The Response of the Leguminous Fodder Plant Bituminaria bituminosa to Water Stress

Abstract

Abstract Bituminaria bituminosa (L.) C.H. Stirton (Fabaceae) is a biennial–perennial species, which grows throughout the Mediterranean basin and Macaronesia. It is cultivated to provide livestock fodder and shows promise as a source of furanocoumarins. This is the first report on its physiological and growth responses to water deprivation. We assessed these in a pot assay, in the field and in hydroponic culture, using two populations from southern Spain and two from the Canary Islands. Proline accumulation was much lower in the field than for pot‐grown plants, supporting recent indications that it is phytotoxic under combined drought and heat stress. In hydroponic culture, imposition of water stress by poly(ethylene glycol) increased the root/shoot ratio and decreased the root hydraulic conductivity. Overall, the results show B. bituminosa to be a species with high constitutive resistance to soil water deficit. For example, leaf turgor did not diminish, demonstrating its capacity for osmotic adjustment, and the specific leaf area in field conditions was similar to that of other species adapted to seasonal drought. Notwithstanding, the two Canarian populations (which complete their life cycles under very different conditions) maintained better their relative water content and water potential to avoid internal stress. Famara (Lanzarote, Canary Islands) is the most appropriate as a breeding line, which can maintain its shoot biomass under drought.