Meeting Abstract
Desert organisms are great for studying adaptive responses to high-stress environments. For example, desert plants must cope with limited water availability, high exposure to solar radiation, and in many cases, with the accumulation of salts into their soils. Saline soils inhibit or even prohibit the growth of plants via ion toxicity and osmotic stress. We investigated the salinity responses of two coexisting desert shrubs, the halophyte Isocoma acradenia and the glycophyte Larrea tridentate, on a slope adjacent to Soda Dry Lake in the Mojave Desert, California, hypothesizing that ion concentrations in these shrubs would be related to the salinity of the surrounding soil. We collected predawn plant and soil samples in 30-40 meter intervals along a belt transect from the dry lakebed up the slope and measured soil conductance and ion concentration in xylem sap and leaves. Conductance was higher in soil associated with Isocoma (mean ± SE: 5447.50 ± 5038.75 µS/cm) than with Larrea (mean ± SE: 90.63 ± 23.13 µS/cm). Isocoma leaves contained about 4× more sodium (mean ± SE: 549.19 ± 19.94 mmol/kg) than potassium (mean ± SE: 133.73 ± 18.75 mmol/kg), and Larrea leaves maintained a 1:1 ratio. Trends were similar in xylem sap, with Isocoma having higher levels of both ions than Larrea. Isocoma may concentrate sodium in leaves or excrete it. It is notable that plants with overlapping distributions have such different ion concentrations. There are no previously described salt-excreting members of Asteraceae, and if Isocoma can be confirmed as such, it will be a new discovery.
