Dear Sandrines,

Please have a look at the recent paper:

Campanulaceae: a family with small seeds that require light for germination (Ann Bot 113, 135, 2014) which you can download from my researchgate site.

It seems that this species germinates at high temps with light of course, but some prechilling is additionally beneficial.

For further info, please contact Katerina Koutsovoulou, at [email protected].

Regards

Costas

Genus Campanula known for both non-dormant and Physiological dormant (PD) seeds. As per your feedback Campanula glomerata seeds requires GA to germinate, which indicates that this species possess PD. If you want to germinate them without GA, I would like to suggest to incubate them in sequence of temperatures that simulate natural habitat of Campanula glomerata as move-along experiments.

Dear Sandrine,

I have no specific knowledge of Campanula glomerata but, with some species I have worked with, cold humid stratification produced similar increases in germination to those obtained with GA3.

Thank you all for your kind reply. We already have tested 2 months stratification in cold-moist conditions (on agar at 5°C in the dark), but so far we didn't get any germination, while the same protocol applied to seeds coming from Czech Republic gave 96% germination.

We think that this pattern could be explained by the fact that fitness components for this species might be lower at the range margin than at the range centre, possibly causing a weak seed viability.

Hi Sandrine, which temperature conditions did you use after the stratification?

Lower fitness at range margin has been often argued as responsible for lower germination/viability; however, in my opinion this topic should be addressed in careful studies as many exceptions to this theory has been reported given the large phenotipic plasticity of many plant species. :)

To answer Angelino's question, after stratification we used a continuous temperature of 20°C with a photoperiod of 8/16h.

Hi Sandrine, 20 °C may be too low? (perhaps 25 °C may be better)

Seed priming is one of the most potent technique to enhance the germination of seeds.I would suggest to go for  hydro-priming, by conditioning of seeds in moist(about 95 to 98% RH) at normal room temperature(about 25°C) for a specified period.The period of conditioning may be standardized starting from 6hrs. to 14hrs. or till you get the desired germination.

Hi Sandrine,

have you tried any alternating temperature regimes after cold stratification?

This could suit to your species as the seeds should be quite small.

Best regards,

Efisio

Thanks, Efisio, for your suggestion. We didn't try alternating temperature regimes because the constant temperature of 20°C worked well for the seeds from Czech Republic. But it's definitely worth to try since we don't have many other options, I'm afraid.

Hi Sandrine. What do you mean by malformations ? A lot of seeds of various species have been stimulated by GA3 without producing any malformed plantlets. And you could made the GA3 treatment as short and low dosed as possible. Otherwise, a lot of species  usually have their germination improved by afterripening, or  stimulated by NO3 ions. Perhaps you can investigate in this way with C. glomerata....

Regards

Thank you, Marc, for your comment. There is plenty of evidence in the literature that the use of plant hormones like GA3 can cause mutations inducing malformations in the further development of the plant (e.g. abnormal flowers or stem elongation, etc.). Since these plants will be used for reintroduction in the wild and subsequently monitored (morphometric measures and demographic survey), we need to start with plant material that is as healthy as possible. For this reason, it wouldn't be neither desirable nor wise to use GA3.

Hi Sandrine

GAs, in my opinion, used at low concentration, are not considered as strong mutagens. The effects you stated (abnormal flower, stem elongation) came probably from long term treatments. And even, if some mutation occurred, what would be the problem ? Plants in the wild are continuously subjected to natural mutagenesis... I have some difficulty understanding your prevention against GA treatment of seeds... Moreover some GAs are produced by fungi present in the soil and can perhaps participate in facilitation of seeds germination  !

We have undertaken 15 g-tests from 6 collections of C. glomerata. All except one test used GA3 at a variety of concentrations on the agar plate. The one test where we didn't use it resulted in 0% germination! Let me know if you want me to pass your contact on to our germination specialist.

Some of our data area here on our Seed Information Database:

http://data.kew.org/sid/SidServlet?Clade=&Order=&Family=&APG=off&Genus=Campanula&Species=glomerata&StorBehav=0

Thanks Tim. Any additional advice from your germination specialist is indeed welcome! Now I would like to try with a fluctuating temperature, as suggested by Efisio. If it doesn't work, then we will have a problem...;-)

OK, often the GA3 is used to replace a cold stratification so, yes do as Efisio suggests. I have alerted our colleague and encouraged her to join ResearchGate.

I do not know this seed at physiological level. That is, if the mother plant produces heterogeneous seeds (color, size, abortions, etc), if the seed has a hard seed coat or, as Marc says, requires afterripening as post-maturation mechanism, among others possibilities. Having said all this, my opinion is that you should add 0.1-1 mM ACC in the imbibition medium. Perhaps the ACC should also be supplemented with GAs. Please, tell me the obtained results.

Lucky