Mineral Nutrition

Lesson Prepared Under MHRD project “National Mission on Education Through ICT” Discipline: Botany Paper: Plant Physiology National Coordinator: Prof. S.C. Bhatla Lesson: Mineral Nutrition Lesson Developer: Basudha Sharma Department/College: M.M.(PG) College, Modinagar, U.P. Lesson Reviewer: Prof. S.C. Bhatla Department/College:Department of Botany, University of Delhi Language Editor: Madhurima Kahali Department/College: University of Delhi, South Campus Lesson Editor: Dr. Rama Sisodia, Fellow in Botany ILLL

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Mineral Nutrition

Table of contents Mineral Nutrition 





Introduction 

History



Importance of mineral nutrition



Essential elements 

Criteria for essentiality



Macro-elements and micro-elements



Beneficial elements

Methods of study and use of nutrient solutions 

Hydroponics



Role of essential elements and their deficiency symptoms

Mineral nutrient in soil 

Soil and the availability of nutrients 

Adsorption of minerals on soil particles



pH of the soil has an effect on nutrient availability



Specialized structure for mineral absorption: Roots



Movement of minerals towards the rhizoshpere



Summary



Exercise/ Practice



Glossary



References/ Bibliography/ Further Reading

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Mineral Nutrition

Learning Outcomes The student will be able to:



Understand the importance of nutrients for plant growth



Differentiate between essential elements and beneficial elements



Understand

the

roles

and

deficiency

symptoms

associated

with

macronutrients and micronutrients



Understand the importance of Hydroponics and nutrient solution



Understand the importance of soil characters with respect to nutrient availability



Learn about migration of nutrients towards the rhizosphere

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Mineral Nutrition

Introduction All living organisms require a number of nutrients for their growth and development, and to successfully complete their life cycle. Nutrients provide energy, and are required for the growth, repair and maintenance of cells. Living organisms can be broadly classified into two groups- autotrophs and heterotrophs.

Autotrophs are able to synthesize

complex energy-rich molecules in presence of sunlight, carbon dioxide, water and minerals.

Heterotrophs obtain these energy-rich molecules from autotrophs.

The

minerals are, thus, assimilated by plants and are transferred to other living organisms. Mineral nutrition refers to the capability of plants to absorb minerals required for their growth.

Being the primary producers, plants exhibit special traits for efficient uptake

and use of these minerals.

History In the early 18th century Van Helmond and Woodward conducted experiments, and demonstrated that: 

CO2 from air and water lead to the formation of plant matter



Growth of plant is dependent on ‘some peculiar terrestrial matter’

De Saussure (1800) worked on the variability in ash (dry matter) of plants grown in different soils, and suggested that some elements were universally present in all plants while others were not. Justus Von Liebig (1840) arrived at the conclusion that carbon, hydrogen and oxygen were supplied from air, while potassium and phosphorus from soil. He proposed ‘Law of Minimum’ according to which growth of a plant is not dependent on the total nutrients present in the soil, but on the one nutrient which is present in the minimal quantity.

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Mineral Nutrition

Figure: Justus Von Liebig, proposed the law of minimum, which became a landmark in plant nutrition. Source:http://en.wikiquote.org/wiki/Justus_von_Liebig (CC) In 1860, Sachs and Knop worked on solution culture and demonstrated that six elements (Nitrogen, Phosphorus, Calcium, Magnesium, Sulphur and Iron) were essential for plants. Since then many physiologists have worked on mineral nutrition and contributed to the growth of the subject. Importance of Mineral Nutrition Mineral nutrition is a part of the complex interaction between the plants, soil and atmosphere. It refers to the uptake of inorganic ions from the soil, for the growth and development of plants. The nutrients required for growth of plants can be obtained from the soil, water or atmosphere.

The elements that are obtained from water or the

atmosphere include carbon, oxygen and water, whereas soil provides other elements in the form of cations or anions. The availability of these minerals limits the plant growth and in turns affects the productivity of plants. It is therefore, imperative to study the minerals

acquired

and

their

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effective

use

by

plants.

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Mineral Nutrition Essential elements Among the different naturally occurring elements, about seventeen elements are termed essential elements. These are termed essential elements as deficiency of these elements renders

the

plant

incapable

of

completing

its

life

cycle.

These

may

play

a

nutritive/structural role, catalytic role (in various enzymatic reactions), or may have a balancing role (maintaining electroneutrality in plants). In the absence of these elements, the plant develops deficiency symptoms, affecting its metabolism and leading to its death. Arnon and Stout 1939, and Epstein 1972, proposed a criteria of essentiality for an element, according to which an element is essential: 

When a plant cannot proceed with its normal growth and reproduction, and therefore, is unable to complete its life cycle, in its absence



When the function of the element is specific and cannot be replaced by any other element



When the requirement of the element is direct and not a consequence of any indirect

effect

for

e.g.

relieving

toxicity

caused

by

some

other

chemical/substance. Table: Essential elements and their concentrations required for normal growth in plants Essential A. Macronutrient (Major elements) Element Symbol Conc. In dry matter (m mole kg-1) A. Obtained from water or carbon dioxide Carbon C 40,000 Hydrogen H 60,000 Oxygen O 30,000 B. Obtained from soil Nitrogen N 1,000 Potassium P 250 Calcium Ca 125 Magnesium Mg 80 Phosphorus P 60 Sulphur S 30

