How do leaf carbon and nitrogen contents of oak hosts affect the heterotrophic level of Loranthus europaeus? Insights from stable isotope ecophysiology assays

Loranthus europaeus is one of the major plant parasites threatening the fragile ecosystems of oak forests in westernIran. The mistletoe is a hemi-parasite plant which grows on forest species, especially oaks. Carbon isotopecomposition (δ13C) has been central to understand the behaviour of mistletoes in the field. This study investigatedC and N isotope compositions in leaves of L. europaeus and of its host oaks (Quercus libani, Q. infectoria andQ. brantii) in western Iran. The goal was to assess the degree of heterotrophy, and to estimate the carbon partitionbetween host and mistletoe and possible consequences of this phenomenon for the ecology of these hemiparasites.Leaf samples from mistletoe and host oaks were collected in the Mirabad forests of Sardasht, Iran.Ten adult trees of each oak species, with the hemiparasite species, were sampled for determination of leaf dryweight and area, concentration in carbon and nitrogen, and contents of stable carbon and nitrogen isotopes. In allthree species, we found that the levels of δ13C of the host, were higher than those of the mistletoes. Quercusinfectoria, with the highest leaf mass per area and the highest carbon and nitrogen contents on a mass basis, wasthe oak species with the highest degree of mistletoe heterotrophy, which was negatively related with the hostmistletoeδ13C difference. Our results also showed that host and mistletoe leaf masses per area can be indicatorsof the heterotrophic degree of the mistletoe and an easy alternative to the determination of δ13C. In conclusion, itseems that the difference in δ13C between host and mistletoe is reduced when the host leaf mass per area, Cmassand Nmass increase. This condition relates to an increased heterotrophic degree of mistletoe. ; info:eu-repo/semantics/publishedVersion