3

votes

How do flavorless chemical defenses in plants ward off predators?

Answered on August 19, 2014
Created November 14, 2011 at 3:52 PM

Cruciferous vegetables are somewhat bitter, Capsicum plants have a hot taste... most of these defense mechanisms might seem effective to keep predators away.

But what about plants that don't have "funny" flavors? How are the defenses (read: toxins) on those plants supposed to work to keep plant-eating animals away?

Medium avatar

(5639)

on November 15, 2011
at 12:58 AM

You're right...birds can't taste capsaicin.

Medium avatar

(19479)

on November 14, 2011
at 09:48 PM

Grains and seeds employ physical as well as chemical barriers (shells, fibrous coatings, saponins, etc.) to resist being digested by predators.

77ecc37f89dbe8f783179323916bd8e6

(5002)

on November 14, 2011
at 06:49 PM

Yeah, that's sounds right. Also, plants would 'want' animals who spread their seeds to eat their fruit, but only when they are ready to spread seed, otherwise they'll get killed or fail to reproduce. So there should be an evolutionary battle with plants and animals manipulating their respective flavors, toxins, and perceived flavors.

F571bcba0e6196c3e53f599924eecab6

on November 14, 2011
at 05:02 PM

Totally - but I was wondering if those "delayed effects" were as efficient as something that puts you off your lunch on the first bite (ie: bitter, hot, etc.).

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4 Answers

1
Medium avatar

on November 14, 2011
at 04:57 PM

They get sick...IBS, headaches, autoimmune diseases. Very passive-aggressive. That's why I HATE grains. I can't stand passive-aggressive behavior.

It's like they're leaving a note after the damage is done... "Oh, BTW...It was me that caused your allergies. Can you not eat us anymore? Thanks."

F571bcba0e6196c3e53f599924eecab6

on November 14, 2011
at 05:02 PM

Totally - but I was wondering if those "delayed effects" were as efficient as something that puts you off your lunch on the first bite (ie: bitter, hot, etc.).

Medium avatar

(19479)

on November 14, 2011
at 09:48 PM

Grains and seeds employ physical as well as chemical barriers (shells, fibrous coatings, saponins, etc.) to resist being digested by predators.

0
96bf58d8c6bd492dc5b8ae46203fe247

(37227)

on November 14, 2011
at 06:43 PM

How do we know they don't taste funny to other animals? Other species may have learned to recognize and avoid those plants. Or, they may work more slowly and limit the maximum population of foraging species in the area. Also, if ruminants only moved through once in a while they may not have done that much damage as they also provided fertilizer and the plants were better off not creating harsh defenses.

77ecc37f89dbe8f783179323916bd8e6

(5002)

on November 14, 2011
at 06:49 PM

Yeah, that's sounds right. Also, plants would 'want' animals who spread their seeds to eat their fruit, but only when they are ready to spread seed, otherwise they'll get killed or fail to reproduce. So there should be an evolutionary battle with plants and animals manipulating their respective flavors, toxins, and perceived flavors.

Medium avatar

(5639)

on November 15, 2011
at 12:58 AM

You're right...birds can't taste capsaicin.

0
77ecc37f89dbe8f783179323916bd8e6

(5002)

on November 14, 2011
at 05:45 PM

From an evolutionary perspective, if the contents of plants function as a fitness disadvantage, then animals who eat them will get selected out. There are countless mechanisms that could fulfill this adaptive role for the plant. Aversive tastes are the most obvious traits, but note how tasting maladaptive contents as sour could also evolve as a defensive phenotype of plant-eating organisms. Making the eater sick is another obvious one. Degrees of sickness vary, though, so these mechanisms could act in subtle ways.

I'm not an expert in evolution, but I love reading and thinking about it, and it comes in handy for questions like these. (Sorry for awkwardness, on my iPhone)

0
673f7ad6052448d51496f177395416b7

on November 14, 2011
at 04:55 PM

hmm, good question. I presume defenses can often be somewhat targeted (i.e. toxins are "funny" or "tasteless" to us might be more unsavory to a more threatening predator.) It is also possible that our taste receptors have evolved through overexposure or that we've genetically altered plants towards our flavor preferences. And isn't it the case with poisonous berries that when a tasteless toxin makes us sick enough we will just learn not to eat it again? Maybe lectins and toxins in nuts made us a lot sicker in the past but we've adapted through overexposure. And I'm guessing that nature doesn't want natural defenses to be too hardy, otherwise there's the problem of plant overpopulation.

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