Masuda Jun-ichiro, Ozaki Yukio, Okubo Hiroshi
Laboratory of Horticultural Science, Faculty of Agriculture, Kyushu University, 812-8581 Fukuoka, Japan.
Planta. 2007 Sep;226(4):909-15. doi: 10.1007/s00425-007-0536-9. Epub 2007 May 23.
We examined photoperiodic response of lotus (Nelumbo nucifera) rhizome morphogenesis (its transition to a storage organ) by using seed-derived plants. Rhizome enlargement (increase in girth) was brought about under 8, 10 and 12 h photoperiods, whereas the rhizomes elongated under 13 and 14 h photoperiods. Rhizomes elongated under 14 h light regimes supplied as 8 h of natural light plus 6 h supplemental hours of white, yellow or red light, but similar treatments with supplemental blue, green or far red light, caused enlargement in girth of the rhizomes. A 2 h interruption of the night with white, yellow or red light, in plants entrained to 8 h photoperiod brought rhizome elongation, whereas 2 h-blue, green or far red light night breaks still resulted in rhizome increase in girth. The inhibitory effect of a red (R) light night break on rhizome increase in girth was reversed by a far-red (FR) light given immediately afterwards. Irradiation with R/FR/R inhibited the rhizome increase in girth. FR light irradiation following R/FR/R irradiation cancelled the effect of the last R light irradiation. It was demonstrated that the critical photoperiod for rhizome transition to storage organ is between 12 and 13 h photoperiod. It was also evident that the optimal light quality range for interruption of dark period (night break) is between yellow and red light and that a R/FR reversible reaction is observed. From these results, we propose that phytochrome plays an important role in photoperiodic response of rhizome increase in girth in lotus. This is the first report on phytochrome-dependent morphogenesis of storage organs in rhizomous plants.
我们利用种子繁殖的植株，研究了莲藕（Nelumbo nucifera）根状茎形态建成（向贮藏器官转变）的光周期响应。在8、10和12小时光周期条件下，根状茎加粗（周长增加），而在13和14小时光周期条件下，根状茎伸长。在14小时光照条件下，即8小时自然光加6小时白色、黄色或红色补充光时，根状茎伸长，但用蓝色、绿色或远红光进行类似处理时，根状茎周长增加。在适应8小时光周期的植株中，用白色、黄色或红色光进行2小时的夜间中断处理可使根状茎伸长，而用2小时蓝色、绿色或远红光进行夜间中断处理仍会导致根状茎周长增加。紧接着给予远红光（FR）可逆转红光（R）夜间中断对根状茎周长增加的抑制作用。用R/FR/R照射可抑制根状茎周长增加。在R/FR/R照射后进行FR光照射可消除最后一次R光照射的效果。结果表明，根状茎向贮藏器官转变的临界光周期在12至13小时光周期之间。同样明显的是，用于中断黑暗期（夜间中断）最佳光质范围在黄色光和红色光之间，并且观察到了R/FR可逆反应。基于这些结果，我们认为光敏色素在莲藕根状茎周长增加的光周期响应中起重要作用。这是关于根茎植物贮藏器官依赖光敏色素形态建成的首次报道。
