Effects of media N content and rhizobial strain on N2 fixation and partitioning in Leucaena seedlings

Research was conducted to examine the effect of Rhizobial race and N fertilization on N2 fixation and N partitioning in seedlings of the genus Leucaena. Seedlings of Leucaena leucocephala (Lam) Dewit variety K-8 and L. retusa Gray variety Yellow Puff were grown in slender tubes filled with fritted clay and watered with nutrient solutions containing 0, 2, or 8 mM nitrate N labeled with 0.1% N15. The seedlings were inoculated with Rhizobia loti race 94A3 or R. logi race 9408. After 12 weeks the plants were harvested and the effects of N fertilization and Rhizobial race on nodulation N2 fixation, and N partitioning were examined. Using the N15-dilution method total N fixed by dinitrogen fixation was determined as well as distribution of fixed versus fertilizer N within the plant. Both Rhizobial races infected both Leucaena species resulting in an effective symbiosis. However, the 2 Leucaena species responded quite differently to N fertilization. The addition of 2 mM N to the nutrient solution effectively eliminated nodulation in L. retusa yet increased both nodulation and N2 fixation in L. leucocephala. The 8 mM N rate eliminated nodulation in both species. Due to the elimination of nodulation and N2 fixation by N fertilization in L. retusa, the effect of N fertilization on partitioning of fixed N was only examined in L. leucocephala. Increasing the N content of the nutrient solution increased the proportion of total N in the shoot and reduced the proportion in nodules. A larger proportion of the fixed N was retained in the root and nodules than fertilizer N. Although the 2 mM N treatment increased the amount of N2 fixed in L. leucocephala compared to the 0 mM treatment, the proportion of fixed N2 was reduced to less than one third of the total N in the plant.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact lbry-journals@email.arizona.edu for further information.Migrated from OJS platform August 202