The Panda subsists on no other plant or food source. Bamboos alone keep them going strong. More on that later. New culms, or shoots, are produced from an extensive rhizome system. There are basically two types of rhizomes'.
Most species exhibit both, to a greater or lesser degree.
Pachymorph rhizomes are very compact. They are associated with autumnal growth and produce a dense clump of culms. Leptomorph rhizomes, associated with spring growth, spread a little more. In other words they are responsible for the lateral growth of a given stand, or clump, of a bamboo species. Knowledge of rhizomes is also necessary for species identification.