Day length vs light intensity

[Moontanman]

In the culture of plants via artificial light I have read in a book on indoor gardening that the day length is not what controls plant growth and flowering but the length of darkness associated with the day is what triggers plant growth.

This opens up the idea of how long does the darkness have to be and how long can the day length be and not affect the growth, maturity, and fruiting of the plants being cultured. 12 to 10 hours of darkness is necessary to trigger the plant growth/flowering/fruiting but would this still work if you used a 12/24 lighting cycle with e day being 24 hours and the night being 12 to 10 hours to trigger fruiting. 

If this is true, and I have researched it a bit and found no real info on this, (it was a rather light search) could a such a day night cycle allow for less light intensity being as effective as a more intense light over less time?   

 

So many trade offs here, I wish i had the ability to experiment with this, I am thinking of a small terrarium in a dark closet but where would you get a timer you could use to make the light cycle? Most if not all commercial timers are based on a 24 hour day length, I'm not sure how to get hold of a timer based on a 36 hour day. 

Any suggestions for a plant small enough to mature in a ten gallon aquarium?  

[swansont]

1 hour ago, Moontanman said:

where would you get a timer you could use to make the light cycle?

There are 7-day programmable timers. You’d only have to reset it once a week. Or do e.g. a 42 hour cycle

I think there are 14-day timers, too

[Moontanman]

1 minute ago, swansont said:

There are 7-day programmable timers. You’d only have to reset it once a week. Or do e.g. a 42 hour cycle

I think there are 14-day timers, too

Thanks, I have done some checking at various local stores and all I could find were timers based on 24 hour days, I'll have to look closer

 

[Sensei]

3 hours ago, swansont said:

There are 7-day programmable timers. You’d only have to reset it once a week. Or do e.g. a 42 hour cycle

I think there are 14-day timers, too

 It would be cheaper and more flexible to buy a $5 Arduino clone.

e.g.

https://www.ebay.com/itm/145160861832

and relay module for $1.5

e.g. https://www.ebay.com/itm/354746987710

You can then control any 110/230-volt electrical system and turn it on or off on demand using a hand-written C/C++ program that you put on the Arduino board. Sample code in the video below. It is very simple.

An 8-channel relay for Arduino costs $6 here, so you can control up to 8 different electrical systems with different parameters.

https://www.google.com/search?q=how+to+use+relay+arduino

e.g.

 

 

Edited March 16 by Sensei

[Sensei]

 

You can purchase an Arduino module with RTC (real-time clock) or even an Arduino clone with built-in RTC or software emulated RTC. ESP8266 has built-in WiFi ($8 cost)

https://forum.arduino.cc/t/setting-the-esp8266-internal-clock/680099

If you keep it online via WiFi, it can automatically update the time.

The ESP8266 is much smaller than a typical Arduino and does not allow external expansion modules to be connected on top of it. For basic work you don't need them anyway.

But there are cool extension modules with built-in SD/SDHC reader/writer with built-in RTC.

This one will work with the ESP8266, because it is not a plug-in from above on the Arduino.

Why you may need it? Writing logs, reading the program, when to turn on the lights or whatever you want to control. Reprogramming via SD/SDHC without touching the C/C++ Arduino source code.

 

 

Arduino with WiFi can be accessed by web browser:

https://www.google.com/search?q=set+up+http+server+arduino

For example, instead of saving SD/SDHC or reprogramming, it can be done from the phone's web browser.

 

[Moontanman]

3 minutes ago, Sensei said:

 

You can purchase an Arduino module with RTC (real-time clock) or even an Arduino clone with built-in RTC or software emulated RTC. ESP8266 has built-in WiFi ($8 cost)

https://forum.arduino.cc/t/setting-the-esp8266-internal-clock/680099

If you keep it online via WiFi, it can automatically update the time.

The ESP8266 is much smaller than a typical Arduino and does not allow external expansion modules to be connected on top of it. For basic work you don't need them anyway.

But there are cool extension modules with built-in SD/SDHC reader/writer with built-in RTC.

This one will work with the ESP8266, because it is not a plug-in from above on the Arduino.

Why you may need it? Writing logs, reading the program, when to turn on the lights or whatever you want to control. Reprogramming via SD/SDHC without touching the C/C++ Arduino source code.

 

Thank you, I think your suggestion might be out of my particular wheelhouse but If I can't figure out a way to turn lights off and on on a 36 hour schedule of 12 hours of dark and 24 hours of light over the course of months this maybe my only recourse.  

[iNow]

4 minutes ago, Moontanman said:

a way to turn lights off and on on a 36 hour schedule of 12 hours of dark and 24 hours of light over the course of months

Buy a smart plug / wall receptacle. Connect it to Alexa similar home automation app. Setup schedule (the bulb and Alexa both do this simply, perhaps as a routine). Then just plug your lights into that  junction with the new smart plug 

[Sensei]

  

8 minutes ago, Moontanman said:

Thank you, I think your suggestion might be out of my particular wheelhouse but If I can't figure out a way to turn lights off and on on a 36 hour schedule of 12 hours of dark and 24 hours of light over the course of months this maybe my only recourse.  

Mechanical analog timer, such as:

 

 

will be a PITA because you will have to rewind the wheel every time the previous cycle ends.... e.g. 48h

The Arduino method will work as long as there is power (if there is no power, the plants also have no light anyway).

 

 

Edited March 17 by Sensei

[iNow]

Edit: It’s even easier. Keep your plain 1960s receptacle and just plug this into it: https://www.amazon.com/Govee-Assistant-Controller-Required-Certified/dp/B08X448XHR/

[Moontanman]

Evidently I have not been keeping up with current tech in this area, I tried to do this about 30 years ago but the timer thing was insurmountable on my budget. 

