It's possible that it's a fertilizer burn. If they used some kind of pellet fertilizer and it adhered to a wet leaf it might cause a burn like this.

Edit: Also, to answer your question, 5-6 hours of direct sun should be fine. Adeniums can tolerate more, but that should be sufficient. Finally, it appears to have some flower buds, so I wouldn't recommend trying to repot it at this time. Hopefully it will be happy enough to flower for you. If so, what a treat. It took me 2 years to see my first bloom from a seed grown plant.

Hi Arena has the plant been in hot weather as these spots are the same as I get in the middle of summer. the plants sweat a black tar like substance when they get to hot it is not a problem it just looks a little bad Rick is right it needs a repot you should put were you live with your name eg USA, Australia ect so someone in your neck of the woods can advise you on what soil mix to use.

Elena, I have hundreds of those black spots on my plants.

No big harm. Rich got you cover.

Marie

Hello Alena...If you don't do a repot now I would definitely be concerned about those roots being exposed on the surface of the soil. They really need to be covered with a layer of mix in my opinion, they are thin and those that don't delve into the soil will dry out and be if no use whatsoever if you leave them like that. Roots as small as this are designed to be under the soil, in the dark and covered. These are feeder roots and are a totally different concept to when we expose the caudex and larger roots that we want to show off and fatten up.

Gill

Just had another look at the pic,....do you think if could have been grafted? The branch joints with the main stem looks rather odd to me almost as if two scions have been grafted onto the top of the stock plant . Just wondered........

Gill

If it was my plant I would take it out of the pot and inspect the roots for any root rot, then, I would trim the roots a little and repot back in its pot with fresh soil, covering all the feeder roots.

Thank you! I've repotted the plant in some cactus soil (sandy and perlite), though I couldn't get a bigger pot. It might have seemed small due to the roots showing but I was able to bury them nicely and it fit just fine. The roots were all white when I repotted it.