobiology is generally concerned with:
Animal health and welfare
Plant Nutrition and Health
Organic AgricultureThe term given by wilcox. There are several universities providing courses of agrobiology e.g. at Aarhus University. There also is a Journal of Agrobiology published in the Czech Republic.Autotroph
An autotroph or primary producer, is an organism that produces complex organic compounds (such as carbohydrates, fats, and proteins) from simple substances present in its surroundings, generally using energy from light (photosynthesis) or inorganic chemical reactions (chemosynthesis). They are the producers in a food chain, such as plants on land or algae in water (in contrast to heterotrophs as consumers of autotrophs). They do not need a living source of energy or organic carbon. Autotrophs can reduce carbon dioxide to make organic compounds for biosynthesis and also create a store of chemical energy. Most autotrophs use water as the reducing agent, but some can use other hydrogen compounds such as hydrogen sulfide. Some autotrophs, such as green plants and algae, are phototrophs, meaning that they convert electromagnetic energy from sunlight into chemical energy in the form of reduced carbon.
Autotrophs can be photoautotrophs or chemoautotrophs. Phototrophs use light as an energy source, while chemotrophs use electron donors as a source of energy, whether from organic or inorganic sources; however in the case of autotrophs, these electron donors come from inorganic chemical sources. Such chemotrophs are lithotrophs. Lithotrophs use inorganic compounds, such as hydrogen sulfide, elemental sulfur, ammonium and ferrous iron, as reducing agents for biosynthesis and chemical energy storage. Photoautotrophs and lithoautotrophs use a portion of the ATP produced during photosynthesis or the oxidation of inorganic compounds to reduce NADP+ to NADPH to form organic compounds.Biocommunication (science)
In the study of the biological sciences, biocommunication is any specific type of communication within (intraspecific) or between (interspecific) species of plants, animals, fungi, protozoa and microorganisms. Communication basically means sign-mediated interactions following three levels of (syntactic, pragmatic and semantic) rules. Signs in most cases are chemical molecules (semiochemicals), but also tactile, or as in animals also visual and auditive. Biocommunication of animals may include vocalizations (as between competing bird species), or pheromone production (as between various species of insects), chemical signals between plants and animals (as in tannin production used by vascular plants to warn away insects), and chemically mediated communication between plants and within plants.
Biocommunication of fungi demonstrates that mycelia communication integrates interspecific sign-mediated interactions between fungal organisms soil bacteria and plant root cells without which plant nutrition could not be organized. Biocommunication of Archaea represents keylevels of sign-mediated interactions in the evolutionarily oldest akaryotes.Chara (alga)
Chara is a genus of charophyte green algae in the family Characeae. They are multicellular and superficially resemble land plants because of stem-like and leaf-like structures. They are found in fresh water, particularly in limestone areas throughout the northern temperate zone, where they grow submerged, attached to the muddy bottom. They prefer less oxygenated and hard water and are not found in waters where mosquito larvae are present. They are covered with calcium carbonate deposits and are commonly known as stoneworts. Cyanobacteria have been found growing as epiphytes on the surfaces of Chara, where they may be involved in fixing nitrogen, which is important to plant nutrition.Cluster root
Cluster roots, also known as proteoid roots, are plant roots that form clusters of closely spaced short lateral rootlets. They may form a two- to five-centimetre-thick mat just beneath the leaf litter. They enhance nutrient uptake, possibly by chemically modifying the soil environment to improve nutrient solubilisation. As a result, plants with proteoid roots can grow in soil that is very low in nutrients, such as the phosphorus-deficient native soils of Australia.
They were first described by Adolf Engler in 1894, after he discovered them on plants of the family Proteaceae growing in Leipzig Botanic Gardens. In 1960, Helen Purnell examined 44 species from ten Proteaceae genera, finding proteoid roots in every genus except Persoonia; she then coined the name "proteoid roots" in reference to the plant family in which it was known to occur. Proteoid roots are now known to occur in 27 different Proteaceae genera, plus around 30 species from other families, including Betulaceae, Casuarinaceae, Eleagnaceae, Leguminosae, Moraceae and Myricaceae. Similar structures also occur in species of Cyperaceae and Restionaceae, but their physiology is yet to be studied.Two forms are recognised: simple cluster roots form rootlets only along a root; compound cluster roots form the primary rootlets, and also form secondary rootlets on the primary rootlets.
