Dear Tsuh Yang: That the broken Veltheima rooted is not surprising, as what you have accomplished is propagated it by scaling, i.e. basal portions of the leaves have rooted. Did you check to see if this is so? If it is you might well be able to separate the 'scales' and end up with numerous plants. Regarding the basal disk, which you say has not done a thing, I doubt if you will get new growth, but you might try giving warmer temperatures, bottom heat would be best, and putting the disc at or even just above the soil, a very sandy mix would be best. Making a couple of notches in the disc might promote the production of growth. Cheers, John e. Bryan