Limits of the Power of Tissue P Systems with Cell Division

Tissue P systems generalize the membrane structure tree usual in original models of P systems to an arbitrary graph. Basic operations in these systems are communication rules, enriched in some variants with cell division or cell separation. Several variants of tissue P systems were recently studied, together with the concept of uniform families of these systems. Their computational power was shown to range between P and NP ∪ co-NP, thus characterizing some interesting borderlines between tractability and intractability. In this paper we show that computational power of these uniform families in polynomial time is limited by the class PSPACE. This class characterizes the power of many classical parallel computing models.