Effect of photoperiod and temperature on inflorescence appearance and subsequent development towards flowering in onion raised from sets |
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Authors: | Khalid Mahmud Khokhar P Hadley S Pearson |
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Institution: | 1. Vegetable Crops Research Programme, Horticulture Research Institute, National Agricultural Research Centre, Park Road, Islamabad, Pakistan;2. Department of Horticulture, School of Plant Sciences, The University of Reading, Reading RG6 6AS, UK |
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Abstract: | The plants of two onion cultivars Sturon and Stuttgarter were raised from sets and placed in a growth room at 12 °C, a light flux density of 120 μmol m−2 s−1 and a 16 h photoperiod. Cultivar Stuttgarter took 195 days to initiate, whereas time for initiation in cv. Sturon was 201 days. After initiation the plants were transferred to wide range of photo-thermal regimes consisting of six set point temperatures (6, 10, 14, 18, 22 and 26 °C) and four photoperiods (8, 11, 14 and 17 h day−1). An overall mean temperature for all developmental stages under each photo thermal combination was 12.2, 12.4, 15.9, 17.8, 23 and 24.4 °C. Time to inflorescence appearance, spathe opening and floret opening decreased linearly as temperature and photoperiod increased. At low to mild temperatures (12.2–17.8 °C), longer photoperiod enhanced florets per umbel, whereas at higher temperatures (23–24.4 °C), the floret number declined with lengthening photoperiods. As the photoperiod extension in each temperature advanced inflorescence appearance, spathe opening and floret opening and this would be beneficial in a programme to accelerate seed production in onion. |
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Keywords: | Inflorescence initiation Flowering Onion Photoperiod Temperature Seed production |
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