• Plant hormones affect plant growth rates and dormancy periods.Juergen Bosse/Photodisc/Getty Images
  
  Hormone chemicals in plants play a vital role in regulating growth and development processes within plant bodies. When secreted, each hormone has certain effects on cell metabolism processes, which ultimately control all areas within the plant life cycle. When secreted in excess or deficient amounts, alterations in normal or natural growth processes can occur.
  
  

Cell Division Effects

• Plant growth and development rely on the different rates of cell division that take place within plant structures. According to the Oregon State University Extension Service, rates of cell division are regulated by the amounts of hormones secreted within different areas of the plant body. Specific hormone chemicals such as auxins and gibberellins affect flower and fruit growth, as well as stem elongation rates. Plant development processes take place as cell division activities give rise to differentiated structures that form plant roots, stems and leaves, according to the Biology Online, a science-based reference site. Developmental processes originate within the DNA coding activities carried out by each cell, which determine the amounts and types of hormones needed for differentiation to occur.
  
  

Seed Germination Effects

• Germination processes involve the growth and development stages that take place inside the embryo, which exists inside the seed part of a plant, according to the Oregon State University Extension Service. These processes occur as certain hormone secretions occur within the seed compartment. Gibberellins and cytokinins are two hormone chemicals that trigger seed germination processes. Both hormones stimulate cell division activities, which result in tissue growth. When applied in synthetic chemical form, gibberellins can also interrupt a seed's natural dormancy period and cause germination processes to begin. Abscisic acid, another synthetic hormone chemical, triggers seed dormancy periods and prevents germination from occurring.
  
  

Ripening Effects

• In the case of fruit-bearing plant varieties, hormone secretions play a significant role in how plant structures respond to external conditions. According to the Oregon State University Extension Service, hormone secretions often originate from one part of the plant and circulate through to other areas of the plant body. In effect, different hormone chemicals target certain types of tissue. Ripening effects occur as hormones trigger physiological processes within the cells that make up the leaf, stem and fruit structures. Hormones involved in the ripening process include ethylene and abscisic acid. Ethylene secretions increase the rate at which fruit matures, while abscisic acid triggers a plant's dormancy period, causing plant cells and tissues to die off.