Optimization of seed germination - Ways to improve protocol? (Feb/12/2008 )

Hello everybody,

I am looking forward to growing spinach in vitro. Usually, and depending on the cultivar used, my seeds make 6 to 15 days to germinate fully (i.e. the cotyledons are starting to go out of the seed) in the dark with water added. Then, I put it on classical MS medium and the first leaves appears ~6-8 days after.

I would like to improve this protocol:

- Do the seeds germinate faster in the dark or light?
- Which temperature could be the best?
- I was told that for Arabidopsis, putting the seeds overnight in the fridge helps them uptaking all the water and then germinate at the same time. Do you think it could work for spinach (seeds are much bigger than Arabidopsis of course)?
- I have a lot of trouble in getting my seeds to germinate altogether... Any advice?

I precise that I have no experience in plant culture of any kind (I am a molecular microbiologist)!

Thanks very much for any help!! ;-)

T.

by putting seeds in the dark you will get etiolated seedlings, which usually are larger but weaker (the cell expands more in the search of light). to find out which temperature is best do a review on spinach. i don't know if spinach presents vernalization as arabidopsis, that's the reason for putting the in the fridge. you could perform a germination test by using a small sample of your seeds, there is a "pink" compound which i can't remember the name, it determines how viable the embrio is. that way you can at least determine the germination % you will have.

The reason why your seeds aren't germinating at the same time is because dormancy wasn't broken. With arabidopsis you do it at 4ºC but with other plants is done with heat. We work with rice and sometimes leave them at 37ºc - or even more- overnight before germinating them. I don't know how it is with spinach... You can try both and see which one is better.

Usually seeds germinate better in the dark - it mimics an underground situation. But for rice 2 days are enough, which is very different from spinach apparently.

The temperature depends on the plant species, but it can influence germination. Try checking the literature for that.

I used to have the same problem when I germinate the Catharanthus seedling. In the MS media, the plant staart germinate after put in 22 C , 60% humidity for 21 day. The problem was solved, when soaked the seeds longer in bleach to remove some of their seed coats, left the seed on MS media in 22 C, 60% humidity for one night and then grew the seeds in 30 C. The seeds were germinate in two days.

I dont know much about spinach but with arabidopsis at least one night at 4C isnt going to do much... You need to leave it for at least 3 days... This will help to germinate the plants and usually helps with syncronisation.

You should also pay attention to the time between seed collection and when you sow it out and ensure that the seeds are dry when you collect them... again with arabidopsis at least if the seed havent dried completly when they have been collected they wont germinate probly and they also need to finish drying in a seed packet for at least a week in a dry place (like a draw) at room temp.