Plant Pores March to Their Own Beat
Plants have pores called stomata that open and close (see 09/13/2006). These gates of the leaf surface provide plant protection from invaders, and allow the transpiration of gases and water vapor in and out, depending on conditions. The stomata of many plants open wide during the day to allow in carbon dioxide, but close at night to prevent water loss. In some plants, the cycle is reversed.
It had seemed that stomates march together by some kind of signalling system, but a new study shows that they operate independently. EurekAlert reported that scientists found the “logic” of the stomata function. Using lasers, they found a couple of interesting things: (1) the opening is triggered by release of a light-sensitive protein called phototropin-1, and (2) it depends on the amount of light reaching the interior of the cell. Some unknown cell signalling takes place between interior and exterior of the leaf that is only beginning to be understood.
The bottom line is that the independent operation of these leaf “drawbridges” provides the most efficient means of harvesting sunlight. Consider the case of one leaf shading half of another. It wouldn’t make sense for all the stomata to open when only half could use the light. “The stomata autonomy confers an advantage on the plant, which opens the lighted stoma, while maintains the shaded neighbour closed,” the article explains. “This behaviour optimises the balance between water loss and CO2 acquisition.” The researchers found that phototropin-1 sensitivity was just above the threshold in the lighted leaf, but below it in the shaded leaf.
The press release added that this discovery could stimulate further research into “cellular autonomy and cell signalling of many other light-induced processes.”
Anybody smell Darwin in these comments? The fresh air of intelligent design “logic” in the operation of living things brings with it a renewed sense of vitality for research.