Studies on nitrogen metabolism of Terfezia spp. and Tirmania spp.

SUMMARY Species of the truffle fungi Terjezia and Tirmania are widespread in the south of Iraq in association with roots of Helianthemum spp., the dominant plants of the area. The truffle mycelia and ascocarps reduced nitrate at much higher rates than did Helianthemum rootlets, suggesting that absorption of nitrate is particularly enhanced by the fungal symbiont. Measurements of the specific activity of representative enzymes of the ornithine cycle indicated that this cycle was operative in ascocarp tissue and led to the acccumulation of urea. It is suggested that this may serve an osmotic function, assisting spore liberation.