When to move seeds under lights?

[GardenFresh]

All-

Have a quick question, at what point do you move the germinated seeds from their germinating place to under lights?

Right now, I keep my seeds before they germinate on a heat mat in a powder room because it stays nice and warm. When I see the plant start to form an upside down "U" I move them to my grow lights. Not sure whether I should be moving them so soon or wait for the actual seed head to stand upright.....?

Hope that makes sense...I was just curious.

Thanks....

[hendi_alex]

Germinating plants will stretch and get leggy very quickly. I move mine under a light just as soon as the seed starts to break the soil. Place the light as close as possible, within 4-6 inches of the seedling.

[GardenFresh]

Thank you sir!

[rainbowgardener]

I just start mine under the lights. Lots of seeds don't need the light, but it doesn't hurt them. As soon as a leaf is showing they need lots of light right away or they get leggy very fast.

[PaulF]

I agree with both above, but I have my fluorescent lights set at 1 to 2 inches above leaves.

[Bobberman]

Keeping the lights close at first will give some additional heat to the seedlings. If you have more than a few flats move the lights to a foot above but keep the on 15 of more hours. I leave mine on 24 hours! My lights are 4 -4 foot bulbs about 15 inches above and I have about a dozen containers under the lights! They are staying nice!

[rainbowgardener]

Fluorescent tubes generally give off very little heat. I keep mine quite close to the plants and on 16 hrs a day. I don't think 24 hrs is better. There are plant respiration processes that only occur in the dark:

To unlock the energy in the carbohydrate produced in photosynthesis, green plants need to respire, just as animals do. Respiration takes place in the plant's cells, using oxygen to produce energy and giving off carbon dioxide as a waste product. So in terms of the gas taken in and the gas given out, respiration is the opposite of photosynthesis. https://www.bbc.co.uk/schools/gcsebitesi ... ory3.shtml

[Bobberman]

Alaska has 24 hours of sunlight at times during the year does it hurt the vegetation?

[PaulF]

The Alaskan sun is not at 24 hours during seedling growth periods and while for a while there are lots of sunlight hours, the sun does drop to the horizon where it is a little less intense. It does make for some really special growing situations. Depending on location, many days have cloud cover which de-intensifies the sun's effect.

[Bobberman]

Plants always have some of their leaves in the shade so I assume those leaves will think its cloudy or getting dark! If you slept in the woods at night would there be 90 percent more carbon dioxide in the air because of the plants I doubt it! I wonder if we had two suns and 24 hour daylight if there would be any plants here or even the human race!

[rainbowgardener]

RE : If you slept in the woods at night would there be 90 percent more carbon dioxide in the air because of the plants I doubt it

No of course not. For one thing plants (fortunately for us) give off 10 times more oxygen in the daylight during photosynthesis than they take back and consume in the dark, during respiration. That is how come we have our current oxygenated atmosphere. For another the atmosphere, even the atmosphere of a given piece of woods or whatever, is huge. Just because plants start giving off more CO2 at night, it would take a huge amount to make a lot of difference in the atmospheric concentration.

But YES, there is a measurable difference (clearly nothing like 90%) between day and night C02 concentrations:

In the summer months, the CO2 typically decreases during sunny, warm days as photosynthesis removes CO2 from the air. At night, the CO2 increases because the plants are giving off CO2 in respiration. It often takes until late morning, before CO2 removal by photosynthesis becomes apparent.... In the winter months, this daily CO2 cycle does not occur because the plants are dormant.
https://weather.usu.edu/htm/file39359/24 ... centration

So, yes during dark hours plants do respiration, which is basically the opposite of photosynthesis, taking in Oxygen and giving off CO2 and yes

Cellular respiration is an essential process for both plant and animal life. During cellular respiration, cells break down nutrients such as sugars in order to create energy that the organism can use to function.

https://www.ehow.com/facts_7408525_purpo ... z2vTKuZSQq

[Bobberman]

You can't beat a nice graphic .Thanks for the post!