Previous studies have examined the effects of red light (R) on phototropism of maize ( Zea mays L. cv. Royaldent Hit 85) coleoptiles. The R effect on time-dependent phototropism (TDP) was further studied by characterizing its fluence-response relationship. The results showed the R effect was a low-fluence-response, unlike those on pulse-induced phototropisms that show a very-low-fluence-response mode. A subsequent pulse of far-red light (FR) could reverse the R effect. TDP responsiveness, however, recovered as the following FR was extended. The FR-dependent increase in TDP responsiveness was obtained even coleoptiles were pretreated only with FR. It suggested that TDP responsiveness could also be established in response to a FR signal. The fluence-response relationship for the effect of FR was then investigated. The effect of FR depended on the time of irradiation and required high photon fluences. Because reciprocity was invalid at the higher fluence range, the effect of FR would be a high-irradiance-response mode. Relation between phytochrome action modes and possible multiple pathways for phototropic signal transduction was analyzed based on the experiment results.
植物光敏素在玉米胚芽鞘不同类型向光性反应中的作用模式
刘玉军1 赵南明2
（1.北京林业大学生物科学与技术学院，北京100083；
2. 清华大学生物科学与技术系生物膜与膜生物工程国家重点实验室，北京100084）
摘要：先前的研究考察了红光对玉米 (Zea mays L. cv. Royaldent Hit 85) 胚芽鞘向光性反应的影响.本研究进一步分析了红光对蓝光照射时间依赖型向光性(TDP)影响的光量-反应曲线,发现该反应不像红光对脉冲蓝光诱导的向光性的影响那样属于超低光量反应,而是一种低光量反应,且之后的脉冲远红光可以逆转红光对TDP影响的效果.但远红光预处理延长后,逆转了的TDP反应性可以得到恢复.不仅如此,暗适应胚芽鞘接受不同时间的单独远红光预处理后可同样获得与预处理光量成比例的TDP反应性,表明暗适应胚芽鞘在接受远红光预处理后亦可建立起对长时间向光性蓝光照射的反应能力.远红光对TDP反应性影响的光量-反应曲线分析揭示,该远红光影响依赖于照射时间并要求高光量.鉴于高光量范围内上述远红光影响不符合所谓反比定律,远红光对TDP反应性的影响很可能属一高辐照反应.根据上述研究发现探讨了植物光敏素作用模式与不同向光性反应信号转导途径之间可能存在的相互关系.
关键词： 远红光；高辐照反应；向光性；植物光敏素；植物光敏素作用模式；玉米胚芽鞘
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