XI Chap 12 Mineral Nutrition Flashcards
In _______, a prominent German botanist named ________ demonstrated for the first time that plants could be grown to maturity in a defined nutrient solution, complete absence of soil.
1860, Julius von Sachs
The technique of growing plants in nutrient solution is known as _____________
hydroponics
When studying mineral nutrients for plants, why is purified water and mineral nutrient salts essential?
Rule out other influencing factors
Hydroponics is not yet successfully employed towards COMMERCIAL production of vegetables. T or F?
False, has been e.g. tomato, seedless cucumber and lettuce
Nutrient solutions must be adequately _______ to obtain the optimum growth
aerated
All minerals present in soil can enter plants through roots. T or F?
False, most can
More than ___ elements out of ____ discovered so far are found in plants
60, 105
Some plant species accumulate selenium, gold and even radioactive strontium. T or F?
True
There are techniques that are able to detect the minerals even at very low concentrations (10 ^ -11 g / mL). T or F?
False, 10 ^ -8g/mL
Plants grown in a tube or trough are placed at a __________
slide incline
In hydroponic plant production, a ______ circulates nutrient solution from a reservoir to ________ of the tube
pump, elevated end
In hydroponic plant production, nutrient solution flows down the tube and returns to reservoir due to ________
gravity
What are the criteria for essentiality of an element?
- Must be absolutely necessary for growth and reproduction
- In absence, life cycle cannot be completed / seeds cannot be set
- Not replaceable by any other element
- Must be DIRECTLY involved in metabolism
Essential elements are divided into 2 categories based on their quantitative requirements. They are?
Macronutrients (large amounts) and micronutrients (trace amounts)
Macronutrients include? (9)
Carbon, hydrogen, oxygen Nitrogen Phosphorus Sulphur Potassium Calcium Magnesium
Macronutrients are in excess of ______ whereas micronutrients are less than than amount
10 mmole / Kg of DRY matter
Carbon, hydrogen and oxygen in plants are mainly obtained from
carbon dioxide and water
Macronutrients other than C, H and O are obtained from ________
soil
Micronutrients include? (8)
Fe, iron Mn, manganese Cu, copper Mo, molybdenum Zn, zinc B, boron Cl, chlorine Ni, nickel
How many essential elements are there?
21
17 + sodium, silicon, cobalt and selenium (higher plants)
What additional elements are required by higher plants as essential nutrients?
Silicon, Selenium, Sodium, Cobalt
Essential elements can be grouped in __ categories based on their functions. What are they?
4;
- Components of Biomolecules (structural elements)
- Components of energy-related chemical compounds e.g. ATP
- Activators/inhibitors of enzymes
- Alter the osmotic potential of cell (solutes)
What are the essential nutrients that function as structural elements for plant cells?
C, H, O and N
What are the essential nutrients that function as component of energy-related chemical compounds?
Mg - chlorophyll
P - ATP
What are the essential nutrients that function as enzymatic activators/inhibitors?
Mg2+ - activator for RuBisCo and phosphoenol pyruvate carboxylase
Zn2+ - activator for alcohol dehydrogenase
Mo - nitrogenase (nitrogen metabolism)
What are the essential nutrients that alter osmotic potential of plant cells?
Potassium - opening/closing of stomata
Other solutes
What are the forms and functions of Nitrogen?
mainly NO3- (nitrate) or NO2- or NH4+
functions: constituent of proteins, nucleic acids and amino acids, vitamins and hormones, chlorophyll
_________ is the essential nutrient required in greatest amount
Nitrogen
Nitrogen is required particularly in __________ tissues and ______________ cells
meristematic tissues, metabolically active cells
What are the forms and functions of Phosphorus?
Phosphate ions: H2PO4- or HPO4 2-
constituent of cell membranes, certain proteins, all nucleic acids and nucleotides, all phosphorylation reactions
What are the forms and functions of Potassium?
