Description: Plants could be used as bioreactors today, although many aspects of this process are known there are also many physiological changes in plants which remain unknown. In this research Solanum tuberosum L. cv. Kardal used as expression host via Agrobacterium mediated transformation to produce human growth hormone as a model protein. Although expression level was not high but potato plants represented some morphological changes. These plants were thicker and shorter than wild type and transgenic plants expressing different genes or transformed with an empty construct. It seems that human growth hormone could change plant morphology