The leaves on my avocado plant are drooping, the difference is, mine is still in the water cup I used to pop the seed. I was waiting to see wilting or burn on the leaves to indicate the time for transplant but the leaves are still green and there is new growth. however, this last week the leaves are drooping and looking sad. It's kept indoors near heat and I use blue spectrum LED grow lamps (Nov in washington). Possible problems: Time to transplant? too much light? I often leave it 24hrs/day algae or fungus? its kinda slimy down there at the roots. I refreshed the water a couple times but no help this time. Could it be the tap water? should I use distilled or bottled water? Help! I am several months into this thing. Thanks
Gus, my guess is that at some point your roots ran out of oxygen in the water. Here's a story - you have a fixed amount of water and suppose it is well oxygenated, unlikely but possible. While the plant root volume is small the air lasts a long time, but as the roots grow larger they eat that O2 at an accelerating rate. Then a point comes where there is no more and root tissue starts to die. When this happens in soil there are various organisms in the soil to help deal with that situation, but in plain water you are out of luck.
If this is right, and be aware there might be alternative narratives, the conclusion is to get the plant into fresh aerated and watered soil ASAP. We know that due to its soft leaves the avocado can get out of balance with its roots very quickly, so no delays. It might look sad for a while, but treat it well with moist but not wet soil and you might come out on the sunny side. Try very hard to do as little damage as possible to the root system when you transfer.