Potassium ion (K+)
Maintain an anion-cation balance in cells, protein synthesis, opening and closing of stomata, activation of enzymes and maintenance of cell turgidity
Potassium is required in more abundant quantities in _______ tissues, ___, ____ and ______.
meristematic tissues, buds, leaves, and root tips
What are the forms and functions of Calcium?
Calcium ions (Ca2+)
During cell division - synthesis of cell wall, formation of mitotic spindle; normal functioning of cell membranes; enzyme activation; regulation of metabolic activities
_________ nutrient accumulates in older leaves
Calcium
During cell division, calcium is particularly used as __________ in the __________
calcium pectate, middle lamella
What are the forms and functions of Magnesium?
Divalent Mg2+
activates respiration enzymes, photosynthesis, DNA/RNA synthesis, ring structure of chlorophyll, maintain ribosome structure
What are the forms and functions of Sulphur?
Sulphate (SO4 2-)
constituent of 2 amino acids - cysteine and methionine;
constituent of several coenzymes (Coenzyme A);
vitamins (thiamine, biotin), and;
ferredoxin (protein)
What are the forms and functions of Iron?
Ferric ions (Fe3+)
constituent of proteins involved in electron transfer (e.g. ferredoxin, cytochromes); activates catalase enzyme; formation of chlorophyll
______ is the macronutrient required in largest amounts, ______ is the micronutrient required in largest amounts
N, Fe
Iron is reversible oxidised from Fe3+ to Fe2+ during electron transfer. T or F?
False, Fe2+ to Fe3+
What are the forms and functions of Manganese?
Manganous ions (Mn2+)
Splitting of water during photosynthesis(!!); activates enzymes involved in photosynthesis, respiration and nitrogen metabolism
What are the forms and functions of Zinc?
Zn2+ ions
activates various enzymes (esp. carboxylases), synthesis of auxin
What are the forms and functions of Copper?
Cupric ions (Cu2+)
overall metabolism in plants; enzymes involved in redox reactions
Copper is irreversibly oxidised from Cu+ to Cu2+. T or F?
False, reversibly
What are the forms and functions of Boron?
BO3 3- or B4O7 2-
uptake and utilisation of Ca2+, membrane functioning, pollen germination, cell elongation, cell differentiation and carbohydrate translocation
What are the forms and functions of Molybdenum?
Molybdate ions (MoO2 2+)
component of several enzymes (nitrogenase and nitrate reductase - nitrogen metabolism)
What are the forms and functions of Chlorine?
Chlorine anion (Cl-)
determining the solute concentration, anion-cation balance in cells, water-splitting reaction in photosynthesis
Water-splitting reaction in photosynthesis leads to _______ evolution
oxygen
Apart from Chlorine and Potassium, what is the third ion required to determine solute concentration and anion-cation balance in cells?
Na+
Nutrients required in meristematic tissues? (3)
Ca, N, K
Nutrients required in proteins/protein synthesis? (4)
P, Fe (electron transfer), N, K
Nutrients required in photosynthesis? (3)
Mg, Mn, Cl
What is critical concentration?
Concentration of essential element below which plant growth is retarded
Element is said to be ________ when below critical concentration
deficient
Morphological changes indicative of certain element deficiencies are called ________
deficiency symptoms
Deficiency symptoms are reversible but if deprivation of element continues, then may lead to _______
death
For elements actively mobilized and exported to young tissues, deficiency symptoms appear first in _____
older tissues
Deficiency symptoms of N, K and Mg are first visible in_______ leaves
senescent
Deficiency symptoms tend to appear first in young tissues whenever elements are _______
relatively immobile
Sulphur and calcium are both relatively immobile structural elements. T or F?