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elements B. Micronutrient (Micro/Trace elements) Element Symbol Conc. In dry matter (m mole kg-1) B. Obtained from soil Chlorine Cl 3.0 Iron Fe 2.0 Boron B 2.0 Manganese Mn 1.0 Zinc Zn 0.3 Copper Cu 0.1 Nickel Ni 0.05 Molybdenum Mo 0.001

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Mineral Nutrition Macronutrients and micronutrients Essential elements can be categorized into macronutrients (major elements) and micronutrients (trace elements) based on concentration at which they are present in the plant tissues. Table: Distinguishing characters of macronutrients and micronutrients Character Quantity Concentration plant tissues Categories

in

Role Osmotic potential Toxicity

Examples

Macronurtrient Required in larger quantities Present in amounts more than10 m mole kg-1 of dry matter Primary nutrients (lacking from soil as required in large amount by plants eg. nitrogen, potassium and phosphorus) and secondary nutrients (present in sufficient amounts in soil eg. Calcium, magnesium) Usually involved as structural components of molecules Play a role in developing osmotic potential in cells They are not toxic if present in slight excess Nitrogen, Potassium, Calcium, Sulphur

Micronutrient Required in smaller quantities Present in amount less than 10 m mole kg-1 of dry matter Present in sufficient amounts in soil

Involved in catalytic and regulatory roles Do not play a role in developing osmotic potential They have a narrow adequate range and become toxic if present in slight excess Iron, Boron, Zinc, Nickel

Essential elements can also be grouped according to their various biochemical and physiological functions Table: Classification of nutrients on the basis of biochemical and physiological functions Element Group 1 N S Group 2 P B Group 3

Function Nutrients part of organic carbon compounds Structural component of amino acids, proteins, nucleic acids, nucleotides, coenzymes Component of amino acid (cysteine, cystine, methionine), Coenzyme A, Vitamins Nutrients important for structural/energy storage Component of nucleotides, nucleic acid, phospholipids, coenzymes, various sugar phosphates, ATP Complexes with pectins present in cell wall, required for nucleic acid metabolism, cell elongation, and translocation of sugars Present as free ions regulation osmotic potential of cells, serves as enzyme activators/inhibitors

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Mineral Nutrition K Ca Mg Cl Mn

Group 4 Fe Zn Cu Ni Mo

Important in establishing cell turgor, cofactor of many enzymes Component of middle lamella of cell walls, required for cell division and as a cofactor in many enzymes Has a role in enzymatic reactions involving phosphate transfer, constituent of pigment chlorophyll Required in the oxygen evolving complex involved in the process of photosynthesis Involved in the oxygen evolving complex, required for activity of enzymes like decarboxylase, dehydrogenases, kinases, oxidases and peroxidase Nutrients having a role in electron transfer/ redox reactions Component of cytochrome complex and involved in processes of photosynthesis, respiration and N2 fixation Component of various enzymes like alcohol dehydrogenase, glutamic dehydrogenase and carbonic anhydrase Component of ascorbic acid oxidase, tyrosinase, uricase, cytochrome oxidase, phenolase, laccase and plastocyanin Constituent of urease and has a role in nitrogen fixation Constituent of nitrate reductase, nitrogenise

Mineral and Non-mineral elements Essential elements can also be categorized into mineral and non-mineral elements. Mineral elements are those elements which are obtained from weathering of rock and are acquired in the form of inorganic ions from the soil, such as Molybdenum, Nickel, Copper, Iron, Zinc, Calcium etc. Non–mineral elements are those elements that are derived from carbon dioxide and water. Eg. Carbon, hydrogen and oxygen` Beneficial elements Other than these essential elements, there are some elements known as beneficial elements, which promote the growth of plants, however are not essential for completing the life cycle of plants.

Beneficial elements are required at concentrations below the

detectable limits of different analytical techniques and include sodium, selenium and cobalt. Table: Beneficial elements, their role and occurrence Element Sodium

Occurrence Atriplex vesicaria

Silicon

Equsetum Grasses

Cobalt

Legumes

avrvense,

Role 1. Essential for plants using C4 photosynthetic pathway 1. Prevent lodging during winds and rain 2. Protect plants against fungal infections 3. Reduces toxic effects of some metals like aluminium and manganese 1. Required for nitrogen fixing bacterial

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Mineral Nutrition Selenium

Astragalus sp.

1. Provides protection against grazing animals.

Did you know? Astragalus sp.,Stanleya sp. and Haplopappus sp. are known to accumulate selenium. An accumulation of seleneium poisons livestock causing alkali disease/blind staggers. Selenium replaces sulphur in amino acids, forming seleno-amioacids. These aminoacids result in formation of toxic proteins

Methods of study and use of nutrient solutions In the 18th and 19th century, several researchers including Nicolas-Thédore de Saussure, Jean-Baptiste-Boussingault, Julius von Sachs and Wilhem Knop were interested to study the interrelationship of plant nutrition and their ability to increase productivity. Sachs designed an experimental system to study the minimal nutrient solution required for the growth of plant. The plants were grown with their roots immersed in aqueous nutrient solution containing inorganic salts. According to Sachs six inorganic salts, having nine nutrients (Potassium, Nitrogen, Phosphorus, Calcium, Sulphur, Sodium, Chloride, Magnesium and Iron) are required for the growth of plants. Table: Sachs nutrient solution (1860) used for the culture of plants Salt Potassium nitrate Calcium Phosphate Magnesium sulphate Calcium Sulfate Sodium Chloride Iron Sulfate

