Scientists have studied ethylene's role in plant physiology for more than a century and the produce industry has long used the gas to manipulate ripening.
Ethylene is an important plant hormone. In bananas and many other fruits, production of ethylene surges when the fruit is ready to ripen. This surge triggers the transformation of a hard, green, dull fruit into a tender, gaudy, sweet thing that's ready-to-eat.
But how fruits regulate production of the hormone has been a mystery. Now scientists have found a master switch that leads the plant to crank up ethylene production when the time comes.
Flipping the master switch "is like breaking the glass on a fire alarm," says study co-author James Giovannoni, a plant molecular biologist at the U.S. Department of Agriculture and Cornell University. "Once you pull that lever, things really start happening."
The switch is critical because ripening too early can have dire consequences for the plant — it might miss its chance to procreate. Making fleshy, delicious fruits is a strategy: the end game is getting an animal to eat the fruit and disperse the seeds within.
When the ripening switch is triggered, genes are activated. This ultimately makes the fruit ready-to-eat: the plant dials up sugar production in the fruit and starts making sweet-smelling compounds to tempt an animal's nose and pigments that catch an animal's eye.
In some fruits, flipping the ripening switch also leads to activation of machinery for making ethylene. Ripening fruit doesn't happen in a moment, it happens over time. Once the fruit starts synthesizing ethylene, the hormone keeps everything that needs to be turned on, turned on, sustaining the ripening process.
Controlling when and where ethylene is turned on is a delicate balancing act for the plant. Ethylene isn't only involved with ripening, it is also a stress hormone. When a plant part, like a leaf, is attacked or damaged, ethylene kicks off the process of decay, causing damaged parts to wither and amputate.
It make intuitive sense that ethylene is involved in both ripening and decay, says Harry Klee, an expert in the genetics and biochemistry of fruit at the University of Florida in Gainesville, who was not involved with the study.
"Fruit ripening is the start of decay," says Klee. "We happen to pick it and eat it at one stage, but it is on its way to being a bag of mush."
Source: npr.org