[Sensei]

33 minutes ago, Moontanman said:

Thank you, I think your suggestion might be out of my particular wheelhouse but If I can't figure out a way to turn lights off and on on a 36 hour schedule of 12 hours of dark and 24 hours of light over the course of months this maybe my only recourse.  

..at least you will have a chance to learn something unknown and have fun.. Plugging in a ready-made solution and voila it's no fun..

 

[iNow]

19 minutes ago, Sensei said:

chance to learn something unknown and have fun.. Plugging in a ready-made solution and voila it's no fun

Alternatively, the fun has been back ended and more time is spent enjoying the outcome you desired instead of grinding along the path needed to get there. 

I’m all for DIY, but sometimes you just want someone else to do it. More time with satisfying ice cream, less time maseraring raw broccolis and tree bark. 

Edited March 17 by iNow

[StringJunky]

9 hours ago, iNow said:

Alternatively, the fun has been back ended and more time is spent enjoying the outcome you desired instead of grinding along the path needed to get there. 

I’m all for DIY, but sometimes you just want someone else to do it. More time with satisfying ice cream, less time maseraring raw broccolis and tree bark. 

If you want to build a house, what's the advantage of moulding your bricks first, is my thought. Also people only have so many hours of free time. Better to spend it on what you want to do.

[Sensei]

35 minutes ago, StringJunky said:

If you want to build a house, what's the advantage of moulding your bricks first, is my thought.

To avoid spending the next 30 years with a home loan?

 

[Moontanman]

5 hours ago, Sensei said:

To avoid spending the next 30 years with a home loan?

 

I have to admit that is a good one! 

[KJW]

On 3/17/2024 at 3:35 AM, Moontanman said:

In the culture of plants via artificial light I have read in a book on indoor gardening that the day length is not what controls plant growth and flowering but the length of darkness associated with the day is what triggers plant growth.

I was reading about photosynthesis in Wikipedia earlier today, and it said that the "dark reactions" (the reactions that in effect reduce CO₂ to simple sugars) do not occur in the absence of light.

 

[Moontanman]

1 hour ago, KJW said:

I was reading about photosynthesis in Wikipedia earlier today, and it said that the "dark reactions" (the reactions that in effect reduce CO₂ to simple sugars) do not occur in the absence of light.

 

What would be your point? 

[KJW]

1 minute ago, Moontanman said:

What would be your point? 

Actually, the reason I chose to read about photosynthesis was because of this thread. I wanted to find out if the dark reactions only occurred in the dark, as suggested by your post. But I found that instead of the dark reactions also occurring in the light, they actually only occur in the light.

 

[Moontanman]

1 minute ago, KJW said:

Actually, the reason I chose to read about photosynthesis was because of this thread. I wanted to find out if the dark reactions only occurred in the dark, as suggested by your post. But I found that instead of the dark reactions also occurring in the light, they actually only occur in the light.

 

I'm not sure what you mean by dark reactions. 

[KJW]

2 minutes ago, Moontanman said:

I'm not sure what you mean by dark reactions. 

Photosynthesis is made up of two sets of reactions: light reactions and dark reactions. The light reactions are associated with the absorption of light to drive the synthesis of two short-term energetic substances as well as the production of oxygen from water. The dark reactions use the two short-term energetic substances from the light reactions to produce sugars from carbon dioxide. The light reactions naturally require light, but the dark reactions do not occur in the dark even though light is not actually used in the dark reactions. Instead, light acts as a regulator of the dark reactions.

What this means is that the synthesis of sugars (or at least those synthesised from carbon dioxide rather than from other sugars) does not occur in the dark. Thus, for growth to occur in the dark, it would seem that the sugars required would have to have already been synthesised during the daytime.

 

[Moontanman]

6 minutes ago, KJW said:

Photosynthesis is made up of two sets of reactions: light reactions and dark reactions. The light reactions are associated with the absorption of light to drive the synthesis of two short-term energetic substances as well as the production of oxygen from water. The dark reactions use the two short-term energetic substances from the light reactions to produce sugars from carbon dioxide. The light reactions naturally require light, but the dark reactions do not occur in the dark even though light is not actually used in the dark reactions. Instead, light acts as a regulator of the dark reactions.

What this means is that the synthesis of sugars (or at least those synthesised from carbon dioxide rather than from other sugars) does not occur in the dark. Thus, for growth to occur in the dark, it would seem that the sugars required would have to have already been synthesised during the daytime.

 

OIC what you are getting at, the dark period vs light period isn't about running photosynthesis in the dark. The length of the night controls hormonal output that controls the growth of the plant and it's seasonal growing, flowering and fruiting. 

My idea that is if the dark length controls these factors, ( I am shooting for 24 hours of day and 12 hours of night) slowly decreasing the length of night should trigger the growth cycle independent of the day length.

At least that is my speculation. 

[KJW]

11 minutes ago, Moontanman said:

OIC what you are getting at, the dark period vs light period isn't about running photosynthesis in the dark. The length of the night controls hormonal output that controls the growth of the plant and it's seasonal growing, flowering and fruiting. 

My idea that is if the dark length controls these factors, ( I am shooting for 24 hours of day and 12 hours of night) slowly decreasing the length of night should trigger the growth cycle independent of the day length.

At least that is my speculation. 

Ok, I'll leave you to it. 🙂

 

[naitche]

If light is not of sufficient strength, the plants will stretch towards the source causing weaker stem growth and greater spacing between leaf nodes, and affect  synthesis resulting in some blanching. I suspect but say can't say definitively that longer 'days' won't alter that.

Stronger light generally results in shorter, more dense and vibrant growth.

Edited March 17 by naitche