True
Kind of deficiency symptoms shown in plants are:
chlorosis necrosis stunted growth premature fall of leaves and buds inhibition of cell division
Chlorosis is?
loss of chlorophyll => yellowing leaves
caused by deficiency of:
S, Mo, K, N, Mg
Fe, Mn, Zn
Necrosis is?
death of tissue, particularly leaf tissue
due to deficiency of Ca, Cu, K, Mg
Lack or low level of __________ causes inhibition of cell division
S, Mo, K, N
_______ delay flowering if their concentration in plants is low
S, Mo, N
Deficiency of any element can cause multiple symptoms. T or F?
True
Deficiency of each element leads to unique deficiency symptoms. Same symptom cannot be caused by two different element deficiencies. T or F?
False, same symptoms may be caused by multiple elements
Moderate increase of micronutrients causes _______
toxicity
Why is there a narrow optimum range of concentration for elements?
decrease => deficiency
increase => toxicity
_________ symptoms are difficult to identify.
toxicity or deficiency
Toxicity
________ is the prominent symptom of manganese toxicity.
Brown spots surrounded by chlorotic veins
Mn competes with ___ and ____ for uptake and with ____ for binding with enzymes.
Fe and Mg,
Mg
________ inhibits calcium translocation in shoot apex
Mn
Excess of Mn may induce deficiencies of …?
Mg, Fe, Ca
Much of the studies on mechanism of absorption have been carried out in ______ cells, tissues or organs.
isolated
Two phases of process of absorption?
- Rapid uptake - free / outer space of cells (apoplast) - passive
- Slow uptake - inner space - symplast - active
Passive movement of ions into apoplast occurs through _____, transmembrane proteins that function as selective pores
ion-channels
Movement of ions is usually called _____
flux
Influx / efflux?
Influx - into the cell
efflux - out of cell
Nutrients become available to roots in soil due to ________ and _______ of rocks
weathering, breakdown
Functions of soil:
- supply minerals
- harbours nitrogen-fixing bacteria
- harbours other microbes
- holds water
- supplies air
- matrix that stabilises plant
Fertilisers only contain macronutrients. T or F?
False, both macro and micro come in ferilisers
Plants compete with ______ for the limited nitrogen in soil.
Microbes
Nitrogen exists as ___ nitrogen atoms joined by a very strong ________ bond
2, triple covalent
What is nitrogen-fixation?
Conversation of N2 to ammonia
In nature, _____ and ______ provide enough energy to convert nitrogen to nitrogen oxides
lightning and UV radiation
What are the 3 nitrogen oxides?
NO, NO2, N2O
Man-made sources of atmospheric nitrogen oxides are:
forest fires
automobile exhausts
industrial combustions
power-generating stations
What is ammonification?
Decomposition of organic N of dead plants/animals into ammonia
Some of the ammonia from ammonification _____ but most of it is converted into ______ by soil bacteria
volatilises and re-enters atmosphere;
nitrate
2NH3 + 3O2 —> 2NO2- + 2H+ 2H2O
2NO2 + O2 —> 2 NO3-
What do these equations represent?
nitrification
ammonia –> nitrite in first step
further oxidised to nitrate
Ammonia is first oxidised to nitrite by _________ (bacteria) and further oxidised to nitrate by ______ (bacteria)
Nitrosomonas and/or Nitrococcus
Nitrobacter
Nitrifying bacteria are _________trophs
chemoautotrophs
Nitrate absorbed by plants is _____ in leaves to form ammonia that finally forms the ______ group of amino acids.
reduced, amine group
Nitrate in the soil is also reduced to nitrogen by process of ______ carried out by bacteria _______
denitrification,
Pseudomonas and Thiobacillus
Very few living organisms can utilise nitrogen in the form N2 available abundantly in air. T or F?
True
Only _______ are capable of fixing nitrogen
certain prokaryotic species
What is biological nitrogen fixation?
Reduction of nitrogen to ammonia by living organisms
Enzyme ________ capable of nitrogen reduction is present exclusively in _______
nitrogenase, prokaryotes
Nitrogen fixing microbes could be free-living or symbiotic. T or F?
