Eur.J.Hortic.Sci. 81 (4) 204-211 | DOI: 10.17660/eJHS.2016/81.4.3|
ISSN 1611-4426 print and 1611-4434 online | © ISHS 2016 | European Journal of Horticultural Science | Original article
Effect of photoperiod and temperature on flower induction in three Aizoaceae genera
P. Braun and T. Winkelmann
Leibniz Universität, Institute of Horticultural Production Systems, Hannover, Germany
Midday flowers (Aizoaceae), whose origin and main area of distribution are located in southern Africa, represent the most species-rich family of succulent plants. Because of their intensively colored flowers, a high diversity of growth forms and relatively high tolerance to drought, several Aizoaceae species are attractive candidates for breeding approaches or direct use as ornamental plants. Despite their advantageous characteristics, midday flowers are rarely offered for sale in Central Europe and only a few commercially traded cultivars were developed so far. A wider use of midday flowers as ornamental plants requires intimate knowledge of means to control their cultivation (e.g., control of flowering time), which is underreported up to now. The present study aimed at determining the effects of different photoperiods and temperatures on flower induction in the genera Delosperma, Cephalophyllum and Lampranthus in two separate experiments conducted in controlled environments. Day length could be ruled out as a flower-inducing factor, because flower organs were observed irrespective of photoperiods (16 h, 9 h and 9 h + 2 h night interruption) in genotypes of all three genera. However, only plants cultivated under longday conditions (16 hours of daily exposure to light) had a desirable appearance, which was reflected in significantly higher dry matter contents. Cultivation in climate chambers for several weeks revealed distinct impacts of mean daily temperatures (MDT) on flower formation. The investigated Delosperma genotype tended to develop more flowers at 20°C than in two variants in which the plants were exposed to 14°C MDT. In contrast, cultivation at 14°C MDT resulted in significantly higher flower numbers in two Lampranthus genotypes. High numbers of flowers were found in the investigated Cephalophyllum genotype at both MDTs and significant differences were not detected.
Cephalophyllum, Delosperma, Lampranthus, midday flowers, novel ornamentals, succulent plants
Significance of this study
What is already known on this subject?
What are the new findings?
Flower induction of Aizoaceae species has not been investigated in a horticultural context before. Flower induction is influenced by water availability and temperature in plants of arid South African ecosystems.
What is the expected impact on horticulture?
The investigated genotypes are neither obligate shortday plants nor long-day plants. In Lampranthus, flower induction was stimulated by low-, and in Delosperma by elevated mean daily temperatures.
The study contributes to the development of cultivation schedules and provides information about the feasibility of production of Aizoaceae in Central Europe.
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Received: 8 April 2016 | Accepted: 1 July 2016 | Published: 29 August 2016 | Available online: 29 August 2016