Why do capsicum (red, gree, and yellow peppers), corn and sesame seeds never seem to digest?
Welcome, Johnny.
Seeds were generally evolved to be indigestible. The point was that animals would swallow the fruit and “deposit” the seeds in the midst of some “fertilizer”. The seed would then sprout into a new plant.
Some seeds aren’t so safe, however. The reason that peppers are spicy is to prevent mammals from eating them, since mammilian digestive systems are too harsh for the seeds. Birds, who can’t feel the capcaisin, are their main “distributors.”
Those seeds have a thick coat of cellulose, basically paper . Humans can’t digets cellulose so as long as that coat remains intact we can’t digets the seeds.
You should note though that corn seeds usually are cracked by chewing, so corn is digested which is why we can use it as a food. A few seeds may remain unchewed and pass through intact but most are digested.
Nope. Pepper seeds, like the seeds of all other members of the Solanaceae, will pass right through the mammalina digetsive tract unharmed if they aren’t chewed.
The reason peppers evolved their taste is to stop mammals from chewing the fruit thoroughly. By encouraging mammals to gulp and not chew the plant ensures a greater proportion of its seeds survive. Many acacias have evolved the same trick of having seed pods that discourage chewing.
Tomatoes and other members of the pepper family usually get around the chewing problem by making the seeds slippery, so that they squeeze out between the teeth rather than cracking, a trait also seen in many melons, which are unrelated.
Different solutions for the same problem. It’s not that mammalian digestive tracts are harsh that is the problem, it’s the fact that mammals chew. Once a seed is cracked it won’t survive digetsion in either a bird or a mammal.
That’s really neat. Thanks for sharing.
It would seem to me that birds would be tougher on seeds than most mammals. Birds “chew” by having a crop which is just a muscular sac full of sand. The muscle continually works the sand and grinds the food. Such a system should crack the protective coat on most seeds.
Not sure how that works. Certainly you’d think that birds like pigeons or game birds would give seeds a tough time, and there are plenty of them that eat fruit. Nonetheless many plants do rely on birds for seed dispersal, so obviously most seeds survive the trip.
OTOH other birds don’t have much in the way of a muscular crop and don’t swallow rocks. These birds also tend to be the fruit eaters. So it may just be that the birds fruits co-evolved.
Also remember flying birds have real weight problems so it may not be advantageous to leave seeds in the crop to digest if you have a supply of fleshy fruit to hand. I know that corvids will regurgitate the seeds of palms and Japanese pepper once the crop has extracted the thin layer of flesh from them. Palm seeds are quite nutritious but it’s presumably not worth the weight penalty to carry them around for days waiting for them to digest. Better to reguritate the bits that don’t digest fast and go and eat some more fresh fruit.
And in large birds like ratites it seems that they just aren’t that fussy. They seem to be high volume feeders rather than relying on efficient digestion.
But that’s all speculation. If you’re lucky Colibri wail be able to explain how these seeds survive the crop of seed-eaters.
While we wait for Colibri – I believe that some seeds benefit from the scoring that occurs in the bird’s crop; it gives a start to opening a tough outer layer. For instance, there are some flower seeds that you score (by rubbing with an emery board or the like) before planting. No, can’t think of an example off-hand.
Okay, one example is sweet peas (scroll down to “tips”).
:looking over at my dog wolfing down breakfast:
:dubious:
Seeds that survive(d) digestion by animals and/or benefited from digestion from animals were spread around and survived at a greater rate than seeds that didn’t survive and/or benefit from digestion.
*Quote Little Nemo "Welcome, Johnny.
Seeds were generally evolved to be indigestible. The point was that animals would swallow the fruit and “deposit” the seeds in the midst of some “fertilizer”. The seed would then sprout into a new plant." -end quote*
This is a bit misleading, as nothing was evolved to be anything, and there is no ‘point’ in evolution. Everything has a consequence, not a point or purpose.
One can observe the results of the seeding process of birds as they make their little deposits any place they tend to congregate. For example, under telephone wires, there are often all sorts of things growing that have been planted by the birds that perch above. Fences often have plants growing along them that don’t grow anywhere nearby (although other factors also are involved, of course, including foraging animals and other competitors). But the fact is that you can see the results of the bird/seed/poop cycle sometimes very clearly in some very clearly defined lines on the ground.
You have to be a bit careful about drawing those conclusions though. Many birds will carry entire fruit with them to a perch and then eat it there and discard the seeds. Other birds will swallow whole fruit and regurgitate the seeds. So although seeds passing through birds play the major role in what you describe you would still see the same pattern even if no seeds survived passage through a bird.
That’s most obvious in the tropics where fruit bats produce much the same effect despite swallowing almost no seeds. Moroever they manage to produce the effect with plants like mangoes and avocados, and there’s no way those seeds are passing through anything this side of an elephant.