Heide Ola M.
Department of Biology and Nature Conservation, Agricultural University of Norway, PO Box 5014, NO-1432 As, Norway.
Physiol Plant. 2004 Feb;120(2):298-302. doi: 10.1111/j.0031-9317.2004.0228.x.
Echinacea purpurea cv. Bravado and Magnus have been reported to be intermediate daylength plants (IDP) which flower in response to photoperiods between 13 and 16 h. The present experiments with E. purpurea cv. Bravado show that E. purpurea is actually a dual induction short-long-day plant which flowers promptly and consistently when grown in short day (SD) followed by long day (LD) conditions, but not with the reverse sequence of photoperiods. The flowering response increased with increasing duration of both the SD and the LD treatments. A minimum of 4 weeks of SD followed by 12 LD was required for complete flowering. No flowering occurred in continuous SD or LD, whereas a high proportion of plants flowered in continuous 14-h daylength. However, flowering was more variable in intermediate daylength than after transition from SD to LD. Furthermore, photoperiods between 13 and 16 h could satisfy both the primary SD induction and the secondary LD induction requirements. As a number of dual induction plants, both short-long-day and long-short-day plants, have such an overlapping window of effective photoperiods that can trigger both the SD and LD responses, the rationale for maintaining IDP as a separate and genuine flowering response group is seriously challenged.
据报道，紫锥菊品种Bravado和Magnus属于中日长植物（IDP），它们在13至16小时的光周期下开花。目前对紫锥菊品种Bravado进行的实验表明，紫锥菊实际上是一种双重诱导的短-长日植物，当在短日（SD）后接长日（LD）条件下生长时，它能迅速且一致地开花，但光周期顺序相反时则不能。随着SD和LD处理时间的延长，开花反应增强。完全开花需要至少4周的SD处理后接12个LD。在连续的SD或LD条件下均未开花，而在连续14小时日长条件下，很大比例的植株开花。然而，在中日长条件下开花比从SD过渡到LD后更具变异性。此外，13至16小时的光周期既能满足初级SD诱导需求，也能满足次级LD诱导需求。由于许多双重诱导植物，包括短-长日和长-短日植物，都有这样一个重叠的有效光周期窗口，能够触发SD和LD反应，因此将IDP作为一个独立且真正的开花反应组的合理性受到了严重挑战。
