Jan-Hendrik's picture

The Otholobium saga continues...

Observed: 12th April 2017 By: Jan-Hendrik
Botanical Society of South AfricaSouth African National Biodiversity Institute
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Otholobium rotundifolium (6)
Otholobium rotundifolium (8)
Otholobium rotundifolium (4)
Otholobium rotundifolium (7)
Otholobium rotundifolium (1)
Otholobium rotundifolium (2)
Otholobium rotundifolium (3)
Otholobium rotundifolium (5)
Otholobium rotundifolium (9)
Otholobium rotundifolium (10)
Description:

So this species' seed is supposed to be very scarce, not really making many and those that do form rapidly disappear. There was some discussion on some of the previous posts as to what disperses the seeds, and here I postulate my theory: wind. I found quite a number of these seeds in a small wind-protected pocket in front of some large rocks. The pod stays attached to the calyx, and the two of them (together with the one seed inside) being very light, are easily blown around by the wind. And thus the mass gathering seen here. With some digging through the bunch of empty calyces it was not long before I found quite a couple of seeds, and like one of the earlier post of Carina (who was the first to document what the seed look like) the majority of the seeds are speckled. So it seems one just has to look in the right place. What a nice find!

Identifications
Species interactions

No interactions present.

Comments

Kenneth Oberlander's picture

Are you going to try germinating these?

?

Jan-Hendrik's picture

Yes

They actually seem to have very thin seed coats so they should do fine with just some pre-soaking in water as is before sowing (don't think scarification will be necessary). Presumably sowing time will also be more or less now?

Charles Stirton's picture

Germination

Great set of pics. Let me know if you successfully germinate them. I have a draft paper of germination and seedlings of Psoralea and Otholobium if you would like to receive it.If you made some measurements I could include them in the paper. Email me. Great you put in a ruler in the seed pictures. The seedlings are easily separated in the two genera. So far I have not found seed from any of the resprouting Otholobiums so I would be very interested in any success you have. I usually put the seeds in a mug and pour boiling water over them then leave to soak overnight before planting them. They germinate quite quickly and Otholobium germinates more quickly than Psoralea. One can also just nick a bit of the testa/seed coat and leave to soak for a while. These seeds are the only polychromatic seeds I have seen in Otholobium; interesting in itself. As an aside, I have been growing Psoralea oligophylla very successfully outside for three years in my UK garden. The plants die back in winter then resprout strongly in spring.
I agree with your idea of wind dispersal. In Psoralea the whippy branches flick the fruits some distance from the plant and then the fruit /seed unit is secondarily dispersed by water. I have observed this quite often.
I just love ispot and its merry observers. Thanks for all the effort.

Jan-Hendrik's picture

Germination

I will let you know if they germinate. I am a bit hesitant for boiling water, some of these have a really thin seed coat (as mentioned), I mean in some instances I broke of parts of it just by trying to get them out of the pods! Maybe lukewarm water? What do you think? Also, I assume that now would be the best time to sow them with the onset of the winter rains? I would love to see the draft of that paper, and I will send you measurements of the seeds. How accurate do you need them? My vernier caliper broke a while back and I have been meaning to get a new one but until then measurements will be limited to the old faithful ruler. You are more than welcome to use some of the pics if you would like to have them, I can send high resolution ones (e.g. via dropbox). Just a question someone actually asked me today regarding these speckled seeds: what would be the purpose of having such speckled seed? I.e. what benefit is in it for the plant?

Charles Stirton's picture

Email me ..

-- and I will send the draft paper. Brian du Preez has my email. The seeds will germinate any time of the year. I would try some of them now and keep some for spring. Drop a few into boiled water (not bubbling hot and a few in luke warm water. Also nick a few and then compare what is best for all approaches. You will see in the paper what is needed to be measured and recorded. Yes, some high resolution pictures will be welcome. The speckling acts as a form of crypsis I think. Eriosema parviflorum, for example, has khaki seeds with purple flecks and mottling but also produces pure black seeds. The seeds in that species are explosively dehisced and can fall anywhere. their habitat is either black turf or pale grey sand. Perhaps something like that occurs here as well. This polychromatic feature is not uncommon in some species, In earlier pictures I notices some size variation and poor filling. Some of them might have been immature when they were shed. or it is a sign of hybrid origin.