氮沉降和接种菌根真菌对灌木铁线莲非结构性碳水化合物及根际土壤酶活性的影响

【目的】通过研究氮沉降和接种菌根真菌处理对植物根际土壤酶活性和非结构性碳水化合物含量的影响,探讨全球氮沉降变化背景下植物根际微生态环境及植物生长的应对策略。【方法】以1年生盆栽灌木铁线莲单一接菌(根内根孢囊霉,编号+R;摩西斗管囊霉,编号+F)、混合接菌(根内根孢囊霉和摩西斗管囊霉体积比1:1的混合菌剂,编号+RF)的菌根苗和非菌根苗(未接菌,编号-M)为研究对象,设置4个氮沉降处理试验,即不施氮CK,0 g/(m²·a)]、低氮LN,3 g/(m²·a)]、中氮MN,6 g/(m²·a)]、高氮HN,9 g/(m²·a)],测定1年生灌木铁线莲苗木非结构性碳水化合物(NSC)可溶性糖(SS)、淀粉(ST)],以及根际土壤酶β-1,4葡萄糖苷酶(BG)、亮氨酸氨基肽酶(LAP)、β-1,4-N-乙酰-氨基葡糖苷酶(NAG)、酸性磷酸酶(ACP)和碱性磷酸酶(ALP)]等指标。基于单因素方差分析、双因素交互作用分析和相关性分析方法,在氮沉降量增加的背景下,研究不同接菌处理对苗木根际土壤碳、氮、磷相关酶活性及苗木各器官内非结构性碳水化合物分配的影响,从而探讨接菌处理下各指标对不同氮沉降水平的响应差异。【结果】①除BG活性外,氮沉降、接种菌根真菌及二者交互作用显著影响灌木铁线莲根际土中氮、磷相关酶活性。HN处理下,接种菌根真菌显著降低苗木根际土壤NAG活性。-M处理下,与磷相关的根际土壤ACP和ALP活性在HN条件下显著增加。+R和+F处理下,ALP均在HN处理达到最大。②氮沉降、接种菌根真菌及二者交互作用显著影响灌木铁线莲苗木非结构性碳水化合物。氮沉降处理下,各接菌处理苗木SS、ST和NSC含量高于未接菌处理苗木的,且在+F处理苗木的SS、ST和NSC含量均达到最大。③在LN、MN和HN处理下,-M处理苗木的各器官NSC含量大小顺序为茎<根<叶,而接菌处理苗木的各部位的大小顺序为根<茎<叶。HN处理下,+F处理苗木根内ST和NSC含量达到最大值,茎和叶内SS和NSC含量均达到最大值。④氮沉降和接种菌根真菌处理下,SS、ST、NSC含量与土壤氮相关的NAG活性显著负相关,而与磷和碳相关的酶显著正相关;其中苗木非结构性碳水化合物与磷相关土壤酶ALP活性的相关性系数最高,与碳相关土壤酶BG活性相关性系数最低。【结论】氮沉降和接种菌根真菌处理对灌木铁线莲苗木根际土壤氮、磷相关酶活性的影响高于对根际土壤碳相关酶活的影响,氮沉降处理显著增强菌根苗根际土壤磷酸酶活性。氮沉降背景下,接菌处理提高了苗木非结构性碳水化合物含量,其中接种摩西斗管囊霉的效果最为显著,且明显增加了高氮环境中苗木对根中非结构性碳的分配。

Responses of the non-structural carbohydrates and rhizosphere soil enzymes of Clematis fruticosa to nitrogen deposition and inoculation mycorrhizal fungi

【Objective】The responses of plant rhizosphere soil enzymes and non-structural carbohydrates(NSC)were investigated in relation to nitrogen deposition and inoculation with mycorrhizal fungi.Strategies for the rhizosphere micro-ecological environment and plant growth were explored in the context of changes to global nitrogen deposition.【Method】One year old Clematis fruticosa mycorrhizal and non-mycorrhizal seedlings(serial No.-M)were subjected to microcosm experiments.The inoculation treatments included single inoculation(Rhizophagus intraradices,serial No.+R;Funneliformis mosseae,serial No.+F)and mixed inoculation(R.intraradices and F.mosseae 1∶1 mixture fungi agents,serial No.+RF).Four nitrogen deposition treatments were established:no nitrogenCK,0 g/(m²·a)],low nitrogenLN,3 g/(m²·a)],medium nitrogenMN,6 g/(m²·a)]and high nitrogenHN,9 g/(m²·a)].The NSCi.e.,soluble sugar(SS)and starch(ST)],and rhizosphere soil enzymesi.e.,β-1,4-glucosidase(BG),leucine aminopeptidase(LAP),β-1,4-N-acetylglucosaminidase(NAG),acid phosphatase(ACP),and alkaline phosphatase(ALP)]of seedlings were determined following the inoculation and nitrogen deposition treatments.One-way analysis of variance,and two-factor interaction and correlation analyses were used to determine the effect of different inoculation treatments with increasing nitrogen deposition in terms of the carbon,nitrogen and phosphorus related enzymatic activities in the seedlings rhizosphere.Additionally,the allocation of NSCs in seedlings organs were explored in response to the inoculation with mycorrhizal fungi and nitrogen deposition.【Result】(1)In addition to BG activity in the soil rhizosphere of C.fruticosa seedlings,the nitrogen deposition,inoculation with mycorrhizal fungi,and their interactions notably affected the nitrogen and phosphorus related enzymes.Under HN treatment,the NAG activity in the soil rhizosphere had notably decreased through the inoculation treatments.The ACP and ALP activities related to the soil rhizosphere phosphorus had notably increased under the-M and HN treatments.The ALP activity peaked in the HN treatment under the+R and+F treatments.(2)The NSC content of C.fruticosa seedlings was notably affected by nitrogen deposition,inoculation with mycorrhizal fungi,and their interactions.Under the nitrogen deposition treatments,the contents of SS,ST and NSC of seedlings in the inoculation treatments were higher than those without the inoculation treatment;the SS,ST and NSC contents peaked in the+F treatment.(3)The seedling NSC content in the-M treatment in ascending order was:stem