Some Proteaceae, such as Banksia and Grevillea, are valued by the horticulture and floriculture industries. In cultivation, only slow-release low-phosphorus fertilizers should be used, as higher levels cause phosphorus toxicity and sometimes iron deficiency, leading to plant death. Crop management should minimise root disturbance, and weed control should be via slashing or contact herbicides.
Many plants with proteoid roots have economic value. Cultivated crops with proteoid roots include Lupinus and Macadamia.Daniel I. Arnon
Daniel Israel Arnon (November 14, 1910 – December 20, 1994) was a Polish-born American plant physiologist whose research led to greater insights into the operation of photosynthesis in plants. In 1973, he was awarded the National Medal of Science for "his fundamental research into the mechanism of green plant utilization of light to produce chemical energy and oxygen and for contributions to our understanding of plant nutrition."
Arnon was born on November 14, 1910, in Warsaw. Summers spent on the family's farm helped foster Arnon's interest in agriculture. His father had lost the family's food wholesale business after World War I and Arnon's readings of the works of Jack London led him to save up his money to head to California. He enrolled in the University of California, Berkeley from Poland, and would spend his entire professional career at the school, until his retirement in 1978. He ultimately earned his Ph.D. in plant physiology at UC Berkeley under Dennis R. Hoagland and some of his earliest research focused on growing plants in nutrient-enriched water rather than in the soil. During World War II, Arnon served in the United States Army in the Pacific Theater of Operations, where he used his prior experience with plant nutrition on Ponape Island, where there was no arable land available and he was able to grow food to feed the troops stationed there using gravel and nutrient-enriched water.After returning from military service, Arnon performed research on chloroplasts and their role in the photosynthesis process. His work was able to demonstrate how energy from sunlight is used to form adenosine triphosphate, the energy transport messenger within living cells, by adding a third phosphorus group to adenosine diphosphate. In 1954, Arnon reproduced the process in a laboratory, making him the first to successfully demonstrate the chemical function of photosynthesis, producing sugar and starch from inputs of carbon dioxide and water. He was elected a Fellow of the American Academy of Arts and Sciences in 1962.A resident of Kensington, California, Arnon died at age 84 on December 20, 1994, in Berkeley, California, of complications resulting from cardiac arrest. He had three daughters and two sons. His wife, the former Lucile Soule, died in 1986. in 1954Fertigation
Fertigation is the injection of fertilizers, used for soil amendments, water amendments and other water-soluble products into an irrigation system.
Fertigation is related to chemigation, the injection of chemicals into an irrigation system. The two terms are sometimes used interchangeably however chemigation is generally a more controlled and regulated process due to the nature of the chemicals used. Chemigation often involves insecticides herbicides, and fungicides, some of which pose health threat to humans, animals, and the environment.Humin
Humins are a class of organic compounds that are insoluble in water at all pH's. The term is used in two related contexts, in soil chemistry and saccharide chemistry. These dark brown solids are inhomogenous and their structures are often vaguely described.
Soil consists of both mineral (inorganic) and organic components. The organic components can be subdivided into fractions that are soluble, largely humic acids, and insoluble, the humins. Humins comprise about 50% of the organic matter in soil.Humins also produced during the dehydration of sugars, as is conducted in the conversion of cellulose to smaller organic compounds. These humins arise by the condensation of sugars with furfural and hydroxymethylfurfural, products of the dehydration of pentoses and hexoses. Since they are generally undesirable for chemical purposes, efforts are made to avoid their formation. Otherwise, humins are used for fuel.Mineralization (biology)
In biology, mineralization refers to a process where an inorganic substance precipitates in an organic matrix. This may be due to normal biological processes that take place during the life of an organism such as the formation of bones, egg shells, teeth, coral, and other exoskeletons. This term may also refer to abnormal processes that result in kidney and gall stones.Mycotroph
A mycotroph is a plant that gets all or part of its carbon, water, or nutrient supply through symbiotic association with fungi. The term can refer to plants that engage in either of two distinct symbioses with fungi:
Many mycotrophs have a mutualistic association with fungi in any of several forms of mycorrhiza. The majority of plant species are mycotrophic in this sense. Examples include Burmanniaceae.
