接种AM真菌对喜树幼苗生长及光合特性的影响

 喜树(Camptotheca acuminata)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备受关注。通过温室盆栽接种试验, 观察了3属6种丛枝菌根(AM)真菌木薯球囊霉(Glomus manihot)、地表球囊霉(G. versiforme)、透光球囊霉(G. diaphanum)、蜜色无梗囊霉(Acaulospora mellea)、光壁无梗囊霉(A. laevis)和弯丝硬囊霉(Sclerocystis sinuosa)对喜树幼苗生长及光合特性的影响。结果表明, 除地表球囊霉外, 其余菌根幼苗生物量显著高于无菌根幼苗, 蜜色无梗囊霉、弯丝硬囊霉和透光球囊霉的菌根幼苗生物量分别达到无菌根幼苗的1.6倍、1.4倍和1.3倍。与无菌根幼苗相比, 蜜色无梗囊霉菌根幼苗叶片的净光合速率(P_n)、气孔导度(G_s)和蒸腾速率(T_r)均有显著提高, 而胞间CO₂浓度(C_i)与气孔限制值(L_s)则变化不明显。接种透光球囊霉、蜜色无梗囊霉、光壁无梗囊霉和弯丝硬囊霉的喜树幼苗叶片叶绿素a含量、总叶绿素含量、叶绿素a/b和类胡萝卜素含量均显著高于无菌根幼苗, 而叶绿素b含量只有木薯球囊霉和弯丝硬囊霉菌根幼苗显著高于无菌根幼苗。接种AM真菌对喜树幼苗叶片叶绿素荧光参数影响较小, 只有透光球囊霉菌根幼苗叶片的最大光能转换效率(F_v/F_m)显著高于无菌根幼苗, 接种木薯球囊霉和弯丝硬囊霉的喜树幼苗的PSⅡ有效光化学量子产量(EQY)显著高于无菌根幼苗, 弯丝硬囊霉菌根幼苗的光化学淬灭(qP)显著高于无菌根幼苗, 非光化学淬灭(NPQ)则显著低于无菌根幼苗。

EFFECTS OF ARBUSCULAR MYCORRHIZAL FUNGAL INOCULATION ON GROWTH AND PHOTOSYNTHESIS OF CAMPTOTHECA ACUMINATA SEEDLINGS

Aims Camptotheca acuminata is a Chinese tree that produces camptothecin (CPT), a monoterpenoid indole alkaloid that inhibits tumor cells. Our purpose was to determine effects of arbuscular mycorrhizal (AM) fungi on the growth and photosynthesis of C. acuminata seedlings. Methods Potted seedlings were inoculated with one of six AM fungi (Glomus manihot, G. versiforme, G. diaphanum, Acaulospora mellea, A. laevis and Sclerocystis sinuosa) and grown under greenhouse conditions. Important findings All seedling roots were colonized by the six AM fungi and formed typical mycorrhizal structures. Except the G. versiforme inoculated seedlings, the biomass of mycorrhizal seedlings was significantly higher than non-mycorrhizal (CK) seedlings. Moreover, biomass of A. mellea, S. sinuosa and G. diaphanum inoculated seedlings reached 1.6, 1.4 and 1.3 times that of CK, respectively. Compared with non-mycorrhizal seedlings, the net photosynthetic rate (P_n), stomatal conductance (G_s) and transpiration rate (T_r) of A. mellea inoculated seedlings were significantly increased, while the intercellular CO₂ concentration (C_i) and stomatal limitation value (L_s) of mycorrhizal seedling leaves did not change significantly. The chlorophyll a content, total chlorophyll content, chlorophyll a/b value and carotenoid content of G. diaphanum, A. mellea, A. laevis and S. sinuosa inoculated seedlings were significantly higher than that of CK, as was the chlorophyll b content of G. manihot and S. sinuosa inoculated seedlings. Effects of AM fungal inoculation on the parameters of chlorophyll fluorescence of Camptotheca acuminata seedlings were small. Only the maximal photochemical efficiency of PSII in the dark (F_v/F_m) of G. diaphanum inoculated seedlings was significantly higher than that of CK. For G. manihot and S. sinuosa inoculated seedlings, the effective quantum yield (EQR) was higher than that of the non-mycorrhizal seedlings. The photochemical quenching (qP) of S. sinuosa inoculated seedlings was higher and the non-photochemical quenching (NPQ) was lower than in non-mycorrhizal seedlings.