autonomy v. automaticity; plant automatic breathing (Evolution)

by David Turell , Monday, April 09, 2018, 18:45 (2208 days ago) @ dhw

Plants open and close breathing pores by automatic molecular reactions:

https://www.sciencedaily.com/releases/2018/04/180409103942.htm

"A team of scientists at Nagoya University has discovered new compounds that can control stomatal movements in plants. Some of the compounds have shown to prevent leaves from drying up and suppress withering when sprayed onto rose and oat leaves.

"Stomata consist of a pair of guard cells and open in response to the blue light present in sunlight. Opening of stomata leads to carbon dioxide uptake, explaining why photosynthesis occurs during the day. When plants are under dark conditions and/or drought stress, a plant hormone, abscisic acid (ABA) is biosynthesized and induces stomata closure. Stomata are closed during the night to prevent water loss from the plant.

"When the guard cells in the stomata detect blue light, the photoreceptor, phototropin is activated and induces signaling within the cell. As a result of the signaling, the enzyme, plasma membrane proton pump (PM H+-ATPase) is activated, leading to the uptake of potassium ions. This triggers water uptake and cell swelling that opens the stomata. Although activation of PM H+-ATPase is known to be significant for stomatal opening, the full mechanism of stomatal opening is yet to be clarified.

***

"Using the herb, Benghal dayflower as a model plant, Dr. Shigeo Toh, Mr. Shinpei Inoue, and Dr.?Yosuke Toda, established experimental conditions to screen over 20,000 compounds. They managed to find hit compounds after a year of random screening of the chemical library. This includes 9 compounds that suppress light-induced stomatal opening by more than 50%, and 2 compounds that induce stomatal opening even in the dark.

***

"Further analysis of stomatal closing compounds (SCLs), SCL1 and SCL2, revealed that that they inhibit the signaling components between the phototropin receptor and the PM H+-ATPase enzyme, thus inhibiting light-induced activation of PM H+-ATPase and leading to suppression of stomatal opening."

Comment: A great example of automaticity.