Abstract Membrane systems with dividing and dissolving membranes are known to solve PSPACE problems in polynomial time. However, we give a P upperbound on an important restriction of such systems. In particular we examine systems with dissolution, elementary division and where each membrane initially has at most one child membrane. Even though such systems may create exponentially many membranes, each with different contents, we show that their power is upperbounded by P. 1

[5] H. Peng, J. Wang, M.J. Pérez-Jiménez, P. Shi. A novel image thresholding method based on membrane