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The Role of Ethylene inPost Harvest BiologyName : T.W.G.F.A NijamdeenReg.No: 612260302

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What is Ethylene?• Ethylene is a colour less gas with a faint sweetish smell that is the naturallyproduced ripening hormone of some fruit. It is also produced as an exhaustgas from petrol combustion engines• The important role of ethylene as a plant growth regulator has only beenestablished over the last 50 years but its effects have been known forcenturies.• The remarkable effects of ethylene on plants were first noted whenFlammable gas used for lighting and heating was piped through the streetsof Europe.(Raid 1992)

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Ethylene-Structure and BiosynthesisStructure of the ethylene molecule

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Ethylene as a growth regulator in plants and fruits• Ethylene is a hormone which is biologically active at very lowconcentration measured in the ppm and ppb range. Most plantssynthesize small amounts of ethylenethat appear to coordinate growthand development.• In vegetative tissue and in non-climacteric and immature climactericfruit tissue ethylene suppresses its own synthesis and in ripeningclimacteric fruit ethylene enhances its own synthesis.• Plants respond to ethylene in a number of ways.Effect of ethylene in plant leaves

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Ethylene stimulates:• Synthesis of ethylenein ripening climacteric fruit• Ripening of climacteric fruit and some non-climacteric fruit.• Anthocyanin synthesis in ripening fruit.• Chlorophyll destruction and yellowing (eg., degreening of citrus).• Seed germination.• Adventitious root formation.• Respiration• Flower initiation eg., pineapple.• Abscission and senescence.Fruit ripening and anthocyaninsynthesis in rambutan

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Ethylene inhibits:• Ethylene synthesis in vegetative tissue and non-climacteric fruit.• Flowering and flower development in most plants.• Auxin transport.• Shoot and root elongation, ie., growth.Stunted growth due to ethylene

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The effects of ethylene in Post harvest freshproduce• Ethylene gas is produced in most plant tissues and is known to be an important factorin starting off the ripening of fruits.• This promote beneficial effects as well as detrimental effects in fresh produce.• controlled ripening, fruit thinning (apples, cherries), fruit loosening prior to harvest(nuts) can give advantages commercially• While promoting senescence, bitterness (carrot)wilt(cut flower)sprouting(potato)cangive much disadvantages.control ripening Fruit thinning wilting of cut flowers

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• Ethylene produce by wounding or stressing may also trigger ripening in thedamaged fruit as well as the undamaged fruits around it.• controlled ripening is the major postharvest use of ethylene and it can alsobe applied pre-harvest to promote postharvest benefits. The chemicalEthephon produces ethylene and is applied in the field.• In post harvest technology the fresh fruits vegetables and horticulturalproduces play a significant role and as well as ethylene.• Ethylene can promote much benefits if they are controlled and applied in aproper way. while it create major losses in post harvest fresh produce if notcontrolled.Proper post storage of freshproducePost harvest loss

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The effects of ethylene in fruits and vegetablesThere are two classes of fresh produce in terms of ethylene production1. Climacteric fruitsRefers to fruits that can be harvested when mature but before ripening hasbegun.These fruits produce a burst of ethylene as they ripe. and the internalethylene concentration of climacteric fruit varies widely when they getripen.2. Non-Climacteric fruitsRefers to those fruits which ripen only while still attached to the parentplant.These fruits do not increase ethylene production when they ripe. And theinternal ethylene concentration change little during development andripening.

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Climacteric fruits Non-Climacteric fruits• Eg:Banana,Apple,Avocado,Tomato,Mango,Apricot,pears• Eg:Strawberry,Cucumber,Eggplant,Grape,Orange.

