Biology Times (^19)
March
Introduction
m Respiration is an energy releasing enzymatically
controlled process which involves a step wise
oxidative breakdown of food substances inside
living cells. Respiration in plants is found similar
in animals and lower eukaryotes. However,
m Respriration is an enzymatic process, which also
known as cellular Respiration/ mitochondrial
respiration. (Respiration takes place both in
cytoplasm and mitochondria)
m It occurs in all living cells of the plants.
m Respiration includes the intake of oxygen and
chemically brings about the oxidation and
decomposition of organic compounds with the
release of energy.
m Most of the liberated energy is trapped as chemical
energy in the form of ATP, which functions as
energy currency of cells.
m The trapping of energy of ATP is highly useful as
(i) It makes any amount of energy available
immediately.
(ii) ATP is mobile inside the cell,
therefore energy is made available away
from the site of respiration.
(iii) Wastage of energy is minimised.
ATP - Adenosine - Triphosphate.
Energy released during respiration is used to
make ATP.
m Cells need energy, ATP broken down in the
presence of water to form ADP and energy is
released.
This reaction is a reverse of Photosynthesis. It
represents a coupled redox reaction. Here sucrose
is completely oxidised to CO 2 while oxygen
serves as the ultimate electron acceptor, being
reduced to water.Difference between Respiration in plants and
animals:
i. The only difference lies in the mechanism of
gaseous exchange, which is called as breathing
(in animals) because of involvement of some
specialised Organs/cells.
ii. Plants do not have any specialised organ for
gaseous exchange; rather this function is performed
in them by stomata & lenticels.
Why plants can get along without respiratory
organs?
i. Because, each part of plants can fulfill their need
of gaseous exchange & very little transfer of
gases occur.
ii. Rate of respiration in root, stem, and leaves is very
low, hence no great demands for gas exchange.
iii. Plant cells are located quite close to surface, so
there is not much distance for diffusion of gases.On the basis of respiratory substrate the organic
substances which can be catabolised in cellular
Respiration for releasing energy are called
Respiratory substrates. Blackmann classified
two types of respiration
m Floating respiration: When respiratory substrate
is fats or carbohydrates, (like glycogen, starch,
sucrose, hexose)RESPIRATION IN PLANTS