水分胁迫下AM真菌对沙打旺生长和抗旱性的影响

利用盆栽试验研究了水分胁迫条件下接种AM真菌对优良牧草和固沙植物沙打旺(Astragalus adsurgens Pall.)生长和抗旱性的影响。在土壤相对含水量为70%、50%和30%条件下,分别接种摩西球囊霉(Glomus mosseae)和沙打旺根际土著菌,不接种处理作为对照。结果表明,水分胁迫显著降低了沙打旺植株(无论接种AM真菌与否)的株高、分枝数、地上部干重和地下部干重,并显著提高了土著AM真菌的侵染率,对摩西球囊霉的侵染率无显著影响。接种AM真菌可以促进沙打旺生长和提高植株抗旱性,但促进效应因土壤含水量和菌种不同而存在差异。不同水分条件下,接种AM真菌显著提高了植株菌根侵染率、根系活力、地下部全N含量和叶片CAT活性。土壤相对含水量为30%和50%时,接种株地上部全N、叶片叶绿素、可溶性蛋白、脯氨酸含量和POD活性显著高于未接种株;接种AM真菌显著降低了叶片MDA含量;接种土著AM真菌的植株株高、分枝数、地上部和地下部干重显著高于未接种株。土壤相对含水量为30%时,接种AM真菌显著增加了地上部全P含量和叶片相对含水量;接种摩西球囊霉的植株株高、分枝数、地上部和地下部干重显著高于未接种株。水分胁迫40d,接种AM真菌显著提高了叶片可溶性糖含量。水分胁迫80d,接种株叶片SOD活性显著增加。菌根依赖性随水分胁迫程度增加而提高。沙打旺根际土著菌接种效果优于摩西球囊霉。水分胁迫和AM真菌的交互作用对分枝数、菌根侵染率、叶片SOD、CAT和POD活性、叶绿素、脯氨酸、可溶性蛋白、地上部全N和全P、地下部全N和根系活力有极显著影响,对叶片丙二醛和地下部全P有显著影响。AM真菌促进根系对土壤水分和矿质营养的吸收,改善植物生理代谢活动,从而提高沙打旺抗旱性,促进其生长。试验结果为筛选优良抗旱菌种,充分利用AM真菌资源促进荒漠植物生长和植被恢复提供了依据。

Effects of AM fungi on the growth and drought resistance of Astragalus adsurgens Pall. under water stress

Astragalus adsurgens Pall. is an excellent grass and sand-fixing plant. The paper mainly studied the effects of AM fungi on the growth and drought resistance of A. adsurgens subjected to water stress using pot experiments. The experimental design included three levels of water regimes (70%, 50%, and 30% of soil relative water content) and three inoculation treatments (uninoculation, control; inoculation with Glomus mosseae; inoculation with indigenous AM fungi of A. adsurgens rhizosphere). The results showed that water stress significantly (P<0.05) inhibited the growth of A. adsurgens such as plant height, number of branches, shoot dry mass and root dry mass whether inoculated with AM fungi or not, and significantly (P<0.05) increased indigenous AM fungal infection rate, but infection rate of G. mosseae was not affected by water stress. The treatment inoculated with AM fungal promoted growth of A. adsurgens and strengthened drought resistance of host plant, whereas the contribution extent varied with fungal species and soil water content. Under different water regimes, AM fungi inoculation significantly (P<0.05) increased mycorrhizal infection rate, root activity, root total N content and leaf CAT activity. Under 30% and 50% water treatments, Shoot total N content, leaf chlorophyll, proline, soluble protein content and POD activity were significantly (P<0.05) enhanced, and leaf malondialdehyde (MDA) content was significantly (P<0.05) decreased for mycorrhizal plants, plant height, number of branches, shoot dry mass and root dry mass of plants inoculated with indigenous AM fungi were significantly (P<0.05) more than those of non-mycorrhizal plants. Under 30% water treatment, shoot total P and leaf relative water content of mycorrhizal plants were significantly (P<0.05) improved compared to non-mycorrhizal plants, while plants inoculated with G. mosseae had significantly (P<0.05) higher plant height, number of branches, shoot dry mass and root dry mass than non-mycorrhizal plants. After 40 days of water stress leaf soluble sugar content of mycorrhizal plants was significantly (P<0.05) increased. Leaf SOD activity of mycorrhizal plants was significantly (P<0.05) higher than that of non-mycorrhizal plants after 80 days of water stress. Mycorrhizal dependency increased with the extent of water stress increasing. The effects of indigenous AM fungi on the growth and drought resistance of A. adsurgens were superior to those of G. mosseae regardless of soil water content. The interaction between water stress and AM fungi significantly (P<0.01) affected number of branches, mycorrhizal infection rate, leaf SOD, CAT and POD activities, content of leaf chlorophyll, proline and soluble protein, total N and total P content of shoot, root total N content and root activity, and significantly (P<0.05) affected leaf MDA and root total P content. In summary, AM fungi increased soil water and mineral nutrient uptake and improved plant physiological metabolic activities, and thereby promoted drought resistance and growth of A. adsurgens. The results provided the basis for selection of excellent drought-resistant AM fungi and the full application of AM fungi resources in promoting the growth of desert plants and vegetation restoration.