It can be confusing I know but it is basically an apples vs. oranges comparison. Two different methods with two very different goals - seed germination vs. root development and later leaf development.

While bottom heat isn't required it does make germination much faster but that is all it is good for. If left on the heat mat not only do you risk cooking the young tender roots, you stimulate heavy top growth. So much top growth that the slower root development can't support it. The goal early on in transplant development is NOT top growth but heavy strong root development and that requires somewhat cooler temps.

Plus you are comparing soil temps and air temps and soil temps are always lower than air temps by as much as 5-10 degrees. So your 75 degree air temp is much warmer than the soil temps.

Sunlight isn't "top heat". Plants use sunlight, or better yet supplemental light, for photosynthesis, for growth energy from sugar conversion. It is the color spectrum of the available light and its intensity that is relevant to them, not the temperature.

Hope this helps.

Dave

Thank you, so if my seedling that just sprouted yesterday is placed behind the glass window and it's 87 almost 90 should the seedling be fine? Should I water it? The peat pellet was wet when I took it from under the dome yesterday but now with all the sun and heat it's dry, but don't want to over water as I am afraid of fungi.