Employablity presentation and Future Career Plan.pptx
Introduction
1. INTRODUCTION
PLANT NUTRITION: involves the uptake from the environment of all the raw
materials required for essential biochemical processes, the distribution of these
materials within plant and their utilisation in metabolism and growth (Raven and
Peter, 2005).
Most of the chemical elements found in plants are absorbed as inorganic
ions from the soil solution.
In addition to light, plants require water and certain chemical elements for
metabolism and growth.
Under favourable conditions, most green plants can use light to transform
carbon dioxide (CO2) and water (H2O) into organic compounds for their
energy source.
They can also synthesise all their required amino acids and vitamins using
inorganic nutrients drawn from the environment.
LIFE SCIENCES (LS3BFET)
UNIT 6: PLANT
NUTRITION AND SOILS
2. ESSENTIALELEMENTS
Early in the 1800, chemists and biologists had analysed plants and
demonstrated that certain chemical elements were absorbed from the
environment.
In the absence of any one of these elements, plants displayed
characteristicsabnormalities of growth or deficiency symptoms.
Three primary criteria by which an element is judged to be essential to a
plant:
1. If it is needed for the plant to complete its life cycle (to produce
viable seed).
2. If it is part of any molecule or constituent of the plant that is itself
essential to the plant suchas the magnesium in chlorophyll molecule
or the nitrogen in proteins.
3. Whether deficiency symptoms appear in the absence of the element
even though the plant may be capable of producing viable seed.
THE ESSENTIAL ELEMENTS CAN BE DIVIDED INTO
MICRONUTRIENTSAND MACRONUTRIENTS
Micro-nutrients or trace elements- chemical elements that are required
in very small or trace amounts (concentration equal to or less than
100mg/kg of dry matter).
Macro-nutrients- chemical elements that are required in large amounts
(concentration of 1000mg/kg of dry matter or greater).
One way to determine which elements are essential and in what
concentration is to chemically analyse healthy plants.
The freshly harvested plants or parts are heated in an oven to drive off the
water, the remaining material or dry matter is analysed.
3. Source: Biology of plants (Raven and Peter, 2005).
Researchers use hydroponic culture to determine which elements are
essential.
4. Source:
FUNCTIONS OF ESSENTIALELEMENTS
Essential elements have many roles in plants, including
1. Structural
2. Enzymatic
3. Regulatory
4. Ionic
ELEMENT FUNCTION DEFICIENCY
Macro-nutrients
Nitrogen (N) Promotes growth
of leaves and
stems
Gives dark green
colour and
improves quality
of foliage
Necessary to
develop cell
proteins and
chlorophyll
sick, yellow-
green colour
short stems, small
leaves, pale
coloured leaves
and flowers
slow and dwarfed
plant growth
5. Phosphorus (P) Stimulates early
formation and
growth of roots
Provides for fast
and vigorous
growth and
speeds maturity
Stimulates
flowering and
seed development
Necessary for the
enzyme action of
many plant
processes
decrease in
growth
slow maturity
older leaves are
purplish colour
Potassium (K) Used to form
carbohydrates and
proteins
Formation and
transfer of
starches, sugars
and oils
Increases disease
resistance, vigor
and hardiness
mottled, spotted,
streaked or curled
leaves
scorched, burned,
dead leaf tips and
margins
Calcium (Ca) Improves plant
vigor
Influences intake
and synthesis of
other plant
nutrients
Important part of
cell walls
small developing
leaves
wrinkled older
leaves
dead stem tips
Magnesium (Mg) Influences the
intake of other
essential nutrients
Helps make fats
Assists in
translocation of
phosphorus and
fats
Interveinal
chlorosis-
yellowing of
leaves between
green veins
leaf tips curl or
cup upward
slender, weak
stalks
6. Sulfur (S) Promotes root
growth and
vigorous
vegetative growth
Essential to
protein formation
young leaves are
light green with
lighter colour
veins
yellow leaves and
stunted growth
Micro-nutrients
Iron (Fe) Essential for
chlorophyll
production
Helps carry
electrons to mix
oxygen with other
elements
mottled and
interveinal
chlorosis in
young leaves
