盐胁迫下AMF对榉树幼苗生长和光合特性的影响

【目的】探究盐胁迫下接种丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)对榉树(Zelkova serrata)的生长和光合特性的影响以及光响应模型的适用性,为利用菌根真菌技术提高植物在盐碱地中的生产力提供理论依据。【方法】以榉树幼苗为试验材料,设置不接种AMF(N)、接种摩西球囊霉(Glomus mosseae)1号(GM₁)、接种摩西球囊霉2号(GM₁)、接种扭形球囊霉(G.tortuosum,GO)4个处理组,进行盐胁迫与非盐胁迫(CK)处理。通过对比分析不同处理间的差异,探索盐胁迫下AMF对榉树生长及光合特性的影响,并评定5种光响应模型的适用性。【结果】(1)盐胁迫下GM₁、GO处理的菌根侵染率显著降低;(2)盐胁迫显著降低了榉树苗高、地径净增长量,而GM₁、GM₁处理显著提高了盐胁迫下榉树的地径净增长量;(3)盐胁迫下,榉树净光合速率明显下降,3种接菌处理均能提升榉树叶片净光合速率、气孔限制值、水分利用效率,并降低胞间CO₂浓度,其中GM₁和GO较未接菌处理变化最大;(4)盐胁迫条件下只有以叶子飘模型拟合的平均决定系数(R²)高于0.900,其余4种模型各处理的R²均低于0.900。【结论】盐胁迫对榉树幼苗生长及光合特性有抑制作用;接种AMF可以促进植物生长,提升植物净光合速率,缓解盐胁迫对植物生长及光合特性的抑制作用。综合AMF对榉树生长和光合特性的影响,GM₁较为突出,为盐碱地林业生产推荐选用菌株;5种光响应模型中,叶子飘模型的拟合效果最好,为探究盐胁迫下AMF对榉树净光合速率影响的最优模型。

Effects of AMF on the growth and photosynthetic characteristics of Zelkova serrata under salt stress

【Objective】In recent years,the area of land salinization has been increasing with the impact of human activities and climate change.Excessive levels of soil salinity may lead to several ecological problems such as soil dispersion,soil salinization,desertification,destruction of vegetation communities,and reduction of biodiversity.As such,soil salinity is an important environmental factor limiting the continuing development of agriculture and forestry.As a crucial part of terrestrial ecosystems,arbuscular mycorrhizal fungi(AMF)play an important role in the management of saline-alkali land,while Zelkova serrata is a tree species with considerable economic and landscape value in China.Both species have wide application prospects in saline-alkali land forestry production.However,most existing research has focused on the physiological and biochemical characteristics and salt tolerance of Z.serrata,while few have investigated the effects of AMF on the photosynthetic characteristics of salt stressed Z.serrata.Moreover,there is a lack of research on the applicability of the light response model under this condition.Accurate characteristic parameters provided by a suitable light response model may directly or indirectly reflect the photosynthetic physiological process of plants,and offer considerable guidance for forestry production in saline-alkali land.As such,this study investigated the effects of arbuscular mycorrhizal fungi inoculation on the growth and photosynthetic characteristics of Z.serrata,and the applicability of light response model under salt stress.In summary,the objective was to provide a theoretical basis to use mycorrhizal combination technology to improve plant productivity in saline-alkali land.【Method】Initially,Z.serrata seedlings that were not colonized with AMF were cultivated through seed and substrate sterilization.This was carried out concurrently while three AMFi.e.,Glomus mosseae separated from Bijie,Guizhou(GM₁),G.mosseae separated from Chuxiong,Yunnan(GM₁)and G.tortuosum separated from Ejin Horo Banner,Inner Mongolia(GO)],were multiplied in the artificial climate room for three months.Z.serrata seedlings with consistent growth were transplanted to the greenhouse of Nanjing Forestry University Xiashu Forestry Farm for the pot experiment and four inoculation treatments were established:(1)not inoculated with mycorrhizal fungi(N);(2)inoculated with GM₁;(3)inoculated with GM₁;and(4)inoculated with GO.After one year of AMF colonization and plant growth,potted Z.serrata seedlings of GM₁,GM₁,GO and N treatments were divided into two groups,and subjected to salt stress and non-salt stress treatments,respectively.In the salt stress treatment,300 mL of 100 mmol/L NaCl solution was poured into each pot every week,and sterile distilled water was used to replace the NaCl solution in the non-salt stress treatment.The treatment was carried out for two months,during which the Hoagland(reduced phosphorus)nutrient solution was regularly replenished.Then,three pots were selected from each treatment to determine the photosynthetic characteristics and mycorrhizal colonization rate.The effect of AMF on the net height growth,net basal diameter growth,net photosynthetic rate,intercellular CO₂concentration,stomatal limit value,and water use efficiency of Z.serrata under salt stress was explored by comparing and analyzing differences between treatments.The applicability of five kinds of light response models was evaluated by plotting the light response curve and comparing the fitting accuracy of each model in each treatment.【Result】There were four key findings from the results.First,the mycorrhizal colonization rate of the GM₁and GO treatments decreased significantly under salt stress.Second,salt stress had a significant inhibitory impact on the net height growth and ground diameter growth of Z.serrata,while the GM₁and GM₁treatments significantly increased the net ground diameter growth under salt stress.Third,under salt stress,there was a clear decrease in the net photosynthetic rate of Z.serrata.All three treatments could increase the net photosynthetic rate,stomatal limit value,and water use efficiency,while reducing intercellular CO₂concentration.Among the treatments,the GM₁and GO treatments exhibited the largest changes compared with the N treatment.Fourth,only the average R² fitted by the Ye Zi-Piao model was>0.900 under salt stress,and the R² of the other four models were<0.900.【Conclusion】Salt stress was likely to inhibit plant growth and photosynthetic characteristics.Inoculation with AMF may promote plant growth,improve the net photosynthetic rate of plant leaves,and alleviate the inhibition of salt stress on plant growth and photosynthetic characteristics.Based on the influence of arbuscular mycorrhizal fungi inoculation on the growth and photosynthetic characteristics of Z.serrata,the GM₁was prominent;this was recommended as the strain for forestry production in saline-alkali land.Among the five light response models,the Ye Zi-Piao model exhibited the best fitting effect,representing the optimal model to explore the effect of AMF on the net photosynthetic rate of salt stressed Z.serrata.