Chemical formula KNO3 Ca3(PO4) MgSO4.7H2O CaSO4 NaCl FeSo4

Nutrient supplied K+, NO3Ca2+,H3PO4Mg2+,SO42Ca2+,SO42Na+,ClFe2+,SO42-

Concentration approx 9.9 1.6 2.0 3.7 4.3 Trace

(mM)

The nutrient media was later modified with incorporation of other essential nutrients. The most commonly used nutrient media has been formulated by D.R. Hoagland and is referred to as modified Hoagland’s solution. Modified Hoagland’s solution contains: Table: Composition of modified Hoagland solution. Salt Calcium nitrate Ammonium phosphate Potassium nitrate

Chemical formula Ca(NO)3 NH4H2PO4 KNO3

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Nutrient supplied Ca2+,NO3NH4+,H2PO4K+, NO3-

Concentration (mM) 2.5 0.5 2.5

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Mineral Nutrition Magnesium sulphate Zinc sulphate Manganous sulphate Copper sulphate Boric acid Molybdic acid Iron sequestrene



MgSO4 ZnSO4 MnSO4 CuSO4 H3BO3 MoO3 Fe

Mg2+, SO42Zn2+, SO42Mn2+, SO42Cu2+,SO42H3BO3 MoO42Fe2+,Fe3+

1.0 0.00039 0.0046 0.00016 0.0234 0.000051 0.179

All required micro and macro-nutrients are present in limits which may not cause toxicity or salinity in plants.



Nitrogen is present in two forms, cationic (ammonium NH4+) and anionic (NO3-), leading to a balance in pH, and allowing plants to absorb and assimilate both the forms of nitrogen



Iron was added as ferrous suphate (FeSO4) which can precipitate out as iron hydroxide. In modern nutrient solution, chelating agents like EDTA (ethylene diamine tetra acetic acid) or DTPA (diethylene triamine penta acetic acid) are used.

Chelating agents form a chelate, a stable complex between metal ion

(Fe/Ca) and organic molecule (ligand).

The metals in the form of chelate are

soluble and stabilized by ionic forces, and therefore are available to plants. Once the metal ion is taken by plants, the chelator diffuses to the nutrient solution and attach to another metal ion

Figure: Ligand ethylene diamine binding to central metal ion (M) with two bonds Source: http://en.wikipedia.org/wiki/Chelation (CC) In soil, there are some naturally occurring chelates of micronutrients like iron. These include siderophores which are categorized as ascatechols, phenolic compounds synthesized by soil bacteria and hydroxamates- peptides formed by fungi.

Technique Hydroponics/Solution Culture (Soilless Culture) Hydroponics is a technique in which plants are grown in nutrient solution, instead of soil. Since the nutrients are available for plants, the root system of plants is compact and plants grow healthier. Hydroponics is an important technique which can be used for research and commercial production of vegetables such as tomatoes and seedless cucumbers.

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Mineral Nutrition Hydroponics is useful in studying essentiality of any mineral and the deficiency symptoms associated with the mineral. Simple solution cultures have demonstrated effect of essential elements on growth of plants. Glass containers containing nutrient media and oxygen supply are covered with opaque paper to protect roots from direct sunlight. In other similar containers, the plant is grown in same conditions, withholding one element of interest, which is correlated with the deficiency symptoms of the particular element. Similarly, excess of micronutrients resulting in toxicity, interaction of different elements can also be demonstrated.

Figure: Diagram depicting nutrient solution culture Source:http://www.hydro-culture.net/images/hydroculture_waterrooting.gif (CC) Simple solution culture has certain disadvantages, mainly depletion of certain minerals after their uptake and pH-associated changes. Therefore, there are several variations for successful hydroponic culture. Standard hydroponic growth system (Typical water culture system) has a large tank with nutrient solution and proper aeration.

The

nutrient solution is frequently checked for radical and pH changes. Continuous-flow solution culture (Nutrient film technique) includes nutrient film technique whereby, a stream of nutrient solution is circulated from the reservoir, bathing the roots of plants. This not only provides proper aeration but also allows the continual monitoring and management of changes of pH and nutrients. Aeroponics is another variation where the roots are suspended in nutrient mist chamber and are continually sprayed with nutrient solution. In ebb-and-flow system, the nutrient media gradually rises towards the roots of plants, and then gradually recedes- providing a moist environment to the plant roots.

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Mineral Nutrition Variations of hydrophonics A.

Standard hydrophonic system: plants are suspended on the tank containing

nutrient media.

B. Continuous-flow solution culture (Nutrient film technique):a stream of nutrient continuously solution runs through the plants

C. Aeroponics: The nutrient media is sprayed to the plants by high pressure pumps.

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Mineral Nutrition

D. Ebb-and-Flow system: the nutrient media periodically rises and then drains back to the main chamber.

Source: http://www.simplyhydro.com/system.htm

Video on the use of hydroponics, featuring nutrient film technique Source: https://www.youtube.com/watch?v=p4mOFtiotj8

Hydroponics allows growth of plants in a controlled environment with regulated supply of nutrients.

