干旱半干旱地区生物结皮层藓类植物氨基酸和营养物质组成特征及适应性分析

Study on moss: the content of amino acid, the feature of nutritive elements and its resistance to draught in the biotic crusts in arid and semi-arid regions

通过对生长在干旱-半干旱地区的藓类体内的氨基酸组成及含量变化、营养元素含量变化和可溶性糖含量变化及藓类结皮土壤相应营养元素含量变化的分析,以揭示藓类的营养组成特征及对环境的适应性机制。研究样地选择在内蒙古鄂尔多斯高原的典型草原区和宁夏腾格里沙漠南缘的草原化荒漠区。通过实验,从藓类植物体内检测出17种氨基酸,表明其体内的氨基酸组成大部分与高等植物相同,其中天门冬氨酸、谷氨酸、丙氨酸、亮氨酸和精氨酸的含量最高,约占总氨基酸的50%。脯氨酸含量在所有氨基酸中处于较低水平,平均只占氨基酸总量的3.12%。草原化荒漠区与典型草原区分布真藓平均总氨基酸含量均大于土生对齿藓,两地区间真藓有10种氨基酸(包括脯氨酸)含量有显著性均数差异(p<0.05),而土生对齿藓只有脯氨酸有显著性差异(p<0.05)。赖氨酸、精氨酸含量在两个地区各种藓类体内有相对稳定的含量,没有显著差异,而脯氨酸的含量在同一地区没有显著的差异,但在不同地区却有显著性差异。藓类体内营养元素显著高于结皮层土壤,表明苔藓植物有很强的元素富集能力,其中N含量最高,P含量最低。不同种类植物体内营养元素Ca、Mg、K的含量存在差异,表明藓类植物对金属营养元素有很强的选择吸收能力。元素相对利用能力(植物/土壤),K最大,P最小,Ca、Mg因种类不同存在差异。N/P比率在草原化荒漠区分别为真藓10.25,刺叶赤藓13.59,土生对齿藓15.78;在典型草原区分别为真藓11.91,土生对齿藓10.55,盐土藓11.37,可知N、P在干旱区不是藓类植物生长的限制因子。元素之间的相关分析表明N和P,Ca和Mg明显相关(p<0.05),而K和Ca、Mg之间则显著负相关(p<0.01),表明K和Ca、Mg之间存在制约关系。可溶性糖和脯氨酸含量分析表明,随降雨量增加二者含量明显呈现递减趋势,说明脯氨酸、可溶性糖的含量与苔藓植物的抗旱性有一定的关系。

The research of mosses usually focuses on how they adjust themselves to the arid environment and on how the nutrients vary within the mosses. The study takes moss crust soils and mosses which grow in arid and semi-arid regions as research materials to explore the mechanism by researching upon the component changes of amino acid of mosses growing in different regions, upon their nutritive elements and soluble sugar changes and upon moss crust soil nutritive elements. Two of research regions are selected, one is in the typical steppe region in Erdos Plateau, Inner Mongolia. The other is in the steppe desert in southern edge of Tengger Desert, Ningxia Hui Autonomous Region. An experimental analysis reveals that seventeen types of amino acids found in mosses plants were mostly similar to the components in higher plants, aspartic acid (Asp) , glutamic acid (Glu), leucine (Leu) and arginine (Arg) were large in amount, accounting for 50%. The lowest content has been determined for cystine and the highest for Glu. The amount of proline (Pro) was also low, averaging 3.12%. Bryum argenteum distributed in steppe desert region had a significant difference (p<0.05) in the amount of ten types of amino acids (including proline) with comparison of those distributed in steppe, while only Pro in Didymodon vinealis had significant difference (p<0.05). B. argenteum distributed in steppe desert region had a significant difference (p<0.05) in the amount of seven types of amino acids with the comparison of D. vinealis in the same region and fourteen types in steppe, and all of this indicated that the contents of amino acids in B. argenteum were more likely to vary than those in D. vinealis with the change of environmental factors. The amount of lysine (Lys) and Arg in various species of mosses in different regions was at the same and relatively stable level, but the amount of Pro was similar within one region and differed greatly in different regions. The average of total amount of amino acids in B. argenteum was higher than that in D. vinealis. An analysis of nutritive elements of moss plants and crust soils showed that mosses had a strong ability to concentrate nutritive elements with the highest N and lowest P in amount, and the amount of nutritive elements of Ca, Mg and K varied in different mosses, which showed that mosses had a strong ability of choosing and absorbing. Ca was more easily concentrated owing to its higher ability of the cation exchange. Plant/soil accumulation ratios are an important tool in understanding the relative availability of elements to plants. The lowest accumulation ratio has been calculated for P and the highest, for K, whereas Ca and Mg varied in different mosses, and in most mosses in this experiment, accumulation for Mg was higher than accumulation for Ca. It showed that the relative availability of Mg was higher than Ca in mosses in arid and semi-arid regions where soil is of great Ca concentration. Favorable ratios for vascular plants are considered to lie between 10 and 14, while ratios>16 indicate P-limited growth conditions in community level. N:P-ratios is 10.25 in B. Argenteum in our experiment in steppe desert, Syntrichia caninervis 13.59, D. vinealis 15.78, and N:P-ratios is 11.91 in B. Argenteum in typical steppe, D. vinealis 15.78,Pterygoneurum subsessile 11.37. N and P were not the N-limited and P-limited factors in mosses growing. The relative element analysis displayed that the correlated relation between N and P was a significant correlation and the correlated relation between Ca and Mg was significant too (p<0.05). The relation between K and Ca, Mg was a negative correlation (p<0.01), which showed that the relation of K to Ca and that of K to Mg were restrictedly related. An analysis of soluble sugar and Pro showed that with the increase of rain, the amount of the both apparently tended to decrease, which had something to do with the resistance to draught.