Transcript Plant Growth & Development

Plant Growth
& Development
Necessities for Plants
• Plants require the following:
– Water, carbon dioxide and light in order to
run photosynthesis and produce energy
compounds (glucose).
– Inorganic substance (minerals) that assist
in making larger organic molecules
function properly.
– Favorable environmental conditions
(precipitation, temperature, soil).
• If any one of these is in short supply, it
acts as a limiting factor and will
impede the development of the plant or
cause it to die.
Soil & Soil Nutrients
• The soil is important because it contains
many nutrients required for proper plant
growth – both macro & micronutrients.
– Macronutrients – these are substances
required in substantial amounts by the
plant daily.
• These include N, P, K, Ca & Mg
– Micronutrients – these are substances
that are required in only small amounts
daily.
• These include Fe, Zn & Cu.
• Nitrogen is the most important nutrient.
Plants rely on nitrogen fixation and soil
bacteria (possibly in nodules) in order to
gain their nitrogen.
Soil Layers
• Soil has several
different layers:
– Humus – Partially
decomposing plant
and animal matter.
(Called “litter” in
grade 10.)
– Topsoil – Primary
supporter of plant
life.
– Subsoil – Soil layer
that contains some
rocks.
– Bedrock – Solid rock
layer
Fertilizers Give Soil a Boost!
• Fertilizers are mixtures that carry
many of the macronutrients needed for
plant growth.
• Fertilizers may be organic (coming
from a living source) or inorganic
(produced chemically).
• Fertilizers often have a three number
sequence on their containers such as
10-20-10. This is the proportion
of macronutrients N-P-K in the
mixture.
• Do Discovering Biology – Pg. 560
Seed Dormancy
• It takes a little more than just sticking
a seed into a hole and covering it over.
• Seeds require the right environmental
conditions in order to start growing. If
conditions are too harsh – the seed will
remain in a state of dormancy.
• When conditions are good, the seed
may come out of this period of
dormancy and begin germination.
Inside the Seed
• The embryo has
three parts – the
radicle, hypocotyl
and the epicotyl –
the embryonic
roots, stem and
upper part of the
plant
respectively.
Germination
• Germination is the development of the
embryonic plant after the seed has
been “planted” and environmental
conditions are favorable.
• The plant embryo, inside the seed,
releases a hormone that breaks down
the starch in the seed into a number of
smaller glucose molecules.
• Water is brought in to balance out the
glucose and the seed swells and
cracks its seed coat.
• Oxygen can now get in and the embryo
can start cellular respiration.
Germination
Plant Hormones and the
Control of Plant Growth
Plant Hormones
• First of all, a hormone is a chemical
that is produced in one part of the
body that brings about a change in
another part of the body.
• There are several hormones that are
key to plant success:
–
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–
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Auxins
Gibberellins
Cytokinins
Abscisic Acid
Ethylene
Auxins
• Auxins are plant hormones that cause
cell elongation. The result is a
controlled growth direction in the
plant.
• Auxins have opposite effects in
different areas of the plants.
– Shoots – Auxins move away from sun to
bend plant toward the sun.
– Roots – Auxins move to the sun to bend
plant away from it.
– Auxins can also respond to touch or solid
objects – the plant will grow around a large
stone in the soil.
Gibberellins & Cytokinins
• Gibberellins are plant hormones that
have several effects:
– Work with auxins to promote elongation of
stems & roots.
– Promote leaf growth.
– Promote flowering.
– Assist in germination.
– Increase fruit production – agriculture uses
this to produce larger produce.
• Cytokinins are plant hormones that
promote cell division and cell
differentiation. They help some plants
from aging to quickly and help keep
them fresher for a longer time period.
Abscisic Acid & Ethylene
• Abscisic acid (ABA) works to inhibit
growth of plants – not help it. It
actually speeds up the fall of leaves
and induces dormancy within the plant.
This may aid in the plant preparing for
the late Fall and Winter months.
• Ethylene is involved in the ripening of
fruit.
• Carbon dioxide is used by industry to
stop the effects of ethylene but it can
not reverse them.
That’s All I Got…