Influence of mycorrhizae in geranium irrigated with saline water: agronomic and environmental responses

No information seems to be available on the effect of mycorrhizae on reducing the environmental impact of saline-water irrigation. This study investigated 1) the behaviour of mycorrhizal and non-mycorrhizal geranium plants irrigated with saline water; and 2) the influence of the symbiosis on the leachates and the substratum. Mycorrhizal (Glomus deserticola and Glomus intraradices) and non-mycorrhizal plants of Pelargonium × hortorum ‘Markab’ were grown in pots for three months in a greenhouse and subjected to three irrigation treatments. Each treatment represented an EC salinity level (0.85 dS m-1, control, C; 3 dS m-1, medium salinity, MS; 6 dS m-1, high salinity, HS). The frequency and intensity of mycorrhizal colonization by G. intraradices in geranium roots was greater than colonization by G. deserticola. For increasing salinity levels, ionic uptake in geranium plants (Cl-, Na+ and Ca2+) was greater and accordingly, ionic concentrations (Cl-, Na+, Ca2+ but also K+) were higher in the leached water. The chemical composition of the substratum was significantly modified by salinity. Mycorrhizae increased leaf area and dry shoot weight and the Cl-, Na+ and Ca2+ concentrations found in mycorrhizal plants were smaller than in non-mycorrhizal plants. A decrease in Cl- and Na+ concentration was observed in MS geraniums inoculated with G. deserticola, while G. intraradices reduced Ca2+ and Cl- in HS plants. In leachates, the impact of salinity was mitigated by mycorrhizae, mainly G. intraradices and in the substratum, G. deserticola reduced Na+ concentration in the HS treatment and total limestone in the MS treatment. Based on these results, mycorrhizal inoculation improves the growth of geranium plants under saline conditions and reduces harmful environmental effects caused by salinity.