FlytrapCare Carnivorous Plant Forums

All plants increase their rate of photosynthesis as the intensity of the light they receive increases. However, there is a point at which increasing the intensity of the light no longer increases the rate of photosynthesis. This is called the light saturation point. Past this point, more intense light will not make the plant grow faster. This research article tested the light saturation point for several different carnivorous plant species. The PAR values in standard PPFD units are listed in the second column from the right in table 1. You can see that the venus fly trap leaves do not benefit from more than 231 PPFD, and the traps top out at 182 PPFD. Since full sunlight on a clear mid-summer’s day is 2000 PPFD, this means that 12% of full sunlight intensity is the max light intensity a venus fly trap needs for maximal photosynthesis. So if you have a PAR meter, this is great for determining if your flytrap is getting bright enough light during various times of the day for maximal rate of photosynthesis.

That is gold for indoor lighting! Thanks for sharing this.

Your graph is interesting too in that it begins as a nearly linear relationship and then tapers off. So if you only provide half the intensity of the saturation point (which I guess would be about 115 PPFD), the photosynthetic rate is reduced by very little. For indoor lighting that means you could use lights that consume roughly half the power and just run them a little longer to achieve max photosynthesis (assuming VFTs don't need max photosynthesis for X hours and 24-X hours of darkness to be their healthiest.) But then if you halve the intensity again, you lose more than twice of the photosynthetic rate that you lost in the first division and you're down to about half of the potential rate so you'd have to run the lights twice as long to reach the same total output? So it seems you could use this to extremely accurately find that sweet spot of providing max lighting while minimizing the cost of energy, again under the assumption that a lower photosynthetic rate for longer is equivalent for the plants' health.

xr280xr wrote:That is gold for indoor lighting! Thanks for sharing this.

Your graph is interesting too in that it begins as a nearly linear relationship and then tapers off. So if you only provide half the intensity of the saturation point (which I guess would be about 115 PPFD), the photosynthetic rate is reduced by very little. For indoor lighting that means you could use lights that consume roughly half the power and just run them a little longer to achieve max photosynthesis (assuming VFTs don't need max photosynthesis for X hours and 24-X hours of darkness to be their healthiest.) But then if you halve the intensity again, you lose more than twice of the photosynthetic rate that you lost in the first division and you're down to about half of the potential rate so you'd have to run the lights twice as long to reach the same total output? So it seems you could use this to extremely accurately find that sweet spot of providing max lighting while minimizing the cost of energy, again under the assumption that a lower photosynthetic rate for longer is equivalent for the plants' health.

The graphic I posted is just for illustrative purposes. The table in the article I linked is what should be relied on for setting up artificial light. Also, note that the plant may not color-up correctly at these light levels. These light levels just measure photosynthesis. Sligtly more powerful light may be needed for traps to get red on the inside.

I have my fly trap under 350 PPFD and its traps are red on the inside even before they open up. So I am pretty confident that 350 PPFD is more than enough in terms of intensity for both coloring and for growth.

hello ; i think you forgot to mention sth very important :

At the beginning of the protocol they put the CP into the greenhouse and a neutral filter in order to get only 10% of the full sunlight , and then the CP got shade adapted ; hence the quite low light saturation point they measured. [(...) :the irradiance at plant level was ca 10.3% full sunlight (...)]

in an other study about D rotundifolia in situ and indoor they find 400umol/m2/s PPFD saturation point in full sunlight ; wich is quite high compared to the shade adapted plants.

Hence you cant really use the paper you're mentionning if you want to check your PAR level if you give enough light to your CP.

I have a PARmeter and I have to give much light to my droseras (especially D rotundiflolia) in order to have them resume their growth after I put them unintentionnaly into dormancy as the light level I then had was far too low!

Now they get around 300 umol.m-2.s-1 and they are waking up!!

best regards

Chris