What Is Endosperm?
Endosperm is largely a form of starch that acts as a food source to keep seeds alive during their dormant state, after plant fertilization, but before the seeds have a chance to germinate. It is a form of plant tissue that surrounds a seed's embryo, and is produced by virtually all types of flowering plants. Seeds can exist for long periods of time as viable offspring of a plant as long as they have sufficient endosperm to fuel very slow metabolic processes for the embryo. Much of the human diet that relies on ground seed, such as that obtained from grains, is based on the nutritional value of endosperm in the grain. Corn endosperm, for example, is either ground into flour, or consumed directly in the form of popcorn.
Seed endosperm is a direct result of the fertilization process in plants. As a male gamete fuses with two female nuclei in the embryo sac, it produces endosperm which has a triploid nature, meaning that it has a complete set of three chromosomes. This gives it a diversity of genetic and nutritional value where it contains essential protein, fats, and starch that both plants and animals rely on for health. The endosperm is divided up into three regions: the aleurone, which is a thin border region that helps the seed to break down starch for growth as it germinates; the transfer layer, which serves as the interface with the plant itself for absorbing nutritional elements; and the bulk of the seed, which is the internal starchy layer.
Plants use endosperm at different rates, with some vegetables such as peas and beans entirely consuming it to reach maturity, and others, such as wheat endosperm and coconuts, retaining it longer, which makes them valuable food sources for the human diet. The process of producing and utilizing endosperm to keep seed viable can be so efficient that some rare cases of stored seed have remained capable of germinating for extremely long periods of time. Seed from a date palm plant carbon-dated to 2,000 years ago was germinated in Israel in 2005, which came from the palace of Herod the Great who ruled Judea in the region of Israel from the year 37 to 4 BCE. Seeds of a type of waterlily or lotus found buried in a layer of peat in Japan have also been proven to be viable. Most of those tested germinated after being removed from museum exhibits, and were carbon-dated to being between 830 and 1,250 years old.
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![The endosperm is the outer, yellow part of the corn kernel.]()
By: rimglowThe endosperm is the outer, yellow part of the corn kernel. -
![Beans, peas and corn all use endosperm.]()
By: Ðиколай ÐÑигоÑÑевBeans, peas and corn all use endosperm.
Discussion Comments
What happens to the endosperm as the seed turns into a plant?
@Izzy78 - Yes, that is interesting. I wouldn't really say that the type or amount of endosperm really makes much of a difference. Where I live, we have a bunch of oaks and a tree called yellow-poplar. Oaks have acorns, of course, and the yellow-poplars have little wings seeds kind of like maples. If you let them grow side by side, though, the yellow-poplars grow extremely fast, and the oaks grow very little, even though they have more endosperm.
When you think about it, though, maybe it is counter-intuitive to what you would think. If a plant has very little endosperm, it needs to grow as fast as possible so that it can develop a strong root system to get nutrients and leaves to get sunlight (like the yellow-poplar). For an oak, there is more endosperm, so the plant can survive a little bit longer and doesn't have to rush itself to make roots and leaves. That is just my theory on it.
@jcraig - Good point. There is a laboratory in Sweden, I believe, that attempts to keep seed samples from every plant on Earth. I don't have any idea of the exact number of plants they have, but I know it is a lot. I guess the idea is that if a plant ever goes extinct in the wild, that we will have a source of seed, so that we might be able to recolonize it someday. I am sure the DNA from the seeds gets used for some research, too. I think in order to keep those seeds viable, they store them at a very low temperature, which prevents them from germinating.
I don't know much about plants, but what I would be interested to know is how the amount of endosperm relates to how fast a plant can grow under the ideal conditions. I wonder, too, about how the form of the endosperm affects the initial growth. The endosperm of a walnut or any nut tree would be much different from a bean.
@titans62 - The endosperm can end up with three sets of genetic material, because the endosperm isn't the part of the seed that is growing and maturing into the new plant. The endosperm is just the food source for the new plant.
When you think about it, the way plants develop is a lot different than how most animals do it, especially mammals. Instead of the plant being connected to the parent and getting its food that way, it needs this endosperm to sustain itself. Unlike animals, a flower can't move around and find its own food once it is born.
As far as some seeds being viable for so long, I think that would have to be under very special circumstances. Like the article says, the palm was buried in peat, and the lotus was in a museum. In those situations, the seeds would have been exposed to very little moisture, bacteria, and other things that could destroy them. As far as I know, if a seed is protected from those things, it can survive a very long time.
I'm not sure I completely understand this. So the article says that the endosperm ends up with three sets of genetic material. Isn't a plant just supposed to have two sets? Wouldn't having three sets mess things up? Could someone explain this part of it for me?
Also, how can a seed from 2000 years ago still be able to grow? What is so special about it that it could be around that long and not have something happen to it? I know just keeping corn outside long enough will make it start to rot. I don't really know what a date palm seed looks like, though, so maybe there is a special characteristic about it that would help keep it viable for that time period.
@turquoise-- I agree with you. I felt the same way when I learned about coconuts and how they reproduce in my biology lecture.
My professor mentioned that coconuts can germinate a long time after it falls off the tree thanks to the endosperm. Not only does this allow coconuts to renew themselves where they are already growing, but they can easily spread to other regions thanks to this.
For example, sometimes coconuts fall into the sea and can spend months in water until it is on land again. Despite this, coconuts often germinate when they reach land. I think this is really cool.
@turkay1: You could be right. It's probably all tied to environmental conditions. Some plants such as those in tropical locations might have very favorable conditions on average for germination whereas others that grow in harsher climates might often miss seasons where they cannot germinate at all, so they have to have an ability to lie dormant for a long time for the species to survive.
I'm studying the fertilization of angiosperms for class and I'm curious about something.
Do you think that the amount of endosperm in a seed depends on how easy or difficult it is for that seed to germinate?
Why is it that some seeds completely use up their endosperm by the time they've developed while others have plenty left afterward?
I think it might have to do with germination rates. If it is difficult for the seeds of a plant to germinate and produce more plants, then a lot of endosperm might make up for that weakness by giving the seed extra time to germinate itself.
If a plant easily and quickly germinates, an endosperm might not be necessary at all after it has grown into full size.
What do you think?
I find it fascinating and amazing that seeds can survive that long as well turquoise. One of the wonders of the natural world that's for sure. (I wrote this article by the way, thanks for commenting on it).
It's absolutely amazing that seeds from thousands of years ago could still germinate today. And this is all thanks to the endosperm without which this wouldn't be possible. I'm not a very spiritual type of person but learning this kind of information, I am more and more fascinated by nature and what it offers us.
Food sources that have endosperms with long lives like wheat can prove to be essential for human existence. I know that there are some seed banks in different parts of the world that collect and store seeds in case of a calamity or disaster that could endanger human life and existence.
If something like this does happen, anyone who remains can find and use these seeds to regrow food, feed themselves and continue human life on earth.
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