红树植物生物钟预测环境和潮汐变化能力对其光合的贡献及机制研究

The circadian clock increase plants’ fitness and competitiveness by regulating physiological responses to the temporal and spatial changes synchronously. The memorizing and predicting the variations in the environment by circadian clock have gradually been in a hot research in Chronobiology. The physiological activities of mangrove plants grown in the intertidal zone are affected not only by the variation of the environment factors but also by the dynamic fluctuation of the tides, and in most of the time, by both. Our previous study found that the photosynthetic rhythm and stomatal activity rhythm in mangroves are different from both terrestrial plants and (sea) aquatic plant. On this basis, the project aims to study the memory and anticipation of the variations in environment factors and tides by circadian clock and subsequent increase photosynthesis in mangrove plants. Pellacalyx yunnanensis grown in the tropical rain forest will be used as the contrast, several Rhizophoraceae plants grown in the intertidal zone will be selected, and the photosynthetic rhythm in them will be tested. Then, the relationship among the variation of environment factor, the tides and the photosynthetic rhythm will be analyzed based on statistical method and numerical model fitting method, and the contribution of circadian regulation to the increases in photosynthesis will be evaluated. Moreover, to discover the signals input to the circadian clock and the circadian regulations on photosynthesis mechanism, the dynamic changes of the signal substances such as ABA and ROS in the vascular bundles of stem, and the expression of the key clock gene and regulatory factor gene will be analyzed in both roots and leaves. The project implementation will provide theoretical guidance to the conservation and sustainable development of mangrove plants and give new useful data for plant circadian study. Besides, the implementation of the project will contribute to the up and coming field of ecological memory and anticipation.

植物用生物钟调控生理活动与外界时空环境同步而增强适应和竞争能力。生物钟环境变化记忆和预测功能近来成为时间生物学的前沿和热点问题。海陆潮间带红树林植物生理活动既受昼夜有规律更替的环境因子的影响，也受节律性动态潮汐的影响，而这两种影响又常交织在一起。我们初步研究发现，与已有报道相比，红树植物光合碳同化和气孔开闭运动生理节律有别于内陆植物，也不同于(海)水生植物。在此基础上，项目以热带雨林山红树为对照，设置现场测定和温室栽培模拟实验，用数理统计和模型拟合方法，弄清潮间带红树植物生物钟对日节律和潮汐节律的记忆、预测能力及对光合贡献程度。为揭示日节律和潮汐节律通过生物钟调控光合作用的途径、方式和机制，项目也拟监测根、叶微管组织信号物质动态和核心钟基因及调节因子表达动态。项目实施为红树林保育恢复及可持续发展提供直接理论指导，为植物生物钟研究提供新资料、新认识，也有助于记忆生态、预测生态新兴学科的繁荣。

生物通过生物钟调控自身生理活动适应时空环境的规律性变化，从而增强生存和竞争能力。植物生物钟对环境变化的记忆和预测功能近年来引起广泛关注，成为生物学诸多分支学科研究的热点。光合作用是植物最重要的生理活动，也受生物钟调控。项目以海陆交汇的潮间带特殊生境内生长的红树林红树科植物中的红树属、角果木属、秋茄属和木榄属为主要材料，以内陆热带雨林生境红树科山红树属和丘陵生境竹节树属为参照，设置潮间带原生境实验，同时辅以温室大棚栽植，人工模拟潮汐等综合实验，研究其光合作用在昼夜节律和潮汐节律共同影响下的生理特征及机制。与已有报道相比，项目取得下述核心发现：1）红树植物生物钟对光照等环境因子及潮汐状况有明显的预测和记忆功能，周期性潮汐改变了红树植物的光合节律，潮汐因子的影响更甚超过其它环境因子的作用，可能是红树植物能够在潮间带生存的关键机制之一；2）周期性潮汐不但改变了潮间带红树植物光合碳同化和气孔节律，对电子传递、光化学效率和热耗散等光反应特性的节律也有明显影响；3）红树植物水上叶片光合碳同化能力随着潮汐的上涨逐渐提升，在潮汐涨至最高潮位前光合能力达到峰值，而随着潮汐的下降，光合能力也下降，潮水降至最低位时，部分植株更甚测不出净光合速率；4）不同于已经报道的陆生高等植物，潮间带红树植物的气孔特性明显保守，即使在环境因子和潮汐都处于比较良好的环境条件下，气孔也不完全打开，并且光合诱导时间明显偏长，有时更甚超过2小时才能达稳态光合；5）红树植物根系、叶片生物钟及光合关键基因的表达有明显的时空差异，且受动态潮汐的直接影响；微管组织中的过氧化氢、细胞分裂素、还原型谷胱甘肽和脱落酸是地下和地上组织器官长距离交换潮汐信息的主要媒介物质。这些研究结果为红树林保育恢复及可持续发展提供了直接理论指导，为植物生物钟研究提供了新资料、新认识，红树植物生物钟理论的拓展也有助于记忆生态、预测生态新兴学科的繁荣。

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