The stages of flower bud development sensitive to low and high temperatures for flowering of summer-to-autumn flowering-type 'Iwa-no-hakusen' chrysanthemum (Chrysanthemum morifolium Ramat.)
Nagasuga, K.; Yano, T.; Yamazaki, H.; Inamoto, K.; Yamasaki, A.
Horticultural Research 7(1): 103-109
Effects of temperature at various stages during flower bud development on flowering time and cut flower quality were investigated in summer-to-autumn flowering-type 'Iwa-no-hakusen' chrysanthemum. Plants grown in a plastic green house were transferred to artificial climate rooms at 0, 5, 10, 15 and 20 days after the start of short days, and were grown under control, low or high temperature for 10 days. The artificial climate rooms were maintained at 25/20 degrees C (day/night) for control temperature, and 20/15 degrees C or 30/25 degrees C in 2005 and 17/12 degrees C or 33/28 degrees C in 2006 for low or high temperature regimens, respectively. The stage that was most sensitive to temperature for anthesis was during petal formation and flower budding in 2005. The development of flower bud after flower budding was delayed by high temperature at this stage, and the number of days to anthesis was increased. In 2006, this stage was extended by a more severe low or high temperature regimen before petal fort-nation compared to that in 2005. High temperature during the late stage of involucre formation and late stage of floret formation increased the weight of inflorescence and number of florets, and decreased the percentage of disk florets, resulting in preferable cut flower quality. In conclusion, unstable temperature during petal formation and flower budding contributes to the annual fluctuation in the flowering time of 'Iwa-no-hakusen' chrysanthemurn.