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Astrid Kubatsch, Heiner Grüneberg, and Christian Ulrichs

Schefflera arboricola was held in light- and temperature-controlled chambers for 6 months under three light intensities of 10 μmol·m–2·s–1, 20 μmol·m–2·s–1, and 80 μmol·m–2·s–1 measured as photon flux density (PFD). Plants also received three temperature regimes: 15 °C, 20 °C, and 25 °C. Reduced light intensity significantly decreased fresh and dry weight and increased chlorophyll content, but did not affect leaf thickness and palisade and spongy mesophyll parenchyma. High temperatures reduced fresh weight and significantly increased chlorophyll content and leaf thickness. The authors conclude that reduced photosynthetic energy flow at low light intensities (10 μmol·m–2·s–1, 20 μmol·m–2·s–1) could not be buffered by a downregulation of energy-consuming processes. Therefore the life span and quality of S. arboricola is reduced at such PFD values, especially at higher temperatures. Plants lose their marketability within 6 months.

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Luise Ehrich, Christian Ulrichs, and Heiner Grüneberg

Because South African Iridaceae have a high potential as new floricultural crops, four spring-flowering geophytic species originating in the Cape Floral Region were investigated. A total of 900 corms for each Freesia laxa, Sparaxis ×tricolor, Tritonia deusta, and Tritonia securigera were exported from South Africa during dormancy in 2 subsequent years. Experiments in Berlin, Germany, focused on storage conditions after export and different temperature and light intensity regimes for forcing, in particular their effect on plant habit, inflorescence induction, and flowering success. The results showed that after export, dormancy could be further maintained in storage at temperatures above 20 °C. Temperature was found to be the main criterion to successfully realize flowering after planting; cultivation at 13 °C at night was essential with temperatures of 17 °C and above possible during the day. During summer months, the failure of inflorescences in the terminal bud to develop completely, or the abortion of flower primordia within the corms, was the result of the high temperatures present. Also, low natural light levels during fall months could be linked to flower abortion of the investigated species. However, the results indicate that if forced as pot plants for the European fall and winter, the low temperature requirements of the investigated species during cultivation could represent substantial energy savings for future growers.