As compared to regular farming, hydroponics provides an opportunity of

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Mineral Nutrition cutting down labour cost and provides a quicker yield. However, the cost of setting up the infrastructure required for hydroponics is high and needs technical expertise. Modern techniques to measure the concentration of elements in plants, nutrient solution and

soil

include

atomic

absorption

spectrometers

and

optical

emission

spectrometers. In these techniques the elements are heated and vaporized.

The

atoms from the ground state absorb a specific wavelength and are temporarily excited. The amount of energy (in the form of wavelength) absorbed can be measured by atomic absorption spectrometer which is directly proportional to the concentration of analyte present in the sample.

In optical emission spectrometer, the electromagnetic energy

emitted by the electrons while moving back to their original ground stage is measured and quantified.

Role of essential elements and their deficiency symptoms Elements are required by plants at a particular concentration.

Each element has a

specific role in the growth of plant, and an inadequate supply leads to deficiency symptoms. Carbon, hydrogen and oxygen serve as principle structural components of organic matter.

Deficiency of carbon leads to quick death of plant and deficiency of

water leads to wilting and desiccation. Table: Essential elements, their available form, relative mobility, function and deficiency in plants Element Nitrogen

Available form NO3-, NH4+

Relative mobility Mobile

Function

Deficiency

1. Constitue nt of various molecules like proteins, nucleic acids. 2. Constitue nt of some hormones (Indole-3acetic acid; cytokinin) 3.

1. Older leaves turn yellow and falls off.

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brown or

Figure: Nitrogen deficiency showing chlororsis of old leaves Source:http://en.wikipedia.org/wiki/ Nitrogen_deficiency (CC) 2. Accumulation of anthocyanin in leaves, petiole and stem.

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Mineral Nutrition

Phosphor ous

H2PO4-, Associatio n in form of mycorrhiz a

Mobile

Constitue nt of chlorophyl l 1. Constitue nt of nucleotide s (RNA and DNA), Phospohol ipids and sugarphosphae molecules 2. Has an important role in reactions involving ATP 3. Constitue nt of Coenzyme A, phytic acid

1. Stunted growth of young plants

Figure: Stunted growth in phosphorous deficient tobacco plants Source http://www.forestryimages.org/bro wse/subthumb.cfm?sub=18127&fa m=2577 (CC) 2. Malformed leaves with dark green coloration containing necrotic spots

Figure: Older leaves turning purple instead of yellow Source:http://gardener.wikia.com/ wiki/Phosphorus_deficiency?file=To mato_Phosphorous_deficiency_Leaf .jpg (CC) 3. Leaves may turn dark green purple due to production of anthocyanin

Figure: Phosphorous deficient plants showing anthocyanin accumulation Source http://www.forestryimages.org/bro wse/subthumb.cfm?sub=18127&fa

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Mineral Nutrition m=2577 (CC) 4. Delayed maturation of plants with reduced fruits and seeds Potassium

Calcium

Magnesiu m

K+

Ca2+

Mg2+

Mobile

Immobile

Mobile

1. Has a role as a cofactor in many enzymes 2. Involved in regulating osmotic potential

1. Compone nt of middle lamella in cell wall 2. Role in spindle formation during cell division 3. Acts as a cofactor for various enzymes 4. Acts as a secondary messenge r during signalling mechanis ms 1. Role in photosynt

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1. Chlorosis in older leaves, followed by lesions at margins.

Figure: Marginal chlorosis of older leaves in Nicotiana Source:http://www.forestryimages. org/browse/detail.cfm?imgnum=14 40091 (CC) 2. Stem may become weak with short internodes, making them susceptible to lodging 3. Roots may be prone to root – rotting fungi. 1. Necrosis of young tissue (tips of young leaves, roots)

Figure: Necrosis of young leaves in lettuce due to calcium deficiency Source: http://www.forestryimages.org/bro wse/subthumb.cfm?sub=18131&fa m=2577 (CC) 2. Distorted young leaves 3. Stunting of plants due to death of meristematic zone 3. Roots may become branched, brown and short.

1. Chlorosis in the older leaves at interveinal regions

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Mineral Nutrition hesis as a constituen t of chlorophyl l molecule 2. Required for the stability of ribosome 3. Required as an activator of various enzymes

Sulphur

SO42(SO2, SO3in atmosphe re)

Immobile

1. Compone nt of amino acids (Cysteine and Methionin e), proteins 2. Constitue nt of Coenzyme A, Vitamins (Biotin, Pantothen ic acid, Thiamine) , iron sulphur proteins 3. Responsib le for the pungent flavours in mustard, cabbages due to

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Figure: Interveinal chlorosis as observed in tomato Source: http://www.forestryimages.org/bro wse/subthumb.cfm?sub=18124&fa m=2577 (CC)

1. Protein synthesis is affected causing chlorosis in young leaves

Figure: Chlorosis of leaves in tobacco Source: http://www.forestryimages.org/bro wse/subthumb.cfm?sub=18129&fa m=2577 (CC) 2. Stunted growth of young plants

Figure: Stunted growth in queen palm due to sulphur deficiency. Source: http://www.forestryimages.org/bro wse/subthumb.cfm?sub=18129&fa m=2577 (CC) 3. Accumulation of anthocyanin

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Mineral Nutrition

Iron

Zinc

Fe3+, Fe2+

Zn2+

Immobile

Mobile

thiocyanat es and isothiocya nates 1. Role in photosynt hesis and resipiratio n, nitrogen fixation as is a part of redox enzymes 2. Activates different enzymes like catalase and peroxidas e 1. Compone nt of enzymes like alcohol dehydrog enase, carbonic anyhdrase 2. Required for synthesis of chlorophyl l 3. Required for the synthesis of tryptopha n

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1. Younger leaves show chlorosis in the interveinal region which may later turn white.

