Responses of cucumber grown in recirculating nutrient solution to gradual Mn and Zn accumulation in the root zone owing to excessive supply via the irrigation water

摘要: A standard and a high manganese (Mn) level (10 160 μM) were combined with zinc (Zn) (4 64 in the nutrient solution supplied to cucumber closed-cycle hydroponic units compensate for uptake. The concentrations of all nutrients except Mn Zn identical treatments. objectives experiment establish critical levels both solutions leaves grown hydroponically, assess impact gradual and/or accumulation external on uptake gas exchange, find whether have additive effects when ions are excessively root zone. first symptoms toxicity appeared reached 900 450 mg kg–1 dry weight, respectively. Excessively or/and reduced fruit biomass production due decreases number fruits per plant, as well net assimilation rate, stomatal conductance, transpiration but increased intercellular CO2 levels. Initially, or recirculating rapidly gradually stabilized maximal levels, while corresponding constantly until end experiment. Mg, Ca, Fe, Cu was negatively affected, that K P remained unaffected by combination seems no parameters investigated.