Transgenic Ornamental Crops - Transgenic Horticultural Crops: Challenges and Opportunities - page 66

high.levels.of.linalool,.which.was.a.repellant.to.aphids. 62 .By.targeting.FaNES1.to.the.
mitochondria. instead. of. the. cytosol,. synthesis. of. 4,8-dimethyl-1,3(E),7-nonatriene.
(( E) -DMNT). and. nerolidol. was. induced. making. transgenic. plants. more. attractive.
to. predatory. mites. 63 . Both. of. these. studies. with. FaNES1. report. a. growth. retarda-
tion.phenotype.that.could.be.a.phytotoxic.effect.of.the.new.volatiles.being.produced.
or.the.new.pathway.causing.a.metabolic.drain.on.metabolites.essential.for.normal.
growth.and.development..In.the.case.of.the.latter,.ine.tuning.expression.through.use.
of.promoters.conferring.lower.or.more.speciic.transgene.expression.may.be.useful.
for. balancing. metabolite. low. between. the. newly. introduced. pathway. and. endog-
enous.pathways.
FLOWER AND LEAF LONGEVITY
Retention.of.high.quality.lowers.and.leaves.for.visual.appearance.is.of.utmost.impor-
tance.to.the.ornamental.plant.industry..Flowers.that.are.short-lived.or.highly.sensi-
tive.to.postharvest.handling.conditions.are.limited.in.their.marketability..Similarly,.
leaf.yellowing.or.senescence.negatively.affects.the.consumer.appeal.of.potted.plants.
and. bedding. plants.. Plant. and. cut. lower. quality. has. been. improved. through. the.
use.of.proper.postharvest.handling.procedures.and.chemical.preservatives..Applying.
transgenic.technology.to.ornamentals.to.improve.their.postharvest.attributes.presents.
the.opportunity.for.saving.on.postharvest.costs.associated.with.labor,.chemical,.and.
environmental.control,.contributing.to.environmentally.sustainable.practices..With.
such.great.importance,.there.are.now.many.examples.where.genetic.engineering.has.
been.successfully.employed.to.obtain.lowers.with.longer.vase.life.and.plants.with.
leaves.that.stay.green.
f loral l onGevIty
The. plant. hormone. ethylene. negatively. affects. lower. longevity. in. many. orna-
mentally. important. plant. species. 64,65 . This. gaseous. phytohormone. is. produced. in.
response.to.pollination,.stress,.and.common.postharvest.handling.procedures.caus-
ing. petal. in-rolling,. abscission,. and. senescence. in. many. species. of. monocots. and.
dicots,.ultimately.eliminating.their.marketability..Van.Doorn.et.al. 66 .surveyed.over.
300.species.of.lowering.plants.from.50.different.families.and.found.that.over.64%.
of.these.were.highly.ethylene.sensitive..To.address.this.issue,.the.molecular.genetics.
and.biochemistry.of.ethylene.synthesis.and.perception.has.been.the.focus.of.much.
research. and. chemical. and. genetic. methods. for. altering. ethylene. responses. have.
been.developed.(Table.3.3).
Flower.longevity.can.be.extended.through.the.use.of.chemicals.that.inhibit.ethyl-
ene.biosynthesis.and.perception..Chemicals.such.as.aminoethoxyacetic.acid.(AOA).
and. aminoethoxyvinylglycine. (AVG). signiicantly. reduce. ethylene. production. and.
delay. petal. senescence. and. abscission. of. many. species. 67-70 . However,. the. concern.
of. potential. toxic. effects. and. lack. of. control. of. effects. due. to. ethylene. generated.
from. outside. sources. halted. their. commercial. use. 67 . Therefore,. inhibiting.ethylene.
perception.is.more.desirable.for.preventing.effects.of.exogenous.ethylene.that.may.
occur. during. storage. and. transportation.. Silver. thiosulfate,. Ag 2 S 2 O 3 . or. STS,. has.