Some mycotrophs are parasitic upon fungi in an association known as myco-heterotrophy.Nutrient
A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excreted by cells to create non-cellular structures, such as hair, scales, feathers, or exoskeletons. Some nutrients can be metabolically converted to smaller molecules in the process of releasing energy, such as for carbohydrates, lipids, proteins, and fermentation products (ethanol or vinegar), leading to end-products of water and carbon dioxide. All organisms require water. Essential nutrients for animals are the energy sources, some of the amino acids that are combined to create proteins, a subset of fatty acids, vitamins and certain minerals. Plants require more diverse minerals absorbed through roots, plus carbon dioxide and oxygen absorbed through leaves. Fungi live on dead or living organic matter and meet nutrient needs from their host.
Different types of organism have different essential nutrients. Ascorbic acid (vitamin C) is essential, meaning it must be consumed in sufficient amounts, to humans and some other animal species, but not to all animals and not to plants, which are able to synthesize it. Nutrients may be organic or inorganic: organic compounds include most compounds containing carbon, while all other chemicals are inorganic. Inorganic nutrients include nutrients such as iron, selenium, and zinc, while organic nutrients include, among many others, energy-providing compounds and vitamins.
A classification used primarily to describe nutrient needs of animals divides nutrients into macronutrients and micronutrients. Consumed in relatively large amounts (grams or ounces), macronutrients (carbohydrates, fats, proteins, water) are used primarily to generate energy or to incorporate into tissues for growth and repair. Micronutrients are needed in smaller amounts (milligrams or micrograms); they have subtle biochemical and physiological roles in cellular processes, like vascular functions or nerve conduction. Inadequate amounts of essential nutrients, or diseases that interfere with absorption, result in a deficiency state that compromises growth, survival and reproduction. Consumer advisories for dietary nutrient intakes, such as the United States Dietary Reference Intake, are based on deficiency outcomes and provide macronutrient and micronutrient guides for both lower and upper limits of intake. In many countries, macronutrients and micronutrients in significant content are required by regulations to be displayed on food product labels. Nutrients in larger quantities than the body needs may have harmful effects. Edible plants also contain thousands of compounds generally called phytochemicals which have unknown effects on disease or health, including a diverse class with non-nutrient status called polyphenols, which remain poorly understood as of 2017.
