Vesicular‐arbuscular mycorrhizas increase chloride concentration in citrus seedlings *

SUMMARY Seedlings of sour orange ( Citrus aurantium L.) and sweet orange ( C. sineusis (L.) Osbeck) were grown in a sandy soil low in phosphorus (P) and either inoculated with Glomus intraradices Schenck & Smith (vesicular‐arbuscular mycorrhizal; VAM) and/or fertilized with soluble KH 2 PO 4 (nonmycorrhizal: NM). Eight‐month‐old VAM and NM seedlings of similar shoot size and P concentration were salinized with 30 and 60 mM NaCl in one experiment for 6 weeks until growth reductions were observed, and in another experiment, seedlings were salinized for 4 weeks before growth reductions occurred. Salinization did not affect colonization by G. intraradices but reduced growth, hydraulic conductivity of roots, and transpiration of shoots. There were no significant growth or physiological interactions between mycorrhizas and salinity which indicates that G. intraradices did not affect salinity stress tolerance of either species. In the first experiment, mycorrhizas increased Cl concentration in shoots and total Cl per plant of sweet orange but not sour orange. NM seedlings fertilized with KH 2 PO 4 , had significantly higher levels of P and K than in VAM plants which may have led to the observed differences in the leaf concentrations of Cl and cations. In the second experiment, VAM plants were also supplemented with KH 2 PO 4 before salinization. This resulted in similar leaf and root concentrations of P, K, and other cations. Root Mn was lower and leaf Cu and root Cu and Zn were higher in VAM seedlings. Salinization negated the mycorrhizal effect on Cu to an extent depending on NaCl level. Mycorrhizas increased Cl concentration in leaves and roots of salinized sweet orange and sour orange in the apparent absence of a P‐nutritional effect.