PLS 172 Lecture 3
1 of 10
Mikal E. Saltveit, Department of Plant Sciences, UC Davis
TABLE OF CONTENTS
Respiration – Basic Mechanism
Overall reactions of respiration
Measurement of respiration
Measurement of gas exchange
Instruments and techniques
Measurement of heat production
Metabolism is comprised of two opposite sets of reac-
tions: anabolism and catabolism.
synthesize molecules such as sugars, carbohydrates,
amino acids, proteins, nucleic acids, DNA, RNA, lip-
ids, membranes, pigments, etc.
breakdown these complex compounds to regenerate
and transform, and release energy.
The two process
work in concert during plant growth and development
Photosynthesis (anabolic) and respiration (cata-
bolic) are the two processes by which carbon and en-
ergy are cycled through the biosphere.
utilizes energy from light to reduce carbon dioxide
from the air and water from the soil to carbohydrates.
In this process water is split into its components of hy-
drogen and oxygen.
The hydrogen combines with car-
bon dioxide to form carbohydrates, while the oxygen,
which is a by-product of the reaction, diffuses away.
Carbohydrates are formed by photosynthesis in
the green, chlorophyll containing tissues of plants (usu-
ally leaves) and are translocated to other cells in the
plant where they are either stored or oxidized.
process of oxidation, carbohydrates are combined with
oxygen from the air to produce energy, carbon dioxide
As glucose is broken down, many of the
resulting fragments are used in the synthesis of larger
molecules that constitute the living cell.
Some of the
energy released during respiration is captured in the
high-energy bonds of ATP, which is used in many cel-
The remainder of the energy that is not
captured is lost and appears as heat.
produced by respiration is dissolved in the liquid por-
tion of the cell and slowly diffuses into the gas phase
within and surrounding the tissue.
Energy (ATP + heat)
Interrelationship between photosynthesis and respira-
tion in aerobic organisms.
RESPIRATION - BASIC MECHANISMS
In the common usage, the term respiration is applied to
"...the physical and chemical processes by which an
organism supplies its cells tissues with the oxygen
needed for metabolism and relieves them of the carbon
dioxide produced in energy-producing reactions"
To biochemists, and particularly those of us
concerned with plant physiology, the term has a more
To us it means ".
..any of various
energy-yielding oxidative reactions in living matter"
It is readily apparent that respiration
is a vital process to humans and other animals (just try
holding your breath for a few minutes!), and we will
see that it is equally important to plants.