古在, 豊樹

富士原, 和宏

KOZAI, Toyoki

FUJIWARA, Kazuhiro

[SUMMARY]The net photosynthetic rate and growth of strawberry (Fragaria×ananassa Duch. cv. Houkouwase) plantlets in vitro under photoautotrophic conditions as affected by initial inorganic ion composition (modified Hoagland and Arnon, MHA; Hoagland and Arnon, HA; Murashige and Skoog, MS) and initial total inorganic ion concentration of the medium (20, 40, 60 and 80 mol⋅m-3 for MHA media) were investigated. Three shoots at the rooting stage, each planted on a 0.13×10-4 m3 liquid medium in a cup, were cultured in a 7.5×10-4 m3 cylindrical polycabonate vessel. Concentrations of K+, Mg2+, NH4+, NO3-, H2PO4- and SO42- in 40 mol・m-3 MHA were 1.3, 1.5, 3.0, 1.1, 3.0 and 1.5 times, respectively, those in HA. The vessel with the number of air exchanges of 3.5h-1 had four membrane microporus filters (pore diameter: 0.5μm) . Cultures were maintained in a room for 21 days at 25°C, 70% relative humidity, 2.0 mmol⋅mol-1 CO2, 16 h⋅d-1 photoperiod and 160 μmol⋅ m-2⋅s-1 photosynthetic photon flux density provided by cool-white fluorescent lamps. Net photosynthetic rate per plantlet on day 21 was the greatest in 4.5 mol⋅m-3 with initial phosphorus concentration of MHA and dry weight per plantlet on day 21 was the greatest in 3 mol・m-3 with initial phosphorus concentration of MHA. Fresh weight, percent dry matter, leaf area and transpiration rate per plantlet on day 21 were greater in MHA with initial total inorganic ion concentrations of 40 and 60 mol・m-3 than in HA, MS and MHA with initial total inorganic ion concentrations of 20 and 80 mol・m-3. Forty and 60 mol・m-3 with initial total inorganic ion concentration of MHA and initial phosphorus concentration of 3 and 4.5 mol・m-3 gave significantly enhanced net photosynthetic rate and growth of the plantlet under photoautotrophic conditions.