HORMONE PHYSIOLOGY AND
SIGNAL TRANSDUCTION
Huseyin Tombuloglu, Phd.
GBE 304 Spring 2015
ETHYLENE
The Gaseous Hormone
Figure
22.1 Triple response of etiolated pea seedlings
Ethylene
Exists as a gas.
Caused such things as sprouting, fruit
ripening, leaf abscission, and flowering.
Ethylene
Only recognized as a plant hormone as
late a 1960s.
Ethylene is a gas with a simple chemical
structure…
Very potent and important regulator of
plant growth!
• DURING THE NINETEENTH CENTURY, when coal gas
was used for street illumination, it was observed that
trees in the vicinity of streetlamps defoliated more
extensively than other trees.
• Because coal gas and air pollutants affect plant
growth and development, and ethylene was
identified as the active component of coal gas
• Cousins reported that “emanations” from oranges
stored in a chamber caused the premature ripening
of bananas when these gases were passed through a
chamber containing the fruit.
Functions of Ethylene
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Fruit ripening….bananas for example.
Seed germination.
Petal and leaf abscission.
Wound healing.
Influences cell divisions and growth.
Floral initiation in some plants.
In the grocery store…
What do you think ethylene does?
Functions of Ethylene
Ethylene will speed up maturation of
fruit tissues….plants will naturally
produce ethylene in fruit tissues as they
ripen.
Apples for example release natural
ethylene as they ripen.
Functions of Ethylene
Natural, or endogenous, ethylene
produced by plants will cause:
Abnormal development in etiolated
(grown in the dark…no pigments) seedling.
Speed up fruit and leaf abscission.
Floral initiation in some plant
species…uniform flowering in pineapple.
Speed up fruit maturation/ripening.
Ethylene production is regulated by
internal signals during development
and by various biotic and abiotic
stresses, such as pathogen invasion,
flooding, freezing, and drought.
Isolation of mutants in the plant
Arabidopsis thaliana affecting ethylene
responses has led to the identification
of ethylene receptors and several
downstream components in the
ethylene signal transduction pathway.
The integral membrane protein ETHYLENE INSENSITIVE2 (EIN2), which
is supposed to act between the soluble serine/threonine kinase CTR1 and the
EIN3/EIL family of transcription factors, is a central and most critical
element of this pathway.
http://www.biologie.uni-duesseldorf.de/Institute/Biochemische_Pflanzenphysiologie/Forschung/SFB590
Ethylene and horticulture
Horticulturally, ethylene is applied as a
gas in enclosed chambers to increase
fruit ripening.
Liquid chemicals that transform into
ethylene in plants have been developed
and are used in a broad range of
applications…
Ethylene and horticulture
Ethephon…(2-chloroethyl)phosphonic
acid)
Used for uniform ripening of pineapple
and tomato.
Change in sex expression in cucumbers.
Initiates pistilate flowers in mostly
staminate plants.
Figure 22.17 Inhibition of flower senescence by inhibition of ethylene action
Figure 22.20 Schematic view of the roles of auxin and ethylene during leaf abscission