Mineral
N: Nitrogen
as nitrate ions NO3-
Other N-containing material may be broken down by microbial action to provide this
Role in plant cells
Used to produce amino acids for protein production, and for nucleic acids DNA, RNA
Hence promotes vegetative growth and development of flowers, fruits and seeds
Deficiency causes
Poor growth, leaves not so green (more yellowy green) - 'chlorosis'
Amount required
ppm
125-224
Good sources
'Chemical' sources:
calcium nitrate,
potassium nitrate,
ammonium nitrate
- also provide Ca
2+, K
+, NH
4+
'Organic' sources;
urea CO(NH
2)
2
Less defined:
'blood, fish and bone'
animal droppings etc
Mineral
P: Phosphorus
as phosphate ions:
PO43-
HPO42-
H2PO4-
Role in plant cells
Component of nucleic acids (DNA, RNA, nucleotides, ATP etc)
All cell membranes are phospholipids
Phosphate groups are involved in activation of carbohydrates in respiration and photosynthesis,
and also in control of enzymic processes and gene expression (phosphorylation and photophosphorylation)
Hence P promotes growth of roots and shoots
Deficiency causes
General stunting of growth
Leaves may be smaller and darker than usual
Amount required
ppm
39-45
Good sources
inorganic phosphate fertiliser
bonemeal
Mineral
K:
Potassium ions K+
Role in plant cells
Involved in the opening and closing of stomata (by regulating the osmotic potential within guard cells), hence controls intake of CO
2 for photosynthesis and the transpiration stream which provides water and other inorganic ions for plants.
It is said to activate a number of enzymes involved in photosynthesis and respiration.
Deficiency causes
Leaf tips become brown and curl; leaf blades become yellow between veins.
Symptoms are more marked in older leaves.
Plant growth and development of roots, seeds and fruits is reduced.
Amount required
ppm
280-350
Good sources
Inorganic potassium salts: potassium chloride (chloride no use to plants), potassium nitrate (nitrate also provides nitrogen)
Pot ash (residue from burnt wood)
Mineral
Mg:
Magnesium ions Mg2+
Forms (the central) part of the
chlorophyll molecule
Magnesium ions are co-factors for the action of enzymes required for important stages in photosynthesis (specifically carbon fixation): Ribulose Bisphosphate Carboxylase (RUBISCO) and Phosphoenolpyruvate Carboxylase (PEPC).
Deficiency causes
Marked chlorosis (yellowing) between leaf veins, which stay green
Good sources
'Epsom salts' (magnesium sulphate)
(also provides sulphate)
Amount required
ppm
48-65
Mineral
Fe: Iron
Fe2+, Fe3+ ions
Role in plant cells
Needed for enzymes involved in chlorophyll production
Deficiency causes
Chlorosis
Noticeable in alkaline soils which reduce solubility of iron compounds
Good sources
Red soils contain iron compounds
Amount required
ppm
2
Mineral
Ca: Calcium
Ca2+
Role in plant cells
Calcium ions are involved in microtubule formation as part of spindle action in cell division - especially important in meristems at tips of roots and shoots.
Calcium pectate is a constituent of plant cell walls
Calcium is distributed mostly into the leaves, less so in seeds, fruits, and roots.
Calcium may function directly in several aspects of photosynthesis. It appears to modulate activity of the phosphatase enzymes in the carbon reduction cycle.
Deficiency causes
Stunted growth of plant, especially roots
Curling of leaves, and darkened appearance
Blossom end rot of fruits, exacerbated by excess nitrate or inadequate water supply
Some plants are affected by the calcium content of soils, and its effect on soil pH and the availability of other ions:
Calcifuges e.g. Ericas (heathers), Rhododendrons, Azaleas, etc require acidic soils so they develop the symptoms of iron deficiency, i.e. interveinal chlorosis, on alkaline soils.
Calcicoles thrive in lime rich soil. In acidic soils they often develop the symptoms of aluminium toxicity, i.e. necrosis, and phosphate deficiency (reddening of the leaves) and stunting.
Amount required
ppm
170-210
Good sources
Chalk and lime is often added to soils, and hard water contains calcium ions.
Nitro chalk - a mixture of calcium carbonate and ammonium nitrate (calcium ammonium nitrate?)
gives nitrate in addition to calcium.
Certain leafy vegetables (Brassicas e.g cabbage etc) grow more strongly when supplemented with calcium, and may in turn make a significant contribution to the human diet.
Some calcium salts (phosphate, sulphate) are insoluble so phosphates and sulphates may lower the availability of calcium to the plant.
Mineral
S: Sulphur
as sulphate ions
SO42-
Role in plant cells
Sulphate ions provide the element sulphur which is needed to produce the amino acids cysteine and methionine which are used in the synthesis of proteins.
Deficiency causes
Poor growth, leaves not so green (more yellowy green) - 'chlorosis'
- leaf veins purple
- especially noticeable in older leaves
Sulphur deficiency can occur when the soil pH is too high, or a large amount of calcium is present.
Amount required
ppm
75
Good sources
'Epsom salts' (magnesium sulphate)
(also provides magnesium)
In this context, fertiliser means something which makes ground more productive by encouraging plant growth.
Of course fertilisation is an important process in Biology, and generally necessary for the production of fruits and seeds which are the products of sexual reproduction.
Mineral supplements can be added to the soil in the form of simple mineral
salts : 'chemicals' in some people's language.