Morphological adaptations of hot springs panic grass (Dichanthelium lanigunosum var sericeum (Schmoll) to thermal stress

Although growth and productivity of most crops are significantly reduced by exposure to temperatures in excess of 35 °C, some plants thrive in geothermally heated soils characterized by chronic temperatures in excess of 40 °C. The morphological adaptations that enable these plants to colonize thermal environments are poorly understood. We characterized trichome development, silica accumulation, stomatal density, and waxy cuticle development in populations of Dichanthelium lanuginosum var sericeum (Schmoll) isolated from thermal and non-thermal environments to determine whether morphological changes existed in populations adapted to thermal environments. Plants isolated from thermal environments of Yellowstone National Park developed an extensive series of trichomes when exposed to chronic temperatures of 45/35 °C (day/night). In contrast, isolates from non-thermal environments of western Oregon showed minimal trichome development during exposure to the elevated temperatures. Leaves that developed during exposure to elevated temperatures had reduced thickness, though the reduction was less marked in plants from populations isolated from thermal environments. Plants isolated from thermal environments also had greater numbers of stomata on adaxial leaf surfaces relative to biotypes isolated from non-thermal environments. These results suggest phenotypic characteristics that may be useful in selection of new varieties of crop species with improved tolerance to supraoptimal temperatures.