PLANT HOMEOSTASIS

1. HOMEOSTASIS &
ITS CONTROL
MECHANISM.
PRESENTED BY :
R A SH MI JA LA N

2. Theterm wascoined in1930bythe physician WalterCannon.
Homeostasis is thetendency toresist change inorder tomaintain
astable, relatively constant internal environment.
Homeo – ‘stable’ ; stasis – ‘standing’.
The pathway of homeostasis is different for bothPlants and Animals.

3. o Plant health depends upon availability of water, air, light and nutrient.
o Regulation and coordination systems in plants are much simpler than in
animals andplants are highly phenotypically plastic.
o As plant has no nervous system; Stomata , Transport system, various kind of
Gradient, Hormones performs the all internal homeostaticmechanism.

4. 1. OSMOREGULATION IN PLANTS
The regulatory mechanismwhich maintain the balance between water and solute context of a
cell is called osmoregulation.
The chief organ involved in osmoregulation is Stomata, whose opening and closing is
regulated by guardcell.

5. Stomata
– Stomata are generally abundant on the surfaces of leaves,
more commonly on the underside.
– Stomatal pores in the epidermis are bounded by two highly
specialised guard cells.
Guard Cells
– Guard cells have three structural features which explain
their function:
 They are joined at their ends in pairs
 Their cell walls are thicker on the side nearest to the stomatal
pore
 Bands of inelastic cellulose fibres run around each cell

6. Regulating Stomata
– Stomata movement is the result of changes in the turgor of the guard cells.
– If water flows into the guard cells by osmosis, their turgor increases and they expand. The
relatively inelastic inner wall makes them bend and draw away from each other. This opens the
pore.
Stomatal Opening
1.Potassium ions move into the
vacuoles.
2.Water moves into the vacuoles,
following potassium ions.
3.The guard cells expand.
4.The stoma opens.
Stomatal Closing
1.Potassium ions move out of
the vacuole and out of the
cells.
2.Water moves out of the
vacuoles, following potassium
ions.
3.The guard cells shrink in size.

7. Why Regulate Stomata?

8. 2. THERMOREGULATION IN PLANTS•
The maintained the temperature of the body within a range is called
thermoregulation. The normal range of temperature in plant is 10˚C to 35˚C. The
adaption of plant to low and high temperature are as follows.
Low Temperature
 At low temperature the nature of plasma membrane is changed and produce
crystalline structure called antifreeze protiens and dehyrins due to which transport
of solute is slow.
 At low temperature plant cell produce unsaturated fatty acid in cell membrane and
become gel like.
 At freezing point ice crystal are formed in the cell. But the plant of cold region
change the composition of solute of cell so ice crystal are not formed in cytoplasm
they form in cell wall. This condition is known as freezing tolerance.

9. High Temperature
 High temperature has more harmful than low temperature for plant.
Due to high temperature all enzyme are denature and metabolic process stop. So
plant increase rate of transpiration and cool the body.
 At above 40ºC plant produce heat shock protein. They protect the enzyme from
destroying.
 In some plant shiny cuticle is present which protest them from high temperature.
 In some plant leaves are reduce in size.
 The cell produces saturated fatty acids in cell membrane and the cell become leaky.

10. 3. EXCREATION IN PLANTS
The removal of harmful substance produce in the metabolic process fromthe body is called
Excretion.
Excretion in Plant
In plant rate of catabolic process is very slow and waste product are produce in less amount.
They are used again in their anabolic process.
Waste Substance of Plant
The substance which are produce in excess amount are
1. Water
2. CO2
3. O2
4. Ions

11. •Transpiration
The extra amount of water removed in
the form of vapor through stomata is
called transpiration.
1. Removal of Water
Extra water is removed from the body of plant by
two methods.
•Guttation
When water is removed from plant in
the form of drop this process is called
Guttation. Guttation occur special
opening called hydathods. Guttation take
place in those plant which grow
in tropical rain forest.

12. 3. Ions
Excess amount of ion are deposit into dead cell
of plant body such as bark.
2. Release of Oxygen and Carbon dioxide
 In day time plant used CO2 for
photosynthesis process and released O2.
 In night time plant released CO2 and
inhale O2 gas.

13. Some astonishing homeostasis phenomenon in plants
Pyriscence, where maturation and release of seeds is triggered, in whole or in part, by fire or smoke;
this behaviour is often erroneously called serotiny.
Some species, such as Macroptilium purpureum, can move their leaves throughout the day so that
they are always orientated to avoid the sun (paraheliotropism).
Raoulia plants found in the uplands of New Zealand are said to resemble ‘vegetable sheep’
as they form tight cushion-like clumps to insulate the most vulnerable plant parts and
shield them from cooling winds.
Plants can sense the wind through the deformation of its tissues. This signal leads to inhibits the
elongation and stimulates the radial expansion of their shoots, while increasing the development of
their root system. This syndrome of responses known as thigmomorphogenesis results in shorter,
stockier plants with strengthened stems, as well as to an improved ancorag

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