is the whole your talking about pictured here?
See where the pollen grain is growing into the structure, to the ovule? That’s the hole, the micropyle (not labeled). In flowering plants, there is no hole. Instead, the pollen grows a little root-like tube through the style, into the ovary, to find the ovule.
1 Like
Ah… That’s the difference! Gymnosperms don’t have a pistil/pollen tube to go thru.
All Angiosperms do right (Even Magnoliids & Basal Angiosperms)?
1 Like
Some of them might have a little ole, but for many, the ovule just sits on the leaf.
1 Like
testa is something all seed plants have, it just a part of the seed, a remnant of the immediate maternal tissue of the ovule - usually it mainfests in a thin, dry layer, like the skin on peanuts, but occasionally, like in ginko, it can be fleshy.
in juniper berries, the whole cones turn fleshy (and those can really be called fruit equivalents).
Female junipers usually have cones of three fertile leaves, and often you can see at the top that why, fleshy and partly fused, the fusion is not complete:
https://botanicalarchive.com/cdn/shop/files/Juniperuscommunis.jpg?v=1711622616&width=990
Gnetum, I think is similar to ginko, but not too sure.
No, naked seeds are, embryo+endosperm+testa
testa is maternal tisue from the ovule (imagine a human baby also taking the ovary); an angiosperms fruit contains more maternal tissue (taking the whole uterus). The human baby analgy is not perfect, as gymnosperms do not even have the “uterus” in question.
1 Like
oh, you are talkig of micropile.
The micropile has nothing to do with this. micropile is open in both angiosperms and gymnosperms, but in angiosperms, the micropile opens to a cavity completely shut off from the outside, and pollen has to grow through some tissue to get to it, but micropyle itself is open into empty space. in gymnosperm micropile opens, to some degree, directly to outside. In some (cycad, ginko), it is more or less unprotected and completely exposed, as the ovule just sits on the carpel. In Pinaceae, ovule sits on a fertile scale, and both of them are sqeuezzed between two woody scales, so the space it opens to is very narrow.
But micropile itself is not closed.
The original state of fertile leaves is like in cycads: the ovules are on the edge of the leaf, exposed. in the lineage leading to the angiosperms, the carpel (fertile leaf) roled inward, to offer more protection to ovules, at the end, this lead to fusion of eaf edges and forming angiosperm ovaries later in the evolution:
The main difference between angiosperms and gymnosperms is that the carpel in gymnosperms is generally flat (or not, but then stillopen), like in cycads. in angiosperms, take the cycad carpel and roll it like a pancake so the ovules are inside, close the ends, and voila, angiosperm carpel is here.
2 Likes
Very interesing.. the pollen grains just fly into those little slits?
In Ginkgo’s the test is fleshy? Now that makes somewhat sense. In Popcorn the Seedcoat was bred out from teosinte, so what we are left with is simple very firm Testa?
Corn is not a Naked Seed right? It does have embryo+endosperm+testa right?
Of course, and it is easy to web search for pictures.
The grain is actually a fruit, not a seed, but the pericarp is fused with the seed coat.
3 Likes
oh wow??? so… what is the seed or fruit then?
If the seed is the fruit, than what is the Cob?
Fantastic Diagram by the way except I wonder why does Corn have a Seed coat/hull???
I thought not having a Hull is what makes Corn different from Teosinte which has a Hull.
I’m so confused, what does Teosinte have?
And what about Gammagrass (Tripsacum spp.), since both Zea spp. & Tropsacum spp. are crossable, what happens to the seedcoat or seed structure?
for corn, as for all the grassess (including Tripsacum), the seed forms almost the entirety of the fruit; only the outer coat (the part of popcorn that gets stuck in the teeth) is not part of the seed. It is highly reduced and forms the thin shell/hull of the seed. This form of fruit is called a caryopsis or, after the grass fruits we use, a grain.
teosinte probably just has a thicker shell/hull, and we selected varieties with thinner ones, so it almost appear as absent.
The cob is an infructescence, which is a fruit like structure, that develops from an inflorescence. Another famous example is ananas/pineapple.
There is a process that happened multiple times of reducing the number of seeds per carpel and hardening and then fusing the carpel walls to the testa; not only grain is form like this, but achenes, samaras, cypsellas… which differ in form and degree of fusion of carpel to the testa. they appear as naked seeds, but the additional layers of tissue are discernable at least in some stages of development.
2 Likes
So the Seeds & Fruits smush together to form 1 Fruit Complex? Much like a Mulberry, Raspberry or Blackberry?