沿海纬度梯度分布红树科植物对温度变化的水力结构和功能响应

Ecologically, mangrove forest are considered as an essential component in protecting adjacent land from wave and storm erosion and are important components of food chains vital to a variety of marine and estuarine communities. Due to climate change, deforestation and so on, mangrove forests decline in area sharply these years. Comparatively, mangroves live in high salinity and high transpiration demand tropical and subtropical intertidal zones, they are exposed to severe tension in xylem so that can be easily suffered from embolism and consequently hydraulic dysfunction. Using the cutting-age optical vulnerability method, our preliminary studies have shown that Bruguiera gymnorhiza has weak xylem cavitation resistance, but how the hydraulic structure of mangrove plants response to the temperature change remains unclear. This project focuses on the xylem hydraulics of mangrove Rhizophoraceae, which distributed in 4 latitude gradient sites across southeastern coastal China. We will test the hypothesis: to adapt to the changing temperature, the hydraulic structure of mangrove Rhizophoraceae species from different site will be different, and the difference of the hydraulic structure could be predicted by changing temperature. When compared to the hot-addicted narrow distributed species, the cold adapted wide distributed species have better plasticity and effectiveness in hydraulic adjustments. Finally, we try to use hydraulic traits as the explanation and prediction for the ecophysiological response and community distribution of mangrove trees. Our aim is to uncover the hydraulic structures and strategies response to the changing climate, which will be a useful tool to predict the adapted response of mangroves, which are important for ongoing efforts to conserve, restore and sustainably utilize mangroves, as well as stimulate future studies of plant hydraulic strategies.

红树林是海岸线防风固沙及为海洋和河口生物提供食物的重要生态系统，因气候变化、人为砍伐等因素，红树林面积锐减。红树生长在高盐、蒸腾拉力大的热带亚热带潮间带，木质部水分运输张力大，可能更易发生气栓，影响水分传导和利用。申请人利用前沿的光学脆弱性曲线测定法，证实红树植物木榄易发生气栓，但红树植物水力结构在响应温度变化的调节机制仍未知。项目以我国东南沿海纬度梯度分布的4个研究点的红树科红树植物为研究对象，测定其木质部水力结构，验证如下假设：各种红树科植物的木质部水力结构特征有差异且与温度相关，且水力结构的变化可被温度变化预测；红树科中的低温广布种较嗜热窄布种水力调节机制有较强的可塑性。目标是利用木质部水力性状解释和预测极端生境红树应对气候变化的生理生态响应。研究结果不仅为预测温度和降雨格局改变红树植物的适应性响应提供理论依据，还为红树植物生物多样性资源的保护和持续利用、及恢复重建提供科学依据。

红树林是海岸线防风固沙及为海洋和河口生物提供食物的重要生态系统，因气候变化、人为砍伐等因素，红树林面积锐减，急需加强对红树植物的研究。项目负责人在该项目实施期间，通过测定红树植物的水力性状，光合和气孔导度，叶片ABA含量，叶片和枝条的解剖特征等生理指标，并分析各指标与其生境的关联，得到如下4个主要成果：.1) 应对干旱时，不同盐分管理策略的红树植物表现出不同的策略，并且抗旱性和光合及气孔调节策略有关。不同种的共生红树气孔调节有ABA依赖和非ABA依赖的。2) 红树植物的根，茎，叶有明显的"脆弱性分区"，即根和叶较茎在干旱时更脆弱。在叶气孔关闭以及根和叶膨压丧失时很窄的水势范围栓塞开始，水力安全边界低。脆弱性和解剖特征之间未发现关联。脆弱性分区可能对限制栓塞从脆弱的根和叶向茎扩散至关重要，脆弱的根系可能是红树在长时间干旱后大面积死亡的原因。3）红树植物适应特殊生境有着特殊的叶片生理性状，如较小的基因组和表皮细胞，以及特殊的表皮细胞，气孔和叶脉之间的协调关系。年均温和盐度对气孔和表皮细胞的可塑性有显著影响，虽然这种影响相较遗传因素较小。4）红树植物适应其胁迫生境有特殊的木质部组成成分，和其它类群植物比较，红树植物有较高的薄壁组织分数和较低的纤维组织分数，而导管组织分数较稳定，无显著差异。当环境年均温和盐度增大，红树植物轴向薄壁组织分数与导管-轴向薄壁组织连接性降低，随着年降雨增大，两者呈增大趋势。导管、纤维和射线薄壁组织等结构无明显变化。低温广布种秋茄和木榄的轴向薄壁细胞表现出较强的可塑性，白骨壤木质部内具有次生韧皮部和连续的形成层的特殊结构可能是使其能够更广泛适应生境的特点。.研究主要解析了红树植物生态适应的特殊生理策略，可为红树植物的利用，保护和恢复提供重要科学依据，并为抗逆植物育种提供借鉴。主要研究结果以项目负责人为第一或通讯作者身份发表于Plant Physiology，Annals of Botany等重要杂志。

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