I transplanted my lemon tree 2 days ago and I positioned it in the corner without lights. How many days should my tree stay without lights after transplanting?
Who told you that a plant should get no light after being transplanted?
Yes, it is probably not a good idea to put a freshly transplanted plant in direct sunlight outdoors, especially if its a small seedling without enough of a rootball. But if you place a plant in an effectively dark corner, you are submitting it to extra stress. Please put it back to its usual place!
Looking at this lemon tree (a seedling, I presume?), it hasn't recieved too much light in the past anyway. The large, slightly wrinkly leaves are a clear indicator. If possible, you should consider transitioning it to being outdoors during the summer. Just don't put it from next to your sofa straight to direct sun or your plant will get sunburn.