Plant Prop. Exam #2

Natural vs. Synthetic Plant Hormones

Phytohormones are natural plant hormones

PGRs are synthetic versions of the natural hormones

Auxins

Primary Functions:

• Advantageous root initiation

Synthetic Versions:

• IBA(natural)

• NAA

• IAA(moves on polar gradient aka from tip to base)(natural)

Other Notes:

• Auxin observations started in 1935 with plants bending toward the light

• Then apical dominance

• Next with the formation of the abscission layer on leaves and fruit

• Then the activation of cambial growth

Cytokinins

Primary Functions:

• Cell division

• Shoot sequences in tissue culture

• Delays or reduces senescence

Synthetic Versions:

• BA

• TDZ

• CPPU

Other Notes:

• Legumes fixed nitrogen in the soil with their nodules where Rhizobium bacteria are which is part of the means of cellular division

• Cytokinins have close relations with bacteria

Auxin/Cytokinin Ratio

High auxin=rooting

High cytokinin=shoots

Equal auxin and cytokinin=callus

Gibberellins

Primary Functions:

• Shoot elongation(through cell division and elongation)

• Controls germination and dormancy

Synthetic Versions:

• GAs

Other Notes:

• Transported in xylem and phloem

• Induces parthenocarpy, especially in grapes

• Applications can overcome genetic dwarfs

Abscisic Acid(ABA)

Primary Functions:

• Plant stress

• Water relations(which is linked with plant stress)

• Embryo development

• Inhibits germination and induces dormancy(which can be in the seeds or buds)

Other Notes:

• The function is dependent on the concentration

• Through stomates it regulates stomata closure and also controls water and ion uptake by roots

• Plays a role in food storage reserves

• Induces abscission and leaf scenesense

Ethylene

Primary Functions:

• Fruit maturity(ripening)

• Stimulates advantageous roots

• Germination(overcomes dormancy)

Synthetic Versions:

• ACC

• ETHEPhoN(liquid form)

Other Notes:

• High concentration=epinasty which is the downward bending of leaves/petioles caused by the top growing faster

• Production is increased when a plant is wounded or stressed

• Stimulates lateral bud formation

• Involved in latex production

What are the five stages in micropropagation?

Stage 0—Donor plant selection

Stage 1—Establishment

Stage 2—Shoot multiplication

Stage 3—Root formation

Stage 4—Acclimatization

When does a culture become stabilized?

When the explants produce a consistent number of “normal” shoots after subculturing

Sterilization vs. Pasturization

Sterilization-has to be heated greater than 212 degrees F which eliminates ALL microorganisms

Pasturization-heated 140-180 degrees F which kills pathogens, weed seeds, pests and their eggs, but leaves the beneficial organisms

Disinfect vs. Sanitize

Disinfect-needs 5-10 minutes of wet contact to kill most bacteria, virus, and fungi

Sanitize-reduces levels of bacteria with a shorter contact time

What is subculturing?

the harvesting of cultures after microshoots have multiplied and reached an appropriate length during stage 2 to be moved to stage 3 or to start new cultures