The plant stem is very weak and the plant does not stand up. I have added substrate to the pot to decrease the size of the stem and it can keep in pi by itself. Will the roots raise and use the new substrate, or in that area no roots will develop?
Yes the stem will start sprouting roots where you buried it so they will use that space. It usually takes about 2 weeks but she will grow new roots right out of the sides of the stem.