Figure: Interveinal chlorosis in Rhododendrons due to iron deficiency Source:http://www.forestryimages.o rg/browse/subthumb.cfm?sub=181 23&fam=2577 (CC)

1. Little leaf disorder/rosette disorder resulting due to short internodes and smaller leaves resulting in a rosette

Figure: Little leaf symptom in zinc deficient condition Source:http://www.forestryimages. org/browse/subthumb.cfm?sub=18 130&fam=2577 (CC) 2. Older leaves may show chlorosis with white nectrotic spots due to reduction of chlorophyll formation

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Mineral Nutrition

Copper

Boron

Cu2+, Cu+

H3BO3

Immobile

Immobile

1. Role in photosynt hesis as a componen t of plastocya nin, in respiratio n as a componen t of cyotochro me oxidase 2. Activates other enzymes like ascorbic acid oxidase, phenolase , superoxid e dismutase 1. Boron is a componen t of cell wall pectin polysacch

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Figure. Chlorosis and necrosis in Maize due to zinc deficiency Source http://www.forestryimages.org/bro wse/subthumb.cfm?sub=18130&fa m=2577 (CC) 1. Growth of plant is retarded 2. Leaves become dark green and distorted 3. Spots of necrosis first appear at the tips of young leaves and then spread towards to margins.

Figure: Necrosis at tips spreading towards margins Source:http://www.forestryimages. org/browse/subthumb.cfm?sub=18 122&fam=2577 (CC) 4. Causes ‘exanthema’ in trees where there is a presence of gums on bark

1. Causes black necrosis of young leaves and buds

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Mineral Nutrition arides 2. It has a role in nitrogen fixation 3. Required for translocati on of carbohydr ates 4. Required for uptake and utilization of calcium 5. Required for pollen germinati on and tube elongation 6. helps in cell division and elongation

Manganes e

Mn2+

Mobile

1. Required for the formation of chlorophyl l 2. Has a role in evolution of oxygen during photosynt hesis 3. Acts as a cofactor

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Figure: The blackening of leaves in palm due to boron deficiency Source: http://www.forestryimages.org/bro wse/subthumb.cfm?sub=18132&fa m=2577 (CC) 2. Causes necrosis of fruits, roots due to breakdown of internal tissue 3. Causes ‘heart rot’ disease in storage roots due death of dividing cells

Figure: Internal necrosis in the storage roots of Swede and turnip due to boron deficiency Source:http://gardener.wikia.com/ wiki/Boron_deficiency (CC) 4. ‘Stem crack’ in celery causing shortened internodes and formation of rosette 1.’Grey Speck’ of cereal grains causing greenish grey spots at the base of young leaves 2. Causes interveinal chlorosis in old leaves due to loss of chlorophyll from chloroplast

Figure: Intervienal chlorosis in old leaves of Maize due to manganese deficiency Source:

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Mineral Nutrition

Nickel

Molybden um

Ni2+

MoO42-

Mobile

Mobile

of various enzymes like carboxyla ses, dehydrog enases, peroxidas es, superoxid e dismutase s 1. Used by nitrogen fixing microorga nisms 2. Compone nt of enzyme urease

1. Role in nitrogen fixation 2. Act as componen t of enzymes like nitrogena se and nitrate reductase

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http://www.forestryimages.org/bro wse/subthumb.cfm?sub=18125&fa m=2577 (CC)

1. Leaf tip necrosis due accumulation of urea in leaves

to

Figure: Chlorosis and necrosis at leaf tips due to nickel deficiency Source: http://www.forestryimages.org/bro wse/subthumb.cfm?sub=61834&fa m=2577 (CC) 1. Causes ‘Whiptail’ in cabbages, causing deformed long young leaves

Figure: The elongated whiptail like leaf in cauliflower due to molybdenum deficiency Source:http://yara.co.uk/cropnutrition/crops/vegetablebrassica/cropnutrition/deficiencies/mo/01-4424molybdenum-deficiency--cauliflower/ 2. Causes interveinal chlorosis and necrosis of mature leaves

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Mineral Nutrition

Chlorine

Cl-

Mobile

1. Role in oxygen evolving complex during photosynt hesis 2. Role in stomatal regulation 3. Present in the vacuoles making them osmoticall y active 4. It has a role in transfer of ions across membran es

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3. Symptoms related to nitrogen deficiency in plants associated with nitrogen fixation 1. Tip of leaves may wilt and may later show signs of chlorosis and necrosis

Fig. Chlorosis in wheat due to chlorine deficiency Source: http://www.forestryimages.org/bro wse/subthumb.cfm?sub=18121&fa m=2577 (CC) 2. Growth of the plant is affected

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Mineral Nutrition

Figure: Summary of various mineral deficiencies occurring on the leaves of a plant Source: Author Mineral Nutrients in the soil In order to maximize the crop yield, an analysis of minerals, in soil and plant tissue is required. Plant tissue analysis refers to the nutritional content in a particular crop type. Plant tissue analysis identifies the status of nutrients at the time of sampling.

