Effects of salt and drought stress on the growth, nitrogen fixation and nutrient uptake of black locust (Robinia pseudoacacia L.) provenances

A field study in Iran and a greenhouse study in Germany were conducted to investigate the following hypotheses. The growth parameters of introduced Robinia correlate with the soil properties in arid and semiarid regions of Iran, the provenance of the seeds affects the nitrogen fixation ability of Robinia and the nitrogen fixation ability and nutrient uptake of Robinia decrease under drought and salt stress conditions. To perform the field study, three stands of Robinia were selected in different climatic conditions of Iran respecting to the amount of precipitation, average temperature and elevation. At each study site, three sample plots (20 ×20m) were randomly placed and soil, stem and leaves samples were collected. Also the height, diameter and crown diameter of Robinia trees were measured at each study sites. To assay the seeds provenance effect on the nitrogen fixation and nutrient status of Robinia, the seeds were collected from the four Robinia stands in Iran and Hungary. The collected seeds were grown at the same ecological conditions in greenhouse for six months. All Robinia provenances were subjected to salt and drought stress, two months after preliminary growth. The isotope dilution method was used to investigate nitrogen fixation ability of Robinia provenances under salt and water stressed conditions.