Bukit Bandar Raya, Kuala Lumpur, Malaysia.
Bioessays. 2009 Nov;31(11):1211-8. doi: 10.1002/bies.200900078.
The plant maintains a 24-h circadian cycle that controls the sequential activation of many physiological and developmental functions. There is empirical evidence suggesting that two types of circadian rhythms exist. Some plant rhythms appear to be set by the light transition at dawn, and are calibrated to circadian (zeitgeber) time, which is measured from sunrise. Other rhythms are set by both dawn and dusk, and are calibrated to solar time that is measured from mid-day. Rhythms on circadian timing shift seasonally in tandem with the timing of dawn that occurs earlier in summer and later in winter. On the other hand, rhythms set to solar time are maintained independently of the season, the timing of noon being constant year-round. Various rhythms that run in-phase and out-of-phase with one another seasonally may provide a means to time and induce seasonal events such as flowering.
植物维持着 24 小时的昼夜节律，控制着许多生理和发育功能的顺序激活。有经验证据表明，存在两种类型的昼夜节律。一些植物节律似乎是由黎明时的光转变设定的，并与以日出为起点测量的昼夜（时间）节律校准。其他节律则由黎明和黄昏共同设定，并与以中午为起点测量的太阳时间校准。随着夏季黎明时间提前和冬季延迟，与昼夜时间相关的节律会与季节同步发生季节性变化。另一方面，与太阳时间同步的节律独立于季节而保持，中午的时间全年保持不变。随着季节的变化，相互之间同步和不同步的各种节律可能为定时和诱导季节性事件（如开花）提供了一种手段。
