Lemna are small water plants found in ponds. Typical of plants, they
reproduce asexually. When they reproduce they form a bud on the edge
of a leaf, which, when big enough, will eventually separate from the
mother leaf and can then reproduce itself. Sometimes lemna plants can
have up to 3 or 4 buds. Exactly the same as plants in soil, they use
the sun's energy for photosynthesis, and water, but they have to take
all their nutrition to grow and reproduce from the water. I am going
to look at how lemna are affected by deficiencies in nitrogen, iron
How do lemna plants cope in ...view middle of the document...
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A complete culture solution contains all of these minerals; therefore
these lemna will live the most successfully. I think that over the
weeks we will see the lemna in the complete culture solution being
healthy and green, gradually building up larger roots and leaves.
Therefore, for the solution containing no nitrogen ions, I predict
that the final outcome will be that there is the least amount of
lemna. I say this because nitrogen is the most important mineral salt
for plants. They get the nitrogen from nitrates in the soil (or in
this case the water). It is essential for the production of amino
acids, proteins, and chlorophyll. What happens is that the nitrogen
ions combine with glucose to form amino acids. Proteins help with
growth, therefore I would expect to see small leaves, perhaps with
some loss of colour due to chlorophyll not being produced so quickly.
Chlorophyll is what makes plants green, therefore a lack of it would
result in the yellowing of the leaves and eventual complete loss of
colour. With no nitrogen, the lemna will be unable to make much amino
acids or proteins, so they will not be able to grow as rapidly. Along
with this the root of the lemna will be reduced in size, making the
plants less able to take in water and other vital minerals. As a
result, I think the plants will lose their colour (become chlorotic)
because they will not be able to make chlorophyll very easily.
For the lemna in the solution containing no iron ions, I predict that
we will not see such slow growth. The plants should not be affected
very much at all, because iron is only a trace element needed in
plants. This means that it is needed, but it can survive without, and
will not die straightaway. I therefore predict that over the weeks we
will see that many of the lemna plants remain green and healthy, while
some begin to turn yellow. This is known as "chlorosis", and is caused
by lack of chlorophyll. Plants need iron for the formation of
chlorophyll, which is what makes the plant appear green. Chlorophyll
is also vital in the production of food for the plant, as you can see
in the word equation. Also, iron is necessary for many enzyme
processes that help respiration and the metabolism of the plant. So I
expect to see that the plants may appear smaller, fewer in number, and
with yellow spots on the leaves. This discolouring will affect the
younger leaves the most. Eventually some will turn brown and die. This
is typical of an iron deficiency.
Finally, for the solution containing no magnesium ions, I predict that
there will be less lemna than in the complete culture solution and the
solution containing no iron, but more than in the solution containing
no nitrogen. This is because...