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Beneficial effects• Trigger ripening• Promotes colour development in fruits• Stimulates ripening in climacteric fruits• Degreening( citrus)• Stimulates dehiscent(nuts)• Alters sex expressions(Cucurbitacea)• Flower induction(pine apple)• Reduces lodging of cerealsTrigger ripeningFlower induction in pineapple

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Detrimental effects• Accelerate senescence• Enhances excessive softening offruits• Stimulates chlorophyll loss• Stimulate sprouting(potato)• Promotesdiscolouration(browning}• Promotes abscission• Stimulate respiration

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Effects of ethylene in ornamentals• many ornamental crops are sensitive to ethylene. Response of ornamental toethylene can be classed into growth, abscission and senescence responses.• Individual species vary widely in their relative sensitivity to ethylene and ingeneral cut flowers and flowering pots plants tend to be more ethylenesensitive than foliage lines.• Some common flowers that are ethylene sensitive includecarnations, delphiniums, freesia, gypsophila and Gerald ton wax.ornamentals

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Beneficial effect• stimulate lateral branchingin potted plants (azaleasand geraniums).• Flower opening.Detrimental effects• Bud and leaf abscission ( fallingoff)• Leaf yellowing, transparency• Loss of deep colour• Flower or petal drop• Irregular bud opening ("sleepycarnations" )• Premature deathEffects of ethylene on pot plants

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The role of ethylene in the post harvestshelf life (One bad apple spoils the whole bushel)• The presence of ethylene is not always beneficial, especially in termsof postharvest shelf life (Optimal Fresh,2000).It seems that because itis a colour less gas that is not often measured in commercialsituations its presence is over looked.• The effect of ethylene is accumulative so continuous exposure to alow concentration of ethylene throughout marketing can causesignificant harm (Wills et al., 2000)• The major reason for the loss of shelf life is that ethylene exposureincreases the rate the product ages.• However, the loss of shelf life will be most frustrating for the finalconsumer as the loss of quality will not be obvious during marketingand retail sale.

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Controlling ethylene In post harvesttechnology• While ethylene is invaluable due to its ability to initiate the ripening processin several fruits, it can also be very harmful to manyfruits, vegetables, flowers, and plants by accelerating the aging process anddegreasing the product life.• The degree of damage depends upon the concentration of ethylene, length ofexposure time, and product temperature.• Preventing ethylene buildup around the product is often the simplestmethod of reducing the damaging effects of ethylene.

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Methods of reducing ethylene concentration• Avoidance of ethylene accumulation- Ethylene sensitive products must be handled carefully.- Good house keeping.- Storing ripe and unripe produce in separate room.- Regularly removal of rotted or damage product.- keeping natural gas pipes, cylinders ect.away from storage rooms.- Lowering the temperature to the possible minimum level.• Ethylene scavengersVentilated store houseEthylene absorbents in sachets

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• Oxidation with potassium permanganate- Affective in reducing ethylene levels.• Oxidation with ozone- Ozone is much suitable since it is gaseous, it readily mixes with ethylene.• Other oxidants- Activated charcoal that has been brominated will effectively oxidize ethylene.- But carries a potential health hazard.- Tetrazine is also an oxidant which react more efficiently with ethylene.• Removing ethylene with ethylene absorbing filters.• Genetically modified cultivars

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• Other chemicals-Chemicals which are toxic to humans can be used as anti ethylene treatmentwith ornamentals.-Most notable cut stems of ornamentals materials can be pulsed with silver ionsupplied as STS-Whole plants or plant parts can be dipped with STS.• Other gases-Adding 5% carbon mono oxide to container or pellet loadsControl test of STS treatment incut flower

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Methods of increasing ethylene concentration• Use of ethylene sensitive cultivars.• Keep an active level of ethylene in the air.• Maintain an optimum temperature.• Sore under adequate of O2 and CO2.• Allow sufficient time for plant response.

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• Ethylene is a very important plant hormone and it plays a significantrole in the postharvest life of fresh produce. Sometimes being positiveand sometimes not. The damage resulting from ethylene exposurecould easily be minimized if there was a greater awareness of thepotential harm and the simple measures that can be used to preventdamage.

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