Water stress marginally increases stomatal density in <em>E. canadensis</em>, but not in <em>A. gerardii</em>

Abstract

In order to better understand the effects of moisture levels on the balance of C₃ and C₄ prairie plants, we planted two common, co-occurring grass species, Elymus canadensis (C₃) and Andropogon gerardii (C₄), in conditions of adequate water and water stress. In our final harvest, after 27d, water-stressed E. canadensis exhibited marginally increased stomatal density, reflecting an attempt to use water efficiently. There were no significant effects of drought on A. gerardiis stomatal density, indicating that its water use efficiency is naturally high. Neither species root:shoot ratio, height, or biomass showed evidence of adaptation, however. The short time period available for drought-induced adaptation, as well as A. gerardiis low germination rate and prolonged germination period, limited the conclusiveness of our results. Neither grass could adapt significantly to drought within a two-week stress period. But longer studies, on a variety of species, will uncover the differences between, and limits of, adaptations of C₃ and C₄ plants to water stress.