Plant nutrients consist of more than a dozen minerals absorbed through roots, plus carbon dioxide and oxygen absorbed or released through leaves. All organisms obtain all their nutrients from the surrounding environment.Rhizobiaceae
The Rhizobiaceae is a family of proteobacteria comprising multiple subgroups that enhance and hinder plant development. Some bacteria found in the family are used for plant nutrition and collectively make up the rhizobia. Other bacteria such as Agrobacterium tumefaciens and A. rhizogenes severely alter the development of plants in their ability to induce crown galls or hairy roots found on the stem. The family has been of an interest to scientists for centuries in their ability to associate with plants and modify plant development. The Rhizobiaceae are, like all Proteobacteria, Gram-negative. They are aerobic, and the cells are usually rod-shaped. Many species of the Rhizobiaceae are diazotrophs which are able to fix nitrogen and are symbiotic with plant roots.Soil pH
Soil pH is a measure of the acidity or basicity (alkalinity) of a soil. pH is defined as the negative logarithm (base 10) of the activity of hydronium ions (H+ or, more precisely, H3O+aq) in a solution. In soils, it is measured in a slurry of soil mixed with water (or a salt solution, such as 0.01 M CaCl2), and normally falls between 3 and 10, with 7 being neutral. Acid soils have a pH below 7 and alkaline soils have a pH above 7. Ultra-acidic soils (pH < 3.5) and very strongly alkaline soils (pH > 9) are rare.Soil pH is considered a master variable in soils as it affects many chemical processes. It specifically affects plant nutrient availability by controlling the chemical forms of the different nutrients and influencing the chemical reactions they undergo. The optimum pH range for most plants is between 5.5 and 7.5; however, many plants have adapted to thrive at pH values outside this range.Soil test
Soil test may refer to one or more of a wide variety of soil analysis conducted for one of several possible reasons. Possibly the most widely conducted soil tests are those done to estimate the plant-available concentrations of plant nutrients, in order to determine fertilizer recommendations in agriculture. Other soil tests may be done for engineering (geotechnical), geochemical or ecological investigations.Soil texture
Soil texture is a classification instrument used both in the field and laboratory to determine soil classes based on their physical texture. Soil texture can be determined using qualitative methods such as texture by feel, and quantitative methods such as the hydrometer method. Soil texture has agricultural applications such as determining crop suitability and to predict the response of the soil to environmental and management conditions such as drought or calcium (lime) requirements. Soil texture focuses on the particles that are less than two millimeters in diameter which include sand, silt, and clay. The USDA soil taxonomy and WRB soil classification systems use 12 textural classes whereas the UK-ADAS system uses 11. These classifications are based on the percentages of sand, silt, and clay in the soil..Substrate (biology)
In biology, a substrate is the surface on which an organism (such as a plant, fungus, or animal) lives. A substrate can include biotic or abiotic materials and animals. For example, encrusting algae that lives on a rock (its substrate) can be itself a substrate for an animal that lives on top of the algae.Trace element
A trace element is a chemical element whose concentration (or other measure of amount) is very low (a "trace amount"). The exact definition depends on the field of science:
In analytical chemistry, a trace element is one whose average concentration is less than 100 parts per million (ppm) measured in the atomic count or less than 100 micrograms per gram.
In biochemistry, an essential trace element is a dietary element that is needed in very minute quantities for the proper growth, development, and physiology of the organism. The dietary elements or essential trace elements are those that are required to perform vital metabolic activities in organisms.. Examples of essential trace elements in animals include Fe (hemoglobin), Cu (respiratory pigments), Co (Vitamin B12), Mn and Zn (enzymes). Some examples within the human body are cobalt, copper, fluorine, iodine, iron, manganese and zinc. Although they are essential, they become toxic at high concentrations. Elements such as Ag, As, Cd, Cr, Hg, Ni, Pb, and Sn have no known biological function, with toxic effects even at low concentration .
In geochemistry, a trace element is one whose concentration is less than 1000 ppm or 0.1% of a rock's composition. The term is used mainly in igneous petrology. Trace elements will be compatible with either a liquid or solid phase. If compatible with a mineral, it will be incorporated into a solid phase (e.g., nickel's compatibility with olivine). If it is incompatible with any existing mineral phase it will remain in the liquid magma phase. The measurement of this ratio is known as the partition coefficient. Trace elements can be substituted for network-forming ions in mineral structures. Trace elements that are not essential to a mineral's defined composition will not appear in the chemical formula of that mineral.Watering can
A watering can (or watering pot) is a portable container, usually with a handle and a spout, used to water plants by hand. It has been in use since at least 79 A.D. and has since seen many improvements in design. Apart from watering plants, it has varied uses, as it is a fairly versatile tool.
The capacity of the container can be anywhere from 0.5 litres (for indoor household plants) to 10 litres (for general garden use). It is usually made of metal, ceramic or plastic. At the end of the spout, a "rose" (a device, like a cap, with small holes) can be placed to break up the stream of water into droplets, to avoid excessive water pressure on the soil or on delicate plants.
Plant nutrition / Fertilizer