It is autumn and the leaves have already left their trees on all birch and other trees that has leaves, except one. This birch has a spotlight pointed to the tree and it is on 24/7. I have recognized that this birch have lost almost no leaves. And if we take a closer look at this birch, the back side of the birch, which is faced away from the spotlight have lost a noticeable amount more leaves than the front side which is directly hit by the light from the spotlight.

My conclusion is that having a lightsource pointing to a leafy tree will postpone the time from when it loses its leaves, relative to trees that does not have a lightsource pointerd at them. But I have no idea why this is happening. I do not know anything about trees, leaves, chloryphyll or the reason why trees drops their leaves in the autumn.

If any one is a expert in this field and might know why this is happening, or just have a hypothesis of why this is happening please provide it since I find this really interesting and I can't find anything on Google about this phenomenon.

You can make your anwer as complicated as you wish, I will understand it even if I might need to Google some of the things in the answer :).


  • $\begingroup$ Hi, first of all i higly recomment you to take a tour in our help center. Belive me, this provide you with lots of information about this site including valueble price. About your question if i understod it right you would like know if light source can post pone the deatf of leaves on tree. I higly doubt it. First off all the light source is very dangerous and tricky energy source. So i think it rather be vice versa. $\endgroup$ – L.Diago Oct 22 '18 at 9:48
  • $\begingroup$ Yes, you have understood my question right. The thing is that I have had this spotlight pointed at many different trees under many years, and I always get the exact same result. So I have started to see a pattern. Lets say you have 2 trees, X and Y. If i point the lightsource at X, that tree will lose its leaves much later than other trees of the same species, while Y will lose its leaves same time as all the others trees. If I then switch the lightsource to Y another year, Y will lose its leaves much later than the other trees and X will lose its leaves the same time as the other trees, $\endgroup$ – Jacce Oct 22 '18 at 14:20
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    $\begingroup$ Don't really have time to write out a proper answer, but the basics is: tree's (as well as many other organisms/animals) are able to measure length of a day using light sensitive proteins combined with circadian/rhythmically expressed regulators. This allows trees (etc) to properly regulate physiological functions - like losing leaves - according to the seasons. Since tree/plants are immobile targeting with a big spotlight will confuse their light sensors and disrupt this system (more than for animals which can/will move away at some point). $\endgroup$ – Nicolai Oct 23 '18 at 14:38
  • $\begingroup$ The leaves drop because of the sharp drop in temp. your 'keeping a spot[heat]light on them 24/7'' ,isn't allowing the tree to 'feel' the drop in temp. Therefore keeping it's leaves longer[postponing falltime] .Trees appear to be sensitive to temp.change. I dont believe trees are 'Photosensitive' that applies to cannabis. $\endgroup$ – Lennie T Jan 1 at 3:09

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