2.1. Plant material
The plant material used was a garden rose, Rosa hybrida
‘Radrazz’, marketed under the name Knock-Out® (KO). It has a
bushy habit, composed of axes with determinate growth and automatic
flowering. The flower is terminal, solitary, simple and red
(Red Group 45 A, R.H.S. Colour Chart) (Anonymous, 1966). This cultivar
can be easily reproduced through vegetative propagation and
has good resistance to pathogens.
The plants used in both experiments were obtained from cuttings
taken from one-year-old potted mother plants grown in the
greenhouse. Cuttings were taken on 14th January 2010 for Exp.
1 and 18th March 2010 for Exp. 2. Cuttings consisted of a single
internode taken from the middle portion of a stem, bearing a leaf
with five or seven leaflets (Le Bris et al., 1998). They were planted in
plugs (diameter: 35 mm; height: 40 mm) composed of a non-woven
fabric containing a mixture of fine peat and perlite. The rooting
phase took place in a glass greenhouse under a plastic tunnel. The
average temperature was 18 ◦C at night and 22 ◦C during the day,
and the relative humidity was maintained at saturation by a fine
misting system.