Plant material
Cut flowers of several cultivars of hybrid tulips (usually indicated asTulipaspp.) with a stem length of about 50 cm, were
obtained from commercial growers. Flowers were harvested at the
commercial bud stage, i.e. the tepal tips still being closed. Flowers
were cut early in the morning, placed in water and transported in
water to the laboratory at the end of the morning. The transport
took 1–2 h. In the laboratory, the stems were recut in air to a length
of 45 cm. All treatments occurred with flowers which were placed
in glass vials in a climate-controlled room at 20
◦
C, 60% RH and
a photosynthetically active photon flux of 15mol m−2
s
−1(from
Philips TDL 36W/84 cool white fluorescent tubes) from 7 a.m. to
7 p.m. Unless otherwise indicated, flowers were individually placed
in glass vials containing tap water. In some experiments five stems
were used per vial. Experiments used ten replications if flowers
were individually placed in glass vials, whilst five replications were
used in tests in which five flowers were placed in a single vial