Biol Fertil Soils (2003) 38:170–175 DOI 10.1007/s00374-003-0636-z ORIGINAL PAPER Bhoopander Giri · R. Kapoor · K. G. Mukerji Influence of arbuscular mycorrhizal fungi and salinity on growth, biomass, and mineral nutrition of Acacia auriculiformis Received: 22 March 2002 / Accepted: 22 April 2003 / Published online: 24 June 2003  Springer-Verlag 2003 Abstract The effect of salinity on the efficacy of two arbuscular mycorrhizal fungi, Glomus fasciculatum and G. macrocarpum, alone and in combination was investi- gated on growth, development and nutrition of Acacia auriculiformis. Plants were grown under different salinity levels imposed by 0.3, 0.5 and 1.0 S m -1 solutions of 1 M NaCl. Both mycorrhizal fungi protected the host plant against the detrimental effect of salinity. The extent of AM response on growth as well as root colonization varied with fungal species, and with the level of salinity. Maximum root colonization and spore production was observed with combined inoculation, which resulted in greater plant growth at all salinity levels. AM fungal inoculated plants showed significantly higher root and shoot weights. Greater nutrient acquisition, changes in root morphology, and electrical conductivity of soil in response to AM colonization was observed, and may be possible mechanisms to protect plants from salt stress. Keywords Salinity · Glomus fasciculatum · Glomus macrocarpum · Electrical conductivity Introduction Soil salinity is a problem of grave concern because it adversely affects growth and development of plants especially in arid and semi-arid regions (Apse et al. 1999). About one billion hectares of the worlds land area is not in use due to salinity stress (Jain et al. 1989). In India alone, salinity affects 7 million hectares of land, which is mainly attributed to irrigation with ground water of high salt content, sodic and alkaline parent material (Abrol 1986). Additionally, in arid lands a high evapo- ration rate and insufficient leaching of ions due to low precipitation result in a supra-optimal level of accumu- lation of salts, which render arid and semi-arid soils unproductive (El-Saidi 1997). Excessive salts in soil lower the availability of water, inhibit metabolic process- es and affect nutrient composition, osmotic balance and hydraulic conductivity resulting in stunted growth and productivity of plants (Hopkins 1999; Al-Karaki et al. 2001). Thus, exploitation of soil microbes for utilizing salt stressed lands and saline water is of great importance. Arbuscular mycorrhizal (AM) fungi are ubiquitous among a wide array of soil microorganisms inhabiting the rhizosphere. Symbiotic association of a plant with AM fungi makes them able to access immobile nutrients in nutrient-poor soils (Marschner and Dell 1994). They constitute an important integral component of the natural ecosystem and are known to exist in saline environments where they improve early plant growth tolerance to salinity (Sengupta and Chaudhary 1990; Juniper and Abbott 1993; Aliasgharzadeh et al. 2001). In salt stressed soil, AM fungi are supposed to improve the supply of mineral nutrients to the plants, especially the supply of P as it tends to be precipitated by ions like Ca 2+ , Mg 2+ and Zn 2+ (Azcon-Aguilar et al. 1979; Al-Karaki and Clark 1998; Al-Karaki 2000; Al-Karaki et al. 2001). Besides improving nutrition, AM fungi improve physiological processes, like water absorption capacity of plants by increasing root hydraulic conductivity and favorably adjusting the osmotic balance and composition of carbo- hydrates (Au ge et al. 1986; Rosendahl and Rosendahl 1991). Thus, they mitigate the adverse effects of excess salt accumulated in the root (Dixon et al. 1993). The role of mycorrhizal fungi in salt stress conditions is still inconclusive. A few studies have demonstrated their effect on osmotic adjustment, (Rosendahl and Rosendahl 1991; Giri et al. 1999) but all these studies have been conducted under low salt conditions. The present investigation was conducted to evaluate the effect of the AM fungi Glomus fasciculatum and G. macro- carpum alone and in combination on growth and nutrient uptake under a wide range of salinity conditions. B. Giri ( ) ) · R. Kapoor · K. G. Mukerji Department of Botany, University of Delhi, 110007 Delhi, India e-mail: bhoopg@yahoo.com