Plant Hormones (part 3) Hormone | Ethylene

Ethylene

• Universally produced by all plants (Angiosperms, Gymnosperms, Ferns, Mosses, Liverworts)
•  Also found in some fungi, yeast and bacteria
•  Important roles in (Abscission, Germination, Senescence, Stress, response to pathogens)

 Ethylene and Fruit Ripening

•  Helps fruits go through colour change, softening of walls, conversion of starch to sugar.
•  Ethylene is produced in low amounts throughout plant life (some “climacteric” plants have sudden peaks in ethylene synthesis which signals ripening changes).
•  Ethylene gas is sprayed on fruit crops to ripen at same time.

 Ethylene and Stress

•  Some stress situations trigger ethylene production (exposure to heat/cold, physical damage, attack by fungal or bacterial pathogens, flooding that limits oxygen)
•  Similar to Abscissa acid’s stress response

 Growth and Messaging

• Ethylene and growth (Promotes root growth and root hair growth, Can cause asymmetric growth in stems and leaves, Ethylene regulates seedlings’ horizontal growth & apical hook formation =“Triple response” of seedlings grown in dark).
•  Can act as second messenger (Auxin, cytokinin can cause ethylene production in seedlings).

Ethylene: Chemical Structure

• Ethylene is a very small, simple molecule compared to other plant hormones
•  Two carbons sharing a double bond
• Ethylene is a gas at room temperature