Mostly, it is due to weather and the direction of sunlight (and due to pests, etc.). Also leaves at the top, those on the outside get more exposed to sunlight and the plant allocates these leaves more chlorophyll for synthesis (hence green). Comparatively, leaves on the inside do not get much sunlight and serve no purpose, so to say. So the plant/ tree sucks the chlorophyll back from these leaves. Now such leaves which do not take part in synthesis can expose the plant to too cold/ too hot weather due to their surfaces area. So the plant/tree sheds them. Of course too severe weather will impact all leaves so in winter etc trees are bare.
I wonder if it's coincidence or not, but I once grew a mango from seed in the US, kept indoors, and it did similarly - grew great for about a year (got to about 2 foot tall), then got sick and died. I wonder if there's something in the US that mango trees arn't used to dealing with?
Very interesting to watch grow though - each set of leaves starting out floppy and purple then stiffening up and turning green, just like the one in the video.
I just planted the whole mango pit as-is, without removing the inner seed, and it had no problem germinating.
Depleted soil leading to -> the margin of the leaves start drying -> so they add hormones or manure -> the plant suddenly experience a "multi branching" event at the end.
I tried to "grow" a couple of mango trees in Switzerland on my balcony, but they all died within 1 or 2 years, I think I burnt one with too much fertilizer, another one due to the weather being too dry and one, I am not too sure but I suspected not enough mineral as it took almost 2 years, I hoped it would grow :(
