The compounds that keep plants fresh

Controlling plant pore openings could help boost drought tolerance in live plants and extend the freshness of bouquets of cut flowers, thanks to an unusual research approach.

Stomata are small pores in plant surfaces that open during the day and close at night or under drought stress.

A team led by Nagoya University’s Institute of Transformative Bio-Molecules (ITbM) identified compounds that can control the opening and closing of plant pores, called stomata. The findings, published in the journal Plant & Cell Physiology, are expected to help suppress the withering of both live plants and cut flowers.

Stomata are small pores present in the surface of plants, including leaves, flower petals and other organs, and are responsible for gas exchange with the atmosphere. Stomata consist of a pair of guard cells that open in response to sunlight during the day to take up carbon dioxide, and close at night or under drought stress to prevent water loss.

Although many aspects of stomatal movements are understood, the full mechanism of their opening is yet to be clarified. In an effort to understand this process more precisely and how it might be controlled, the team took an unconventional approach. Instead of investigating genetic-based methods, they decided to explore molecules that might affect stomatal opening, taking advantage of ITbM’s massive library of both commercial and synthetic compounds.

“We were keen to use a chemistry-based approach to overcome draw- backs of classical genetic techniques,” says ITbM plant biologist Toshinori Kinoshita, who led the study. “We also thought that using compounds to regulate stomatal movements would be useful for develop- ing agrochemicals.”

Using Benghal dayflower as a model plant, the team established experimental conditions to screen over 20,000 compounds. After a year of randomly screening the chemical library, they found nine compounds that suppressed light-induced stomatal opening by more than 50%, and two compounds that induced stomatal opening even in the dark. The researchers sprayed one of the compounds on rose and oat leaves and found that withering was suppressed for six hours.

“This was the best moment in our re- search: to find that the molecules that we had discovered had an effect on suppress- ing the withering of leaves,” says Kinoshita.

Further analysis of two of the compounds revealed that they interrupt the opening process by inhibiting the signals between a light-responsive receptor and an enzyme called the plasma membrane proton pump.

The compounds could provide a good starting point for developing solutions to boost drought tolerance in live plants, the researchers say. They could also prove useful as a spray to keep cut flowers fresh for longer. The group is looking for partners to further investigate the mechanisms behind stomatal movements and to develop compounds that could be applied to crops or flowers.

Did you know?
A larger variety of leaves could be used in the Japanese traditional flower arrangement, called ikebana, if they lasted longer, since current practice avoids types that easily wither.

For further information, contact:

Professor Toshinori Kinoshita
Institute of Transformative Bio-Molecules (WPI-ITbM)
Nagoya University
E-mail: [email protected]