Seeds require oygen, water and a sowing medium for germination, the amount of light or dark is a very variable factor. Do you have any links to share to help hone in your needs?

Most also require warmth. I think light or darkness is an either/or factor, rather than variable. No, I have no links.

Have never encountered one that required light - tomato seed that is - and have germinated hundreds of varieties.

The only reference I could Google up on light effect on tomato germination is linked below.

Dave

Here is a link that might be useful: Tomato Seed Germination: Far Red Inhibition

The rootstock seeds I have, Maxifort and Beaufort, were bred by DeRuiter Seeds who specify that the seeds require light. I have established that this is true by burying some in the "normal" way--they did not germinate.

It's not either or.

Do you not realize that for every day there is also the night?

Mother Nature has been growing tomatoes on her own for a really long time. They reseed in our gardens without our assistance and outside there is both sunlight and darkness. Tomato seeds don't need only light or only dark to germinate.

There is a link, and it says don't put the seed flats into a dark shed. They suggest greenhouse germination, shich, btw, is a structure with glass windows that allow in daylight during the day and at night, well, unless there's a moon or they've got a light set-up and timer going, there is no light once the sun goes down.

How deep did you sow your seeds?

Planting seeds too deep is one of the first culprits of failed germination--they have only so much energy to sprout and get to the top of the soil to begin photosynthesis.

Did you maintain soil moisure, did the flat every dry out?

How long has it been since you sowed your seeds? Patience is a virtue. Some seeds can take a few weeks, not a few days to sprout.

Here is a link that might be useful: DeRuiter Seeds Instructions

Trudi, thank you for the advice. I should explain that I am not a novice. I have a degree in biology, I am a master gardener, a garden writer, and a commercial grower, so I know what seeds generally need. Note that the DeRuiter instructions say "Rootstocks are typical light germinators, which make the light the most important factor to achieve a more equal plant." Because rootstocks are F1 hybrids, it seems likely that at least part of their parentage is also photoblastic. What I am trying to find out is which specific varieties or cultivars (in addition to rootstocks) REQUIRE light to germinate, and which do not.

Why don't you contact the National Agricultural Library in Belstville, MD and ask one of their librarians to look for some data that can assist you in narrowing down your search, specifically ask them is there are any photoblastic tomatoes.

Or, you could do the logical thing, and ask DeRuiter what they specifically mean.

Years back I went through the debunking that Delphiniums need dark to germinates. It was just silly that people would cling to such an idea when they reseed outside where there is both light and dark. The crap stopped after Dodswells Delphiniums not only linked to my site but approved the method for germination.

My experience is that a tomato is a tomato is a tomato, germination requirements are the same for hybrids or OPs. Tomatoes are non-photoblastic.

Here is a link that might be useful: NAL

Gan

I dont know of a list of specific varieties but there has been research done that shows some varieties have seeds with sensitive phytochromes that trigger hormonal responses (and it goes both ways some need light, some don't). I have posted this info in the past with references. It seems to come up every year.

Also, there are some varieties reported that are photosensitive for flowering/vegetative states. The reference for that would be the CRC Handbook for Flowering. I do not recall the specific volume for tomato. Many wild species are photoperiodic.

I suspect that more modern lines, which tend to be more genetically diverse, might show more sensitivity. This is because these lines have been bred with wild species to introduce usually disease resistance and there can be genetic material (DNA artifacts) from the wild species still present. Recent molecular work has shown that even the backcrossing method that theoretically can remove 99% of the genes after several generations is not actually the case. This could be the partial reason why the rootstocks you are using are sensitive and may be why some other lines have been shown to be sensitive - they are the result of more recent crosses with wild relatives.

Mulio, thank you. Your last paragraph gives me a clue, because I think at least some commercial rootstock F1's were bred from "wild" relatives. This is not conclusive evidence of course, but I do notice a physical similarity (size and shape) between the rootstock seeds and those of the currant tomato, L. pimpinellifolium, which also requires (or at least germinates much better) with light than without it.

I think those rootstocks are probably from S. habrochaites (L. hirsutum) or S. peruvianum.

Selections of S. peruvianum from mountain ecotypes tend to have light sensitives and S. habrochaites flowers around the equinoxes (similar to equatorial day lengths).