Anatomical responses of leaf and stem of Catalpa bungei C.A.Mey. to nitrogen application and Rhizophagus intraradices inoculation

Abstract

Plant morphology and anatomical structure are closely related to plant function, and their changes may affect physiological processes and may also be altered by nutrient availability or arbuscular mycorrhizal fungi (AMF) inoculation. To our knowledge, studies on the effect of AMF on plant anatomical characteristics under different nitrogen (N) levels are very scarce, especially in trees. Here, a pot experiment was carried out to evaluate the response of leaf and stem anatomy of Catalpa bungei using a two-factor completely randomized block design, including mycorrhizal inoculation (inoculation with Rhizophagus intraradices or not) and N application (low, medium, high). Regardless of the inoculation status, moderate N addition promoted leaf and stem development, while excessive N had a significant negative impact on the anatomical structure of seedlings. Compared with the non-inoculated treatments, AMF inoculation increased most of the leaf stomatal characteristic parameters and stem structural parameters of C. bungei seedlings, while significantly reduced leaf upper epidermis thickness (UET), lower epidermis thickness (LET), spongy tissue thickness (STT), and leaf thickness (LT) at low to medium N levels. In addition, the lenticel density (LD) at low N levels and the lenticel length (LL), width (LW), and area (SLA) at medium N levels in mycorrhizal seedlings were significantly higher than those in non-mycorrhizal seedlings. We concluded that AMF inoculation may significantly improve the water and gas exchange capacity of seedlings at least at low to medium N levels.