Normal reaction to hps?

[migraineur]

I just put my 3 week (from seed) AK-48 babies into my 400w hps cab. I put them about 20" away from the cool tubed light until they adjust, and the temps are about 85 around the canopy, with RH around 35%.

They are kind of droopy, but still healthy looking otherwise. Is this a normal reaction for the first couple days of switching to hps from fluros? Just the leaves trying to get away from so much light?

They are on 24/0, and i don't have the cab light proofed enough to want to go to an on/off schedule yet, so i was considering putting them back under the fluros for one day, then back to the hps (kind of like hardening them off before going outside full time). Anything wrong with that?

 

[migraineur]

Well, I went ahead and put them back under the fluros for the night. I guess i'll find out for myself if they perk back up, and post the results here in case anyone is interested.

 

[migraineur]

This morning they look great again, no drooping at all, so I moved them back to the 400w hps @ 20". I also noticed they were pretty dry last night (earlier then usual - time to transplant in a couple days), so I watered them too... now I'm wondering whether they were drooping from being thirsty, or from the hps. Probably a combination of the two. Sorry I don't have any pics. Can't really even afford batteries for my camera right now.

 

[sproutco]

They may droop when going to a stronger light. Here is the hps lighting chart that shows distance. http://www.icmag.com/ic/gallery/showphoto.php?photo=150896&sort=1&cat=500&page=1 I think I would have the light about 24" (60cm) from the tops to start. After several days, lower the light to about 12" (30cm) from the tops. Use your hand to make sure the heat from the lamp is not too hot on the plants.

 

[R4st4]

hey mig, im using a box for veg with fl-tubes, when i set them under hps lamp i dont get droopy leafs but the top leafs get bleach.... after 1 week they r back to normal, and yea when u set them under hps they will drink faster

 

[Rosy Cheeks]

Depending on how many watts of fluoros you used, when the plants go from a low light wattage environment to a high wattage (400w and up) environment, the plants will increase the photosynthesis radically, which means that plant metabolism in general speeds up. Suddenly, the plants need more food, to grow quicker. I've occasionally been too conservative in nutrient dosage after flipping to high output HID:s and have experience deficiency symptoms after a while, but never droopiness.

Plants can droop for several reasons. When they lack water, the plant's metabolism and photosynthetic process slows down and the leaves droop as a direct cause. When they get too much water, the lack of oxygen in the wet soil causes stress to the roots, and a similar shutdown in metabolism takes place. High temperatures equally causes stress, many indoor growers with temp problems experience droopiness at the end of the light cycles. During the dark, photosynthesis shuts down, the plant does not need to direct the leaves at the light source, therefore they droop. Other forms of stress can cause droopiness, such as disease.
It's hard to say if your plants experienced any kind of stress from the change of environment. Radiation wavelenght differences between fluos (around 4000-5000 kelvin) and a classic HPS (2500-2000 kelvin) will affect plant growth and metabolism, but it should adapt without too many difficulties. The most likely answer is that the droopiness was caused by one of the above reasons. Give your plants some time to adapt to the new environment, and respond to its increased needs of water, nutrients, etc. If the droopiness persists, perhaps you've got a problem.

 

[sproutco]

They are on 24/0

Somehow I missed that before. No 24/0 with hps. Use 18/6. Because the light is so intense, the plants get saturated and "refuse" to accept more light. They will begin to droop. Are they 24/0 hps?

 

[migraineur]

Somehow I missed that before. No 24/0 with hps. Use 18/6. Because the light is so intense, the plants get saturated and "refuse" to accept more light. They will begin to droop. Are they 24/0 hps?

Yes, they are on 24/0 hps. Is it ok to have small light leaks during 18/6? I know it's bad for flowering, so i was going to get it all fixed before 12/12, but i've been hesitant to use 18/6 for veg because of a couple small leaks. I think 18/6 would do my plants some good though as it's a little above the recommended ambient temps in there ( 81 - 84 degrees ). Would 24/0 in these conditions cause more stress than 18/6 with small leaks for a few days?

 

[migraineur]

I think it may have a lot to do with them drying up so fast under the hps. The pots are already dry again this morning, and plants drooping quite a bit.

 

[sproutco]

Light leaks or "breaking the night" don't matter in vegetative growth. Switch the hps to 18/6.

 

[migraineur]

Thanks for the great info sproutco! I switch to 18/6 today.

 

[dre86]

jsut a reminder you'll have to water more frequently now

 

[migraineur]

ok, thanks dre

My babies seem to be a little less droopy after their nap today