Sharma Vijay Kumar, Bardal Tom Kristian, Johnsson Anders
Chronobiology Laboratory, Evolutionary and Organismal Biology Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore-560 064, Karnataka, India.
Z Naturforsch C J Biosci. 2003 Jan-Feb;58(1-2):81-6. doi: 10.1515/znc-2003-1-215.
The movements of the lateral leaflets of the Indian telegraph plant Desmodium gyrans (L. F.) DC, have earlier been studied in detail with regards to the effects of chemicals, DC currents, and static magnetic fields. In the present paper we have discussed the oscillation of the lateral leaflets under the influence of white light of various light levels (0-75 micromol x m(-2) x s(-1)), produced by an array of LEDs (light emitting diodes). LEDs were used in contrast to fluorescense tubes as in earlier studies in order to minimize changes of wavelength when light intensity was decreased or increased. Furthermore, care was taken to ensure that the temperature in the experimental chamber was constant. When the oscillations were first monitored in bright light, the oscillations were found to be very rapid and with decreasing light intensity the oscillations slowed down. For light levels lower than about 20 micromol x m(-2) x s(-1) the period of the oscillation of the lateral leaflets was almost constant (or even decreased slightly towards complete darkness). We also show that the oscillations could completely stop under prolonged darkness (for longer than about 6 h) and that such halted oscillations could be restarted in most of the leaflets when he light was turned back on. Such stopping of the oscillation of the lateral leaflets in prolonged darkness suggests that these short period oscillations of the lateral leaflets could have a daily component and in natural environment these oscillations could serve the purpose of optimising the amount of light falling on the leaflets or/and facilitating transpiration of water through stomata. Such a finding could have an implication for the answer to the long standing question of adaptive significance of short period oscillation of the Indian telegraph plant Desmodium gyrans (L. F.) DC.
对于印度电报草（Desmodium gyrans (L. F.) DC）侧小叶的运动，此前已针对化学物质、直流电流和静磁场的影响进行了详细研究。在本文中，我们探讨了由一组发光二极管（LED）产生的不同光照水平（0 - 75微摩尔×米⁻²×秒⁻¹）的白光影响下侧小叶的振荡情况。与早期研究中使用荧光灯管不同，此次使用LED是为了在光强降低或增加时将波长变化降至最低。此外，还注意确保实验室内温度恒定。当在强光下首次监测振荡时，发现振荡非常迅速，且随着光强降低，振荡速度减慢。对于低于约20微摩尔×米⁻²×秒⁻¹的光照水平，侧小叶振荡的周期几乎恒定（甚至在接近完全黑暗时略有下降）。我们还表明，在长时间黑暗（超过约6小时）下振荡可能会完全停止，并且当重新打开灯光时，大多数小叶中这种停止的振荡可以重新开始。侧小叶在长时间黑暗中停止振荡表明，这些侧小叶的短周期振荡可能具有日节律成分，在自然环境中，这些振荡可能有助于优化落在小叶上的光量或/和促进通过气孔的水分蒸腾。这一发现可能为长期存在的关于印度电报草（Desmodium gyrans (L. F.) DC）短周期振荡的适应性意义问题提供答案。