stunted growth
and slender, short
stems
Copper(Cu) Helps in the use
of Iron
Helps respiration
young leaves are
small and
permanently wilt
multiple buds at
stem tip
Zinc (Zn) plant metabolism
helps form
growth hormones
reproduction
retarded growth
between nodes
(rosetted)
new leaves are
thick and small
spotted between
veins, discoloured
veins
Boron (B) affects water
absorption by
roots
translocation of
sugars
short, thick stem
tips
young leaves of
terminal buds are
light green at base
leaves become
twisted and die
Manganese (Mn) plant metabolism
nitrogen
transformation
interveinal
chlorosis
young leaves die
Molybdenum (Mo) plant
development
reproduction
stunted growth
yellow leaves,
upward curling
7. leaves, leaf
margins burn
Chlorine (Cl) essential to some
plant processes
acts in enzyme
systems
usually more
problems with too
much chlorine or
toxicity than with
deficiency
Nitrogen deficiency Phosphorus deficiency
Potassium deficiency Calcium deficiency
9. THE SOILS
Soil is the primary nutrient medium for plants (Raven and Peter, 2005). Soils
must provide plants not only with physical support but also with:
adequate inorganic nutrients.
adequate water and a suitable gaseous environment for the root.
The earth is composed of 92 naturally occurring elements, which are often
found in the form of minerals. Minerals are naturally occurring inorganic
compounds which usually composedoftwo or more elements in definite
proportions by weight (Raven and Peter, 2005).
Soils consist of layers called horizons:
A horizon (“topsoil) is the upper region, that of the greatest physical,
chemical and biological activity (example, humus- the dark coloured
mixture of colloidal organic decay products accumulates).
B horizon (“subsoil”) is a region of deposition. Contains less organic
material and is less weathered than the A horizon above it.
C horizon or the soil base, is composed ofthe broken down and
weathered rocks and minerals from which the true soil in the upper
horizon is formed.
10. Soils are composedofSolid Matter and Pore Space
Pore space:the spaces around the soil particles, consist of different
proportions of air and water that occupythe pore spaces.
Solid matter: consists of both organic and inorganic materials.
the organic components include:
Remains of organisms in various stages of decompositions (humus).
Wide range of living plants and animals but living phase is dominated by
fungi, bacteria and other microorganisms.
Structures of as large as tree roots may be included.
Soils retain cations
The inorganic nutrients taken in through the roots of plants are present in
the soil solution as ions (charged particles -/+).
Cations- positively charged ions such as Ca, K, Na, and Mg.
Clay particles and humus may have excess of negative charges on their
colloidal surfaces, where cations can be bound and thus held against the
leaching (draining of ions and minerals mixed with water) action of
percolating water.
These weakly bound cations can be replaced by other cations and thus
released into the soil solution, where they become available for plant
growth. This process is called cation exchange.
11. Cation Exchange:
When CO2 is released by the respiring root.
It dissolves in the soil solution to becomecarbonic acid (H2CO3).
The carbonic acid then ionizes to producebicarbonate (HCO3) and
hydrogen (H) ions.
The hydrogen ions produced in this way may exchange for the nutrient
cations on the clay and humus.
Soils leach Anions
The principal negatively charged ions called (NO3, SO4, HCO3 and OH
are called Anions.
Anions are leached out of the soil more rapidly than soil more rapidly
than cations because anions do not attach to clay particles.
NUTRIENT CYCLES
Essential elements are available in limited supply.
Therefore, recycling of these elements is important.
Macro-nutrients and micro-nutrients are recycled through plant and
animal bodies, returned to the soil, broken down and taken up into plants
again.
Each element has a different cycle, involving many different organisms
and enzyme systems.
Nutrients cycles involve both living organisms and the physical
environment, they are called biogeochemical cycles.
