Submitted to: International Conference on Mycorrhizae Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: July 8, 2001
Publication Date: July 8, 2001
Citation: BARROW, J.R., AALTONEN, R.E. UNIQUE ACTIVE INTERNAL MORPHOLOGY OF DARK SEPTATE FUNGAL ENDOPHYTES ASSOCIATED WITH ROOTS OF NATIVE GRASSES AND SHRUBS IN AN ARID ECOSYSTEM. THIRD INTERNATIONAL CONFERENCE ON MYCORRHIZAE. 2001. ABSTRACT NO. P1-69. Technical Abstract: Plants in arid ecosystems are exposed to severe nutrient and drought stress. Mycorrhizal fungi alleviate these stresses in natural ecosystems. Native grasses and shrubs in arid southwestern USA rangelands are more extensively colonized by dark septate fungal endophytes (DSE) than by conventional mycorrhizal fungi. The function of these endophytes is presently unresolved. Roots of grasses and shrubs native to the northern Chihuahuan Desert were stained with sudan IV, specific for lipids, and analyzed with high magnification differential interference microscopy. Unique, atypical extensions of DS fungi were observed that are not visible using fungus specific stains. Their prevalence in physiologically active roots suggested an active phase of DSE. Hyaline hyphae grew both inter- and intracellularly within the cortical cells and sieve elements and varied in visibility. Some hyphae had distinct hyaline walls, while others sin the sieve elements walls were evident only by positive staining of lipids in their vacuoles. These vacuoles were arranged in a typical linear and branched hyphae manner or they were highly irregular in shape. Large 5-8 um, lipid filled, hyphal vacuoles extended from the vascular cylinder through the cortex to the root surface which was coated with mucilage. The substantial lipid accumulation in hyphae extending from sieve elements to the root surface suggested that DSE fungi enhance rhizodeposition of carbon, the formation of a protective mucilage sheath that maintains hydraulic continuity and root function in dry soil.