A study was conducted in a greenhouse, to investigate the effects of arbuscular mycorrhizal fungi (Glomus intraradices), soil salinity and P availability on growth (leaf area and dry weight), nutrient absorption and ion leakage, chlorophyll, soluble sugar and proline content and alkaline phosphatase activity of pepper plants (Capsicum annuum L.). Plants were grown at four levels of salinity (0, 50, 100 and 200 mM NaCl) and two P levels (10 and 40 mg kg-1). Colonisation was 80% to 51% in non-stressed and high salt-stressed plants, respectively. The mycorrhizal dependency was high and only reduced at the higher salinity level. Mycorrhizal plants maintained greater root and shoot biomass at all salinity levels compared to non-mycorrhizal plants, regardless the P level. Interactions between salinity, phosphorous and mycorrhizae were significant for leaf area, root and shoot dry mass. Non-mycorrhizal plants accumulated higher Na and lower K and P compared to mycorrhizal plants. The cell membrane integrity was greater in mycorrhizal plants than in non-mycorrhizal ones. The proline content increases with increasing salt stress and was significantly higher in leaves than in roots. The results indicate that the mycorrhizal inoculation is capable of alleviating the damage caused by salt stress conditions on pepper plants, to maintaining the membranes stability and plant growth, and this could be related to P nutrition.

Este estudo avaliou os efeitos da inoculação de fungos micorrízicos arbusculares Glomus mosseae, Glomus intraradices A4 e Glomus intraradices B1 e duas doses de fósforo (10 e 40 mg kg-1) sobre a colonização radicular, crescimento, absorção de nutrientes e óleos essenciais em Mentha piperita L. O estudo foi conduzido em casa de vegetação no delineamento inteiramente casualizado em esquema fatorial 4x2. Sessenta dias após o transplantio, as plantas micorrizadas apresentaram massa fresca, massa seca, e área foliar significativamente maior em comparação as não-micorrizadas. A inoculação aumentou o teor de P, K e Ca na parte aérea sendo superiores em 40 mg P kg-1 de solo. As plantas cultivadas com 40 mg P kg-1 de solo aumentaram a produção de óleo essencial por planta cerca de 40-50% em relação às cultivadas com 10 mg de P kg-1, independentemente da micorrização. Dentre as espécies fúngicas estudadas, a inoculação com G. Intraradices A4 e com um elevado nível de P, aumentou significativamente o crescimento e rendimento de óleos essenciais em comparação com outras espécies de fungos micorrízicos estudados. Em conclusão, a inoculação dos fungos micorrízicos arbusculares em plantas de hortelã é uma alternativa viável para aumentar a produção de óleos essenciais e reduzir o uso de fertilizantes necessários para a produção econômica de hortelã-pimenta com deficiência de fósforo no solo.

This study evaluated the effects of inoculation with the arbuscular mycorrhizal fungi Glomus mosseae, Glomus intraradices A4 and Glomus intraradices B1 and two phosphorus levels (10 and 40 mg kg-1) on root colonization, plant growth, nutrient uptake and essential oil content in Mentha piperita L. The experiment was carried out in a greenhouse, in 4x2 factorial arrangement, in completely randomized design. At sixty days after transplanting, the mycorrhizal plants had significantly higher fresh matter, dry matter and leaf area compared to non-mycorrhizal plants. The inoculation increased P, K and Ca levels in the shoot which were higher under 40 mg P kg-1 of soil. Plants grown with 40 mg P kg-1 soil increased the essential oil yield per plant by about 40-50% compared to those cultivated with 10 mg P kg-1, regardless of the mycorrhizal treatment. Among the studied fungal species, inoculation with G. intraradices A4 and a high level of P significantly increased plant growth and essential oil yield, compared to the other studied mycorrhizal fungal species. In conclusion, inoculation of arbuscular mycorrhizal fungi into peppermint plants is a feasible alternative to increase the essential oil production and reduce the use of fertilizers required to obtain economic production of peppermint under phosphorus-deficient soil condition.