The

relationship of nutrient concentration and crop growth shows three different zones

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Mineral Nutrition

Figure: Plant tissue analysis curve showing relationship of plant growth (relative yield) and the concentration of nutrient tissue 

Deficiency zone- it is the zone at which a nutrient becomes deficient and symptoms of deficiency are visible on the crop. The symptoms of deficiency can be removed with the addition of that nutrient. However, on continual absence of that element plant death may eventually occur.

If the elements are relatively

mobile, they can be relocated from within the plant and hence the deficiency symptoms appear in the older leaves, whereas in case of immobile elements, deficiency symptoms first appear in the younger leaves.

Once the element is

supplied, the plant growth rate increases, and reaches a point where it does not increase any further, it is known as the adequate zone. Critical concentration refers to the concentration of the nutrient in plant tissue below which the growth of plant is reduced by 10%. 

Adequate zone-It is the zone above the critical concentration where additional nutrient content does not benefit the plant



Toxic zone-Further addition of nutrients causes toxic effects on plants hampering their growth. Micronutrients generally have a narrow adequate zone and show toxic symptoms.

Excess of one element may also compete with the

uptake of a different element, thereby showing toxic symptoms.

Critical

toxicity level refers to the concentration of element which reduces the dry weight of the tissue by 10%. Soil and the availability of nutrients

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Mineral Nutrition Soil is a mixture of solid, liquid and gaseous material which supports growth of a plant. The various nutrients that are required for the completion of the life-cycle of plants are obtained from the soil.

A number of characteristics including soil solutions, cation

exchange sites, soil pH, soil mineral and soil organic matter have an effect on the presence and availability of nutrients.

Video showing the availability of minerals to plants from soil using iron as an example Source: https://www.youtube.com/watch?v=6aC-WTAWgOg Adsorption of minerals on soil particles Soil particles, whether originating from inorganic (rocks) or organic (decomposition of plants and animals) matter are negatively charged.

Due to this negative charge,

positively charged nutrients (cations) like ammonia NH4+ and potassium K+ can bind to the exchange sites in the soil. The degree at which soil particles can adsorb and exchange cations is known as cation-exchange capacity (CEC). The cation exchange capacity is dependent on the type of soil and the reservoir of nutrients present in the soil. A high CEC denotes more nutrients are held on the soil making them less soluble in water and therefore unavailable to plants. Addition of more cations like Ca2+, Mg2+ and Na+can replace the mineral nutrients already adsorbed to the soil particles, a phenomena known as cation exchange, making them available to plants.

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Mineral Nutrition

Figure: Soil particle showing cation exchange occurring on the surface of the soil. Addition of more cations like K+ can replace Ca2+ from the surface of soil which can be then taken up by the plant. Source:http://www.caes.uga.edu/Publications/pubDetail.cfm?pk_id=8087,

,

http://extension.missouri.edu/explorepdf/mastergardener/mg0004.pdf Nutrient anions like nitrate (NO3-) and Chloride (Cl-) cannot bind to the negatively charged soil particles and hence are dissolved in the soil solution and can be leached. The capability of soils to exchange cation is therefore higher than the anion-exchange capacity. A low CEC denotes that few nutrients are held in the soil. Phosphate anions can bind to positively charged ions like (Al3+, Fe2+,Fe3+) in soil, forming aluminium and iron complexes with phosphate. This results in reduced availability of phosphate to the plants. An addition of cations, fertilizers, or liming causes an increase in soil pH and release of cations for the uptake of plants. pH of the soil has an effect on nutrient availability pH refers to the hydrogen ion concentration in soil solution, containing minerals in ionic state.

dissolved

The soil solution may be acidic, alkaline or neutral and. The

nature of the soil solution has an important effect on the availability of nutrient and the growth of roots. In general most plants require a slightly acidic pH (above 5.5), at which most of the nutrients are available. The pH of soil can be controlled by use of chemicals like lime and sulphur. Lime raises the pH of acidic soil whereas sulphur reduces the pH of alkaline soils.

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Mineral Nutrition

Figure: Nutrients available to the plants with respect to pH. Note that all the nutrients are available at pH 5.5-6.5 Source: http://extension.missouri.edu/explore/images/mg0004art03.jpg

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Mineral Nutrition Specialized structure for mineral absorption: Roots Plants absorb nutrients and water through specialized structures known as root. Root hairs on the roots further increase the surface area for absorption of nutrients. Roots consist of:

Figure: A longitudinal view of root revealing different zones Source:https://www.boundless.com/biology/textbooks/boundless-biologytextbook/plant-form-and-physiology-30/roots-180/types-of-root-systems-and-rootgrowth-and-anatomy-689-11914/ (CC) 

Meristematic zone (apical meristem): This is the zone of active division, the cells form root cap at the apex. The root cap secretes mucilege which protects the root meristem and allows the root to penetrate deeply into the soil. In the centre of the meristem is quiescent centre, where the cells divide infrequently. The cells around the quiescent centre divide rapidly, leading to formation of root tissue.



