Cytokinins in the root pressure exudate of Citrus jambhiri Lush. colonized by vesicular-arbuscular mycorrhizae

Abstract

The influence of vesicular-arbuscular mycorrhizal (VAM) symbiosis on the transport of cytokinins from the root to the shoot of Citrus jambhiri Lush. seedlings inoculated with cultures of Glomus etunicatum (Becker and Gerd.), G. fusciculatum (Thaxt.) Gerd. and Trappe, or G. mosseae (Nichol. and Gerd.) was investigated. Cytokinins collected from root exudates over a 90-day period were analyzed by high-performance liquid chromatography, mass spectrometry and a bioassay. The flux of cytokinins was independent of root exudate flux. Seedlings inoculated with G. fasciculatum or G. mosseae yielded a greater flux of zeatin, dihydrozeatin and zeatin riboside than non-inoculated seedlings. The flux of zeatin riboside was significantly greater than the flux of zeatin in seedlings inoculated with VAM symbionts. Vesicular-arbuscular mycorrhizal relationships apparently contributed to, or influenced, the export of cytokinins from the root. The elevated cytokinin flux of inoculated seedlings was associated with improved tissue phosphorus nutrition and a significant increase in seedling biomass.