Nitrogenand the nitrogen cycle
The chief reservoir of nitrogen is the atmosphere, nitrogen gas (N2)
makes about 78% of the atmosphere.
Most living things, however, cannot use elemental atmospheric nitrogen
to make amino acids and other nitrogen-containing compounds and
therefore are dependent on more reactive nitrogenous compounds suchas
ammonium and nitrate present in soil.
Shortage of nitrogen in the soil is often the major limiting factor in plant
growth.
12. The process bywhich limited amount of nitrogen is recirculated
throughout the world of living organisms is known as the nitrogen cycle
The three principal stages of this cycle are:
o Ammonification
o Nitrification
o Assimilation
Ammonification
Soil nitrogen is derived from dead organic matter in the form of complex
organic compounds suchas proteins, amino acids, nucleic acids and
nucleotides.
These nitrogenous compounds are decomposed into simpler compounds
by saprophytic bacteria and various fungi.
These organisms incorporate the nitrogen into amino acids and proteins
and release excess nitrogen in the form of ammonium ions (NH4) by a
process known as ammonification or nitrogen-mineralization.
Within the soil, the ammonia produced byammonification dissolves in
the soil water, where it combines with protons to form the ammonium
ion.
Plants growing in these soils are able to take up NH4 and use it in the
synthesis of plant proteins.
Nitrification
13. Several species of bacteria common in the soil are able to oxidize
ammonia or ammonium ions.
The oxidation of ammonium or nitrification is an energy- yielding
process.
The energy released is used by bacteria to reduce carbondioxide
Such organisms are known as chemosynthetic autotrophs.
The chemosynthetic nitrifying bacterium Nitrosomonas is primarly
responsible for oxidation of ammonium to nitrite ions (NO2).
Nitrite is toxic to plants, but it rarely accumulates is soil.
Nitrobacter bacterium oxidizes the nitrite to form nitrate ions (NO3),
again with a release of energy.
Nitrate is the form in which almost all nitrogen is absorbed by most crop
plants grown on dry land where nitrification is strongly favoured by
oxidizing tillage of agriculture.
Assimilation (the conversion of inorganic Nitrogen into organic compounds)
Nitrogenfixation
is the process bywhich atmospheric N2 is reduced to NH4 and made
available for transfer to carbon-containing organic compounds.
14. the most common of the nitrogen-fixing bacteria are Rhizobium
commonly called rhizobia which invades the roots of legumes, clovers,
peas, soybeans and beans.
In the symbiotic relationship between bacteria and legumes, the bacteria
provide the plant with a form of nitrogen that it can use to make proteins.
The plant in turn provide the bacteria with an energy source.
Nitrogen-fixing nodules
Rhizobia enter the roothairs of leguminous plants when the plants are
still seedling.
Attachment of rhizobia to emerging root hairs in responseto chemical
attractants released by the root hair.
The roothair typically develops into tightly curled structures, entrapping
the rhizobia.
Rhizobia develops into bacteriods (enlarged nitrogen-fixing bacteria).
Proliferation of the membrane enclosed bacteriods results in the
formation of tumorlike growths called nodules.
15. source: Biology of plants (Raven and Peter, 2005)
HUMAN IMPACT ON NUTRIENT CYCLES AND EFFECTSOF
POLLUTION
The need to adequately feed an exponentially growing human population
has had drastic effects on some cycles.
Crop removal and increased soil erosion have accelerated phosphorus
loss in the soil.
The build-up of high levels of phosphorus and nitrogen (eutrophication)
in aquatic habitats in the form of sewage and drainage has resulted in
massive growth of algae and flowering plants, reducing the recreational
value of the affected areas.
Increasing introduction of fixed nitrogen (nitrites) into the environment
through the extensive use of commercial fertilisers, the efficiency of the
nitrogen cycle declines.
The beneficial effects on the soil of growing leguminous plants have been
recognized for centuries.
In modern agriculture it is common practice to rotate a non-leguminous
crop such as maize with a leguminous crop such as wheat.