Stomatal size predicts genome size within angiosperms. Correlation is not, however, proof of causality and here our interpretation is hampered by unexpected deficiencies in the scientific literature. Firstly, there are discrepancies between our own observations and established ideas about the ecological significance of stomatal size; very large stomata, theoretically facilitating photosynthesis in deep shade, were, in this study (and in other studies), primarily associated with vernal geophytes of unshaded habitats. Secondly, the lower size limit at which stomata can function efficiently, and the ecological circumstances under which these minute stomata might occur, have not been satisfactorally resolved. Thus, our hypothesis, that the optimization of stomatal size for functional efficiency is a major ecological determinant of genome size, remains unproven.

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The Iranian species of Nepeta were investigated as part of a phylogenetic study of the genus. The relationships among species revealed the status of some taxa including three new species. The new species are recognized by differences in morphology as well as molecular characters. Nepeta balouchestanica, N. mahanensis, and N. hormozganica are described as new and their relationships with closely related taxa discussed.