Elongation zone:

Above the meristematic region is the zone of elongation,

where the cells elongate and form central endodermis, on the radial walls of which a suberin layer, casparian strip, is deposited which does not allow the transfer of water from the cortex to the stele 

Maturation zone: Maturation zone of the root is above the zone of elongation, where the epidermal cells elongate to form the root hairs. The root hairs increase the surface area for the absorption of water and nutrients.

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Mineral Nutrition

Figure: Diagrammatic representation root with profuse root hairs Source: http://en.wikipedia.org/wiki/Root_hair (CC) The zone surrounding the roots, including the soil,water,minerals and the microflora constitute rhizosphere. Minerals can be absorbed in the form of ions from all over the root surface or from the apical meristematic region.

Movement of minerals towards the rhizosphere Nutrients in the soil can move towards the roots by 

Bulk flow/Mass flow: Movement of nutrients dissolved in water from the soil towards the roots.

Bulk flow is dependent on the pressure built up by

transpiration rate and nutrient concentration in the soil. 

Diffusion:

Movement of nutrients from a higher concentration to a lower

concentration.

As the nutrients are absorbed from the root rhizosphere, and

transported to the xylem, a zone of nutrient depletion zone is created near the root surface (0.2-2.0 mm). This depletion zone causes diffusion of nutrients in the soil solution, resulting in mobility of nutrients towards the rhizoshpere. The nutrients transfer into the roots from the rhizoshpere may be passive (without the involvement of energy) or active (energy is required and the nutrient is transferred with the help of a carrier molecule) 

Symbiotic association (Mycorrhizae; Nitrogen fixing bacteria)

Mycorrhizae are symbiotic association of plants and fungal groups that are present in soil. Mycorrhizae help in the indirect absorption of water and minerals like phosphorus, copper and zinc from soil or by solubilising these minerals from the organic matter of soilduring the process of mineralization. These minerals are then passed to the root cells in exchange for carbohydrates which are essential for the growth of mycorrhizae. Mycorrhizae may be categorized as ectotrophic mycorrhizae and vesicular arbuscular

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Mineral Nutrition mycorrhizae. Ectotrophic mycorrhizae are generally found in roots of gymnosperms and woody trees. These mycorrhizae form a sheath of mycelia around roots. Some of the mycelium hypahe may enter roots and surround cortical cells, which are known as Harting net. The mycorrhizal mycelia outside plant roots extend further out of the nutrient depleted zone and absorb fresh nutrients releasing them into the plant cell through Harting net. Vesicular arbuscular mycorrhizae (VAM) enter root hair and penetrate into the cells of root cortex, where they form vesicles and branched structures known as arbuscules. Arbuscules surround the plasma membrane and increase the surface area for exchange of nutrients between the plant cells and mycorrhizae. Symbiotic nitrogen fixing bacteria can be found in the root nodules of members of family Leguminoseae, some non-leguminous plants and root nodules of some gynmnosperms. Nitrogen fixing bacteria, due to enzyme nitrogenase convert atmospheric nitrogen into ammonia (NH4), which is directly taken up by plants. Nitrogen fixation is an outcome of the symbiotic relation and is not possible by any one partner in isolation. Plants provide anaerobic conditions in the root nodule with the help of leghaemoglobin, whereas the bacteroids have an enzyme called nitrogenase, a Mo-Fe protein which reduces nitrogen to ammonia.

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Mineral Nutrition Summary Plants are autotrophs capable of forming energy rich organic compounds with the help of sunlight, carbon dioxide, water and 14 other elements together known as the essential elements. The essential elements are required for the completion of life cycle of plants, in contrast to beneficial elements which promote the growth of plants.

The essential

elements can be further divided into macronutrients and micronutrients according to their requirement in plants. Hydroponics is an important tool employed to understand the role of essential elements in the physiology of plants, role in various metabolic reactions, and the deficiency symptoms associated with them.

The availability of

nutrients to plants is dependent on the characteristics of the soil and specialized plant structures of roots. The various aspects of soil like presence of nutrients, adsorption of the minerals to soil particles and the pH of the soil attribute to the availability of minerals to the plant.

Minerals are absorbed in the form of ions from the soil by

meristematic region of plant roots.

Minerals are also absorbed from symbiotic

association with nitrogen fixing bacteria and mycorrhizae, which aid the plant to acquire certain elements like nitrogen and phosphorus which may otherwise be unavailable/ immobile in soil.

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Mineral Nutrition Exercises 1. State whether the following are true or false and justify your answer i. Death of meristem is caused in the absence of calcium ii. All the elements are absorbed in the form of ions iii. The deficiency symptoms of immobile elements is first observed in young leaves iv. Cation exchange capacity refers to ability of cations to be exchanged for anions bound to the soil surface v. All the minerals present inside the cell, are essential for it. Ans. i. True, ii. False, iii. True, iv. False v. False 2. Fill in the blanks i. Silicon is an essential element of ___________ and diatoms ii. _______ has an important role in the formation of middle lamella of plant cells iii. Sodium is an essential element required in the process of photosynthesis in ______plants iv. ______ is required for the translocation of organic substances v. ______and ____ have a role in oxygen evolving complex during the process of photosynthesis vi. Grey speck of oats is caused due to deficiency of ____________ Ans. i. Grasses, ii. Calcium iii. C4 iv. Boron, v. Mn and Cl, vi. Manganese 3. Multiple choice questions i.

ii.

