EFFECT OF ELECTRICAL CONDUCTIVITY LEVELS OF NUTRIENT SOLUTION ON GROWTH, GAS EXCHANGES AND YIELD OF TWO GERBERA CULTIVARS IN SOILLESS SYSTEM

     In order to evaluate the response of two Gerbera cultivars to EC level of nutrient solution, a greenhouse experiment was carried out in Naples from April to November 2002, on 1-year plants fertigated with two EC values, 1.6 dS m^-1 and 2.4 dS m^-1, at pH 6.0. Plants of Brittani and Golden Serena cultivars were grown in pot, on 7:3 mixture (v/v) of peat and perlite. Water and fertilizers were supplied by a drip-system and the number of pulses was 1 per day from April to June and from September to October, 2 per day in July and August, and 3 per week in November. 400 ml of nutrient solution was applied per pulse, whit about 20% of leaching. Gas exchanges were unaffected by EC level of nutrient solution and Gerbera cultivars and higher net photosynthesis (15.02 μmol CO₂ m^-2 sec^-1) was recorded in spring months, with the maximum transpiration rate in may (11.18 μmol m^-2 s^-1). During the 8-month period, daily water uptake was higher in plants fertigated with 2.4 dS m^-1 compared with 1.6 dS m^-1 (471 vs 423 ml per plant), according with the difference in leaf area (65.8 vs 60.4 dm²) and yield (34.3 vs 29.9 flowers). Higher EC level increased the content of N (3.89 vs 3.36% DM), N-NO₃ (0.56 vs 0.39%), P (0.14 vs 0.10%) and K (4.30 vs 2.89%) in young leaves. No difference was found between the cultivars in water uptake and nutrient composition of leaves. Brittani yielded higher number of flowers (35.2 vs 29.1 per plant).

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