Stomatal clustering in Cinnamomum camphora

Stomata play a crucial role in productivity and survival of land plants by regulating photosynthesis, respiration and transpiration through controlling exchanges of CO2, O2 and water vapour between the interior of the leaf and the atmosphere. Stomatal clusters (groups of two or more stomata that make direct contact) have been found only in a few plant species to data, while stomatal clustering has been found to be a very common phenomenon in Cinnamomum camphora in our observations. The ontogeny of stomatal clusters, their distribution on leaves and their density under different soil moisture conditions were surveyed. The results showed that: (1) the developmental pathway of stomatal clusters is similar to that of loss-of-function mutations in four lips (FLP) mutants that may result in additional divisions of guard mother cells (GMCs); (2) stomatal clustering occurs along the veins, and the leaf bases have the most stomatal clusters; and (3) there is a negative relationship between stomatal cluster density (SCD) and soil moisture (SM). Therefore stomatal clusters are probably able to assist in water conservation.