Natures wonders: new found plant defenses (Introduction)

by David Turell @, Friday, September 14, 2018, 05:56 (743 days ago) @ Balance_Maintained

Electrical impulses and glutamate use demonstrated:

"'We do know that if you wound a leaf, you get an electrical charge, and you get a propagation that moves across the plant," Gilroy adds. What triggered that electric charge, and how it moved throughout the plant, were unknown.

"But calcium was one candidate. Ubiquitous in cells, calcium often acts as a signal about a changing environment. And because calcium carries a charge, it can also produce an electrical signal. But calcium is ephemeral, spiking and dipping in concentration quickly. The researchers needed a way to see the calcium in real time.

"So Toyota developed plants that showed calcium in a whole new light. The plants produce a protein that only fluoresces around calcium, letting the researchers track its presence and concentration. Then came caterpillar bites, scissor cuts and crushing wounds.

"In response to each kind of damage, videos show the plants lighting up as calcium flows from the site of damage to other leaves. The signal moved quickly, about one millimeter per second. That's just a fraction of the speed of animal nerve impulses, but it's lightning fast in the plant world—quick enough to spread out to other leaves in just a couple minutes. It took just a few more minutes for defense-related hormone levels to spike in distant leaves. These defense hormones help prepare the plant for future threats by, for example, increasing the levels of noxious chemicals to ward off predators.

"Previous research by Swiss scientist Ted Farmer has demonstrated that defense-related electrical signals depended on receptors for glutamate, an amino acid that is a major neurotransmitter in animals and also common in plants. Farmer showed that mutant plants missing glutamate receptors also lost their electrical responses to threats. So Toyota and Gilroy looked at the flow of calcium during wounding in these mutant plants.

"'Lo and behold, the mutants that knock out the electrical signaling completely knock out the calcium signaling as well," says Gilroy.

"Where normal plants blaze brightly with fluorescent calcium waves during wounding, videos show the mutant plants barely sputtering marginal flashes of light. These results suggest that glutamate spilling out from wound sites triggers the burst in calcium that spreads across the plant.

"The study connects decades of research that has revealed how plants, often seen as inert, dynamically respond to threats by preparing distant tissues to deal with future attacks. Glutamate leads to calcium leads to defense hormones and altered growth and biochemistry, all without a nervous system."

Comment: Plants must have this kind of defense or they would not have survived. Must have been designed, because it could not have developed by chance mutations.

Tony: The interesting thing is that this could be looked at two ways. One way is using the 'competitive ecology model' that views this as a defense mechanism. The other way is to see this as a negative feedback loop to segregate vegetative food sources. The plant gets wounded, sends out a signal that raises toxicity, herbivores sensitive to the toxin would get deterred, probably through getting ill, while those that were immune to it munched their way through their food supply. In short, it may be a food/animal matching mechanism. Dollars to doughnuts, animal noses are keyed negatively to those particular toxins that they are not immune to or positively towards those they are immune to. Like the different UV signalling of nectar and pollen bearing plants.

What is also fascinating is that glutamate is active in our brains.

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