1. Plant Hormones - Ethylene
Found in
Tissues of ripening fruit
Nodes of stems
Aging leaves and flowers
Major functions
Changes of ovary to become fruit
Degradation of cell walls; softening
Dropping from plant
Leaf abscission
Loss of leaves to prevent water loss
Tissue at base of petiole dies
Senescence (aging)
Autumn leaves; withering flowers

2. ETHYLENE
Ethylene is a gas that acts as a plant hormone. It is neither truly lipid nor peptide based. The formula is C2H4 making it a hydrocarbon which is lipid soluble. It is produced from the breakdown of methionine present in all plant cells and as such all plant tissues produce it.
Ethylene can cross the cell membrane, but is picked up by a receptor protein creating a signal transduction pathway.

3. Activates transcription of numerous enzymes
Ethylene Signal Transduction
Activates transcription of numerous enzymes

4. TWO-COMPONENT SIGNALING SYSTEM: Receptors in the membrane.
CTR1
Phototropism: response to light, achieved by action of auxin.
Auxin produced in apical meristem moves downward by active transport to zone of elongation and gnerates growth.
When all sides equally stimulated by light, growth is straight.
When stem is unequally stimulated by light, auxin moves to shady region for elongation. = differential growth.
TWO-COMPONENT SIGNALING SYSTEM:
Receptors in the membrane.
Receptors in the ER membrane

5. ETHYLENE:
Frequently used commercially to allow “green” fruit to be shipped and ripened at the vendor or in route.
As fruit ripen, ethylene is released causing production and release of ethylene in other fruit close by. Domino Effect!
Silver and Cobalt ions are found in soil, water, and fertilizers
As fruit respires in the ripening process, CO2 is released and can compete for ethylene receptors.