The low steady‐state basic respiration of iris bulbs (Iris bollandica cv.‘Wedgwood') at 30°C can be enhanced by ethylene. When ethylene is administered continuously a lag period of 4 hours is followed by an increase in the rate of respiration showing two peaks, one after 24 hours and the other after 3 to 4 days. Thereafter, the respiration rate decreases gradually, notwithstanding the presence of ethylene. Concentrations of less than 0.05 microlitre ethylene per litre have no effect, and the maximum effect is observed at concentrations of 3 microlitre per litre and higher. Between 0.2 and 2 microlitre ethylene per litre the peak values of the first maximum are linearly proportional to the logarithm of the ethylene concentration applied.
The characteristics of the respiratory response in iris bulbs are probably similar to those described for potato tubers and non‐climacteric fruits.
Low root zone temperatures in summer stimulate generative development of Alstroemeria, resulting in a higher flower production in winter. The effects of greenhouse soil and air temperatures on vase life and ornamental value were evaluated. Preharvest treatments were two locations (field stations), four air temperatures (9, 12, 15, 18C), four root zone temperatures (11, 14, 17C, uncontrolled) and three varieties ('Flamengo', 'Jubilee', 'Wilhelmina') in a factorial design. The flowers were placed in a commercial pretreatment solution for 24 hours immediately after harvest. After a two day transport simulation and rehydration for 3 hours at 5C, flowers were kept at 1.5 W.m-2 PAR (12hr/day), 20C and 60% RH. The experiment was done three times. Results from the first harvest showed that lowering the soil temperature increased the number of stems that had two whirls of flowers opening after harvest. Average vase life was two weeks. Low air temperatures increased whirl opening as well, and increased vase life by one or two days. Ornamental value and number of flower branches per stem were not affected.
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