Dias, T., Martins-Loução, M.A., Sheppard, L. & Cruz, C. (2015) Plant tolerance of ammonium varies between co-existing Mediterranean species.Plant and Soil, 395(1), 243-252. DOI:10.1007/s11104-015-2552-z (IF2015 2,969; Agronomy)
Previous studies showed that the two main Mediterranean plant functional groups, summer semi-deciduous and evergreen sclerophylls, differ in soil characteristics and nitrate (NO3−) use strategies: even though summer semi-deciduous plants have higher NO3− availability than evergreen sclerophylls, NO3− reduction (i.e., nitrate reductase activity-NRA) is lower, and is not stimulated by substrate (NO3−) availability.
Test if in Cistus albidus plants, a summer semi-deciduous species, ammonium (NH4+) can inhibit NRA, despite the availability of NO3− , and whether Olea europaea plants, evergreen sclerophyll, are more tolerant of NH4+ than the former.
One-year-old C. albidus and wild O. europaea potted plants were supplied with both NH4+ and NO3− at increasing levels (0.1; 0.2; 0.4; 0.8 and 1.6% N). Tolerance of NH4+ was evaluated using integrative (mortality and biomass accumulation) and plant nitrogen metabolism parameters (in vitro NRA and concentrations of NO3− and NH4+) determined in roots and leaves.
C. albidus plants were consistently less NH4+ tolerant than O. europaea, displaying: higher mortality; growth and NRA inhibition and NH4+ accumulation above 0.2% NH4NO3-N in the soil. In contrast, O. europaea plants seemed to buffer the full range of tested NH4NO3 levels.
C. albidus plants were less NH4+ tolerant than O. europaea. The ecological implications of this contrasting NH4+ tolerance are discussed.