NUTRITION OF Dendranthema grandiflora PLANTS OBTAINED in vitro DURING THEIR ACCLIMATION TO GREENHOUSE

Abstract

Chrysanthemum vitroplants obtained from shoot apices, were grown under greenhouse conditions covered with plastic polyethylene at 50 % of solar radiation and a high relative humidity, and incandescent lamps providing 100 W m^-2 during 4 h at night. During the five weeks of acclimatization two experiments were carried out: in the first, plants were submitted to 15 treatments consisting of five substrate mixtures (100: 0, 75: 25, 50: 50, 25: 75 and 0: 100 of perlite and organic forest soil) and three forms of fertilizing (with no fertilizer; fertilizer with 22.5 g N, 3.35 g P and 31.3 g K per m³ of substrate; and fertigation with 360 mg L^-1 N, 12 mg L^-1 P and 520 mg L^-1 K). Most plants (95 %) became adapted to greenhouse conditions, and the highest growth was obtained in the substrate with the greatest organic matter content, where plants reached 10.5 cm of height, 1.9 mm of stem diameter, 26 leaves and 620 mg of biomass. In the second experiment the plants were established in pots with a 1:1 mixture of sand and vermiculite, and fertigated daily with six levels (1, 25, 50, 75, 100 and 125 %) of the Steiner´s universal solution. All the plants became adapted; those which received the solution at 125 %, with 171.6 mg L^-1 N, 38.3 mg L^-1 P, 393.9 mg L^-1 K, 175.8 mg L^-1 Ca, 26.8 mg L^-1 Mg and 93.1 S, and the plants that received the solution at 1 %, had 5.3 and 4.1 cm of height, 1.9 and 1.7 mm of stem diameter, 18.9 and 9.4 leaves, 27 and 5.9 cm2 of leaf area, 565 and 231 mg of biomass, 2.4 and 1.7 % of N in leaves, and 1.45 and 1.15 mg of chlorophyll g^-1 of leaf fresh weight, respectively.