[chadly]

Do plants have an internal clock? OR do plants adjust to your lighting schedule no matter what span of time you set your lights on?

example:

J has his lights on from 12pm to 10pm ~ 10 hrs

c had his lights on from 6pm to 3am ~ 9 hrs

 

[chadly]

I'm only posting to prove a point because IMO plants just grow in the schedule you give them....

 

[hoppycalif]

We buy plants from Hong Kong or Singapore at times, which are flown here as cuttings to be planted in our time zone. They grow. If plants had internal clocks that should make doing that very difficult.

I'm guessing that you could set your light timer for any 8 hour period during the 24 hour day and the plants would do fine, as long as the aquarium wasn't in bright natural light in the middle of the lights off period.

 

[rjfurbank]

I agree.

I have been running mine for 11 hrs/day with a 5 hr break in the middle (so I can maximize my time at home w/ the lights on) and this has been working well for me.

So it seems the plants can adapt to different lighting cycles. Previously I was running w/out a break and had similar results.

 

[chadly]

yeah, it just didn't seem logical to me.

 

[wiste]

I'm only posting to prove a point because IMO plants just grow in the schedule you give them....

Anecdotal evidence may have practical value but it does not prove anything. Proof by giving examples is not valid.

The fact that plants grow on the schedule that is provided does not necessarily negate the existence of an internal clock. E.g. flowering activities in some plants may be governed by an internal clock.

Observations on a limited set of plants may not apply to all plants.
More study has been made of plants with agricultural applications than have been done with the plants we grow. It is my understanding that the cyclical nature of plants is not fully understood.

My own observations agree with those already stated. Shifting the time that the lights are on does not appear to adversely affect plant growth.

It often rains in the middle of the day in the tropics. So, turning lights off a few hours in the middle of the day would not seem to be that unnatural.