excretion in plants
TRANSCRIPT
EXCRETION IN PLANTS
IntroductionAnimals are known to excrete wastes and usually have a special set of organs or a system that carries out that function. Do you think flowering plants like these also carry out excretion?
Objectives
You should be able to:
1. give examples of waste substances and how they are excreted
by plants.
2. state the importance of excretion to plants.
3
Salt crystals on the leaf surface of the
Black Mangrove
4
Salt glands on Button mangrove leaf petioles
5
salt gland
What is Excretion?
Excretion in Plants 6
Why carry out excretion?
O2 is excreted from photosynthesis
7
What ‘waste’ from respiration is
excreted?
Glucose + Oxygen Carbon Dioxide + Water + Energy
released and made available
C6H12O6 + 6O2 6CO2 + 6H2O + Energy
This means that oxygen combines with sugars present in cells to
break molecular bonds, thus releasing the energy contained in
those bonds.
The other products of the respiratory reactions are carbon
dioxide and water, which can be excreted if not needed then by
the plant.
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Guttation - The loss of excess water as liquid drops from
the margins of leaves of herbaceous plants, occurring when root
pressure is high and transpiration is low. The water usually
contains sugars and/or salts.
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Ornamental plants form Calcium
Oxalate crystals in (leaf) cells for
excretion
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The cells of these plants
contain Calcium oxalate
crystals which are
eliminated when the leaves
die and fall off.
www.flowersgrowing.com/.../12/diefenbachia.jpg
Calcium Oxalate crystals from Pomegranate
leaf (left) and Tilia sp.
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Development of the calcium oxalate
crystal in pomegranateCalcium oxalate crystal in Tilia sp.
Water, brought to leaves via veins, is excreted
during transpiration
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Functions of stomata1. Gas Exchanges and 2. Transpiration
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Oxygen, Carbon dioxide can diffuse in/out
Water vapour diffuses out.
Guard cell
,
Excretion of gases by diffusion
On woody stems - openings
or pores in the layer of bark
which is impervious to gases
or water. Oxygen and Carbon
Dioxide can diffuse through
lenticels that develop in
the bark.
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Various wastes are removed during leaf fall
• Waste compounds are often stored in dead heartwood,
bark and leaves which die/fall off.
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• When chlorophyll breaks
down, other compounds in
leaves give the
characteristic autumn
colors seen just
before leaf fall.
Latex (white) can be excreted from plants
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Gum oozes out of a branch
Gum
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Summary• Excretion is the removal from the organism’s body of waste
substances produced during cellular metabolism.
• Plants do not have any set excretory system, so, getting rid of wastes often involves storing the substance (e.g. Calcium Oxalate, tannins) in some plant tissue, passing it out onto leaf surfaces (e.g. salts) or diffusion (e.g. O2, CO2).
• Because salts are so removed, excretion also serves the important function of osmo-regulation which maintains homeostasis.
Excretion in Plants 18
