• Auxin plays a role in cell division and cell elongation in plants.Jupiterimages/Comstock/Getty Images
  
  The term "auxin" originates from the Greek "auxein," which means to increase or to grow -- a description of its function in plants. Experiments with plant movement in the late 19th century led to the identification of the plant hormone, auxin. Auxin plays a vital role in plant growth and development. In plant physiology research, the pea plant is often used as a model system to understand how plant hormones, such as auxin, influence growth.
  
  

Tropism

• Plants bend in response to light, gravity and even touch. These plant movements are known as tropisms and involve the hormone auxin. When plants receive light from one direction, the stem will curve toward the light. This is called phototropism and occurs when auxin accumulates on the shaded side of the plant and stimulates cell elongation, causing the plant to curve. Auxin is also involved in thigmotropism, growth in response to touch. Pea plants display this type of tropism when tendrils curl around a trellis.
  
  

Apical Dominance

• Apical dominance is the repression of lateral bud growth by the apical meristem or terminal bud. It is thought that a high amount of auxin produced in the tip stimulates growth of the apical meristem but inhibits growth of lateral buds. Removal of the tip releases apical dominance, which allows lateral buds to grow. Apical dominance occurs in pea plants as well as many other plants. Gardeners prune the tips from some plants, releasing apical dominance, to induce more branching for a bushier plant.
  
  

Abscission

• Auxin is involved in the abscission of fruit and leaves. The concentration of auxin is high in young leaves which keep the process of abscission at bay. As leaves mature, auxin levels decrease and the process of abscission begins. Applying auxin to a plant yields different outcomes depending on its stage of development. An application of auxin to a plant early in the growing season will delay abscission, whereas an application when leaves are more mature will speed leaf drop.
  
  

Root Initiation

• Auxin stimulates root initiation on leaf cuttings.plant seedlings image by Shannon Workman from Fotolia.com
  
  Auxin plays an important role in the initiation of lateral and adventitious roots. Leaf and stem cuttings, when placed in a moist medium at ideal growing temperatures, will produce roots from the cut end. This is due in part to an increase of auxin near the wound which stimulates root growth. When additional auxin is applied as a powder to the cut end, root growth is further stimulated. This propagation technique is effective on pea cuttings and many other plants from your garden.