T
Match the following:
Beijerinckia Rhizobium Anabaena Azotobacter Rhodospirillum Nostoc Frankia
free-living OR anaerobic free-living OR cyanobacteria free-living OR symbiotic
Beijerinckia - free-living Rhizobium - symbiotic Anabaena - cyanobacteria free-living Azotobacter - free-living Rhodospirillum - anaerobic free-living Nostoc - cyanobacteria free-living Frankia - symbiotic
Most prominent symbiotic biological nitrogen-fixing association is? And most common form of association is?
Legume-bacteria (Rhizobium)
Nodules
Rhizobium has symbiotic relationship with which plants (7)?
alfalfa, sweet clover, sweet pea, lentils, garden pea, broad bean, clover beans
Frankia produces nitrogen-fixing nodules on roots of __________ e.g. ____
non-leguminous plants e.g. Alnus
Rhizobium and Frankia are free-living in soil as well as can be symbionts. T or F?
True
What makes symbiont nodules pink?
Presence of leg-haemoglobin
How does nodule formation occur?
- Rhizobia multiply and colonise root surroundings, get attached to epidermal and root hair cells
- Root hairs curl, bacteria invade root hair
- Infection thread carrying bacteria into cortex, where they initiate nodule formation
- Bacteria release from thread into cells, modified into rod-shaped bacteroids => inner cortical and pericycle cells to divide => differentiation of specialized nitrogen fixing cells
- mature nodule formed with direct vascular connection with host
Nodule contains all necessary biochemical components such as enzymes _____ and _____
nitrogenase, leghaemoglobin
Enzyme nitrogenase is a ____ protein that catalyses the conversation of _______ to _____
Mo-Fe,
nitrogen to ammonia
_____ is the first stable product of nitrogen fixing
Ammonia
The enzyme nitrogenase is highly sensitive to _________ and requires _______ conditions
oxygen, anaerobic
Leg-haemoglobin is a ______ scavenger that protects nitrogenase
oxygen
Nitrogenase is operational in nodule forming bacteria in free-living conditions and as symbionts. T or F?
False, only in symbionts
Nitrogen fixation is reduction reaction that requires very high amount of ATP. T or F?
True
___ ATP are required for each NH3 produced
8
_____ ATP are required for each N2 atom that is reduced
16
Energy required for nitrogen fixation is obtained from _________ process of host.
Respiration
At physiological pH, ammonia is ________ to form _________
protonated, NH4+ ions
Most plants can assimilate both nitrates as well as ammonium ions. T or F?
True
Ammonium ions are quite toxic to plants, cannot accumulate in them and are hence used to synthesise _________
amino acids
Two ways to use ammonium ions to synthesise amino acids?
- Reductive amination - ammonia reacts with alpha-ketoglutaric acid to form glutamic acid
- Transamination - transfer of amino group from one amino acid to keto group of a keto acid.
_______ is the main amino acid from which transfer of NH2, the amino group takes place.
Glutamic acid
Enzyme ______ catalyzes all reactions in transamination
transaminase
The two most important amides in plants are ____ and ______. What function do they play?
asparagine, glutamine;
structural parts of proteins
Asparagine is the amide formed from _______; glutamine from _______ by addition of ________
aspartic acid;
glutamic acid;
another amino group
The hydroxyl part of glutamic or aspartic acid is replaced by ___________ in formation of amides.
Another NH2- radicle
Why are amides transported to other parts of plants via xylem?
Since they contain more nitrogen than amino acids
Along with transpiration stream, nodules of some plants like soyabean export the fixed nitrogen as _______ which have a particularly high nitrogen to ____ ratio.
ureides, carbon
Not all minerals absorbed are required by plants. T or F?
True
Nitrogen fixation requires a strong oxidising agent and energy in the form of ATP. T or F?
False, strong reducing agent
