Influence of root-zone temperature on growth and nitrogen fixation in three Iranian grasspea landraces

In order to study the effects of different root-zone temperature (RZT) and two Rhizobium leguminosarum strains (originating from cold area and temperate area) on some grasspea (Lathyrus sativus) landraces (Ardabil, Shahrekord, and Zanjan) of Iran, an experiment was conducted in a controlled-environment chamber. In this experiment, four root-zone temperatures (5, 10, 15, and 25 degrees C) and a constant air temperature were considered. Results showed that there were differences among the grasspea landraces for nodulation and nitrogen fixation, growth and development, and dry matter. Low RZT reduced growth, nodulation, and nitrogen fixation in grasspea landraces. Strains had different effects on landraces. Inoculated plants with strain originating from cold areas produced the most nodule number, and plant nitrogen concentration at 15 degrees C RZT, whereas inoculated plants with strain originating from temperate area produced the most nodule number, and plant nitrogen concentration at 25 degrees C RZT. Nodulation, nitrogen fixation, and nitrogenase activities of inoculated plants with a strain originating from cold areas in inoculated plants were higher at low temperature than in inoculated plants with a strain originating from temperate areas. This experiment also showed that grasspea production is not likely to be successful when RZT is below 10 degrees C, especially during vegetative development. Therefore, in the zones where soil temperature is greater than 10 degrees C RZT, grasspea landraces have normal growth and produce average yields.