The Influence of Stock Plant Light Exposure on Optimum Storage Conditions and Rooting Behaviour of Plectranthus coleoides Cuttings

摘要

Mother plants were cultivated under two separate sets of conditions to establish the impact of exposure to different levels of light intensity on the storage and rooting of Plectranthus coleoides cuttings. One set of mother plants was cultivated in aclimate chamber with aphotosynthet-ic photon flux density (PPFD) of 1000 μmol m~(-2) s~(-1) (Halogen HQI) for 12 h a day at a temperature of 20 °C simulating southern latitudes. The other set was exposed to climatic conditions in a greenhouse with an average PPFD of 84 μmol m~(-2) s~(-1) per average daylength of 10.3 h and an average temperature of 16.6 °C simulating Central European conditions. Then, all cuttings were wrapped in polyethylene foil, stored for periods of 3, 4, 5,6,7 or 14 d at temperatures of 1,5 or 12 °C. For rhizo-genese, they were inserted into a propagation substrate (white peat, perlite) and cultivated in the greenhouse at an average temperature of 20 °C and an average PPFD of 88 μmol m~(-2) s~(-1). Damage to shoots was influenced by preharvest light conditions. Cuttings from the climate chamber (1000 μmol m~(-2) s~(-1)) were particularly susceptible to a storage temperature of 5 °C, where they developed damaged shoots in fairly, large numbers, whereas cuttings produced in the greenhouse (84 μmol m~(-2) s~(-1)) were more susceptible to such damage at a storage temperature of 12 °C. Cuttings from both treatments did not differ in regards to rooting percentage when they were stored at 5 or 12 °C. Storage at 1 °C generally resulted in a large number of decayed cuttings during the rooting period, regardless of the preharvest conditions. The experiments demonstrated that exposure to high PPFD during the cultivation of stock plants and the cutting production stage resulted in a pronounced preference of the cuttings for certain storage temperatures. Plectranthus cuttings can be easily stored for 7 d without any adverse effect on quality, but the storage and transport temperatures will have to be adapted to the conditionsunder which the cuttings were produced. Storage and transport temperatures for cuttings produced in southern latitudes under high PPFD should not fall below 10 °C, whereas for cuttings produced under central European conditions in the winter and early spring, a storage and transport temperature of 5 °C is most suitable,