接种双色蜡蘑对酸性铝胁迫下马尾松幼苗生长、养分和铝吸收与分布的影响

Effects of Laccaria bicolor on Growth,Uptake and Distribution of Nutrients and Aluminum of Pinus massoniana Seedlings under Acid Aluminum Exposure

【目的】探索菌根化植物在田间条件下对酸性铝胁迫的抗性和营养机制,并筛选出抗铝性强的菌根苗,为我国酸性土壤林区的造林和植被恢复提供理论和实践支持。【方法】选用双色蜡蘑的3个菌株(Lb S238A、Lb S238N和Lb 270)分别接种马尾松,形成3种菌根苗,并以非菌根苗为对照,在酸性山地冷砂黄壤中培养4周,每周分别施入p H 3.8的不含A1和含1.0 mmol·L-1Al的Hoagland营养液,连续处理12周后取样检测并分析接种双色蜡蘑对酸性铝胁迫下马尾松幼苗生长、养分和铝吸收与分布的影响。【结果】酸性铝胁迫促进Lb S238A菌根苗的生长及对磷、钙、镁和铝的吸收,抑制Lb S238N和Lb 270菌根苗的生长及Lb 270菌根苗对钙和镁的吸收。与非菌根苗相比,接种双色蜡蘑均能促进酸性铝胁迫下马尾松幼苗的生长及对磷、钙和镁的吸收,抑制或不影响铝的吸收。其中接种Lb S238A的效果最好,可使酸性铝胁迫下苗木的生物量提高69.9%,磷、钙和镁吸收量分别增加68.9%、69.7%和81.5%。酸性铝胁迫下,接种双色蜡蘑对马尾松幼苗生长的促进作用主要表现在地上部分尤其是茎的生长上;接种Lb S238A或Lb S238N降低根、茎、叶中的铝浓度,而接种Lb 270降低根和茎中的铝浓度,尤其是降低茎中铝浓度;接种Lb S238A和Lb 270分别使茎和根中钙浓度减少,但接种Lb S238N却提高叶中钙浓度;3株双色蜡蘑的侵染均使磷浓度在根中降低而在叶中增加,使磷、钙和铝的分布在根中减少而在叶中增加。【结论】接种双色蜡蘑通过促进酸性铝胁迫下马尾松幼苗对磷、钙和镁等养分的吸收,推动磷、钙和铝向地上部转运,抑制或不影响铝的吸收且稀释铝浓度来提高马尾松苗木对铝毒的抗性。供试苗木中,抗铝性和养分吸收能力最强的是Lb S238A的菌根苗,适于在铝浓度较高的酸性土壤上种植;Lb S238N或Lb 270的菌根苗虽对铝敏感,但却能在铝浓度较低的酸性土壤上生长优良。

Aluminum toxicity is a primary limiting factor for plants grown in acidic soils. Some ectomycorrhizal（ ECM）fungi may improve the tolerance of their host plants against Al toxicity mainly by enlarging the uptake scope of nutrients,enhancing the availability of mineral nutrients,and/or inhibiting Al uptake by the host. Although these benefits have been partly illustrated in some ECM fungus species in vitro or in hydroponic or sand culture experiments,most focused on rhizoshere and fewer studies have examined the roles in field,and the transportation of nutrients and Al in plants still remained unclear.【Objective】 In order to learn about the Al-tolerance of ectomycorrhizal seedlings,to select excellent ones,and to explore the nutritional mechanism,【Method】 three isolates of Laccaria bicolor,namely Lb S238 A,Lb S238 N and Lb 270,respectively,were used to inoculate Pinus massoniana seedlings to evaluate the growth,uptake and distribution of nutrients and Al in plants under Al-exposure. The seedlings were pre-planted for 4 weeks in native acid yellow soil from a masson pine stand,and then irrigated weekly with Hoagland nutrient solution containing 0. 0 or 1. 0 mmol·L-1 Al3 ＋supplied with Al2（ SO4）3·18 H2 O at p H 3. 8 for 12 weeks.【Result】Exposure to Al stimulated the growthand uptake of P,Ca,Mg,and Al of seedlings inoculated with Lb S238 A,whereas inhibited the growth of seedlings inoculated with Lb S238 N or Lb 270,and inhibited uptake of Ca and Mg of Lb 270 seedlings. However,inoculation with any of the three isolates improved the growth and uptake of P,Ca,and Mg,but reduced or maintained Al uptake of seedlings under Al-exposure,with Lb S238 A the best,compared to nonmycorrhizal（ Non-ECM） seedlings. Inoculation with Lb S238 A increased the seedling’s growth by 69. 9%,P uptake by 68. 9%,Ca uptake by 69. 7%,and Mg uptake by 81. 5% under Al-exposure. Meanwhile,the improvement on growth from inoculation with any of the three isolates mainly exhibited on stem and on needles,with higher increment on stem than on needles. Inoculation with Lb S238 A or Lb S238 N decreased Al concentrations in each part of the seedlings,and Lb 270 decreased that in roots and in stem,with higher decrement in stem than in roots and in needles; Lb S238 A or Lb 270 decreased Ca concentration apparently in stem and in roots,respectively,but Lb S238 N increased that in needles. Inoculation with any of the three isolates decreased P concentration in roots but increased that in needles,and reduced distributions of P,Ca,and Al in roots but promoted those in needles.【Conclusion】Inoculation with any of the three isolates of L. bicolor improved the Al-tolerance of masson pine seedlings through the following ways： 1） enhancing the uptake of P,Ca,and Mg; 2） reducing the distribution of P and Ca in roots and proceeding them upward to the stem and needles; 3） inhibiting or maintaining Al uptake and diluting Al concentration to a non-toxic value in seedlings. Among the tested three isolates,Lb S238 A should be the best for masson pine seedlings to plant in acidic and allitic soils,and Lb S238 N or Lb 270 should be suitable in acidic soils containing less aluminum. It needs to explore the role of ECM fungus on mechanism about transporting of nutrients and Al in ECM seedlings exposed to Al in the further study.