松嫩退化草地芦苇不同叶位叶片营养元素代谢特征

Characterization of nutrient elements at different leaf positions in Phragmites australis in Songnen degraded grassland

对松嫩草地不同退化程度样地的芦苇(Phragmitesaustralis)各叶位叶片的生长及营养元素代谢特征进行分析,以探讨土壤盐碱化对芦苇叶片营养元素代谢的影响及其适应机制。结果表明:松嫩草地土壤中Na+含量、全盐含量、pH值是衡量土壤盐碱化程度的主要决定因子,从典型草地到重度退化草地,土壤盐碱化程度逐级加剧。芦苇具有一定程度的耐盐碱性,植株高度和地上部分生物量随土壤盐分增加而降低。检测出10种营养元素:K、Na、Ca、Mg、Fe、Cu、Zn、Mn、P、B,主成分分析结果显示全部样本均处于95%的置信区间内。方差分析结果表明,芦苇不同叶位叶片对营养元素的富集能力有所差异。K、P含量随叶位降低而减少;而Na、Ca、Mg呈现相反分布规律。Fe、Cu集中分布在功能叶和老叶中; Mn只大量聚集在老叶中;而Zn集中分布在幼叶中。表明土壤盐碱化对老叶营养元素的影响大于幼叶, Na在老叶中的大量积累保护了幼叶免于或者减轻离子的毒害。功能叶和老叶中Ca、Mg、Fe、Cu的积累有利于保障芦苇正常的光合作用。盐碱胁迫下幼叶仍维持较高K、P含量,这不仅为幼叶的生长提供所需营养,同时提高了其抗逆性,这可能是芦苇的生理响应策略。

Aims This study was performed to compare the growth and characteristics of nutrient elements at different leaf positions of reed（Phragmites australis） under salinity stress. The adaptive mechanisms by which reeds at a Songnen grassland tolerate salinity stress were determined. Methods Samples were collected from normal grassland, moderate degraded grassland and severe degraded grassland, respectively. Plant height, shoot dry mass, and nutrient elements at different leaf positions of reeds were measured. Important findings The Na^＋ content, total salt content and pH value of soil are important factors that determine soil salinity in the Songnen grassland. The degree of soil salinity was aggravated stepwise from the single dominant reed communities to the reed coexisted with Suaeda salsa communities. Height and shoot dry mass decreased with increased salinity. The profiles of 10 key nutrient elements were measured, namely, K, Na, Ca, Mg, Fe, Cu, Zn, Mn, P, and B. Results from the principal component analysis indicated that all samples were distributed within the 95% confidence interval. The results showed that K and P contents decreased with lowered leaf positions; while Na, Ca, and Mg showed the opposite distribution trends. Fe and Cu contents were less in young leaves than in the other leaves, Mn accumulated in the old leaves. However, a large amount of Zn accumulated in the young leaves. No obvious change in B was observed. Thus, salinity stress produced a small effect on the distribution of nutrients in young leaves, but strongly affected the older leaves. Under salinity stress, old leaves accumulated more Na^＋ to protect the young leaves from ion harm. High accumulation of Ca, Mg, Fe, and Cu in mature and old leaves was more beneficial to maintain and protect the function of photosynthesis. The increased K and P contents in the young leaves could provide the necessary nutrition and improve the salinity resistance of reed. This process contributes to the physiological response strategy of reed under salinity stress.