The white water lily, Nymphaea odorata, is an indicator species for the slough communities of the Everglades. Similar to other emergent aquatic plants, it has a gas flow-through system characterized by a pressure gradient that is controlled by differences in temperature and humidity between the inside and outside of the leaf. This flow-through system has not been completely described in N. odorata, but stomatal control may contribute to this system. The purpose of this study was to quantify stomatal size and density in the navel and lamina of N. odorata and determine if these morphological traits contribute to regulation of the flow-through system. Stomatal density, stomatal size, leaf area, and navel area were measured, in plants contained in high and low water treatments; stomatal measurements were made using compound microscopy and image processing was done with ImageJ software. Stomatal conductance, transpiration and leaf temperature were measured using a steady-state porometer in order to assess differences in gas exchange in different parts of the leaf and with different leaf ages. This study found that there is a large difference in navel and laminar stomata size with navel stomata being 2.4 times larger. There is also a difference in navel and laminar stomata density with laminar stomata being 10.44 times denser. Navel area forms a linear relationship with lamina area but only in the high water treatment. Porometer measurements showed that there were no differences in stomatal conductance, transpiration nor leaf temperature between the navel and lamina nor between old and new leaves. This study demonstrated that although navel and laminar stomata differ morphologically in N. odorata, they do not differ in stomatal conductance.
