沂沭河流域虉草衰亡期的氮磷富集调控机理研究

Nitrogen and phosphorus enrichment (NPE) capability is an key factor, influencing effects of purifying water for wetland plant. At present, only a few studies has paid attentions to NPE of perennial plant during decline phrase, although it is of ecological significance to reduce nitrogen and phosphorus level in litter and water, and thus avoiding secondary pollution. Phalaris arundinacea is one of the dominant species with strong NPE capability in Yihe and Shuhe river basin ecosystem, and it is of obvious decline phrase in its life history. Therefore, how to evaluate the ecological effects of NPE in P. arundinacea (underground part), is an important scientific problem with theoretical and application value. The project proposed to reveal mechanisms of recycling and enriching nitrogen and phosphorus in P. arundinacea during decline phrase, via investigating changes of compounds degradation, nitrogen and phosphorus contents (total nitrogen, total phosphorus content) and material transportation capacity (key enzyme for active transport, H+-ATPase) in stems and leaves; to verify mechanisms of absorbing and enriching nitrogen and phosphorus in decline phrase, by way of determining root vitality, nitrogen and phosphorus contents and material transportation capacity in underground part of P. arundinacea; to elucidate regulating mechanism of NPE (underground part) in P. Arundinacea, via determining photosynthesis, activities of respiration enzymes (cytochrome c oxidase), botanic hormone content (abscisic acid), and thus providing theory basis for evaluating ecological effect of P. arundinacea during decline phrase, as well as rational exploitation and utilization of P. arundinacea resource.

氮磷富集能力是影响湿地植物水体净化效果的关键因素，但针对多年生植物衰亡期的研究较少。植物衰亡期的氮磷富集（地下部分）对降低枯落物与水体氮磷水平，避免二次污染具有重要生态意义。虉草（Phalaris arundinacea）是沂沭河流域优势物种，富集氮磷能力强，其生活史存在明显衰亡期。如何评价虉草衰亡期氮磷富集（地下部分）的生态效应是一个具有重要理论与现实意义的科学问题。本项目拟通过测定虉草衰亡期茎叶物质降解（叶绿素等）、转运能力（H+-ATPase活性）、氮磷水平（总氮、总磷），探究虉草衰亡期的氮磷回收富集机理；测定虉草衰亡期根系活力、地下部分氮磷水平和物质转运能力等，探明虉草衰亡期的氮磷吸收富集机理；测定虉草衰亡期的光合强度、呼吸代谢酶（细胞色素C氧化酶等）活性和植物激素（脱落酸等）含量，阐明虉草衰亡期氮磷富集的调控机理，为科学评价虉草衰亡期的生态效应及合理开发利用虉草资源提供理论依据。

湿生植物衰亡期氮磷富集是降低其二次污染的重要途径。本项目以沂沭河流域优势物种虉草为材料，采用植物学、植物生理学等方法系统研究其衰亡期氮磷富集调控机理。首先，定量测定了虉草衰亡期不同部位（叶片、茎、根茎和根）生物量鲜重、氮磷含量（总氮，TN和总磷，TP），结果表明虉草衰亡期能富集氮磷，虉草衰亡期单株生物量、单株氮磷总量均无显著差异，根系氮磷富集抵消了衰亡期地上部分衰亡而造成的氮磷损耗。其次，分析了虉草各部位TN和TP动态，以及可溶性蛋白含量、根性形态和活力动态，结果表明虉草衰亡期可通过地上部分物质回收和根系吸收富集氮磷。虉草衰亡期，茎TN、TP和可溶性蛋白含量显著上升；根系生物量、比根重、根TN等显著上升，而TP和根系活力无显著变化。第三，定量检测了虉草衰亡期物质转运、能量供应及氮磷代谢关键酶活性（H+-ATP合成酶；丙酮酸脱羧酶（PDC）、乙醇脱氢酶（ADH）；硝酸还原酶（NR）、谷氨酰胺合成酶等），结果表明虉草衰亡期氮磷富集受能量供应调控，PDC可能为其限制因子，虉草可能主要对无机氮吸收富集，对有机氮转化能力有限。虉草衰亡期各部位H+-ATP合成酶、PDC活性显著下降；ADH、NR显著上升，叶片枯死后保持稳定。第四，测定了虉草返青期物质含量（可溶性糖和可溶性蛋白）动态、物质转化中间物质（丙酮酸、谷氨酸）及关键酶（谷丙转氨酶）活性，结果表明虉草返青期的重要生理过程为蛋白质合成，衰亡期物质积累和返青期的物质转化（可溶性糖与可溶性蛋白）是虉草返青生长的生理基础。虉草返青期可溶性糖含量显著下降，可溶性蛋白、丙酮酸、谷氨酸和谷丙转氨酶活性显著上升。通过以上研究，验证了湿生植物虉草衰亡期氮磷富集调控机理，提出了利用衰亡期生理特征评价虉草生态效能的新思路。这对系统了解虉草生物学特性，评价作为净水植物可行性，合理开发利用虉草资源均具有科学指导意义。