This document discusses ethylene, a plant hormone that plays an important role in fruit ripening. It describes how ethylene is produced through the methionine pathway and triggers climacteric fruit to ripen. Factors like stage of development, auxins, injuries and temperature can influence ethylene production. The document also categorizes fruits based on their ethylene production rates and discusses how ethylene can be removed or its action inhibited during storage to extend shelf life.

1. PRESENTED BY
V.DHANALAKSHMI

2. Introduction
• Ethylene is a natural plant hormone released by all
plant tissues and microorganisms.
• It is also called ‘Ripening hormone’, as it plays an
important role in ripening process.
• Low concentration of 0.1-1.0 microlitres is sufficient
to trigger the ripening process in climacteric fruits.

3. • It has autocatalytic activity because of which such
small quantities can trigger further release of large
quantities of ethylene by the fruit tissue.
• Very little response is only seen to exogenous
application of ethylene in case of non-climacteric
fruits.

4. Effect ethylene on fruit ripening
• Ethylene decides the post harvest life of fruits, vegetables
and cut flowers.
• Synthesis of ethylene varies with maturity of fruits,
vegetables and flowers.
• Synthesis of ethylene is less in young buds while it is
more in opened and senescing fruits, vegetables and
flowers.
• Endogenous ethylene production takes place in the style
which triggers wilting and senescence of flowers.
• The most accepted pathway for synthesis of ethylene is
methionine pathway.

5. Biosynthesis of ethylene
Inhibitors Enzymes
Methionine
Adomet synthase
SAM (S Adenosyl Methionine)
AOA, AVG
ACC synthase
ACC (1 - Amino Cyclo propane 1 - Carboxylic acid)
Cobalt, Temp > 35 o C, CO2
ACC oxidase
Ethylene

6. • AOA - Aminooxyacetic acid
• AVG - Amino ethoxy vinayl glycine
• ACS - ACC Synthase
• ACO - ACC oxidase (Ethylene forming enzyme, EFE)

7. Factors governing the activity of ACC synthase
Stage of senescence
• Production of ethylene is less in young flowers. Production of
ethylene increases during flower maturation, opening and
senescence of flowers.
Auxin level
• During pollination, auxin is transferred from pollen to stigma.
Auxin induces the production of ethylene. This auxin induced
ethylene increases the synthesis of ethylene
Physical injury
• Physical injury induces the synthesis of ethylene
Chilling injury
• Chilling injury induces the synthesis of ethylene

8. Action of ethylene
• C2H4 + Receptor (Copper) C2H4 -
Receptor complex Accelerate senescence
• Ag ++ replaces the copper which delays the
senescence

9. Classification of horticultural commodities
based on ethylene production rate
Class Range at 20o
C
(μ C2H4 kg /
hr)
Commodities
Very low < 0.1 Artichoke, Asparagus, Cauliflower, Cherry, Citrus fruits, Grape, Cut
Flowers, Leafy Vegetables, Pomegranate, Potato, Root Vegetables,
Strawberry
Low 0.1-1.0 Brinjal, Chilli, Cucumber, Green Capsicum, Okra, Pine apple,
Pumpkin, Water melon
Moderate 1.0 -10 Banana, Guava, Fig, Litchi, Melon, Mango, Tomato
High 10-100 Apple, Apricot, Avocado, Kiwi Fruit (ripe), Papaya, Peach, Plum,
Pear
Very high > 100 Sapota, Passion Fruit

10. Sources of ethylene
• Ethylene gas – Pure C2H4 gas enclosed in the can/cylinder is
sprayed /injected into chamber. Ethylene portable can which
contain 3 g sufficient to ripe 2-6 ton of produce is available
commercially
• Ethephon – Used as spray/ dip, acidic in water releases C2H4
• Ethylene mixture - C2H4 + inert gas like CO2. Inert gas because
not enough O2 remains in the chambers to provide an
explosive mixture. Eg, Ripegas contain 6% C2H4
• Ethylene generators - Widely used method where in liquid
spirit produces C2H4 when heated in the presence of catalyst
platinised asbestos.
• Use of ripe fruits – Cheap and simple, where in ripe fruit with
high C2H4 producers such as apple, banana, mango, sapota
and tomato is used at home to ripe / degreen

11. Removal of ethylene
• Eliminate the ethylene sources
• Provide proper ventilation
• KMnO4 oxidizes the ethylene
KMnO4
C2H4 CO2 + H2O
• Brominated or activated charcoal absorbs ethylene

12. Ethylene inhibitors
• Silver chloride (AgCl2)
• Silver nitrate (AgNO3)
• Silver Thio Sulphate (STS)
• Methyl Cyclo Propane (1- MCP)

13. Regulation of ethylene in storage
Hypobaric storage
• In hypobaric storage, action of ethylene is low due to
the easy movement of silver ions at low pressure.
Controlled atmosphere storage
• The rate of ethylene synthesis is low at high CO2 and
low O2.