丛枝菌根对喜树幼苗生长和氮、磷吸收的影响

EFFECTS OF ARBUSCULAR MYCORRHIZAL FUNGI ON THE GROWTH AND ABSORPTION OF NITROGEN AND PHOSPHORUS IN CAMPTOTHECA ACUMINATA SEEDLINGS

喜树(Camptothecaacuminata)是我国特有的多年生亚热带落叶阔叶树种,因其次生代谢产物喜树碱具有良好的抗肿瘤活性而受到人们的广泛关注。该文通过温室盆栽接种试验,观察了2属6种丛枝菌根真菌即蜜色无梗囊霉(Acaulosporamellea)、光壁无梗囊霉(A.laevis)、木薯球囊霉(Glomusmanihot)、地表球囊霉(G.versiforme)、幼套球囊霉(G.etunicatum)和透光球囊霉(G.diaphanum)对喜树幼苗生长和氮、磷养分吸收的影响。结果表明,丛枝菌根的形成对喜树幼苗的生长以及氮、磷营养的吸收均有影响。从生物量看,除幼套球囊霉和光壁无梗囊霉侵染形成的丛枝菌根喜树幼苗与无菌根幼苗(CK)差异不显著外,其余菌根幼苗的生物量均明显大于无菌根幼苗,透光球囊霉和蜜色无梗囊霉菌根幼苗尤为突出,分别达到无菌根幼苗的1.9和1.4倍。丛枝菌根的形成似乎不利于喜树幼苗的氮素营养吸收,并且主要体现在叶片的氮含量上。相反,丛枝菌根形成总体上促进喜树幼苗对磷素营养的吸收,并且主要体现在根的磷含量上。与无菌根幼苗比,所有菌根幼苗根的氮、磷分配比例增加,而叶片的氮、磷分配比例减少。

Background and Aims Caraptotheca acuminata is a special Chinese tree that produces camptothecin （CPT）, a monoterpenoid indole alkaloid, which has gained great attention for its remarkable inhibitory activity against tumour cells. Methods After 70-day growth period, seedlings were inoculated with the arbuscular mycorrhizal （AM） fungi, Glomus manihot （Gm）, G. versiforme （Gv）, G. etunicatum （ Ge）, G. diaphanum （ Gd）, Acaulospora mellea （Am） and A. laevis （Al）, respectively. Key Results We investigated the effects of six species of AM fungi, belonging to two genera, on the growth, absorption of nitrogen and phosphorus in C. acwninata seedlings grown in the greenhouse. All inoculated seedlings were infected by six AM fungi and formed arbuscular mycorrhiza. The seedling growth and nitrogen and phosphorus absorption were affected by the formation of arbuscular mycorrhiza in C. acuminata. The biomass of mycorrhizal seedlings was significantly higher than that of non-mycorrhizal seedlings. For most mycorrhizal seedlings, the ratio of root to shoot was larger than that of the control. Nitrogen contents in Gin, Gv, Ge and Al were significantly lower than in the control. In contrast, phosphorus contents in plant of all mycorrhizal seedlings were higher than in non-mycorrhizal seedlings. Arbuscular mycorrhizal formation also changed the allocation of nitrogen and phosphorus in different organs of seedlings. Conclusions These patterns suggest that the symbiotic association between C. acuminata roots and AM fungi effectively maintains nutrient homeostasis through changes in physiological properties, including nutrient uptake and allocation.