Field and Laboratory Investigation of Contractile Roots in Agave and Yucca

The goal of this investigation was to examine how certain environmental factors affect root contraction in the genera Agave and Yucca . In the field, the effect of slope on root contraction was examined by measuring Agave deserti, Yucca brevifolia, Hesperoyucca whipplei , and Aloe vera plants established in a common garden on Mt. Fiji (on the Occidental College campus) that included both a flat region and a sloped region. Only Agave deserti showed a highly significant difference in root contraction between the two conditions. The hot, dry conditions on Fiji may have caused the roots of the other species, which are native to slightly cooler, wetter habitats, to dry out and not function properly. In the lab, the effect of exposure to air and light was investigated by measuring Agave mckelveyana, Agave parryi, Agave toumeyana , and Yucca baccata , half of which were planted with the roots covered with soil, the other half with two centimeters of the proximal root region exposed. All species demonstrated a highly significant difference in root contraction between the two conditions. The plants with exposed roots may have contracted and pulled their roots into the soil faster to keep them from drying out and to remain functional