Vinterhalter Dragan, Vinterhalter Branka, Motyka Vaclav
Institute for Biological Research "Siniša Stanković", National Institute of Republic of Serbia, University of Belgrade, Bulevar Despota Stefana 142, 11060 Belgrade, Serbia.
Institute of Experimental Botany of the Czech Academy of Sciences, Rozvojová 263, 165 02 Prague, Czech Republic.
Plants (Basel). 2022 Jul 29;11(15):1982. doi: 10.3390/plants11151982.
This study presents the hypocotyl elongation of sunflower seedlings germinated under different light conditions. Elongation was rhythmic under diurnal (LD) photoperiods but uniform (arrhythmic) under free-running conditions of white light (LL) or darkness (DD). On the sixth day after the onset of germination, seedlings were entrained in all diurnal photoperiods. Their hypocotyl elongation was dual, showing different kinetics in daytime and nighttime periods. The daytime elongation peak was around midday and 1-2 h after dusk in the nighttime. Plantlets compensated for the differences in the daytime and nighttime durations and exhibited similar overall elongation rates, centered around the uniform elongation in LL conditions. Thus, plants from diurnal photoperiods and LL could be grouped together as white-light treatments that suppressed hypocotyl elongation. Hypocotyl elongation was significantly higher under DD than under white-light photoperiods. In continuous monochromatic blue, yellow, green, or red light, hypocotyl elongation was also uniform and very high. The treatments with monochromatic light and DD had similar overall elongation rates; thus, they could be grouped together. Compared with white light, monochromatic light promoted hypocotyl elongation. Suppression of hypocotyl elongation and rhythmicity reappeared in some combination with two or more monochromatic light colors. The presence of red light was obligatory for this suppression. Plantlets entrained in diurnal photoperiods readily slipped from rhythmic into uniform elongation if they encountered any kind of free-running conditions. These transitions occurred whenever the anticipated duration of daytime or nighttime was extended more than expected, or when plantlets were exposed to constant monochromatic light. This study revealed significant differences in the development of sunflower plantlets illuminated with monochromatic or white light.
本研究展示了在不同光照条件下萌发的向日葵幼苗下胚轴的伸长情况。在昼夜（LD）光周期下，伸长具有节律性，但在白光（LL）或黑暗（DD）的自由运行条件下则是均匀的（无节律）。在萌发开始后的第六天，幼苗在所有昼夜光周期中被诱导。它们的下胚轴伸长是双重的，在白天和夜间表现出不同的动力学。白天伸长峰值在中午左右，夜间在黄昏后1 - 2小时。幼苗补偿了白天和夜间时长的差异，并表现出相似的总体伸长率，以LL条件下的均匀伸长为中心。因此，来自昼夜光周期和LL的植株可以归为抑制下胚轴伸长的白光处理组。DD条件下的下胚轴伸长显著高于白光光周期下的伸长。在连续的单色蓝光、黄光、绿光或红光下，下胚轴伸长也是均匀且非常高的。单色光和DD处理具有相似的总体伸长率；因此，它们可以归为一组。与白光相比，单色光促进下胚轴伸长。在两种或更多种单色光颜色的某些组合中，下胚轴伸长的抑制和节律性再次出现。红光的存在对于这种抑制是必不可少的。在昼夜光周期中被诱导的幼苗，如果遇到任何自由运行条件，很容易从节律性伸长转变为均匀伸长。这些转变发生在预期的白天或夜间时长比预期延长更多时，或者当幼苗暴露于恒定的单色光时。本研究揭示了用单色光或白光照射的向日葵幼苗发育存在显著差异。
