Manitoba-North Dakota Zero Tillage Farmers Association February 9 Workshop Bismarck, ND

Plant Physiology

Plant Growth Regulators

Dr. Edward Deckard, Dept. of Plant Sciences, NDSU

Plant Hormones

• Made within the plant in small quantities

• Produce changes in growth

Plant Growth Regulators

• Manufactured chemicals that are like plant hormones

• Chemically similar to plant hormones

• Produce changes in growth

Plant Hormones

v      Limited Number

v Cause multiple effects     

§ in different plant

§ in same plant at different times

§ in same plant at different tissue

v Two or more hormones often found   together and        often act in concert

v Movement from sites of production may not       occur

Plant Growth Regulator Types Include

• Auxins – generally growth promoter

• Gibberellins - generally growth promoter

• Cytokinins – generally growth promoter

• Ethylene – often associated with ripening

• Abscisic acid – generally acts as a inhibitor

• Brassinosteroids – generally acts in concert with others

• Oligosaccharins – associated with pathogen defense

Cracking

Ethylene:  Promotes early seedling growth (arch)

Auxin:   Promotes straightening of the arch.

Apical Meristem

Cell division: auxin, cytokinin, gibberrellin

Cell elongation: auxin, gibberellin

Leaf

Growth:  gibberellin
Senescence:  ethylene inhibit senescence: cytokinin

Stem

Elongation: auxin, gibberellin

Lateral Bud

Inhibit growth:  auxin
Promote growth: cytokinin

Fruit

Growth :auxin, cytokinins

Ripening: ethylene

Root

Initiation:  auxin promoted, gibberellin inhibitors

Growth:  auxin inhibitors

Flower

Initiation:  unknown

Differentiation:  auxin, gibberellin

Commercial Uses of Growth Regulators

Is “bigger” better?

such as gibberellins can increase flower, leaf, and fruit in the right context. 

Balancing root and shoot. 

Balancing Source and Sink

What is limiting economic yield?

Conclusions

• Plant hormones play an important role in growth and development

• Most growth regulators mimic plant hormones

• Many commercial uses of plant growth regulators

• Most of these current uses are for more simple regulated characteristics

– Plant height, senescence,…

• Crop growth and development are complex characteristics-influenced by genetics, environment, management practices, and their interactions.

Take Home Message:

Experiment - Start Small!