Low temperature effects on the flowering of Chrysanthemum morifolium Ramat
Vince, D.
Jour Hort Sci 35(3): 161-175
1960
DOI: 10.1080/00221589.1960.11513981
Accession: 014098896
A low night temperature of 40-50[degree]F (4.5-10[degree]C) has been found to delay flowering in several varieties of English glasshouse chrysanthemums when compared with 60[degree]F (15[degree]C) throughout. When low night temperatures were given during long days, the delay in flowering was usually accompanied by an increase in leaf number to bud formation. The terminal inflorescence bud frequently failed to develop to anthesis when plants were transferred from low temperatures during long days to 60[degree]F during short days. When low night temperatures were given during short-day induction, the delay in flowering was not usually accompanied by an increase in leaf number to bud formation; an exception was the variety Mayford Crimson. When low night temperatures were given after the bud had become visible macroscopically, little or no delay in flowering occurred. A reduced light intensity during short days markedly delayed flowering; an interaction between light intensity and temperature occurred and, at low light intensity, the leaf number to bud formation was increased by low night temperatures during short-day induction. Light intensity during long days did not affect the time of flowering. Flower diameter was increased by low night temperature and was primarily determined by the temperature after the buds became visible macroscopically. With favourable light intensity and temperature, flower diameter was greater when short-day induction consisted of 14-hour followed by 13-hour photoperiods than when 8-hour photoperiods were given; the former day-length treatment, however, delayed flowering.