We study regulation of stomatal development and we are interested how environmental fluctuations modify this process at the molecular level. When stomatal lineage behavior is modified this alters not only stomatal numbers, but also numbers of non-stomatal cells. Thus, regulation of stomatal development is essential for formation of a leaf suitable for prevailing environmental conditions and it also impacts plants resource allocation, CO2 uptake and water loss. Our goal is to identify the molecular mechanisms underlying the stomatal developmental plasticity in seed plants.