Natures wonders: new found plant defenses (Introduction)

by David Turell , Thursday, September 17, 2020, 19:12 (1309 days ago) @ David Turell

Another review:

http://nautil.us/issue/90/something-green/when-plants-go-to-war-rp?mc_cid=0b8d3e5c0f&am...

"The voracious appetites of pests put plants under constant stress: They have to fight just to stay alive.

"And fight they do. Far from being passive victims, plants have evolved potent defenses: chemical compounds that serve as toxins, signal an escalating attack, and solicit help from unlikely allies.

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"Rather than pump out chemical defenses 24-7 (a waste of resources), plants hold off production until an attack is underway. As soon as an insect bites a leaf, the leaf sounds the alarm by emitting volatiles—chemical flares that tell other parts of the plant, as well as its neighbors, to start manning the barricades.

"This early warning system works via a cascade of molecular events. First, it triggers the release of “jasmonate” hormones, which in turn break down proteins known as JAZ. These proteins silence genes that direct the manufacture of various toxic and protective chemicals. By eliminating JAZ, jasmonate hormones free these genes to express themselves, thus powering up a plant’s weapons assembly line.

"Plants also make use of underground networks to warn each other of impending danger. Many species have a symbiotic relationship with a soil-borne fungus, which penetrates the outer layers of a plant’s roots, feeding off its carbon stores and helping it take up vital nutrients such as nitrogen and phosphorus in return. The fungus grows by sending out long, threadlike branches called hyphae, which colonize nearby plants, forming vast underground webs.

"In experiments with bean plants, when researchers placed aphids on a plant encased in a polythene bag (so it couldn’t broadcast warnings by air), other plants hooked up to the subterranean fungal web began churning out defensive compounds. Their unconnected neighbors, however, did not. The fungus appears to work like a biological Internet, carrying vital intelligence from plant to plant.

"Plants also conserve resources by recruiting allies to fight some of their battles for them. Among a plant’s armaments are volatiles that beckon predators of its insect attackers.

"When caterpillars graze European maize, for example, the plants emit the volatile β-caryophyllene, which attracts parasitic wasps. The wasps lay their eggs inside the caterpillars, slowing their feeding and eventually, when the eggs hatch a few weeks later, killing them. European maize also releases β-caryophyllene below ground in response to rootworm attacks. This signal drifts through pores in the soil, calling to predatory roundworms: “Dinner’s ready, come and get it!”

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"Plants in the Brassicaceae family (including broccoli, cabbage, and mustard) store seemingly harmless compounds known as glucosinolates in cellular compartments next to stores of enzymes called myrosinase. The two reserves are separated only by a thin cell wall. When an unsuspecting herbivore chews through this wall, the myrosinase enzymes mix with the glucosinolates, catalyzing chemical reactions that engulf the attacker in a toxic cloud.

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"Aphids, for example, release the pheromone β-farnesene when a predator attacks. This warning tells other aphids in the area that they’ve been rumbled and it’s time to skedaddle. Plants often emit β-farnesene during an aphid attack, perhaps in an attempt to scare off their aggressors by aping their distress call. But not just any β-farnesene signal will do.

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"During a hard-fought battle, a plant must tend to its injuries. A range of compounds known as green leaf volatiles act as antiseptics, protecting damaged tissue against bacterial or fungal infection. (These volatiles, which make up the fragrance of freshly cut grass, send another warning to neighboring plants, reminding them that danger is at hand.)

"An injured plant also produces traumatic acid, known as the “wound hormone,” which stimulates cell division to close up a laceration in much the same way that blood clots in an animal’s wound. These responses happen within minutes of attack: Plants begin patching themselves up while still fighting off invaders".

Comment: An amazing list of plant defenses, by God's design. How would chance mutations solve these problems? Would plants survive the time it took to find answers?