POSITIVE EFFECTS OF ARBUSCULAR MYCORRHIZAL FUNGI ON BIOMASS PRODUCTION, NUTRIENT STATUS AND WATER RELATIONS IN DATE PALM SEEDLINGS UNDER WATER DEFICIENCY

The contribution of arbuscular mycorrhizal fungi (AMF) Glomus clarum (GC), Glomus deserticola (GD), Glomus monosporus (GMO) and Complex Aoufous (CAF) to biomass production and mineral nutrients acquisition was investigated in date palm seedlings subjected to water deficit under greenhouse conditions. Two watering treatments (75 and 25% of field capacity) were applied 4 months (WT1) or 8 months (WT2) after AMF inoculation. Results indicated that water deficiency, WT1 and WT2, reduced shoot dry weight and plant concentrations of P, K, Ca, Mg and Mn both in mycorrhizal and non-mycorrhizal plants. However, under both water stress regimes, AMF plants showed higher nutrient level than non-AMF plants. Highest biomass and nutrient concentrations were recorded in plants inoculated with CAF both in WT1 and WT2. Water relations related to drought tolerance were investigated in non-inoculated and CAF inoculated date palm seedlings. Results showed that under water deficit (25% FC), CAF-inoculated seedlings maintained their RWC content and water potential at a higher level and their cell modulus of elasticity and symplastic water content at a lower level than non-mycorrhized plants. AMF seedlings showed higher (less negative) Ψ_π0 and Ψ_π¹⁰⁰ than non-AMF seedlings both under well watered (75% FC) and water stress (25% FC) conditions. These data suggest that the strategies developed by mycorrhizal date palm seedlings under prolonged water deficit were related to modifications in cell wall elasticity and redistribution of water between apoplastic and symplastic compartments.