Tomato Seedling Temperature Question

[RosieRenee]

I apologize if this has been answered already in this forum. I have read here and elsewhere that the ideal temp for tomato seedlings (post-germination) is 55-65 F as it makes them stronger. I have adopted that practice but am curious:

1. Why do cooler temps make them stronger? What do cooler temps do to make tomato stems thicker?

2. Would the same be true for their fair-weather friends, peppers and eggplants?

Thanks much. I'm mostly just curious as to why. The inner geek must want to know!

[digitS']

I'm convinced of it, Rosie Renee!

Warmer temperatures "permit" growth but growing has a great deal to do with photosynthesis. Light.

Too little light and the plants will s t r e t c h! Not all but some plants really benefit from very bright sunlight.

Steve

[Bobberman]

I would have to say that at the higher temp nitrogen is more abundant for the leaves but at the lower temp potassium that grows the roots and stems will make them grow thicker! Light has also a lot to do with it. No light the first two days of seed emersion will cause the stems to be very thin searching for light! .

[applestar]

...wow just realized its 1am...

No time to find links, but my recollection is that cooler temps slow down growth -- as in cell wall structure and division, etc. -- so that with same or nearly similar amount of material, shorter cells are made. Shorter = thicker walls = sturdier.

I do put tomato seedlings outside when at least 50°.

While the principle is the same, pepper seedlings need around 5-10° warmer temps 60-70°F and I believe eggplant seedlings need another 5° (or 10-15° warmer than tomatoes) 65-75°F

[RosieRenee]

Thank you all for the quick responses. I am growing them under lights in a cool room on tile floor. They've all sprouted, so it must be warm enough for that. I'll post some results in April or May to spread the word. Thanks!

[ion]

I don't think 55-65F are ideal for growth.
Below is a table showing tomato growth 5wks from seeding, it shows that seedlings grew best with soil temp of arounf 85F. The table came from a study by Jaworski and Valli, Tomato Seed Germination and Plant Growth in Relation to soil Temperatures and Phosphorous Levels.
It was about soil temp and P levels instead of room temp, but I think it gives us some idea that warmer temps are better (upto a certain point) for germination and growth.

[Juliuskitty]

The " sweet spot" for tomatoes to grow healthy foliage and set well shaped and sized fruit is about 73F.

[applestar]

Yes that's all true -- germination in the higher temp mentioned, and blooming and fruiting in the middle range, but I thought the question is about "post germination seedlings" ....

[rainbowgardener]

And there are different issues going on here. What temperature is going to give the fastest growth and what temperature is going to give a slower growing but very stocky plant that is more ready to handle outdoor temperatures and take off when planted in the ground.

I know from experience, that the tomato seedlings I leave on the heat mats longer grow faster than the ones that are taken off it as soon as they get true leaves. But I also know the more a little plant gets babied and pampered, the more difficult time it has making the transition to outdoors.