Nutrients are released from the decomposition of organic matter, during the process of a. Mineralization

c, Nitrification

b Volatization

d. Immobalization

Nitrogen is absorbed by plants in the form of a. Nitrate ion (NO3) c. Nitrogen gas N2 b. Ammonia ion (NH4) d. both a and b

iii. Which of the following groups are referred to as secondary nutrient a.

Nitrogen, phosphorus,potassium

b. Carbon, hydrogen, oxygen

c. Phosphorus, calcium and iron d. Calcium magnesium and phosphorus

iv. Aeroponics is a variant of hydroponics where the roots are suspended in a. Nutrient solution c. Nutrient mist chamber b. air d. Nutrient film growth system v. Harting net is present in a. ectotrophic mycorrhizae b. vesicular arbiscular mycorrhizae

c. root nodules d. both a and b

vi. Which among the following in not a true statement about mycorrihzae a. Mycorrhizae extent the rhizosphere and the nutrient depletion zone b. Mycorrhizae facilitate of immobile minerals like phosphorus

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Mineral Nutrition c. Vesicular arbusular mycorrhizae form a sheath around the root surface d. Ectomycorrhizae penetrate the roots and surround the cortical cells of the roots vii. Root hairs involved in the absorption of water and nutrients appear in the a. Meristematic zone c. Maturation zone b. Elongation zone d. Both b and c viii. The formation of stele consisting of the xylem and phloem is differenciated in a. Meristematic zone c. Maturation zone b. Elongation zone d. both b and c ix. Leghaemoglobin, in root nodules of plants serve to a. Provide molybdenum to the cells c. regulate oxygen levels in cells b. Regulate carbodioxide levels in cells d. Provide energy for the conversion of nitrogen to ammonia x. Which of the following element has low mobility a. Nitrogen c. Calcium b. Potassium d. Magnesium xi. Which of the following micronutrient is required in least quantity a. Copper c. Zinc b. Boron d. Molybdenum 4. Match the following i. Nutrient Deficiency symptom/disease Cu Mouse ear of Pecan Mn Whip tail in Cauliflower Ni Grey speck in cereals Mo Exanthema in trees ii. Nutrient Ca Cl Br P

Deficiency symptoms Chlorosis and necrosis of old leaves at tip region Black necrosis of leaves Dark green leaves with necrotic spots Chlorosis and necrosis of young leaves

5. Short answer type questions i. Distinguish between a. Macronutrient and micronutrient b. Essential element and beneficial element. c. Mineral and non-mineral element ii. How can you determine the essentiality of any nutrient? iii. What are chelating agents? nutrients?

How do chelating agents aid in the availability of

iv. What is meant by a. Critical concentration of a nutrient b. Critical toxicity level of a nutrient v.

How do mycorrhizae aid in the availability of nutrients to plants?

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Mineral Nutrition Glossary Aeroponics: chamber.

A variation of hydroponics in which plants are grown in a nutrient mist

Beneficial elements: Elements which promote the growth of plants, but are not essential for completing the life cycle of plants Cation Exchange capacity: cations.

It is the ability of soil to attract, retain and exchange

Chelates: Complex substances like EGTA that form stable complexes with metal ions, thus avoiding precipitation of the metal ion. Critical concentration: It is the transition between the deficiency zone and adequate zone below which the plant growth is hampered Chlorosis: Yellowing of leaves due to the deficiency of some mineral nutrient resulting in loss of chlorophyll Diffusion: Movement of molecules from a region of high concentration to a region of low concentration Hydroponics: Growing plants in a nutrient rich solution in absence of soil Macro-elements: Essential elements required in higher concentration for the growth of plants. They form 0.5-3% of the dry weight of the plant. Mass Flow: Movement of nutrients dissolved in soil solution towards the roots. Due to transpiration pull, a pressure is created which pulls the soil solution towards the roots Microelements: Essential element required in low amounts for the growth of plants. They form only few parts per million of thee dry weight of the plant. Mycorrhizae: Symbiotic association between the plant root and fungi which helps in the absorption of minerals by the roots Necrosis: Death of leaf tissue due to deficiency of some mineral. Nutrient depletion zone- A low nutrient level created near the root zone, due to absorption of minerals. Rhizosphere: The immediate surroundings of the root consisting of complex association between root, soil and the microflora. Siderophores: Stable natural chelates which are produced by soil inhabitating bacteria and fungi

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Mineral Nutrition References/Further Reading Introduction to Plant Physiology (2009) 4th ed. Hopkins WG and Huner. John Wiley and Sons, Inc (USA) Plant Physiology (2006) 4th ed. Taiz L and Zeiger E. Sinauer Associates Inc. (USA) Plant Physiology (2000) 4th ed. Devlin RM and Witham FH. CBS Publisher and Distributers, India Mineral Nutirition of Plants: Principles and Prespectives (1972) Epistein E. Wiley, New York Introductory Plant Biology (2008) Stern KR, Bidlack JE and Jansky SH. Mc-Graw Hill, New York Plant Physiology (1995) Salisbury and Ross,CBS Publisher and Distributers, India Web links http://www.soilhealth.com http://nrcca.cals.cornell.edu/nutrient/CA2/CA0212.php http://www.forestryimages.org/browse/subthumb.cfm?sub=18130&fam=2577 science.uq.edu.au/edition1/?q=content/feature-essay-16-1-brief-history-plant-nutrition

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