Stomata on the pericarp of species of the genus Rosa L. (Rosaceae)

see link below


I have believed that hips can carry virus/disease by way of the achene. In the photo Fig.4h (in this very interesting article)they show, but do not comment on, a fungal hyphae very clearly entering a stoma. This seems to confirm at least the likelyhood of this not being a totally unique or isolated event. I’m not exactly a scientist, but I am sure that the Peronospora I witnessed in new seedlings (of mine) was something they carried within the seed, and not something that was able to reveal itself as the cotyledons were unfolding. (And many of the most previously infected roses aborted or just did not produce crosses at all.) Am I interpreting this fungal hyphae entering the pericarp wrongly? Could’t any number of viral and fungal disease be transferred (perhaps in a limited number)to a new seedling? These stomata on the achenes seem pretty uniform except on the spinosissima.

"This is the first report of stomata on fruits of Rosa. "

Actually, it’s not. There is an electron micrograph of rose pericarp tissue in a fairly recent Chinese paper that clearly shows stomata. When I get a chance I’ll dig it out.

The obvious question is what function they have. I have a strong suspicion that they regulate gas transport in and out of the seed and, in doing so, affect viability and germination. That is to say, I think oxygen get into the achene by active processes rather than passive diffusion, and that not only the pericarp has active regulation of gas transport but the testa does too.

Who saw the stomate first is an interesting question. Not to be cynical but I reckon that the Chinese paper came to the attention of the Polish group and they quickly went about looking back through their earlier data for images that would show one. Quite possibly it was during the review process itself. Such events are not uncommon in science. When it becomes a real problem is when the reviewer rejects a paper so that he can be the first to report an observation. That also is not terribly rare.

Alternatively, the Polish group did not have access at all to the Chinese work and really thought they were first.

Zielinski has been studying roses for a very long time. He did his work on the Hulthemias in the early 1980s or before.

I always assumed the embryos got gas exchange somehow. I have some peony seeds I found locally in the fridge. I cut the bottom off of a 1 liter diet pepsi bottle (so its like 2" T x 2" W, put some aquariam gravel on the bottom 1/2" of it and filled it with water to like 1/8" above the gavel mark. I then set the seeds on top of the aquarium gravel where the seeds rest half way in the water and half way out of the water. I did this because I actually do believe they must be partially exposed to air (just like rose seeds) as well as moisture. I am unsure as to what optimum for either type of seed is but its nice to know that rose seeds (and likely others) do have stomata that could possibly mechanize this idea.

This may be of interest.

Don’s probably thinking of A systematic study of Rosa sericea (Rosaceae) complex: Are R. omeiensis and R. sericea conspecific? Journal of Systematics and Evolution (formerly Acta Phytotaxonomica Sinica) 46 (6): 919

Neil, the link you gave is a very useful general one. One minor exception to the main opening statement though. Water lilies and some submerged plants including deepwater rice, actually do transport gases long distances to their roots. But they use some special tricks.

Other than that, potatoes probably set the record. Blackheart is caused when there is insufficient air (oxygen) access to the center of a really big spud. You can cover 90 % of the lenticels of a standard 8 oz Russett Burbank potato with wax or water and it will be OK. But, put it under a continuous film of water and it rots really quickly.

Rose achenes are really hard to interpret. Wood looks impermeable but can allow rapid diffusion. That’s why a board warps as it shrinks. On the other hand a layer of suberin can make a root or leaf almost impermeable to water loss. That’s how a cactus can survive a year without water. (Technically the cladode is a stem but the point is the same.)

If you look at the evolutionary origins of the rose inflorescence, it used to be more like a raspberry with the achenes outside, then on top, then in a cup, finally enclosed as we see most of the time today. There was a paper recently on that which got discussed either on the forum or in the newsletter, I forget which. Perhaps some exogenous seeds would be useful to examine, in comparison with the enclosed ones of the same hip. the surface of exogenous seeds ought to be like the ancient rose seed. An achene undergoes lignification and apparently it traps the stomates in the process. Do they connect to gas passages inside? Obviously at some point they did, but does suberin get deposited to block them? And do the hips have stomates? I suppose so. If only there were a student wanting a neat project in plant anatomy for a M.S.

Thanks larry: It seems fantastic to me that stoma has flexible biological containers able to withstand 450psi as guard cells. The things one learns.