风沙流对民勤荒漠灌木幼苗形态特征的影响及其生理生化响应机制

The climate of Minqin desert area belongs to typical continental climate, where rainfall is few, drifting sand current is frequent and desert shrub is main vegetation. However, the natural and artificial shrub communities degrade gradually in recent years. Natural regeneration of these shrubs is unhealthy and lower survival rate of shrub seedling is one of the causes. So, it has important science significance and practice significance to study the relativity between the harm of seedling and its physiological and biochemical response mechanism. Thus, we can understand the drifting sand current is or isn't the limiting factor of vegetation regeneration in arid area. This project will study the changing pattern of morphological characteristics, anatomic structure, osmotic regulation substances, activities of protective enzyme and membrane permeability in the leaves of Haloxylon ammodendron, Sarcozygium xanthoxylon and Calligonum mongolicum under the condition of different intensities, continuously blow time and blow partition time of drifting sand current which is simulated in sand tunnel. In the basis of measured and experiment data, we can analyze the physiological and biochemical response processes and adaptation mechanism of these shrub seedlings under condition of drifting sand current, and infer the causes of death under serious abrasion of drifting sand current, and confirm the quantitative relation between extent of damage and conditions of drifting sand current, to reveal response mechanism of seedlings to drifting sand current and to provide basic data for vegetation recovery in arid area. The research results not only have an important sciences significance to explore response mechanism of shrub seedling in wind-sand environment, but also provide theoretic guidance to raise survival rate of the shrub seedling. But so far, there are lesser literatures about the related research.

民勤荒漠区属典型的大陆性气候，降水稀少，风大沙多，荒漠灌木是该区主要的植被类型。但这些荒漠灌木普遍存在退化、衰败现象，幼苗存活率低是其天然更新困难的主要原因之一。因此，开展风沙流对荒漠灌木幼苗影响的研究对于了解干旱区植被天然更新的关键限制因子具有重要意义。本项目利用风洞模拟不同风沙流输沙强度、不同风沙流持续时间和不同间隔时间，研究不同风沙流胁迫条件下梭梭、霸王、沙拐枣幼苗的形态变化和解剖结构特征，以及有机渗透调节物质含量、保护酶活性和膜透性变化规律，分析这几种灌木幼苗对风沙流胁迫的生理生化响应过程。以上述研究结果为基础，确定幼苗受损程度与不同风沙流条件之间的量化关系，揭示荒漠灌木幼苗对风沙流胁迫的响应机制，从而为干旱区荒漠植被恢复提供基础数据和资料。研究结果对于揭示风沙环境中荒漠灌木幼苗的受损过程和生存机制具有重要的科学意义，同时为改进防风固沙灌木的栽植方式，提高其天然更新率提供科学指导。

我国西北荒漠区风沙天气常年出现，尤其在春季（3-5月）最为频繁，会对植物种子萌发、幼苗生长、枝条萌动和展叶等过程产生不利影响。近年来，风和风沙流对植物的影响得到了研究者们的广泛关注，并开展了相关研究工作。已有报道多侧重于对乔、灌木幼株或成株的研究，而较少涉及风沙流对植物幼苗的影响。荒漠植物种群普遍存在更新不良、幼苗存活率低的特点，但是风沙流对幼苗存活的影响还不清楚。鉴于此，本项目以典型的荒漠植物梭梭、沙拐枣和霸王为研究对象，采用风洞模拟的方法，研究了风沙流胁迫强度和风沙流持续时间对三种灌木幼苗的形态特征、细胞膜脂过氧化、叶绿素、光合作用和叶绿素荧光特性的影响，以及三种灌木幼苗的渗透调节物质和抗氧化酶系统对风沙流干扰的响应机制。结果表明，轻度风沙流吹袭对幼苗形态特征影响不明显，会使其净光合速率略有升高，光系统Ⅱ的光化学量子产量稍有降低；幼苗则通过启动热耗散途径的光保护机制以避免受到光破坏；同时脯氨酸含量升高，渗透调节机制启动；抗氧化酶活性升高或降低，通过不同抗氧化酶之间的协调作用机制，以避免幼苗受到自由基的破坏。随着风沙流吹袭强度的增加或吹袭时间的延长，幼苗同化枝或叶片的气孔关闭；净光合速率下降，水分利用效率下降；光系统Ⅱ的光化学量子产量显著降低，脯氨酸含量降低；此时，幼苗热耗散途径的光保护机制失效，丙二醛含量增加，细胞膜受损，严重者导致幼苗枝叶脱落，甚至死亡。该研究结果在揭示荒漠植物耐受风沙流吹袭机理研究方面具有重要的理论意义，同时在优良耐风沙植物筛选方面具有重要的实际意义。