How many hours of indoor light per day?? - Page 3

Blueaussi · March 10, 2015

According to Epic Tomatoes, the plants need a rest time, and the lights should be off for at least part of the night.

That's not the only place I've read that, but it was what was on the Kindle, and thus handy.

FarmerShawn · March 10, 2015

Quote:

Originally Posted by Stvrob

I would be careful with your onions, if you go above a certain number of hours daylight, they will take that as their signal to begin bulbing. I assume your intention is to grow a big strong plant and have it in the ground before bulbing is initialized. Different onion types have different daylength periods before they begin bulbing.

Also, its actually the length of the dark period that triggers the bulbing, though everyone speaks of daylength. Theoretically, you could have say 20 hours of lights on, and 12 hours of light off (complete darkness) and still not initialize bulbing. That would be an interesting experiement to see if you could raise transplants quicker.

Thanks for that. It's what I sort of thought, but never verified. 12 on and 12 off seems to have worked the past couple of years, and seems to be working now, so I guess I'll stick with it. At this latitude, by the time the onions get planted out, the nights are really quite short - it's light enough to work in the garden past nine o'clock!

joepertsx · March 15, 2015

I provide 18 hours each day. They do well.

spuriousmonkey · March 17, 2015

This one review paper is quite interesting:
http://www.cbsg.nl/media/6652/velez-...%2003-2011.pdf
Cause of Continues light (CL) sensitivy are not clear and could differ in the various CL sensitive species.

interestingly, if solar light, partially or totally (see
below, Future research), provides CL, the injury is reduced
or even absent, respectively [34,42,46]. Hence the question
arises if the CL-induced injury is caused by the continuity
of light itself or by an interaction between photoperiod and
light spectral distribution?

It appears sunlight is the best. You might improve the growth of your own seedlings by exposing them to direct sunlight for a few hours a day if you are intent on using grow lights.

High temperatures also seem to increase the negative effect of CL sensitivity.

Higher temperatures also increase CL-induced injury
[33]. CL caused injury in tomato plants grown at 24 8C but
not at 12 8C [33].

So you might want to keep a close eye on your enviromental temperature if you are using artificial lights.

Similar to most physiological processes, carbon metabolism
is influenced by the diurnal cycle. During the day,
plants open their stomata, fix CO2 and accumulate starch.
At night, stomata close, carbon fixation stops and the
accumulated starch supports plant metabolism until the
next morning [7].

So some plants could be more prone to messing up balances created by this cycle. In the article they give various regulatory processes that could be messed up. No information is given on tomatoes themselves in this case.

Several lines of evidence suggest that CL significantly
increases photo-oxidative pressure. For instance, compared
to tomato, pepper plants show lower CL-induced
injury which correlates with higher carotene and xanthophyll
content [42].

yes, oxygen is toxic. Apparently tomatoes are more sensitive to this than some other plants.

But they discovered wild varieties of tomatoes that are not CL sensitive.
Grafting experiments located the CL
tolerance (CLT) trait in the shoot [96]. Interestingly, the
CLT trait was inherited in the F1 as dominant in an
S. lycopersicumS. pimpinellifolium cross [96], and the
F2 segregated in a proportion close to 3:1 [96]. Altogether,
these results suggest that CLT is a monogenic, dominant
trait, functionally located in the shoot.

So it would be possible to introduce this trait into existing varieties I guess.

March 10, 2015	#31
Blueaussi Tomatovillian™ Join Date: Apr 2009 Location: South Carolina Zone 8a Posts: 1,205	According to Epic Tomatoes, the plants need a rest time, and the lights should be off for at least part of the night. That's not the only place I've read that, but it was what was on the Kindle, and thus handy.

March 15, 2015	#33
joepertsx Tomatovillian™ Join Date: Mar 2015 Location: Houston Posts: 4	I provide 18 hours each day. They do well.

March 17, 2015	#34
spuriousmonkey Tomatovillian™ Join Date: Apr 2014 Location: Finland Posts: 28	This one review paper is quite interesting: http://www.cbsg.nl/media/6652/velez-...%2003-2011.pdf Cause of Continues light (CL) sensitivy are not clear and could differ in the various CL sensitive species. interestingly, if solar light, partially or totally (see below, Future research), provides CL, the injury is reduced or even absent, respectively [34,42,46]. Hence the question arises if the CL-induced injury is caused by the continuity of light itself or by an interaction between photoperiod and light spectral distribution? It appears sunlight is the best. You might improve the growth of your own seedlings by exposing them to direct sunlight for a few hours a day if you are intent on using grow lights. High temperatures also seem to increase the negative effect of CL sensitivity. Higher temperatures also increase CL-induced injury [33]. CL caused injury in tomato plants grown at 24 8C but not at 12 8C [33]. So you might want to keep a close eye on your enviromental temperature if you are using artificial lights. Similar to most physiological processes, carbon metabolism is influenced by the diurnal cycle. During the day, plants open their stomata, fix CO2 and accumulate starch. At night, stomata close, carbon fixation stops and the accumulated starch supports plant metabolism until the next morning [7]. So some plants could be more prone to messing up balances created by this cycle. In the article they give various regulatory processes that could be messed up. No information is given on tomatoes themselves in this case. Several lines of evidence suggest that CL significantly increases photo-oxidative pressure. For instance, compared to tomato, pepper plants show lower CL-induced injury which correlates with higher carotene and xanthophyll content [42]. yes, oxygen is toxic. Apparently tomatoes are more sensitive to this than some other plants. But they discovered wild varieties of tomatoes that are not CL sensitive. Grafting experiments located the CL tolerance (CLT) trait in the shoot [96]. Interestingly, the CLT trait was inherited in the F1 as dominant in an S. lycopersicumS. pimpinellifolium cross [96], and the F2 segregated in a proportion close to 3:1 [96]. Altogether, these results suggest that CLT is a monogenic, dominant trait, functionally located in the shoot. So it would be possible to introduce this trait into existing varieties I guess.