Oddities

General Discussion
1

I’ve come across 2 oddities this year, my first year of growing roses from seed in any quantity. Any comments or explanations for them?

  1. 2 seeds in one achene. I’ve had this at least 3 times so far. In each case, both seeds have grown. When this happens are these akin to fraternal twins in humans? I’m guessing I’m not getting 2 identical plants here but rather that these seeds are no more related than other seeds from the same hip.

  2. Cotyledons with 3 leaves. I have multiple seedlings with 3 cotyledon leaves instead of 2. Why? Is this some accident of cotyledon formation, or is this normal in some gene pools of roses?

Alicia

2

Good questions.

I’d be curious to see what the twins look like when they mature. In a totally different plant (gamagrass-Tripsacum), twins (two embryos in one seed) are fairly common. I’m growing two pairs of these in my basement right now. And hopefully I won’t scare you off with “ploidy” talk, but from what I’ve read, (in Tripsacum) one embryo is usually tetraploid like the mother and the other is often diploid. Both pairs of grass twins I have, are “one big normal twin and one smaller more delicate twin”. So I think they really are tetraploid and diploid. It’d be really neat if this happened in roses too.

As for the extra cotyledons, I’ve seen those kind of seedlings before too. But, they seem to end up pretty normal looking after a little more growth.

Good luck with those first year babies. We’ll be looking forward to hearing how they turn out.

Tom

3

I’ve had some seedlings with 3 cotyledons. Last year, I had one with 4. It looked like a little 4 leaf clover until the first true leaf formed. I don’t know what causes it, but it doesn’t seem to be detrimental to the seedling.

I’ve also had three cases of two embryos in one seed. In all three cases, both seedlings died young. I’ve also had one case of a siamese twin seedling. It had two stems joined at the root, with one cotyledon on each stem. I carefully split it, and it grew into two identical seedlings.

4

Twin embryos is very interesting. Like mentioned, one can be the ploidy expected from the cross and the other the ploidy expected from an unfertilized egg (haploid). A synergid (next to the egg with an embryo of the same genetic composition of the egg) can develop into an embryo without fertilization. If you saw the twins germinate you may have noticed if they shared the same papery covering (testa). If they did, it is likely this is the case. If they did not share the same testa they are probably two separate fertilization events. I have gotten 4x/2x seedlings with twins. I have also gotten fraternal twins too 4x/4x and very different phenotypically. Also, I have gotten identical twins as well, but only once. If one is much smaller than the other you may have a set of twins with the weaker one being haploid. If they are about the same size, you probably do not have a haploid twin member. Please keep us updated.

Sincerely,

David